Where to start?
 

Ok, so hello and thanks for the warm welcome.

Now that I'm relaxing after a 500 mile drive home today I figure I'll toss it all out there and see what you all think.

Ok, so I bought my 94 6.5 turbo 3500 off of EBay and flew down to Charlotte NC from Ohio to pick it up last Sunday. In the listing it was described as "having 12K in new parts" the Transmission, the heads, the radiator, batteries, bearings, rotors and all, and much more.

I landed 6 hours late after missing my connecting flight out of NJ and didn't get down there until 8:30 at night in the driving rain rather than the 3:30 in the afternoon I was supposed to (when a guy can see). The guy agreed to drive the truck to me from Hickory, about an hour out side of Charlotte, and he got the right after I did. That was nice of him hu?......

Well, i took a light out there and looked it over as best as I could, and drove it around the block a few times. It "felt" ok to me, but what the hell do I know? (Noob)

Anyway..... I took it. and off he went with his wife who had followed him down.

The next morning, I took off in it around town, and it smelled of coolant and the check engine light was now on....... AND the low coolant light was on....... AND it starting shutting down on me while driving. So now what right?

Well, I manage to get back to my brothers house with out running above 180 or so on the temp. I start looking, and find that a freeze plug had a pin hole in it (from cavitation I guess from poor maintenance) I find the temp sensor broken and not getting a good connection. So I get a ride to a parts store and get the plug and sensor, and somehow managed to get them changed, and I flushed the creek water out and filled with new. So thats good now, but was a pain.

I go for a ride and all is good..... until it shuts down again. It does this several times and restarted easy after a few minutes. I learned that this was the PDM... (is that right) anyway, it already has a remote unit mounted to the intake... (too hot still). I dont have the cash to fix it the right way at this point down there after forking ALL my money out to get there and get the truck in the first place. But I did manage to find a place that tossed me 3 used ones that they had replaced already from other trucks. He said they was all working when removed, but they changed them anytime they had fuel delivery issues, so I swapped one of them out under the hood and it worked fine for a while and then it shuts off again. I swapped another out on the side of the road and it fired right up and away I go. (for a couple miles).... GRRRR!

So I get one the phone and start yelling and managed to get a refund of my deposit, but that was it.

Now I changed the pump thing under the driver seat on the frame on the fuel line with the wires coming out... (the sending unit or LP??? I think it was called) And she fired right up and ran like a champ.... I drove around and across town for about 2 hours, and then the check engine light came back on and it dropped power and started cutting out at over half throttle, but still run and never shut down again.

I was out of cash for parts now, and just had enough to get me home 500 miles, and I was convinced that it would get me here if I baby it. And I'll be darned if it didn't get me here. It was noisy under the hood and all, but I assume that after doing some reading already in here that that was just the IP making all the noise? I couldn't give it more than half throttle or it would cut out bad and fall on its face, but NEVER shut down in 500 miles. (I know some of you are giving me that :td: WTF :td: face right now, but I HAD to get home) :ouch:

So now I'm home and can do something with it.

I go to show the wife the truck and she wants to go for a ride. I warn her about it not being right and all.... but when I hit that key.... she fired up all pretty and ran smooth like new. I take off down our street and romp on it and it was fine, I turned around in a parking lot and "accidentally roasted the tires"..... Dumb @ss.... The light came back on and it got all loud again and cut out at mid throttle. It didn't shut down.

Ok... If your tired of reading, now would be a good time to laugh at me and then maybe shoot me some advice, other than getting the PDM updated to the new gray one and getting it out of the engine compartment. (I'm on that like a fly on poop) But what all the cutting out and light on? I wont run it again until I get what I need for it.

:s::s::s::s:

First all get the code that be big help

Most of the time bad PMD will not set code or light off

check the OPS if it bad it will shut down the LP

check fuel filter

here some good info read and 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. For more information on this see this thread on electricity and how it can affect your voltage readings with loads and no-load situations.

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.

