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Discussion Starter · #1 ·
Recently bought a 94 gmc k2500 6.5l turbo diesel for hauling water. Test drive fine and ran great the 45 minute trip home, but after getting home the problems started the next day.

I thought it was the PMD, it was tempted to top of the intake, but still would shut off randomly. I replaced the corroded ground wire and it ran great for one day of hauling then had issues again.
I replaced the PMD but it still shuts off after a few minutes of running and it difficult to restart. Upon restart, great clouds of black smoke and it runs poorly until you spend a few minutes reving it to clear the smoke but then it shuts off again after a few minutes.

The chemo I got for cancer screwed my brain up and it's hard to get it to work well enough for diagnosing the truck.

I think it might be the optical sensor in the injection pump but I can't be sure.

What should I check and how should I check it?
 

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Welcome to DieselPlace

Go back through all the grounds using this link for reference: Grounds-Grounds-Grounds The importance of good grounds.....
Perform a lift pump test: Reference Material: Lift Pump/OPS
If it fails that test then replace the lift pump and the ops ( Oil pressure switch supplies power to the lift pump and will get weak)

Install a piece of clear fuel line on the return side of the Injection pump to help locate any air in fuel issues, as shown in this link: Question: - 1999 GMC Bluebird 6.5L TD - PMD &amp...
 
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Discussion Starter · #3 ·
Lift pump has already been replaced. Ive got pressure at the filter as fuel flows when I crack open the bleeder valve on top the filter.

I also get good flow from the bleeder at top front of engine.

Thanks for the reply, I'll check the grounds and the return flow.
 

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I think your next step should be check for trouble codes.
 
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Try unplugging the optical sensor.
It may take some cranking to get it started, from memory maybe 10 to 30 seconds with just the crank sensor, and it runs poorly. But if it starts and runs with the optical sensor unplugged, then the computer is upset with the mismatched signals from the optical sensor and the crank sensor. Note, this can be caused when you have a good optical sensor and bad wiring!

10. Disconnect the optical sensor connector from the injection pump. This is the large square black connector directly on top of the injection pump. Again try to start the truck. If the truck starts and runs, this means that the optical sensor is outputting faulty data preventing the truck from starting. By unplugging the sensor, you put the system into backup mode and the computer relies on information from the crankshaft position sensor. In the very unusual case that both sensors were bad, the truck would not start with the optical sensor disconnected.
from 6.5 Diesel Engine Won't Start? | 6.5L No-Start Diagnostic Guide
 

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I stupidly reset them. Now, since it hasn't run for more than a few minutes, it won't give me the code "1-2 x3" ready.
So you are not even getting the code 12? . You should get that anytime you put PCM is in diagnostic mode. By jumping pins A & B on the data link connector.
If no code 12 you may have power or ground issues to the PCM.
 
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On the lift pump being new, that doesn’t mean good.
I have gone through 4 now. Only lasting a few months each. I’m not sure what the deal is.
I bought the Delco one and keep using the stores warranty.
I’m about two more pumps away from demanding a refund and installing an aftermarket one.
I have a fuel pressure sensor telling me I’m under 3 lbs of pressure and when the pumps are new I’m closer to 6.

I have the ops relay installed so amps isn’t an issue.
 
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Eskimoman. Have you checked to make sure the tank sock/strainer is not clogged? The LP does not have a lot of suction power.. Having a clogged sock can wear out a LP in a short time.
 

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Discussion Starter · #10 ·
So you are not even getting the code 12? . You should get that anytime you put PCM is in diagnostic mode. By jumping pins A & B on the data link con
Eskimoman. Have you checked to make sure the tank sock/strainer is not clogged? The LP does not have a lot of suction power.. Having a clogged sock can wear out a LP in a short time.
Haven't checke it but I have good fuel flow.
I'll check again tomorrow on the codes. That's good info about the PCM ground.
 

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Discussion Starter · #11 ·
On the lift pump being new, that doesn’t mean good.
I have gone through 4 now. Only lasting a few months each. I’m not sure what the deal is.
I bought the Delco one and keep using the stores warranty.
I’m about two more pumps away from demanding a refund and installing an aftermarket one.
I have a fuel pressure sensor telling me I’m under 3 lbs of pressure and when the pumps are new I’m closer to 6.

I have the ops relay installed so amps isn’t an issue.
I'll try and find my fuel pressure gauge and check that.
 

