94 looses power and will not accelerate
 

T\runs perfect for around 100 miles then if i hit a hill loose power and engine will not acceleate
it will get worse untill 15 mph is top speed if i stop shut off and wait a while then everything is fine for a short distance then same problem again. If seems if the injector timing is going extremely slow. when the slow n o power and no accelaration i get BLACK smoke that smells
of raw fuel.


:argh::argh:

how many miles on the truck and do you exhaust leak and do you have boost gauge first check air filter second do OPS and LP test to make sure LP pumping fuel to the injector pump and it also could be PMD going bad on you and is it still on the injector pump or front bumper also check make sure waste gate working

we have 270,000 and i don t have any exhaust leaks i can find. dont have a boost gage
have a new air filter what is the PMD how do i check the waste gate?

if your PMD is still on the side injector pump it may be going bad on you . you need get move to front bumper with heat sink

before we stay it bad PMD need do few test first to see LP (lift pump) working
here some reference material to read how test

Reference Material: Lift Pump/OPS
Here’s another one for the newbie’s out there.

After frequenting the boards for awhile, you’ll notice there seems to be a few things that come around, and around, and around again. One of those things is the Lift Pump, official title: Fuel Lift Pump. So, what is a lift pump, and why does it lift fuel? The lift pump is an in-line fuel pump mounted on the frame rail under the driver’s seat. This is a small electric pump that “helps” bring fuel out of the tank and up to the injection pump. This is to help prevent the expensive injection pump from having to “suck” it’s own fuel all the way up from the tank, which it can do, but can cause damage to itself and it's driver module - more on that in another section*.

Now, that’s pretty straight forward isn’t it? So, why so much fuss about a lift pump anyway? Only because it causes so many issues* when it’s not working.

Will my truck run without the lift pump? Yes it will. How well? Well, to some it will be very noticeable when it’s not working. Some may not even notice.

If I don’t notice that my lift pump isn’t working, I’m okay right? Not exactly. That means that your expensive injection pump is doing all the work in the fuel system. This is NOT a desirable thing. Plus you are setting yourself up for problems*.

How can I tell if my lift pump is working? Do the famous “lift pump test.” How do you accomplish this highly scientific experiment you ask? Very simple. Pop the hood - you’re half way there. Find on the front top of the engine the thermostat housing. You should see a little T-handle valve standing proud there in front of you. (If you have a van, you’ll have a schrader valve down deep behind the oil fill) That T-valve is calling your name saying “turn me.” Pay attention, ‘cause there’s a hose on the end of the T-valve. That hose should have diesel fuel come out of it when the engine is idling and you open the T-valve. When you open the T-valve and the engine is idling, and no fuel comes out, you’ll hear your engine cough, sputter, and die within 30 seconds. If it doesn’t cough, sputter and die with the T-valve open and no fuel coming out, something is plugged up in your fuel system between the fuel filter cannister and the t-valve, perhaps even inside the fuel filter cannister.

If the engine does die, it has emptied the fuel cannister and run out of fuel, so you will need to close the T-valve, then troubleshoot and repair the lift pump system, as follows in the text below.

Now, if you get a continuous stream of fuel out the hose, then close the T-valve and open the plastic air-bleed valve on the top of the metal filter cap - if fuel spurts out there, then congratulations! You are the proud owner of a working lift pump. Not everyone is as blessed as you are at this moment. If you're not, keep reading.

To those not as blessed, pickup reading here. You must determine why you have no fuel supply coming to your injection pump. There are two main culprits to the demise of a lift pump. Either it’s out to lunch, or it’s in the morgue. See, one means it still might work, the other means it’s dead. How do you tell? Check to see if it has power.

First, find the lift pump under the truck. With the engine idling along, pull the plug for the lift pump. You can either use a test light, or a meter to see if you have voltage at the pins. Make sure you get a good connection, otherwise you may condemn the wrong thing. Sometimes it is difficult to get a probe to meet up with the pins inside the plug, so make double sure you’ve got it.

If you have voltage, *chances* are you have a dead lift pump. Not always, but could be a dead lift pump. You may have voltage present under a "no load" condition. This means that voltage may be present when the lift pump is not attached to the circuit, but once the lift pump is connected, the load exceeds the amount of power the circuit can provide because the OPS contacts are creating a high resistance.

