Please Help Running issues!
 

Hey peeps,

I am hoping that someone here can give me some assistance with my issue..

My truck is a 1994 GMC K2500 6.5L diesel VIN F 4x4
Truck has about 192K miles on it. About 6 months ago I swapped out the motor as the stock one blew up from lack of oil.. I installed a 1996 Chevy 6.5 with 201K in it. I swapped out the injector pump from my motor,the intake, the drivers side head and some other stuff.

When I first ran the motor is had somewhat of a skip to it, but was only noticeable if you revved it up in neutral.

A few months later I was pulling my bobcat up-hill in a snow storm and the thing started to pop and skip bad. Since then no matter what I have tried I cannot get the skip and lack of power to go away. :argh:

Truck seems to act up more when its under a load: like plowing or climbing a hill even if its empty. I don't notice the issue much on short local trips. It really gives me trouble during snow storms when I have her running for 12+ hours at a time.

Here is what I have done: Since issue started
8 new Injectors (Bosch)
AC delco lift pump
Fuel Filter (napa)
Crankcase Depression Breather (napa)
AC Delco crank Pos. sensor

Since I bought truck 1 year ago:
Remote mounted PMD (behind front bumper w/ heat sink) Grounded straight to battery
2 New batteries
Starter
Alternator
Airtex sending unit (in tank) Have AC Delco one that i plan to swap out..
8 AC delco Glow Plugs
a/c compressor
thermostat & Coolant
air filter
oil and filter changes
Oil pressure switch
coolant temp sensor
drivers Head gasket
Serp Belt
Diamond eye 4 inch turbo back exhaust (no muffler)


I am sure there are tons more things I can't think of off the top of my head right now lol

Any idea?

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also wanted to add:

When the truck starts to really act up, it runs so bad that it wont really stay running! I pops and skips and puffs tons of white smoke. when you rev it in neutral you get black smoke which i think is kinda normal.

Couple of things that I notice were not mentioned.

Did you buy a new PMD when you remote mounted it? Or the same one?
Have you checked for proper operation of the turbo and vacuum system?
Have you checked for computer codes?
When you replaced motor, did you perform the TDCO relearn?

Yes the PMD was new when i relocated it.
Yes the turbo and vacuum are working fine.
There are no codes in the computer.
what is a TDCO relearn??

Top Dead Center Offset. When the IP physical timing is reset, the TDCO relearn tells the computer the new timing offset, so that the computer adjusts correctly. Racer or someone more knowledgeable about the electronic IP can tell you more and use the correct terminology.

Search the forum for "TDCO" and you should find plenty of threads on how to do it.

Have you done a compression test?

No i just bought a compression tester for it today. I am not sure why it would have no compression.. it runs fairly good for awhile and then it kinda falls on its face...

That being the case, I would look at your fuel system very closely.

Run about 3/4 gallon out the T drain, Note the flow and look for crud.

Have you redone the fuel lines under the intake?

The sending unit could present an issue, I've heard the screen on the suction tube is not as good as the AC Delco's and blocks up easier.

I'm assuming you cleaned the tank when you changed the sending unit.

I'm also assuming you cleaned the bowl when you changed the fuel filter.

When changing the filter, I fill the bowl about 1/2 full of Sea Foam. Hot wire the lift pump, bleed the filter. Turn the key to run for about 15 minutes or so with the lift pump hot wired.
Turning the key to run should open the Fuel shut off solenoid and allow some of the Sea Foam to get in the Injection Pump.

Check all battery connections and cables. Check and clean all grounds, Add additional grounds, try a known to be good PMD. Even on a heat sink, PMD's can have a terribly short life span. They have even been known to be bad out of the box.

I also do the allen screw battery bolt upgrade. I use a 1 1/2" or 1 1/4" stainless allen screw in place of the battery cable bolts then washers and a nut.

The brass seals for your from brake lines work well - or any similar sized washer- I prefer brass, copper or stainless washers. I always save them and end up using them. I coat everything with Kopper-Kote - all connections to prevent corrosion in the future.

