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Discussion Starter #1
Not sure where to start here but I'll provide as much info as I can.
I have a 94 GMC 3500hd cab & chassis 2wd dump truck. DS4, 112xxx currently, purchased with ~107k. Around Jan 14 2021 I went to start it & it didnt start. Cranks, no start, no codes. I had driven the vehicle week of Thanksgiving 2020, it had sat outside in Ohio weather since. Upon realizing it wasnt going to start I moved it in to the shop, ~65°F. Since moving it inside I've topped it off with fresh fuel & additive, replaced all 8 GPs, new PMD (amazon) & relocated to bumper, 8 new reman injectors from diesel care (100k maintenance), LP relay rewired to function with key, still no luck. Assuming good mechanical condition considering it ran & was driven last time it was used with no (major?) issues. (Its always had a bit of a sputter since I purchased it, just chalked it up to being an older truck). Continuing diagnostics I went over the checklist provided by accuratediesel.com and got to the end, assuming it to be IP. Ordered & replaced IP from Pensacola diesel. No fuel in the Valley. Installed clear return hose & supply hose to IP, looks as good as I expect it to for a truck that wont run? Small air bubble at top of bend, mostly fuel otherwise. Fuel at T valve & filter bleeder. Fuel squirt at injectors with line removed. Fuel & air Filters were replaced when I bought the truck, approx 5k ago.Working GPM & power to GPs. Light smoke while cranking but still no start. New gold batteries (pair) & alternator from autozone approx dec of 2019. Oil looks good & is in range. New crank sensor because it's cheap & the thing wouldn't start. PMD checked out good, as did every other electrical thing I checked. Now it's throwing a code 17 & 18 but not a 12, optical sense I believe. Slow cranking starter? ECM? Compression? Im mentally exhausted with it, any help or advice would be much appreciated. I'm sure theres other details I'm missing but ask & I will inform as best I can
 

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Wow that's a lot of parts and new variables into the mix. I'm thinking I would try cranking it without the glow plugs installed. You should see fuel mist coming out the glow holes. This will confirm you actually have fuel coming out the injectors. Try to verify it in as many holes as possible. If you do see fuel then that leaves you with non working glows or a basic mechanical issue.

Speaking of fuel are you sure you are trying to run on good clean diesel fuel? Would not be the first time someone spent a lot of time trying to get an engine run on something that wasn't good pure fuel.
 

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Welcome to DieselPlace
Going back through your parts install list...
When you replaced the PMD did you make sure the PMD has a resistor installed onto the pins? The resistor is important for proper PMD function.
Did you also purchase the PMD relocation kit from Amazon? If so, try disconnecting the PMD from the relocation harness and plug it into the OEM harness on the IP to rule out a faulty relocation harness.

Regarding the Injectors, If you Google diesel care you will find a bunch of bad reviews from them regarding parts...
Regarding the IP, did you verify TDCO after install? The DS4 IP timing must be verified.with the proper timing software ( Snap-on scanners do not give the correct timing value in a 6.5L).
When you replaced the crank sensor did you install an AC/Delco brand sensor? If, not, aftermarket brands will bring electrical gremlins into your issue. Replace it.

I would go back through all grounds. Apply a jumper to the lift pump to help prime things. When you remove the IP you introduced a ton of air into the fuel system and that all has to be purged out and will take some time.

You can find links on timing and grounds, plus more in the 6.5L FAQ page: Info: - The 6.5L FAQ's... The Master List of...
 
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Discussion Starter #4
Wow that's a lot of parts and new variables into the mix. I'm thinking I would try cranking it without the glow plugs installed. You should see fuel mist coming out the glow holes. This will confirm you actually have fuel coming out the injectors. Try to verify it in as many holes as possible. If you do see fuel then that leaves you with non working glows or a basic mechanical issue.