Now, if you don’t have voltage, you’ll have to verify upstream from there why there is no voltage present. What is upstream? The infamous OPS (Oil Pressure Switch), or fuse.

What does the OPS have to do with the lift pump? Doesn’t sound right does it to have oil pressure tied to fuel does it? Well, some think that it is a fail safe that in case your engine ever lost oil pressure, it would shut off the lift pump so that engine would stall. Guess what? If you read a little bit ahead of this paragraph, you’ll find 'dat ain’t so'. The real reason why this circuit even exists is because of an accident. In case you should be in a wreck, the last thing you would need is to have your lift pump going to town pumping out that precious, expensive, fuel all over the accident scene. After all, should you be bleeding and having a thumpin’ head - the last thing you’ll be thinking is “Hey, I just paid $2.50 a gallon for that, somebody get a shop-vac!”

Why would the OPS not allow my lift pump to work? Well, from time to time, or shall we say in the corporate world, from dime to dime, some decisions get made. Some for the good, and some for the good of the keepers of the money. The OPS has a set of contacts inside to power the lift pump. This set of contacts are not heavy enough to carry the pathetic amount of current to the lift pump. Sad, I know, but true. So, what ends up happening is your lift pump works fine, but the OPS gets smoked, and then it quits. You think the pump is bad, but it’s not.

Can I just eliminate the OPS? Well, be careful, it is a safety device in some people’s eyes, and to the rest of us, a pain in the rump. Eyes, rump, pick your part. Anyway. If you just “jump past” the OPS, then your pump will run all the time. Not just all the time, but ALL THE TIME. Christmas and Easter included. It will stop when your batteries are dead. Because, while you are grocery shopping, that pump is running. While you are down for a long winter’s nap, it’s pumping. Doesn’t matter if the key is on or off, it’s pumping.

You can make up another circuit and repower it some other way, but be careful how you do it. Some methods have kept the truck running after the ignition is shut off and keys in pocket.

Back to our little friend the lift pump.

The lift pump may fail in a variety of different ways. It may fail “open” meaning that the coil driving the pump no longer has continuity. It may fail mechanically where it is just frozen and nothing moves. It may even (not as often) fail to pump. This means, it makes noise, but doesn’t actually pump.

Does the lift pump make noise? Yes it does. The model year of your truck will determine if your lift pump is powered during the Wait To Start period. That’s the time where that light is on before actually starting your engine. '96-up OBD2 models pre-run the lift pump during WTS and during START, '94-'95 OBD1 models pre-run the lift pump only during START.

The lift pump is characterized by a kind of “purring” noise heard beneath the truck. That noise is quickly drowned out by the engine, once started. When you shut your engine off, you will hear that pump run briefly, maybe only a quick second or two. If you shut your engine off when cold, you will hear the pump run much longer, sometimes up to 30 seconds or more.

A loud clacking noise would indicate no fuel from the tank, or the lift pump is failing or failed - it will run without pumping fuel when the one-way valve(s) fail.

A faint purring or vibration when touching the lp body indicates it is running, but the internal valve-shuttle armature is stuck due to mechanical failure.

So what kind of problems will it cause if the lift pump isn’t working? Many. It will cause all sorts of fuel related issues*. It can be some of the following:
°Stumbling
°Hard Starting
°Lack of Power
°DTC (Diagnostic Trouble Codes) on the Computer
°Stalling

There are be other* issues too, but these seem to be a very (un)popular list.

Where do I get one of these? Some of our site vendors, or any of the popular auto parts stores, or the dealership. More often than not, the auto parts store is a good bet for Ineeditrightnow.

Diesel Place tip: Ask for the version for the '93 6.5TD truck - it is a direct-fit HD replacement that will supply increased fuel pressure and volume to the Inj Pump, which is a good improvement for the '94-up EFI trucks.
FYI: don't mention that you have a '94-up truck, or you will just confuse the parts guy\gal - just describe your truck and drivetrain as a '93.
The ACDelco or Delphi lift pumps are the best replacement, which you can get from O'Reilley's or NAPA , and some of the site vendors, such as Heath Diesel.
Also FYI: the parts-guy\gal may call it a fuel pump.