Thanks guys I appreciate it much. Like i said though, I already replaced the PDM and the LP down in Charlotte. so it looks more like Crazy"s idea of voltage to the LP.
When I changed it.... I bled the air out and it flowed nicely from that bleed valve. But now mentioning that, it reminds me that I read something in my manual about the writing on the filter cap has to be facing a certain way?.... well mine has no writing on it, must be worn or cleaned off.

I will test voltage to LP tomorrow. but I do have tons of codes for you that I have looked up already and found that it all a bunch of sensors. And I also found my left battery had loose cables, and i tightened then at some point, so some codes could be from that maybe?

Here are all the codes, and keep in mind that I dont have a reader or whatever yet.... I did the paper clip and count trick and then Googled them.

17- Camshaft pos. sens.
18- pump cam
35- IAC problem or idle error
36- MAF sens. error
24- Crankshaft pos. sens. circuit error "OR" 4T60-E shifting error
54- Fuel pump cir. low voltage "OR" Digital EGR valve solenoid
78- Wastegate solenoid fault
92- Cyl. Bal. fault
97- Cyl. Bal. fault

PLEASE tell me some of those are flukes..... :humm:

thinking with all them codes may be grounds


check all the grounds they play important part to a 6.5 you have some grounds at back right motor and strap from back right to the frame both battery and one from the pass side battery to the fender check and clean all

Ok. Thanks.

I kinda thought that too. But can you tell me how to clear codes so I can read fresh ones since Ive done stuff already?

just disconnect both battery's for 10 mins

good luck. Crazy basically covered everything

thanks Woody35

Thanks Guys!
 

Hey Diesel Dudes,

Thanks for all the help on this thing already.

Its weird. I ended up getting up with Bill Heath and he walked me through a couple tests.

I opened the "t" valve 5 full turns and ran the truck at idle for 2 minutes and gut close to a full gallon of clean fuel. I guess that tells me that the Lift Pump I replaced is working good.

I ran the truck and slowly throttled up to 2000 rpm and slowly back to idle several times and it was smooth with now erratic RPMs, Don't know what that test told me.... but I did it.

Thinking along the lines of a bad connection and or ground somewhere, I traced them all down and checked and moved a couple to where they are supposed to be, rather than where the hack that worked on it had them.

I freaked out when I saw the down tube smashed to hell until I found that the goof balls at GM was responsible, so thats now on the list for one thats not squished half shut.

Anyway, I felt like changing the fuel pump relay for the 12 bucks it cost, and guess what?.... It ran beautiful...... for about 15 miles, and then the light came back on, and It started cackling all loud and I lost power AGAIN! Grrr! :s:

This HAS to be electrical that way it acts.

I'm no good with a meter and I dont even have one, so what now? If the IP is pooping out will it do it like that and come and go like it is? :humm:

the 2000 rpm test tells you if you have a good pump. its not a definite yes or no test but it sure helps because if it couldnt of done it then it would of probably been the pump failing but since it passed most likely not. if you plan on keeping this truck i would get a brand new pmd and mount it behind the bumper so it can be ruled out of the equation. did you clean the grounds? also after cleaning i would clear codes again and see what comes back.

Yes, it already has a bumper PMD and I replaced the unit as well.
It also has a back up one mounted there too just in case.

Grounds are all good now as far as I found so far.

Just keeps coming and going with the low power and light. I replaced the pump relay today as well.

ix-2 what woody35 said

Fuel filter only goes in on way just look at bottom of the cap and u see what talking about

Hu? where did that come in?
what the importance of the print on top of the filter housing and why does it need to be facing a certain way?
My print is gone :bat:

some filter don't gave you that info

ahh, ok.
I was looking at the manual and it had a picture and explanation that the wording on top of that housing had to be pointing a certain way or what not. So had to ask.

Your a mechanic I assume since you have allot of knowledge in the field.
I went through a diesel coarse years back but only work in a garage for a couple years. I got into some of the internals at times, but did allot of brakes and bearings and tires and PMs. But the trucks and parts was much bigger than this things parts, and was in different places I could get too, lol.... but it wont take long to figured it out. Its gonna be fun for sure.

