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Discussion Starter · #1 ·
Hi all!
I’m an avid reader of these forums but never ask questions. This has me stumped.

I made what was probably abad decision and purchased a 1995 Suburban with the 6.5. Fell in love. But, as also with my love life, brining something like this home has turned into a nightmare.

I’ll be filling out my signature as soon as I figure out how.

When I purchased this vehicle the prior owner was able to make it run for about two minutes. It sat for roughly a year. Prior owner said that it was the lines under the intake sucking in air.

I replaced those lines and raised the FFM. Well, then the FFM was leaking like the titanic.

So, I ordered a new ffm and another PMD just in case (the one that came with it was “new” but probably something from the great beyond online).

After replacing the FFM and lines, I used clear tubing to the return to monitor.

It would still, occasionally, (meaning once in a blue moon) start briefly then die (even changing between PMDs). There was still air in the system.

Crud.

So I save up and got a set of new steal lines for the rear and made rubber lines for the front. It was like Christmas morning.

Still nothing. Wouldn’t even start at all.

Pulled an injector line and no fuel. So, I spent today bleeding the system.

I got it to run ten minutes this time before it shut off.
And there was no fuel in the lines again. But there’s no air in the return like the last time.

I’ve gotted the shutoff selinoid at the IP.

some weird things:

1.). The wait to start light is rare. But when it was running it stayed on. The glow plug relay is… terrible. It’s wired by twisted wires together. I’ve jumped it at 5 second intervals. Maybe there’s an issue there. Might try ti address it tomorrow.

I’ve also replaced the OPS (not ac delco… already too deep in this hole)

Im getting fuel to the FFM and the cleartube on the return doesn’t have any more bubbles.

still, I’ll bleed the lines and best I’ve gotten is a ten minute run and then no fuel in the lines.

Help? Save my from my poor life choices?
 

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Discussion Starter · #3 ·
Welcome

Start by testing the lift pump
Apply a 12v. jumper wire to the lift pump relay https://www.dieselplace.com/forum/attachments/63-gm-diesel-engines/21-6-5l-diesel-engine/175946d1386973232t-cycle-lift-pump-lpr-jumper-installed.jpg"

Once you have the jumper applied then open the t valve and let fuel drain into a container.
You should see 1/2 pint of fuel in the container within 15 seconds on a healthy lift pump.
I was able to do that and did that with the bleeding.

I’m unsure if my lift pump is working correctly other than with the jumper. One of the times it ran I forgot to jumper it and died due to fuel (at least I’m thinking)

just assuming the pump is good but that it’s not running unless jumpered.
 

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I was able to do that and did that with the bleeding.

I’m unsure if my lift pump is working correctly other than with the jumper. One of the times it ran I forgot to jumper it and died due to fuel (at least I’m thinking)

just assuming the pump is good but that it’s not running unless jumpered.
Don't assume or be unsure.
Replace the lift pump and the Oil Pressure Sensor (OPS).
The OPS supplies power to the lift pump and the contacts inside of the OPS do go bad.
 

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Discussion Starter · #5 ·
Don't assume or be unsure.
Replace the lift pump and the Oil Pressure Sensor (OPS).
The OPS supplies power to the lift pump and the contacts inside of the OPS do go bad.
For the last couple times, as well as when the prior owner showed me it could start for a brief time, the lift pump was jumpered at the relay.
I’ve replaced the OPS (twice now) but if won’t run with it jumpered I’m hoping to solve the only runs a few minutes spurdically issue before I fix that issue. I know the lp relay is likely an issue (be it the relay or ops) but I’m normally jumping the relay.

thanks!!
 

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1999 K2500 6.5 turbo diesel VIN F Ext. Cab Long bed
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I’m assuming no check engine light? I’d also make sure grounds are good and tight since these 6.5s are sensitive.
 

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Discussion Starter · #7 ·
I’ve got the check engine light when I turn the key. But I don’t have a code reader. I do NOT normally get the code air to start light. I cleaned the two front grounds yesterday.

BUT I think I made an important discovery.