Are they difficult to change? No - loosen the tubing-fitting nuts on either end, remove and reinstall. Now, if it were only really that easy. Let’s get real here, no camera out-takes…. You’ll end up getting a Diesel bath. You see, depending upon how much fuel is in your tank, there will be fuel that wants to come out of the fuel line. Be ready, because your chances of a date after changing that lift pump dwindle a bunch, unless they are really into the smell of a Diesel cologne. J

After the successful fuel lift system repair you will need to refill the fuel filter cannister - after opening the air-bleed valve, which is the plastic nut on the very top of the metal cap, power up the lift pump, then close the air bleed when the bubbles stop and fuel begins spurting out - if you still get no fuel, you likely have a stopped-up fuel filter - no need to tell you what to do in that event, right?
FYI: after successful fuel flow out the air-bleed, the engine may take a while to restart and run as the Inj Pump begins to draw fuel from the filter, fills internally, then starts pump-up to 1900psi injection pressures.

This is at least enough to get you started on your lift pump journey. If you have any specific question, feel free to post them by starting another thread. We’ll be glad to help you out.

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So where did your getty-up-and-go, go anyway?

The most famous part of the 6.5TD engine is the “TD.” That stands for Turbo Diesel. We all love the singing of that turbo under the hood. Some sing, some are of key, and some don’t sing at all. So, let’s dive into the common turbo issues.
One of the most common problems that comes around on these turbos are:

“I'm blowing black smoke”
“I don’t have much power anymore”
“My service engine light comes on”

So how does this macho piece of hardware work? Pretty simple actually. It is an exhaust-driven turbine motor driving a centrifugal air compressor. There are two “wheels” connected by a shaft. One wheel or turbine-fan is in the exhaust stream, the other wheel or compressor-fan is in the intake path. As the engine runs it pushes the exhaust gas out through the exhaust system. The turbine-fan wheel is driven by that exhaust gas. It in turn spins the compressor wheel. The compressor wheel pushes more air into the intake of the engine. More air, more fuel, more exhaust. More, more, more, which means more power “available” to be made. This increase of air is called boost.

What is a wastegate? The wastegate is a flapper-type valve that opens up on the exhaust turbine side of the turbo. This flapper will allow exhast gas to bypass and not spin the turbo as much. This will reduce boost pressure. This flapper remains closed under most conditions (idle, cruising, etc). It is designed to usually open up during high-load conditions, which causes high cylinder and exhaust heat.

So does more boost mean more power? Not really. It means that more power can be made. Boost is air. Air is cheap. If you want power, you have to pay for that at the pump. Power is fuel. More boost means you can burn more fuel. You can always dump in more fuel (to a point) but it won’t burn effectively until you have enough air to complete combustion.

So how much boost can I build? There seems to be ongoing discussion as to how much boost you can make. Some people like the idea of engine-splitting boost pressures, others like longevity. Which ever you prefer will be the answer to your question. The fine folks at GM have said the 12 is plenty. You can run higher levels, but you better do some reading, and have some cash ready too. That will be spent on modifications to the engine, or modifications to the engine after it’s failure. You can run more than 12 psig of boost without blowing it up. How long will you get away with this? That’s a variable not yet established, but the event is usually marked with exciting noises and other fanfare.

So why doesn’t my turbo work? There is are some common failing parts on these systems that will put your turbo on holiday. They would be:
°Wastegate solenoid
°Vacuum leaks
°Vacuum pump


Wastegate solenoid - This little piece of s. . . Plastic, yeah, that's it.....plastic....is a small solenoid-valve that PCM pulses in order to regulate the vacuum supply to the wastegate actuator.
Wastegate actuator - this is the small gold canister on the side of your turbo that pulls the rod to the wastegate. It opens and closes the wg by vacuum on a diaphragm which creates thrust on the rod.
Wastegate - This is a flapper-valve on the exhaust turbine side of the turbo that allows exhaust gas to bypass the turbine fan, reducing boost pressure.
Compressor - That is the intake air side of the turbo. It pushes the air into the intake.
Spool-up - That is the spinning-up of your turbo.


So, with that covered, now we talk about what is going wrong with all this pieces and parts. When the turbo stops working, it is usually because the wastegate is open, or opening. The wastegate is used to regulate the amount of boost coming into the engine. Why, you ask? Well for some very simple reasons.

