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6.5L Diesel Engine Discuss the 6.5 GM diesel engine & associated components. Automatic transmission questions & problems belong in the 4L80/85 - 4L60E - 6L90 Transmission Forum

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Old 09-03-2019, 10:41 AM   #11 (permalink)
JMJNet
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Quote:
Originally Posted by jnlperformance View Post
The OEM setup is quite sufficient for a stock engine. (As far as fuel delivery is concerned)

I only skimmed ^^^ all that up there.

You have the correct fuel cap? The incorrect cap can strain fuel delivery.

I would have left the correct diesel tank sock. The lp is designed for that. Lift pumps push better than they pull.

If you have or you suspect you have major debris or corrosion in the tank you should pull the tank. Empty it. Rinse it out and let it bake in the sun to dry (if the tank is recoverable) if not replace the tank.

Disconnect line to fuel filter housing. Disconnect return line. Disconnect lift pump on both sides. Blow all lines out with compressed air while tank is dropped.

Install a new fuel filter in the ffm if you have not already.

With the truck running... open the air bleed valve on top of the filter. Does the engine struggle to run? Stall? Or does it pump fuel out just fine. Use a clear hose and a Jerry can so you can see if you have air bubbles present and if they are constant or if they go away.

If the engine stalls or has trouble running when the bleed valve is open the lp is weak and failing or was never strong enough to begin with. I always recommend the delco lp.
JNL, OP is adding an extra filtration before the LP.
So, that is why I said the stock LP may not be sufficient.
The 93 model year LP is a bit stronger than 00 model year.
Get an ACDelco LP.

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Old 09-03-2019, 12:25 PM   #12 (permalink)
JMJNet
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The best way is to measure the pressure (even volume if possible).
First at the t-valve, you need around 4 psi at idle steady not average.
Then somehow, measure the pressure when the problem happens, not sure if that is all the time.

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Last edited by JMJNet; 09-03-2019 at 12:25 PM.
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Old 09-03-2019, 10:08 PM   #13 (permalink)
Mdifed
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I have bought a new tank with new sending unit. I never replaced fuel lines / return lines. Also the back tank is disconnected (which is plastic). I have a Delphi Lift Pump currently on it. When we blew threw the hose last time there was debris inside them. Not sure if it's preventing the diesel from reaching the fuel housing. When I stalled the other night I kept priming the fuel filter until it was full, than the truck started right up. I'm not sure why not enough diesel is being lifted to the housing when the truck is on.
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Old 09-03-2019, 10:09 PM   #14 (permalink)
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So to see if the lift pump is working I should measure how much fuel (psi) is coming out of the t valve when the truck is on?
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Old 09-03-2019, 10:39 PM   #15 (permalink)
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Quote:
Originally Posted by Mdifed View Post
So to see if the lift pump is working I should measure how much fuel (psi) is coming out of the t valve when the truck is on?
If you start the truck and then open the T Valve for a minimum of 30 seconds, you should see a healthy stream of fuel flowing out of the drain line and the engine continue to run..

If you see no fuel flow from the drain line and/or the engine dies then your lift pump is too weak.
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Old 09-04-2019, 12:44 PM   #16 (permalink)
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Not sure if this is it but have you checked to see if you install the LP in the correct direction.

I think it flows one way and it is very easy to reverse the LP.
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Old 09-04-2019, 07:30 PM   #17 (permalink)
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I believe jnlperformance's reply is absolutely spot on. I had similar problems and after dropping the tank, flushing it out and replacing the entire fuel pickup assembly including the OEM sock, Brunhilda runs fine. Don't skimp on cleaning the tank, take the time to do it right. This was after replacing the LP, which only brought temporary relief.
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Old 09-04-2019, 10:47 PM   #18 (permalink)
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I have cleaned the tank and sucked out the old diesel and particles. I believe the particles keep reappearing In the new tank because of the old return line and fuel line. Therefore, I put a filter to catch the debris until I get new lines. The lift pump is on correctly, the fuel housing just doesn't stay filled like it's suppose to. Something is preventing the fuel from reaching to the fuel housing to stay full, not sure what it could be, I just put a brand new lift pump. My next step is to try replacing the return and fuel lines. People have told me the rubber hose could of gone bad, or that hard line is corroded inside. My next step is to blow out these old fuel lines, and try again.
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Old 09-04-2019, 10:55 PM   #19 (permalink)
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Quote:
Originally Posted by Mdifed View Post
I have cleaned the tank and sucked out the old diesel and particles. I believe the particles keep reappearing In the new tank because of the old return line and fuel line. Therefore, I put a filter to catch the debris until I get new lines. The lift pump is on correctly, the fuel housing just doesn't stay filled like it's suppose to. Something is preventing the fuel from reaching to the fuel housing to stay full, not sure what it could be, I just put a brand new lift pump. My next step is to try replacing the return and fuel lines. People have told me the rubber hose could of gone bad, or that hard line is corroded inside. My next step is to blow out these old fuel lines, and try again.
Try disconnecting the fuel line, pre lift pump and attach a can of fresh fuel to the lift pump via a hose and start it to see if things improve..
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1996 K3500 6.5L,( "F" Eng #141 cast block) 5 speed manual, crewcab, dually longbed: 208,000mi.
Diamond Eye 4" Turbo Back Exhaust w/2.5" Flo-Pro Crossover
AirDog II DF165 w/ tank sock delete - XDP
TD-Max boost controller - Kennedy Diesel
OPS extension hose - Leroy Diesel
Glow Plug Harness- PT Wiring Solutions
Glowshift Maxtow EGT,Boost, Fuel gauges
Boost & Fuel Pressure Bolts - Leroy Diesel
2/0 Battery Cable Upgrade - PT Wiring Solutions
PMD w/#9 resistor and Re-Location Kit, mounted to bumper - Leroy Diesel
GM-5 Turbocharger
4.10 gear ratio
OptiLube summer + Formula


Proud member #1039 of The 3500 Dually Club


Last edited by OkDually; 09-04-2019 at 10:56 PM.
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Old 09-09-2019, 10:39 PM   #20 (permalink)
Mdifed
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The truck starts running bad as soon as I take it for a spin and warm it up. Than the truck begins to shake like not enough fuel is getting to all the injectors. I changed the oil today and sometime this week will change the OIL pressure switch. I feel the LP is working but i don't know if its working when Im pushing the gas. The truck only stalls when I give it gas. I will update you guys what happens after I replace the OPS. Truly running out of options, the OPS is the last thing to switch, hopefully it resolves all my problems with this truck.
- Thanks for the feedback guys!

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