I remove the passenger side battery and add a ground to the battery box bolt, to the frame ground by the starter, to the PMD heat sink and to the stud at the back of the engine - by the firewall that has the really important grounds attached to it - I have seen these studs lose ground or have intermittent ground - many times.

I also add a ground from the heater blower to the dash bracket just inches away. Make sure the ground to the top of the Injection pump is there. I also run a ground wire from there to the ground cable from the battery close by. I use at least 10 ga black stranded wire for all the additional grounds with the exception of the ground on top of the IP. That I generally use 12 ga.

I like to solder my electrical connections.

If you redo the battery cables, do not use the cheesey clamp on battery cable ends. Get the solder on/crimp on style. I crimp them and then fill them with solder. I have recently had trouble finding this style of side post connector and ended up using heavy duty 3/8' eyelets instead. I need to find more of the appropriate connectors and order them.

On a 1994, you will want to do the dual lift pump relay upgrade. You can google for a schematic by Buddy. You can check my threads on dieselplace.com and the truckstop for when I did mine on my 1994.

Use an AC Delco lift pump for a 1993 - they have slightly higher flow - if replacing with an OEM style lift pump.

I'd do the ground and dual lift pump relay upgrades first.

What brand of PMD did you use? Every brand is hit and miss. I've had 3 short lived gray Standynes while others have had good longevity - so far from them.

I've heard bad reports on the Dorman made in China PMD's - angelofishes says that he has sold 140 plus of those with lifetime guarantees and no returns.

For now I am sticking with Flight Systems PMD's only.

TDCO relearn can only be done with 1 of 3 scan tools on 94/95 trucks.
Tech 1,TechII with OBD1 expansion module or GMTD ScanTech pro version.

AC Delco ONLY for OPS.parts store OPS are often bad straight out of the box.
OPS relay mod mandatory for long term reliability.

I would also with the engine running,carfully crack each injector loose and then tighten 1 at a time and note what if any difference ther is in how the engine runs-don't get hurt or caught in moving parts!

A dead or weak cylinder could mean a bad injector or low compression and could help narrow down an issue with an affected cylinder.

So will the computer programs you can buy for a laptop not work for the relearn?

I have replaced the sensors with AC Delco that have gone bad. I will not use NON-AC Delco stuff at all in the future.

Yes my buddy that is a tech for the US Army recommended the cracking of lines with the truck running but that is easier said than done as you cannot get to the pass side lines with the upper intake and turbo stuff connected. :( I will have to do the compression check when i get a bit of time.


Truck is just sitting collecting snow at this point.

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The Previous owner had replaced all the fuel line after the frame mounted pump to the filter housing with rubber house. What do you think of that? Do you know if there are replacement steel lines available anywhere? Far as I know there are no leaks anywhere as I have checked a few times.
I am not sure if I changed the lines under the intake, I pretty sure that I reused the lines when I swapped the motor. Should I change them?
Yea the sending unit is only about a year old, I plan to swap that AC Delco unit is as soon as I have time. Been snowing like crazy here haven’t had much time to mess with the truck. I did not clean the tank as it’s fairly new. I did look inside was nothing noticeable so I just installed new unit.
Yes when I change the filter I drain and wipe out the bowl and then I also fill it up with sea foam. I have a switch under the dash that I wired in to jump out the lift pump just in case.
The battery connections and grounds are deff good as I have an OCD with dirty battery connections. I have brass adapter on the batteries that are used to add accessories in the aftermarket world. I have tons of them from FISHER as they come with all new snow plows.
The PMD is a stanadyne brand. I was thinking that it may be part of my issue but they are $3-400 bucks and that’s a bit steep to just fire up the parts cannon in my book…. What brand do you recommend? The PMD is grounded direct to the battery. I did add a few in rear of motor but I will add more this weekend!
Hmmm I know that the ground on the top of the injector pump is off ill have to to take care of that!
I have never heard of the dual lift pump relay… I will have to do some research on that and figure out how to do it…
I was thinking of removing the lift pump yet again and installing this one:
Fuel Delivery
What do you think?