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Discussion Starter · #12 ·
Try unplugging the optical sensor.
It may take some cranking to get it started, from memory maybe 10 to 30 seconds with just the crank sensor, and it runs poorly. But if it starts and runs with the optical sensor unplugged, then the computer is upset with the mismatched signals from the optical sensor and the crank sensor. Note, this can be caused when you have a good optical sensor and bad wiring!

10. Disconnect the optical sensor connector from the injection pump. This is the large square black connector directly on top of the injection pump. Again try to start the truck. If the truck starts and runs, this means that the optical sensor is outputting faulty data preventing the truck from starting. By unplugging the sensor, you put the system into backup mode and the computer relies on information from the crankshaft position sensor. In the very unusual case that both sensors were bad, the truck would not start with the optical sensor disconnected.
from 6.5 Diesel Engine Won't Start? | 6.5L No-Start Diagnostic Guide
Awesome info, thank you. I'll be trying that tomorrow if it doesn't rain.
 

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For folks looking for a decent fuel pump your probably better off going to eBay and find a new old stock American made lift pump from the 90s under acdelco EP158.They are still out there and more than likely better built than what’s offered nowadays.

Grounds are definitely important.Everything should be grounded such as the engine to the chassis and another ground strap going from the chassis to the cab.All that makes a difference in the way the electrical system functions.
 

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Discussion Starter · #14 ·
Welcome to DieselPlace

Go back through all the grounds using this link for reference: Grounds-Grounds-Grounds The importance of good grounds.....
Perform a lift pump test: Reference Material: Lift Pump/OPS
If it fails that test then replace the lift pump and the ops ( Oil pressure switch supplies power to the lift pump and will get weak)

Install a piece of clear fuel line on the return side of the Injection pump to help locate any air in fuel issues, as shown in this link: Question: - 1999 GMC Bluebird 6.5L TD - PMD &amp...
Replaced the fuel filter, cleaned the bowl, and jumped the fuel pump relay til fuel came out the opened vent. Did the clear fuel return line. When it started up there were a few miniscule bubbles from the filter swap but cleared right up. Let it idle for 5 minutes and fuel was clear. Drove it 25 yards and it died. Had to pump the hell out of the pedal for a restart. Restarted really rough and had to pump/floor the pedal to get it to smooth out, stay running, and get the rpms up. Once it smoothed out I beelined for my driveway. It died again just as I got it parked. Popped the hood and fuel in return line was HIGHLY arriated. The IP quit blowing bubbles after a minute or so, then a minute later blew a bunch more bubbles. It did the quit and start bubbles several times over several minutes.
 

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Replaced the fuel filter, cleaned the bowl, and jumped the fuel pump relay til fuel came out the opened vent. Did the clear fuel return line. When it started up there were a few miniscule bubbles from the filter swap but cleared right up. Let it idle for 5 minutes and fuel was clear. Drove it 25 yards and it died. Had to pump the hell out of the pedal for a restart. Restarted really rough and had to pump/floor the pedal to get it to smooth out, stay running, and get the rpms up. Once it smoothed out I beelined for my driveway. It died again just as I got it parked. Popped the hood and fuel in return line was HIGHLY arriated. The IP quit blowing bubbles after a minute or so, then a minute later blew a bunch more bubbles. It did the quit and start bubbles several times over several minutes.
Is your PMD relocated?
 

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Try disconnecting the PMD from the relocation harness and plug the PMD into the OEM harness on the IP.
This will rule out a relocation harness issue
 

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Discussion Starter · #18 ·
Try disconnecting the PMD from the relocation harness and plug the PMD into the OEM harness on the IP.
This will rule out a relocation harness issue
It's plugged into the original harness and relocated to intake.
 

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Discussion Starter · #19 ·
This is video of clear fuel return right after it dies.

Trying to restart after it dies.

Trouble codes. Note: no '1-2' X3 before codes flash.

I really appreciate any and all help and suggestions. Chemo fried my brain and I can't diagnose anymore and searching for answers online has been fruitless.
 

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This is video of clear fuel return right after it dies.

Trying to restart after it dies.

Trouble codes. Note: no '1-2' X3 before codes flash.

I really appreciate any and all help and suggestions. Chemo fried my brain and I can't diagnose anymore and searching for answers online has been fruitless.
Next time it dies try pouring a bottle of room temp water on the IP and see if it starts back up.
If it does that is a sign of a tired injection pump
 
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