I'm looking into a full air bag system, front and back..... and ideas for tank mounting and stuff?

Thanks for everything so far Crazy!

You say the light keeps coming and going did you recheck the codes to see if there all the same ?

Still cutting out
 

Ive had a chance to do some more tinkering and what I did was this:

I changed the fuel pump relay.
I found that the vacuum line to the waist gate was rigged and was leaking, so I fixed that.
The grounds are all good now.
The boost gauge vacuum line was cracked so i fixed that.

It started and ran fine, but after a while the light came back on, and I lost power again.
I shut it off for a while and then it restarted fine and ran fine again for a bit, and then pooped again.
Just a bit ago I ran up to Auto Zone (and got pulled for the tinted windows lol) and it was running rough on the way up, but after restarting at Auto Zone, it ran fine all the way home again, till just before my driveway and then back to poop.

I bet it runs fine in the morning again.

So if there are any ideas other that the LP just going bad.... (because I really hope its not) shoot them at me.

How about the little black rubber thing under the intake that is plugged into the top the the LP in the center of that short harness? It must be like a resistor or something. (I hope you know what I mean)

I did see that the wastegate vacuum thing is working (it moves when I unplug the vacuum and I can hear it dump when I let off)

Still Spit Choke and Puke when the light is on and I'm giving it more than half throttle.
But when that light is off..... WEEEEEeeeeeeee!! :tu:

what the code when light come back on

I just fix my buddy truck today that was doing thing we found it was bad OPS

Bad OPS will shut off the LP

Thinking the black rubber you are talking about is OS filter harness take it off plug wire back in see how it runs

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try this next time it running rough open the t-valve see if there good flow fuel and next thing you can try is put 12v to LP and see how it runs

The other day when I did the T valve test it was with it running rough and it pumped near a full gallon.

Ill try the other things in the morning.

And what is the "OPS"? and where is it?

Oil Pressure Switch (OPS)

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Ok i just went back reading so of your post other thing to when you unplug OS filter harness see if it stay running and if it don't you most likey have bad CPS (Crankshaft Position Sensor)

Ok, so Im just gonna replace the OPS since its only 22 bucks, now where is that sucker located, cause I be darned if I see it lol.

k on 94 should be on the back of the driver side head n the inside and going need 1 1/6 deep socket

Ok, I also see I deed to remove the fuel filter to get to it, so is fuel gonna spill out?

just undo the two bolts and move it to the side

I also just sent you pm

Going out now, Thanks Man.... I got your PM as well.
Yer a hell of a guy Crazy.

should have told if you get ops to get ac delco ant other will not last long

Ok.... I give up. I'll call you tonight after 7. It wasnt the OPS.... and "someone" failed to mention that I had to REMOVE the intake to even get the socket on that sucker. :w2:

Anywho..... lol...... Its changed, and while under there I noticed that the CPS harness was brand new as well, so thats been looked at so the only other thing is that dang IP I guess.

on 94 it should have been on the head it self not in valley maybe newer motor

Hey guys, what I did this morning was got rid of the harness filter on top of the IP, and I hot wired my LP. It drove with the same loss of power for a 20 minute ride. I shut it off for about 10 minutes and when I restarted it, it ran fine. I have shut it off a couple time so far and it starts and runs as fine as it probably can. I am getting a little blow back through the oil filler tube when cap is off. But I think if it stays running like it is now, I'll take care of the engine in the spring.

So what could cause the LP to not work other than what Ive done so far?
It runs fine now with LP hot wired and NO engine lights are on. But I just used an alligator clip to the battery for the hot wire, so I either have to find whats causing the LP to shut off, or I need to better hot wire it to a switch in the cab with a light on it so I will remember to shut it off when not running.

try it this way

try this if you want to
 

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.

Ok, so only thing I dont see, is what kind of relay you used there.

By the way.... after I talked to you on the phone today.... and after I changed the filter, it went back to safe mode and hasnt come off yet. :argh:

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