Thanks again for your input! I am ready to pull my hair out this truck is kicking my a$$!!
:argh:

For a 94 GMTD ScanTech Pro version is a great laptop program and is the ONLY laptop program that can do TDCO relearn-it is money well spent for the license and cable if you intend to keep the truck for a good while yet,it is OBD1 ONLY though,great for your truck but little else.

PMD's have become much mor reasonable as of late,about $130 with lifetime warranty from Amazon,they also have heatsinks,extension harnesses and resistors available.

The brand is dorman but since they are all poor brand does not seem to matter anymore-warranty does.

Nothing wrong with rubber fuel line after the LP if it is not reacting with any chemicals in the diesel.

Big thing with rubber fuel line is most people do not seem to know that you need to use bio-diesel rated hose or it can be like a PMD. Might last forever and it might last a week.

I like buying Made in the USA STUFF. i DO NOT LIKE BUYING mADE IN cHINA STUFF.
So I do not like Dorman stuff.

But I am curious to see how their lifetime guaranteed PMD's hold up. Angelofishes also has the Dormans, He says he has sold about 140 with no returns. Is that because they are performing well or because people are saying "I knew I should not have bought a Dorman. I'll just bite the bullet and buy a new Standyne or Flight Systems rather than try another.

From what I've read, I would stay away from the Dorman. They do not seem worth the lifetime warranty.
For now I will only use new Flight Systems PMD's from Leroydiesel.com

I know others that have excellent luck with the new gray Standynes. But I had 3 bad.

I would definitely get the heat sink that somebody sells that has the flange coming off the finned side. with a bolt hole on each end. Not the style Leroy sells.

The style I like will mount to the license plate bracket bolt without removing and changing the bolt. Just the nut. The connection also points towards the bumper nostril for easy connection removal

Well guys. I finally bought the GMTDScan program and got the cord in! I am going to hook it up to my truck this weekend and see what she tells me.....

I hope I get somewhere with this headache! My truck has been sitting for over a month now because I havent had time to mess with it. :(

I am still on the fence about buying the "dorman" PMD module... Not sure I want to go thru the hassle of swapping it over and over if its a piece of crap.

But I guess its best to run the scan, check all the sensors and check the TDCO before I go too much further.


Are any of you guy aware of a place out there to get pre-bent fuel lines for my truck by any chance?

There are some places that will custom make oem style lines. I can not think of any names right now. Dang ole alzheimer's or was it the scotch

update
 

Ok so I ran the scan tool... I had 0 codes present but there were a couple in the history. They were 78-wastegate solenoid fault & 92 Cylinder Balance Fault #2

Dont forget I just did all 8 Injectors in the truck a few weeks ago and it has not ran much since then.

I quickly scanned thru everything And I did not notice anything out of the ordinary.

I ran the TDCO. when the truck was cold it seem to be right on the money once it warmed up it was off by about +1 degree. Would this cause my issue? I have included some pics of what I found. I also noticed that when it was warm and running the actual timing was jumping all over the place.

I cant upload the pics they are too big i guess...:argh:

Matt the easiest way to bleed them passenger side injector lines is to remove the inner wheel well takes 5 minutes with a impact gun 10 to 15 mins without And you will have all the room in the world to do what ever you want on that side of the motor

The engine temp MUST be 170F+ to run TDCO relearn and there can be no codes.

Injectors will self bleed on a running engine-no need to worry about them once the truck starts.
Might have a bad new injector?

Desired timing and actual timing should be close-don't expect exact,it's a moving target the ECM is always chasing.

What do you mean exactly about timing being off +1 degree?
The TDCO value or the actual timing?

I redid the test and played with the pump a bit. I did have the truck at over 170... I have the desired and actual timing about 4.4 and the TDCO -1.94

Should I keep trying to get it down closer to the -1.50?

Will the #9 resistor I have in the make any difference with these setting?

Also i still seem to have a slight skip when I rev it up in neutral.

As for bad new injector... I am not sure. I have no codes, I ran the injector test. As I shut each one off truck ran like shit which would tell me that they are all working... no??