How do I check to see if I have wastegate problems? A quick test would be, at idle, see if the wastegate rod is pulled up into the actuator housing. If it is, that is a good start. Now, pull on the rod, and see if you are able to move it. Pulled in means there is vacuum. Suction is good, but how much? If you are able to move it, then you may not have sufficient vacuum to maintain boost.

To really test the system you should get a vacuum gauge to verify readings - with engine idling you should have 26"hg at the vacuum pump and 15"hg at the wastegate, but the above 'pull-test' will show if you're in the ball park.

The wastegate solenoid is the most common failing part in the whole system. Chances are if you have problems, this is it. Now, don’t just condemn it because it’s everyone else’s problem. Verify first that it is bad. How?

How do I determine if my Wastegate Solenoid is bad? You must see if there is vacuum before and after it. Locate the solenoid by tracing the vacuum line back from the wastegate actuator. You will need to determine if you have vacuum after the solenoid. You’re looking for about 15” of vacuum. Many refer to this a pressure. It’s not really pressure, but suction. Notice I did not say 15 psig, but 15”.
This little valve has three ports. Only two of which you hook vacuum lines to. One is the vacuum source (to the vacuum pump), the wastegate actuator, and vent. Vent, is not something you hook anything to. Why a vent? That is how it regulates the amount of vacuum going to the actuator. There is a little steel ball inside the valve that switches back and forth between vacuum and vent. Here lies the problem. That ball will rust. When it rusts, it won’t roll anymore, so your engine power no longer rocks. Thus, you ain’t rock’n’rollin’ anymore. When the ball doesn’t move, it will get stuck and not allow vacuum (usually) to the wastegate actuator, leaving it open all the time. This means a no-boost situation.

The solenoid can fail in a vareity of different ways. It can fail to provide no vacuum to the actuator. (most common) It fail to provide vacuum always (not as common, but possible), the coil could fail, or no power to the coil from the ECM. Sometimes the ball will “stick” causing erratic boost, where it will spike up and down.

Can you fix this? Yes, replace it. No repairs ever found really. You can “limp it along” by spraying something like WD40 into the port. This may help to free it up, but it won’t live forever.

Where can I get one? Usually it’s a dealer item. Local parts stores don’t seem to have this item for some reason. Check around, there are some on-line parts sources.

I have no vacuum before the solenoid? You should check to see if your vacuum pump is working. If you have no vacuum present before the solenoid, then you either have a bad vacuum pump, or a leak somewhere. Chances are if you have an EGR equipped engine, you’ll have EGR codes if you have no vacuum, because they are all vacuum driven.
Weak vacuum too will also cause problems. You should have around 26"hg of vacuum available at the pump.

Where is my vacuum pump? It is driven by the serpentine belt. Look here.

Don’t rule out vacuum leaks. If you have a leak, you maybe changing parts that work just fine.

I am blowing black smoke, does this mean I have a turbo issue? Sometimes it does, if you have gone through all of the above diagnostics, and everything is okay, then may need to check some other things.
Does my computer (ECM) indicate problems with my turbo? Yes, depending upon your year, will depend upon what codes you will get. There are two generations of computer, OBD-I, OBD-II. The first one can be checked with a paperclip. The second needs a code reader. 96+ vehicles have the second generation that needs the reader. Check the FAQ section of this forum for specific codes.

What if my vacuum pump is bad? Well, economically speaking, you’ll have to make the determination if you want to replace it, or go with a simple spring on your wastegate to regulate vacuum. Yes, you can eliminate the problematic vacuum system on your turbo if you would like. So, why doesn’t everyone do this? Well, there are some things you need to watch in doing this. Your computer regulates everything with the stock system. You eliminate that, you will have to take over being the “brains” of the engine in the boost department. DO NOT replace with the spring system unless you have a mechanical boost gauge to monitor the boost pressure. Aftermarket products are available for a turn-key spring system, or you may fabricate your own.

How do I know if the actuator is bad? Well, this is not as common a problem, but does happen. You can check this by providing vacuum to the wastegate actuator, and see if it holds. If it leaks, then you may either replace the actuator, or go with the spring/mechanical system.
What happens if I build too much boost? Then, that’s called over boost. This is where the computer takes evasive action to prevent from blowing up. Depending upon what your computer is programmed to do, it will either dump the boost, or go into limp mode (may limit engine to 2000 rpm, and no power) This will also set the Service Engine Light.

