6.5 diesel

[smdv806]

I started my 1994 c 1500 6.5 diesel the other day and it only ran for about 15 seconds. It will not start back up. I checked the lift pump and it is working. I changed the fuel filter and I tried several pmds, but it still won't start. I bled the filter out. I also tried to bleed the injector lines, but nothing will come out. Are there some tests I can perform to see if it is a mechanical or electrical thing that is keeping the pump from working?

 

[mike in mo]

mind did that about 3 years ago and it was the fual shut off switch on the pump.id check that and the oil presser switch first.

 

[Randy S]

I have a 94 3/4 ton and it did the same thing a few years ago. It was the oil pressure cut off switch. Not easy to get to but is doable. Its located on the rear of the block on top behind the fuel filter just a little to the driver side.

Thats where id start.

Good luck
Randy

 

[smdv806]

How do you test the oil cut off switch?

 

[T. G. [GA]]

Does the shut-off click when ignition key is turned "ON". Is there 12 volts at the shut-off solenoid. The injection pump shaft could have sheered, this is the most expensive. The 94 has an electronic injection pump. You may need to use a scan tool to chek for an electronic problem. The driver module on side of pump could be defective.

 

[huntingreen]

mine has been doing the same thing. i replaced the PMD and thought I had the problem cured. Turned out I did not. Determined last night it is a bad wiring harness. It is about 6 inches long and one end plugs into the top of the injector. My son was cranking the truck and I was moving the wires. It started right up when I messed with that one. Kept messing with it and it died. Went through that several times. Ordered a new harness section today for $ 54.00

 

[Anonymous-0]

put it in the front yard with $50 on the windshield and go to town, someone will take it while your gone.

Just kidding

 

[Kevin (FL)]

The oil pressure sending unit serves two purposes. Besides sending a signal to the oil pressure gauge, it also provides voltage to the lift pump once oil pressure builds up. While cranking the engine, the lift pump gets it voltage (temporarily) from the starting circuit. Once the engine starts and oil pressure builds up, the contacts close inside the oil sending unit and then voltage is provided to the lift pump. These switches are "under-designed" and don't hold up very long. On our '95 Suburban, I've probably changed the switch at least 10 times. Used to be a dealer only item but now you can buy them at most auto parts stores. Cost about $25 or more.

The only test you need to do is while engine is running, place hand on lift pump and if its running, the oil switch is working. I'm about to install a green LED to provide a "pump running" indicator so I don't have to check it so often. The engine will run without the lift pump but not under heavy load. Also it helps if the tank is full or near full.

If you're getting pressure while cranking, then make sure you've bled all air out of the filter and only fuel is coming out the vent. You may have to crank awhile to get it running. You can also open up the air cleaner and spray some WD40 while cranking. Don't use ether on the 6.5!!!

If it doesn't crank, then I would expect a fuel stop solenoid failure or injection pump failure.

 

[smdv806]

The lift pump is working fine. There is good fuel flow to the pump. No fuel will come out of the injection lines though. I checked the shutoff solenoid and it does click as it should when the key is turned or when 12 volts is put to it. When I pull off the return line fuel shoots out of the pump when i crank it. This would indicate that mechanically most of the pump is working. What else could it be? What electronic tests can I do?