-1.94 is ideal TDCO value leave it alone.

ok I will not mess with it anymore.

So would a bad or failing PMD cause a skip?

I drove the truck home last night. Drove it for about an hour seem to run ok.. I started it up this morning, Started and ran fine. I drove it for about 30 minutes then I decided to run her thru the automatic car wash here in town. When I pulled back out onto the main road it skipped a few times and then stalled. I pull over. cycled the key a few times and she started back up. It hasnt really stalled like that in quite awhile.

I am just at such a loss with this truck... UGH!! :argh:

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Hey Racer,

Do you know anything about the Duramax 21" engine fan swap?? If I upgrade to the 2000 Model year water pump and fan clutch with the 21" fan fit inside the stock fan shroud on my truck?

Some shroud's need a bit of trimming to clear that fan-others don't,its the luck of the draw.

PMD's cause a lot of strange running when they start to go bad,a skip or fish biting as it is called is often from a bad OS electronic noise filter or air in the fuel confusing the OS.

OS= Optical Sensor?

have you found a good way to check for air in fuel? I drained a bunch of fuel into a bottle the other day when I was setting the TDCO. It looks clean as a whistle with no water in it at all.

I still have to go in and pull the air-tex sending unit out of the fuel tank. I have brand new delco one on the self. I was waiting for the guy from leroy's diesel to come back so I can remove the sock and Install the remote WIX filter at the same time.

BTW thanks a million for all your help man!!!!!! I feel like I am slowly getting somewhere. Its like impossible to find anyone that knows anything about these motors locally. So I have been firing the parts cannon at this truck for a bit now.

Easiest way to identify air in the fuel is to replace the IP fuel return line with clear diesel rated line and with the truck safely parked and idling-watch that line for bubbles.
Bubbles indicate air entry pre LP.

So anywhere between the fuel level in the tank and the LP input are the possible leak areas.

A hole after the LP will result in fuel coming out,not air going in unless the engine is shut off.

So clear line from the IP back to the small steel rail just behind the T stat housing?

Ya the frt line on the IP that connects to the T line where the injector returns connect to.

So I got a chance to take my truck for a good ride tonight. I took my laptop with me and left it plugged in.

I noticed 2 times I gave her full throttle on some back roads, soon as I took my foot out of it she stalled. Few key cycles and she started back up.

Next I took her for a quick ride on the interstate...I got up to about 55-60mph nice and easy, then I hammered it and she starts to bog, pop, & skip! Even tho she was doing all that it continued to pick up speed. Around 70mph the check engine light popped on and I got a code 78- Wastegate Control Solenoid. When I took my foot out the CEL went right out.

So I went in to the wastegate control section and I set the desired duty cycle to 100. Once I did that I got back all over the throttle and she ran good. I then got of interstate and came to a complete stop then did a full throttle pull and she ran right up good with no issues. I noticed at idle the wastegate duty cycle is always around 60ish then when i hammer it drops to the low 50's. With it set to 100 it never dropped below 60. ANY IDEA IF THIS IS NORMAL?

other thing I noticed was that if I look at "fuel rate-throttle requested" and "fuel rate" the FUELRATE is almost always 8-10 lowered than requested when I am in the throttle. Even if I power brake her this is the case...

Any thoughts on all this jibberiesh? haha

I owe you bigtime for all this help! :s:

Boost is load dependent when the ECM controls it.

Meaning you only get good boost when you really need it-hard acceleration and when towing heavy.

Might want to spray some WD40 in the boost solenoid vac ports to lube the bleed ball-they can stick without a bit of lube every now and then.

Boost solenoids also fail and have wiring problems as well.

Check the vac readings at the pump side of the solenoid and at the wastegate actuator at idle.
Min from pup is 24"
min at actuator is 18"

any less means you need to find the leaks or weak point.

If you want to take control of boost away from the computer for improved performance buy and install a turbo master from Heath Diesel-an aftermarket ECM tune would help with that a lot also.

The #'s you give don't mean a whole lot to me unless I was in the truck with you.