Speaking of fuel are you sure you are trying to run on good clean diesel fuel? Would not be the first time someone spent a lot of time trying to get an engine run on something that wasn't good pure fuel.
I'm assuming it's good fuel as I have always gotten my fuel at the local truck stop & try not to run it below ½ tank
 

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Welcome to DieselPlace
Going back through your parts install list...
When you replaced the PMD did you make sure the PMD has a resistor installed onto the pins? The resistor is important for proper PMD function.
Did you also purchase the PMD relocation kit from Amazon? If so, try disconnecting the PMD from the relocation harness and plug it into the OEM harness on the IP to rule out a faulty relocation harness.

Regarding the Injectors, If you Google diesel care you will find a bunch of bad reviews from them regarding parts...
Regarding the IP, did you verify TDCO after install? The DS4 IP timing must be verified.with the proper timing software ( Snap-on scanners do not give the correct timing value in a 6.5L).
When you replaced the crank sensor did you install an AC/Delco brand sensor? If, not, aftermarket brands will bring electrical gremlins into your issue. Replace it.

I would go back through all grounds. Apply a jumper to the lift pump to help prime things. When you remove the IP you introduced a ton of air into the fuel system and that all has to be purged out and will take some time.

You can find links on timing and grounds, plus more in the 6.5L FAQ page: Info: - The 6.5L FAQ's... The Master List of...
Not sure what you mean by resistor on the pins but I will check.
I have tried with the PMD plugged directly into IP, tried old PMD at both locations as well. When running diagnostics, I was using new PMD & extension harness.
As far as diesel care & the injectors go, they're in there now & I'm not quite ready to point that finger just yet as truck wouldn't start before they were installed.
Not sure what TDCO is, TDC I'm familiar with & no didnt verify as I dont have an obd1 scan tool & didnt move the engine timing. I have a friend that is a gm tech, I will ask him
Used an autozone crank sensor, still have the factory one i took out that I can put back in.
LP comes on with key as I used it to purge & bleed after replacement.
I will recheck & clean grounds
 

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Not sure what you mean by resistor on the pins but I will check.
I have tried with the PMD plugged directly into IP, tried old PMD at both locations as well. When running diagnostics, I was using new PMD & extension harness.
As far as diesel care & the injectors go, they're in there now & I'm not quite ready to point that finger just yet as truck wouldn't start before they were installed.
Not sure what TDCO is, TDC I'm familiar with & no didnt verify as I dont have an obd1 scan tool & didnt move the engine timing. I have a friend that is a gm tech, I will ask him
Used an autozone crank sensor, still have the factory one i took out that I can put back in.
LP comes on with key as I used it to purge & bleed after replacement.
I will recheck & clean grounds
Info on the resistor: 6.5 No Fuel at Injectors
If there is no resistor installed on the pins of the PMD you will more than likely get a no start condition..
The AC/Delco Crank Position Sensor is important too. Aftermarket parts will cause electrical gremlins on top of your other issues, making diagnostics kind of difficult.
 

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I was in a similar situation in 94y Suburban last year.

Without knowing the cause, I replaced the parts one by one and finally replaced it with the AC DELCO crank positioning sensor, and the engine started up successfully.

In my experience, if the crank positioning sensor becomes NG while the engine is running, it will continue to operate in the limp mode, but once the engine is stopped, it will not be able to start.
 

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The 2 part sources that caught my eyes not having reputable parts:
1. Diesel Care (injectors)
2. Pensacola Diesel (IP) <- this is probably more problematic.

Try putting the old IP back and you are probably ok.
I suspect on a 94, the OPS and/or LP are bad. OPS controls the LP when engine is running.
This is always an issue on 93-95 at that mileage.

Anything that say Sensor or Sender (CPS, OPS, etc). needs to be ACDelco.
 