So I can have either too much, or too little boost? Yes you can. Either is undesirable. Too little will not provide complete combustion, and cause higher EGT (Exhaust Gas Temperatures). Too much boost will cause unnecessary stress on the engine.

Are there any other things that will effect this system? Yes, the air filter. If it is dirty, it will reduce the amount of air that the engine can ingest. This can make noticable engine power losses. Don't trust that little pop-up thingy to tell you when it's dirty. Open the filter box up and check for yourself.

Does the turbo work all the time? Yes it does, mostly. At idle, under load, etc, it's spinning, or supposed to at least. The wastegate opens to bypass some of the exhaust gas to reduce boost under high-load situations. There is no occurance where the turbo "shuts off" under normal conditions or at idle. It will always be spinning.

What are the drawbacks to this turbo system? Well, it performs well under the conditions it was designed for. If you begin to take it outside of those operating parameters, it becomes an expensive hairdryer. Turbo compressors produce heat.

What's wrong with heated air coming out of the turbo? Well, the heat makes the air less dense. You are wanting more density of air to burn more fuel. That's what a turbo is for. It's for jammin' more air into the intake. Once you heat the air, it becomes less dense, and starts to be counter-productive.

How can I overcome this? You must come up with some method of intercooling. That is a way of cooling the air charge before it enters the intake. Under high boost conditions, your intake air temperatures can rise to 200°+F. That's the INTAKE, not what's happening in the exhaust, or the clyinder, that's BEFORE it gets there.

How can I intercool my engine? There are intercoolers available on the market that uses air to cool the air charge. There is also water mist injection. There are posts out there on these topics, feel free to search them, with forum's search feature. You may also check out the FAQ's, or follow this link.

Do I need an intercooler if I don't do any towing or have any performance modifications? Well, it's up to you. The current stock setup will get pretty hot still. It's all in where you want to spend your money. Do some more reading on the subject and see if this is something that suits you and your budget. Of course we'd all like to have our engines as souped up as possible, but then again, we have other payments that are calling our names. . .

How can I put an intercooler in, and how does it fit? Check this link. Do a search, there are many others.
Hope this helps to you to better understand everybody’s favorite part of their engine: The turbo.

so this only happens on hills?

usually the first time it happens is on a hill that is steep enough for a down shift to happen.
after i get back on level or on down hill i can not accelerate much. until finally the truck will only run at 20 mph no matter what. it smokes black but has no speed it seems to have plenty of power at idle. It is almost like a super jake brake on it. once i stop let it rest for a few minutes and restart everything is ok for a few miles. this happens on the freeway at 60+ mph. once i restart i can run up to normal speeds. Usually I am pulling a
4000 lb trailer. I do not know if it will happen with nothing in tow.
I have also noticed that sometimes when the truck downshifts pulling a hill instead of more power i get a feel like i added several times the load .

I have a 94 half ton that did the same thing but not to the extent of only being able to go 20 mph. Whenever I would get on it going up a steep hill and downshift it would go into what seemed like " limp mode" and the check engine light would come on and the engine would de fuel and only pull about 6 psi boost. When I first got the truck the wastegate controller was bad and it pulled about 19psi and it went into this what I called limp mode often. After I turned he boost down to safe levels it doesn't do it as much. But all in all, it sounds like a wastegate solenoid is bad because you said lots of black smoke and no power = no boost. But checking the ip ops lp and Pmd would not be a bad thing. O and what codes do u get when It does this?

I don't get any codes and the light does not come on the light on mine is check electonic accelarator??? I dont have a code reader for the plug on the truck

being 94 truck OBD-1 all need is paper clip to check codes

The Data Link connector is located below the steering wheel lower left rim of the dash just about knee cap height.


Use a jumper (paperclip, etc) to connect these terminals. The connection/removal of the jumper between terminals (A&B) should be done with the ignition switch OFF. Also to prevent potential volt spike to PCM remove clip with Key OFF also.Once jumper is installed then turn key to on/run (not full start) to begin the flashing sequence


The Service Engine Soon light will flash Code 12 three times to indicate that the diagnostics are working. Trouble codes will then follow, one at a time, three times each. DTC 12 will only appear if there are no other codes.


here a pic show you A & B spots



2 The codes appear in numerical order, and each code repeats itself three times before the next begins. This is different from some other ECM's.