Ya I found a trouble tree in ALLDATA to diag DTC-78. Tomorrow night I will run thru those steps and see what I come up with.

I was thinking about going to one of those waste gate systems but I like to get the bugs worked out before I go nuts with upgrades. You said ECM upgrade... You talking installing a CHIP?

Yes if you should decide to go with a turbomaster then you could also order a custom chip at the same time from the same place-they work hand in hand but you don't have to.

So I am at my shop now. I just started checking out my waste gate issue. I have no vacuum at all at the waste gate. I pulled the lines of the control on the valve cover and I have less than 1" of vacuum coming directly from the pump.

I guess I need a pump lol


Can I use any replacement pump from NAPA, or should I get a delco pump?

The delco pumps last longer.

Most reports of aftermarket vac pumps have them lasting a year or less.

Might get by with a used pump from a wrecking yard for a while if it's not already bad too?

So I found a AC Delco pump brand new on Amazon for $121.00 !!!!

It just showed up today and I also decided to try out a DORMAN PMD module. I will let you know how it works out!

be sure the FSD/PMD is mounted on a heatsink with heat transfer medium between them and a PMD resistor is installed.

Yes I have the PMD on a heat sink,. It is mounted between the holes in the front bumper.

I put that DORMAN one in the other day. seemed to run good drove it home from my shop. Only a few miles.

Next morning I went out started the truck let her warm up and then started to my shop. In a few mile ride she stalled 3 times! I dont think this cheap PMD was worth my time...

Today a had some time so i went ahead and installed the "feed the beast" kit on my truck. While i was in there I also installed 3 gauges on the pillar (fuel pressure, boost, Exhaust temp)
While is was doing the 3/8 fuel line I made a T so that I could screw in the sender for the fuel pressure gauge. The T is between the fuel filter and the IP.

Once I got her all back together and running I noticed that I have only 5psi at idle. I revved her up and held it at about 1700 RPM and the fuel pressure dropped to about 0-1PSI. The fuel pump is a ACDELCO pump and its only about 2 months old with less than 100 miles on it, as my truck has been sitting. What do you think??

:argh:

About normal fuel pressure-t Delco LP to get for replacement is from a 93 model that has higher pressure.
AC Delco #EP158
GM #25115224

Make sure that you don't have air in the fuel before you condemn the PMD.

Also did you use heat transfer paste/pad between the PMD and heatsink,did you install a PMD resistor in the new PMD?

So dropping to little to no fuel pressure at 1700RPM is correct? I am thinking about buying a new pump from leroy diesel....

I am about 90% sure there is no air in the system but i will get a clear hose and check it out. This is unlikely as it was stalling before i even thought about installing "the Feed the beast"

Yes i installed that small rubber pad that came with the new PMD and yes I have a #9 resistor in the module, I have always ran one

0 psi fuel pressure at wide open throttle is correct with a stock LP.

Loosing fuel pressure too quickly would make me think about the tank sock getting plugged,a plugged vent in the filler cap or air getting the lines.

Wow WTF huh? I guess I should really upgrade the stupid LP! I am going to order the pump from Leroy diesel today!

I am unsure of the sock... I have a brand new AC Delco sending unit. I am going to try to get it in this weekend. I just need some time to pull the bed off. lol Actually I think ill oder the remote filter assembly from leroy too that way I can just do away with that stupid sock!!

So can I use any clear fuel line? its 1/4" line correct??

The fuel line must be diesel rated-some lines don't play well with diesel.

Take an old piece with you for sizing.

Ok so I went to napa and got a piece of Tygon line and installed the between the injector pump and the steel fuel rail that runs left to right on the front of the motor.

As far as I can see I do not have any air in the system!

No bubbles in that line when the engine is idling?

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Is the IP/PMD harness ground fastened to an OS screw on top of the IP-It must be there.

Also I noticed you got new injectors-were they ever tested for pop pressure or were they marked for turbo use or naturally aspirated?

Lastly have you tried running with the fuel cap loose?
A plugged fuel cap vent can cause running out of fuel type issues when the truck runs for extended periods-or a gasser cap does the same thing.