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I just fixed a no start and previous sluggish start, hit/miss idle throttle response by bypassing the PMD extension harness I got from Amazon. It's cheap trash (brand was APDTY). Try connecting PMD without the extension. Try both PMD you have in case the new one is a dud. I was suggested this by OkDually
 

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Codes 17 and 18 are many times associated with PMD problems. No or bad resistor, Cheapo wiring harness extension,
Even the trucks stock harness and connection for the PMD could be bad. It is exposed to a lot of heat in its location in the valley. Is the ground wire for the PMD still attached to the IP.? It should be.
When you turn the ign switch to ON. Does the CEL light up?
 
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Discussion Starter #11
The 2 part sources that caught my eyes not having reputable parts:
1. Diesel Care (injectors)
2. Pensacola Diesel (IP) <- this is probably more problematic.

Try putting the old IP back and you are probably ok.
I suspect on a 94, the OPS and/or LP are bad. OPS controls the LP when engine is running.
This is always an issue on 93-95 at that mileage.

Anything that say Sensor or Sender (CPS, OPS, etc). needs to be ACDelco.
LP is rewired, not controlled by OPS.
 

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Discussion Starter #12
Codes 17 and 18 are many times associated with PMD problems. No or bad resistor, Cheapo wiring harness extension,
Even the trucks stock harness and connection for the PMD could be bad. It is exposed to a lot of heat in its location in the valley. Is the ground wire for the PMD still attached to the IP.? It should be.
When you turn the ign switch to ON. Does the CEL light up?
Ground wire is good.
Yes CEL comes on.
Checked all the connections when I had it apart, all looked good
 

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OK. There is an electronic filter plugged inline with the optical sensor. They do go bad and cause rough running and a no start. You can remove the filter from the harness, and plug wires in directly to the OS and try starting.
Also for more trouble shooting. Try un plugging the OS totally and try to start. If it starts then the OS may be bad.
You can do the same with the CPS. Just dont unplug them both at the same time. If one or the other is unplugged or bad the PCM will run the engine in limp home mode. Doing these tests may help to narrow down the problem.
 
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i feel your pain. I would check the Amazon pmd...I personally bought two bad ones in a row and ended up buying a real Stanadyne grey unit. NAPA let me buy one and test it with return privilege for 48 hours without restocking fee. Good rule of thumb is that if under $100–its complete non-functional junk. The NAPA one worked fine and solved my problems. As others have mentioned the pmd plug should have a greenish tiny circuitboard with a resistor bridging two pins. You don't need a #9 to run...if it has any resistor installed its probably ok. The wiring harness is much the same..the IP puts out signals in microvolt range and requires a harness with a 50 ohm impedence. cheap cables just wont carry the signal..its low frequency..so good news is you can measure harness with a good ohmeter. If both are ok..then check timing of pump itself. The good news here is that a 94 is much easier to adjust than later models—-no dual thermostat set to get in the way. To the best of my knowledge—the only scan tool for OBDI 1 is gmtd scan tool. Its great a great product. There are lots of great threads on this site for procedure.
 

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OK. There is an electronic filter plugged inline with the optical sensor. They do go bad and cause rough running and a no start. You can remove the filter from the harness, and plug wires in directly to the OS and try starting.
Also for more trouble shooting. Try un plugging the OS totally and try to start. If it starts then the OS may be bad.
You can do the same with the CPS. Just dont unplug them both at the same time. If one or the other is unplugged or bad the PCM will run the engine in limp home mode. Doing these tests may help to narrow down the problem.
No limp home mode on a ‘94–that was in post 96 models to the best of my knowledge
 

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I just fixed a no start and previous sluggish start, hit/miss idle throttle response by bypassing the PMD extension harness I got from Amazon. It's cheap trash (brand was APDTY). Try connecting PMD without the extension. Try both PMD you have in case the new one is a dud. I was suggested this by OkDually
second that on the harness...long harnesses can be problematic if not top quality
 

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1995 Chevrolet Silverado Z71 6.5 TD
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Ground wire is good.
Yes CEL comes on.
Checked all the connections when I had it apart, all looked good
639576
Resistor for PMD use 5 or 9 most use 9

639579
Set resistor down on the pins it installs only one direction then plug in the cable.
 
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