3. It is helpful to the diagnostic process to know when codes are setting, particularly if there is more than one. Hence, clearing the codes is something you may wish to do. Clearing the codes may be accomplished by simultaneously depressing the brake and accelerator pedals fully while the PCM is in diagnostic mode (terminals A and B connected). It will not appear that you have cleared the codes until the next time you power up in diagnostic mode, however.

None of the parts described in the lift pump check are where the post says they are.
the lift pump is on the passenger side but i can not find the fuel canister with a handle
Could everything be in a different place this is a 94 3500 ??

lift pump is on driver side on the frame under driver door

when say handle i guest you mean T-Valve it be bass T-Valve on the T-stat housing

It is copper in color as soon as u open hood reach ur right hand forward u should be touching t hander or close to it:c:

See what you think 94 3500
 

Check these pics see if you got any ideaAttachment 19015

Attachment 19016

look like some remove the water drain valve take few more pic of the engine and see if there didn't put in diff spot and could use top of the see if lift pump working or feed hose at the injector pump it self buy pulling it off

this looks like a factory move
 

the fuel filter is in back with no water release what is that unit in the front of the tunnel
it looks almost like a international injector unit??Attachment 19018

Attachment 19019

Attachment 19020

on that first pic i see metal line going long side the injector pump going to rubber line can you get more pics it where it going to

OK the lines you see are return lines from the injectors they tee together then go in the rubber hose on the top. the line above the black box is from the filter.
Should I get fuel if i take the black plug out of the top of the filter and turn the switch on?
If so then I got a bad lift pump.

More pictures of 6.5
 

here are a few more pictures shows what i can figure out
Attachment 19021

Attachment 19022

Attachment 19023

the first 2 pics i see is showing fuel feed line from the fuel blow housing and the other line is return line that the one on the right
the 3rd pic is return line from the driver side injectors

all most look like they took off the water drain T-Valve you going have try see down at bottom of the fuel blow and see if they don't one port plug off or see where they run the line too something just not right there

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hey i also seen the PMD on the side of the pump is the one you running off of

I guess I am running off that little black box there'
Yea it doesnt mach up with the book at all but it still looks "Factory" I don't think the LP is running. I release the top of the filter and don't get any flow of fuel even when i crank the engine.

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I would think there is some way to drain the water and junk from the bottom of the filter
I will crawl around with a mirror and see what i can find.
thanks for the help.
first day above 20 just been too cold to check things out.

take 12v right to LP and see if it pump fuel if it does most likey you have bad OPS run the LP on your truck and if it is bad OPS make sure you put only ACDelco in any other brand won't last you 6 months

Thanks will give it a try.

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Where is that OPS the pump is good

here are part #er you should just go with ACDelco and you going want pull the bolts out fuel housing so move to the side gave more room and you will need 12pt socket remove and install


Oil Pressure Sensor:

* OEM: 12555492
* ACDelco: D1808A
* Car Quest: PS262

injector pamp i have a 93 that had the same thag hapin to it

That is the OPS top back of the engine down under everything??

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That switch looks like a P I A. I may just build a circuit to run the pump without the switch.
if it ever fails again I will for sure.

yes

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i post you mod by pass if you want it

Give it to me.. I may can make it better, In my other life i am a electrical control engineer Retired.
Just have to find a good source for switch on power.

OPS and LP Mod
 

The first pic is of the OPS location. The second pic is of the OPS plug and the wire colors. The third pic is of the items I used to do the project. The fourth pic is of the wires cut and crimped.

The length of the extension wires were 24“, I removed the convoluted tubing from the OPS wires before I started cutting. my wire colors for the relay extension were :

Orange for the hot: I cut the orange wire from the OPS plug about 3” from the plug and tied in the orange extension wire. Crimped and shrink wrapped it.

Gray for the OPS plug: approximately 2.5” from the plug I cut the gray wire. The wire from the OPS plug I connected the gray extension wire. Crimped and shrink wrapped.

Light purple for the LP: on the cut wire going to the LP I connected the Purple wire. Crimped and shrink wrapped.

