ok guys im totally stumped i have diesel experience but this one has me banging my head against a tree so here it goes


truck runs fine when i can get it to start usually have to prime filter to do so starts runs ill idle it up to about 1500 rpm for two or three minutes let it idle and after about 5 minutes it starts to spit and sputter and then dies will not start again until i prime the filter (bleed) acts like it runs out of fuel lp works no issues new pmd with relocation in bumper new cps had a code no longer has new ops new filter changed ip with a working used one have checked for leaks none that i have found or seen changed the pick up tube in the fuel tank and strainer sock new lp relay just totally at a brick wall with this i really like the truck have had experience with the 6.2 and 6.5 before but have never had this issue everything points to the pmd but im just not sure anyone help

 

I had similar issues a while back. It turned out to be bad grounds. I ran fresh ground wires from the battery to the pump, PMD, and the stud on the engine block .This seend to cure the symptoms you are talking about.

 

i guess ill have to bite the bullet and give that a shot thanks for the advice ill do it tomorrow and let you know what happens

 

HAve you tried running with the lift pump jumpered?

Sounds like you might still be sucking air.

On a 95 and older 6.5 you will want tot do the dual lift pump relay upgrade or buy fromLeroydiesel.com

If you make your own, do not do it like many instructions to be found on the internet say. Do NOT cut and splice anything. Make it plug and play.

I have posted the connectors and schematic previously. Not sure if here but definitely on other forums. I would repost, But I do not have time to look it up right now.

Search dual lift pump relay upgrade and see what you find.

Leroy's kit has 14 ga wire, the prime feature and a toggle to run the lift pump for diagnostics and priming. If I recall, it is not terribly pricey. I have done my own, But if I had another to do, I would probably just buy his.

X2 on the grounds. I also add grounds to the frame by the starter, the battery box and from the heater blower to the dash mount bolt, just inches away.

You can also unhook the injection pump return line and run it to a container. A plugging return line can cause similar issues.

Did you use Ac Delco parts for the electrical components and tank sock?

The tank sock is mandatory to be GM or AC Delco. The aftermarkets are not the right part and tend to plug easily - a lot of the time, right out of the box.

Use a lift pump for a 1993 - higher flow and more pressure.

I have also taken to replacing the engine wiring harnesses on my old 6.5's. My harnesses were all starting to look ruff and caused me a couple of issues.

Now I just change them when I work on a vehicle as a matter of standard maintenance. I wouldn't run on 20 year old tires and I feel the same way about these engine harnesses.

I run the main engine harness on top of the intake, on the right hand side.

If you have not removed the optic sensor filter harness yet. Take it off, throw it away and plug directly into the injection pump

 

ok so here is what ive done


Ive added extra grounds changed the fuel filter (seems like i had a different design) changed the pmd resistor to the 5A (had a 9A in it) changed the fuel lines from the filter to the pump and the bleeder all parts that have been changed have all been ac delco and still having the same issue im just not sure what the deal is any other help would be greatly appreciated

 

Could you be sucking air between the lift pump and the tank.Still sounds like a leak down issue to me.

Sometimes they will not leak a noticeable amount of fuel, but they will suck air.

Could be the IP leaking down. Could be the FFM / Fuel Filter Manager.

Have you tried running with the lift pump jumpered? I would try installing a fused lift pump jumper in the cab. Turn it on for a few seconds before trying t start and see what that does for you.

I f your lift pump is putting out enough furl and NOT sucking air, it should not die while running. Try the toggle switch and see if that changes anything.

On a 1996 and newer, there is a spade connector between the under hood fuse box and the firewall. If you apply 12 volts to that connector, your lift pump will run.

Have you run about 1/2 gallon of fuel out the T drain with the lift pump jumpered?

I use a gallon pickle jar. Time how long it takes to run 1/2 gallon to see that you are getting proper flow.

Might want to use a clear line off the T to check for air bubbles.

You can also run a clear line from the Injection pump return line to look for air bubbles while the truck is running. Another place to check is the line going to the injection pump.

Since you have to prime the fuel filter to start the truck, it would seem to me that you are getting air someplace.

The FFM can be a main culprit as well as the fuel line going to the tank

 

i have checked all the fuel lines for leaks and the only one i have found is a return line to the tank near the tank would that cause an issue i changed the lift pump to a 93 model pump and at first it seemed like it was ok but now it misses and dies still stumped and need this truck running soon

 

I had a crank position sensor fail that also caused similar problems.