Ive got the two grounds from the harness at the back passenger side. And I’ve got a ground strap from the starter. What am I missing? A ground strap from the bolt on the two harness grounds to the frame.

the prior owner had a wire that ran from the body to the frame and a part of a broken ground strap attached to that wire but thestrap from the engine to the frame is missing.

mill replace today and report back. Could that be a reason for this???
 

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1999 K2500 6.5 turbo diesel VIN F Ext. Cab Long bed
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I’ve got the check engine light when I turn the key. But I don’t have a code reader. I do NOT normally get the code air to start light. I cleaned the two front grounds yesterday. BUT I think I made an important discovery. Ive got the two grounds from the harness at the back passenger side. And I’ve got a ground strap from the starter. What am I missing? A ground strap from the bolt on the two harness grounds to the frame. the prior owner had a wire that ran from the body to the frame and a part of a broken ground strap attached to that wire but thestrap from the engine to the frame is missing. mill replace today and report back. Could that be a reason for this???
Very possible I would clean and repair all grounds. Then see if you could borrow or get a cheap code reader to be sure there is no codes. And you normally don’t get the wait to start light?
 

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Discussion Starter · #9 ·
I get all the normal warning lights when I power on but I don’t see any “wait to start light”. On the few times I’ve had it running, the wait to start light comes on while it’s running.

The glow plug controller is wired in in a very sketchy fashion. (Think electrical tape and twists)
 

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I get all the normal warning lights when I power on but I don’t see any “wait to start light”. On the few times I’ve had it running, the wait to start light comes on while it’s running.

The glow plug controller is wired in in a very sketchy fashion. (Think electrical tape and twists)
It is normal to see the WTS light come on the dash briefly after a cold morning, first start.
 
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I’ve put it another ground and tried to start but no dice yet. Re-bleeding the system again.
As long as the WTS light comes on the dash for approx 5-10 seconds, after you turn the IGN key to ON you should be good
If you do not see that on your dash then you might want to address the electrical wire issue first
 

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The ground setup on these rigs is not very well designed.
With age they get worse.
As long as the PCM grounds and the heavy black ground are connected to the engine it will run, even with no lift pump.
The Lift Pump is grounded to the frame somewhere between the LP and the fuel tank.
Most of the cab electrical is grounded to the cab just above the DLC connector on the lower dash brace tube.
Run a 10ga. wire from that ground bolt above the DLC to the engine.
Run a 10ga. wire from the LP ground bolt to the engine.
I do not think grounds are your problem, but those 2 added grounds will make sure they are not.
The photo is the 95-96 OEM grounds at the pass. head rear.
There should be no ground wires attached to the starter, but would not be a problem.
If the engine will run for 10 minutes then the GPR is not the problem although shorts in the wiring to it could cause the engine to stop running.
Is air collecting in the FFM or do you mean the injection lines have no fuel?
Have you had the intake manifold off for any reason?

Line Bicycle part Metal Gas Steel
 

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Discussion Starter · #15 ·
Thank you all for the responses!!

here’s where I am now. I’m slowly rebleeding the thing to get fuel from the IP to the injectors.

I get fuel to the ffm and have bled that system.

new steel lines back from LP to tank. New strainer in the tank.

Clear line hooked up from IP to return. One tiny bubble but seems good.

New ground installed from passenger side rear engine stud to frame. Cleaned and sanded other grounds.

I only noticed two eyelets grounding at the passenger side rear stud on the engine, not three.

the mystery is that when I turn on the ignition I get all the lights except no wait to start light. It comes on when I finally get the truck running in rare instances.

I’ve replaced the OPS. FFM is completely new. Switching between both PMDs that have had it run. Having a hard time bleeding the system to the injectors. No leaks between tank and ffm now and all new lines above the intake from ffm to IP and water drain.
 

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Find the 2 PCM grounds, the TAN/WHT and BLK/WHT and make sure they are bolted down.
I do not see them in your photos.
Those 3 ring terms may not be on the same stud or bolt.
 
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FSO on these is redundant and for over-rev shutdown.
PCM controls injection.
 
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