Brown for the ground: The brown ground wire is much shorter because it is just ran to the relay’s mounting screw.

My pics don’t show the shrink wrap installed on the wires (I thought I had took one but this was the time the grandson decided to interrupt me). The fifth pic is of the wires from the OPS re-loomed and the relay wires Loomed. I decided to mount the relay under the electric shroud pic # 6 on the passenger’s firewall pic # 7 . It seemed to be the most likely place to put it. Being that the factory saw fit to have already put holes there and the other relays were there as well. I mounted the ground with the same screw I mounted the relay with. Then replaced the shroud.

The relay is numbered and the extension wires hook to the relay in this order. #30 is the orange power wire (by the way this wire is hot with key off don’t let it ground out. Please don‘t ask how I know). #85 is the brown ground wire, #86 is the gray wire from the OPS and #87 is the purple wire to the LP.

The bosh relay number is 0-332-209-161.

Is the Grey wire only hot when the switch is on?

yes that the wire from the OPS

Does the oil pressure gage still work?

yes gauge still all you doing is setting it like 97+ where LP will run of the relay instead OPS but it still be set up if happen to roll over the truck the OPS will shut off the LP yes there are easy ways of doing but not safe

the OPS contacts are not heavy enough to run a load. they will all fail when used to run a pump. I have always ran a pump with relays designed for load. Thanks for the help.
If it is not to cold out I will do the fix Monday. I still may have a Turbo problem and I got to move that black box on the Injector pump..

Did this ever get fixed?
 

Hi Ed or anyone who might know. Did you get this problem fixed?
I'm having the same problem. It seems significant that I can turn the truck off for 10-20 seconds and the problem goes away, then it comes back again in a few minutes. It seems like heat might be triggering the problem except that I wouldn't expect that the heat dissipates so quickly.

Putting the truck in neutral doesn't fix anything, but putting the truck in neutral and turning the ignition off while I coast on the road, seems to fix it temporarily. This, of course, is dangerous since the truck has power steering and power brakes.

Mostly what I do is pull over, turn the truck off and wait a few minutes. The longer I wait, the longer the "fix" works.

The truck runs great for the first 30-40 miles then it progressively gets worse. Used to run about 100 miles before having this problem. It all started about 6 months ago. Before that it ran great, even took it on a 3000 mile trip 2 years ago.

Hi does anyone know if this problem was fixed??
 

I have a 1996 6.5 t.d with the exact same problem! I actually parked it 6 months ago after putting a new lift pump in it and injection pump! It didn't fix my problem and I was tapped out and frustrated! History of truck. I bought it cheap with what I thought was a blown headgasket.......... yup cracked head, replaced both sides and while I was there did the glow plugs and injectors, push rods etc. Truck ran like a top. Then one night I was backed down on the boat ramp and I heard my truck stumble and watched her blow black smoke. Jumped in and barely made it up the ramp, good thing the tide was very high or I wouldn't of! Truck seemed to straighten out and I forgot about it then one day shortly after I was on the highway and she lost power hesitated and I pulled over and she was running real rough so I turned it off. Started it back up and it seemed fine for 5 minutes s then same thing. Went to my shop thinking it was electrical at first so I bought a crankshaft sensor from AutoZone only place open and put it in and it didn't start so I put the old one back in and it started took it for a ride and same thing happened. Lift pump was working but I put a new one in anyways and put my brand new back up and in and same problem still. Changed fuel filter put a number 5 resister in and took the 9 out no different so I figured gotta be the injection pump....... new one and still same problem so instead of driving it off a cliff I parked it and bought a gmc 5.7!!! So the truck is sitting. I have a tech one machine but the truck will not throw a code! I have been thinking it's a clogged fuel sock and soon was planning on dropping the tank but came across this thread and man I am praying someone knows the cause and fix because I'm desperate! Very mechanically inclined but diesels not so much but after this truck I feel like I'm becoming some what k owlegable about the 6.5!!! HELP

Welcome to DB you might want to start a new thread this one is a few years old, first thing you want to do is remove that CPS and dig a hole in the ground about 6 ft deep and bury it in the hopes it's never seen again lol seriously only use AC/ Delco parts for these trucks a few more dollars will save you tons of headaches and heart aches down the road.