Help please ? 6.5 td lift pump problems
#11
02-23-2015, 01:05 AM
Diesel Enthusiast
Just because you see no fuel leaks doesnt mean theres no air leaks.
If it were only that easy, fact is many air leaks dont exhibit wet spots.
Air can creep into the system when parked for extended periods (system unpressurized), an inop, weak, and/or faulty lift pump will often expose airleaks that otherwise wouldnt exist. However, once the fuel supply system (fuel pressure) is restored, those newly exposed air leaks usually dont just disappear. They often become the aforementioned creeps..
Whats tougher to find than an air head? an air head as a result of a fuel restriction eg clogged fuel strainer, fuel filter, anything that creates/exposes the fuel to an excessive vacuum. Thats why I dont advocate using "in-line" fuel filters pre lift pump in lue of OEM fuel strainer, and never use them together...
Want to give him a gift.. Start by downloading and give him these GM Training manuals. Very educational stuff, lots of diagnostic aids, and step by step troubleshooting guides.
GM 6.5 Liter V8 Turbo Diesel Engine
GM 6.5L Diesel Electronic Fuel Injection
Heres a most helpful diagnostic aid to "bleed air" and avoid excessive cranking..
Also use it to perform most "Fuel Supply System Checks."
Open underhood fuse/relay box, remove LPR.
Use the LPR as a model to fabricate a jumper from a paperclip (see attached).
Jumper installed, lift pump ON. Jumper removed, lift pump OFF..
Next time it doesnt start right away. Stop cranking. Bleed Air thoroughly from the FFM vent (not WIF drain) using jumper method (no cranking necessary). When primed, close bleeder vent, leave LP jumper installed, try starting the engine...
If it were only that easy, fact is many air leaks dont exhibit wet spots.
Air can creep into the system when parked for extended periods (system unpressurized), an inop, weak, and/or faulty lift pump will often expose airleaks that otherwise wouldnt exist. However, once the fuel supply system (fuel pressure) is restored, those newly exposed air leaks usually dont just disappear. They often become the aforementioned creeps..
Whats tougher to find than an air head? an air head as a result of a fuel restriction eg clogged fuel strainer, fuel filter, anything that creates/exposes the fuel to an excessive vacuum. Thats why I dont advocate using "in-line" fuel filters pre lift pump in lue of OEM fuel strainer, and never use them together...
Want to give him a gift.. Start by downloading and give him these GM Training manuals. Very educational stuff, lots of diagnostic aids, and step by step troubleshooting guides.
GM 6.5 Liter V8 Turbo Diesel Engine
GM 6.5L Diesel Electronic Fuel Injection
Heres a most helpful diagnostic aid to "bleed air" and avoid excessive cranking..
Also use it to perform most "Fuel Supply System Checks."
Open underhood fuse/relay box, remove LPR.
Use the LPR as a model to fabricate a jumper from a paperclip (see attached).
Jumper installed, lift pump ON. Jumper removed, lift pump OFF..
Next time it doesnt start right away. Stop cranking. Bleed Air thoroughly from the FFM vent (not WIF drain) using jumper method (no cranking necessary). When primed, close bleeder vent, leave LP jumper installed, try starting the engine...
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jrsavoie (08-31-2015)
#12
02-23-2015, 10:26 AM
#13
02-23-2015, 10:40 AM
Ok so I'm going to fix the waste gate, and since findin the leak will be hard the easiest thing to do is replace the entire fuel line the way it's suppose to be and make sure there is no debree, and see how that goes, I will kept your posted if you keep your eye on here , and he has been pretty good with help lokmong for information and helping with the truck haha he is trying at least but I will give him those sites thank you very much
#14
05-23-2015, 10:18 AM
Diesel Enthusiast
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jrsavoie (06-02-2015)
#16
07-25-2015, 06:33 PM
A few weeks ago 1999 Suburban 6.5L left my wife stranded and had to tow it home. Cranking fast, no start. Strange thing was the shifter would not go into park, so I was dead sure that was the one and only problem. I have since fixed the shifter and now I am very experienced with bleeding the air out of the fuel to get it to start. I had replaced the fuel filter with Auto Zone brand (which now I am suspecting). I also replaced the lift pump with AC Delco EP309, even though the original pump passed tests. I temporarily connected a fuel pressure gauge and hooked it to the windshield wiper (not safe). 7 PSI when decelerating/braking. 6.5 to 5.5 PSI when cruising. The lowest I could get it was 3.5 PSI under heavier than normal acceleration. When parked and idle, fuel flow into a container is a little more than 1/2 pint in 15 seconds ok. The reason I replaced the lift pump is because there was some slight fuel wetness (no drip) at the fuel pump fittings. Yesterday I used compressed air and shop vac to push and pull fuel 20 times thru the return line with the fuel cap removed. So I can rule out a plugged return line. I have a piece of clear vinyl tubing at the return fitting of the injector pump. I think my next step is to pursue a more robust/permanent fuel pressure gauge so I can monitor properly on longer trips. Also I have an AC Delco fuel filter TP1256 to replace the newly installed Auto Zone fuel filter.
Last edited by Jeffc607; 07-25-2015 at 06:38 PM.
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jrsavoie (08-31-2015)
#17
08-30-2015, 04:41 PM
No more air in the fuel lines
New sending unit and all is well. No more problems with air in the fuel lines.
More info, someone might find this useful....
Before pumping out the tank for the second time, I had the fore-thought to first loosen the straps while the floor jack was under the tank. This way, the weight of the fuel helped to dislodge the tank from the black tar-like protective layer that holds it stuck to the frame. After dis-lodging, I pumped out the tank to drain as much fuel as I could. Removed the straps, the began lowering little by little until I could inspect the fuel lines going to the top of the tank. I could see the steel lines that are integral to the sending unit were wet and rather swollen with heavy rust flakes. even with the two-wrench method, I still ended up breaking the rotted steel lines. Got a new sending unit from Napa and re-installed everything and bled the fuel lines one last time and started it. Initially I kept a tally for how many trips in a row it would re-start without the need to bleed the lines, but now I have given up and I am now more than convinced and pleased that I have it properly fixed.
More info, someone might find this useful....
Before pumping out the tank for the second time, I had the fore-thought to first loosen the straps while the floor jack was under the tank. This way, the weight of the fuel helped to dislodge the tank from the black tar-like protective layer that holds it stuck to the frame. After dis-lodging, I pumped out the tank to drain as much fuel as I could. Removed the straps, the began lowering little by little until I could inspect the fuel lines going to the top of the tank. I could see the steel lines that are integral to the sending unit were wet and rather swollen with heavy rust flakes. even with the two-wrench method, I still ended up breaking the rotted steel lines. Got a new sending unit from Napa and re-installed everything and bled the fuel lines one last time and started it. Initially I kept a tally for how many trips in a row it would re-start without the need to bleed the lines, but now I have given up and I am now more than convinced and pleased that I have it properly fixed.
#18
08-31-2015, 09:11 AM
Diesel Enthusiast
You can try Inlinetube.com for new lines.
On a 1995 and older 6.5 a dual lift pump relay upgrade is a good idea. It takes the load off the OPS and gives a prime feature for strarting.
Leroydiesel.com Sells a relay upgrade kit for a reasonable price. The onl;y thing I do not like about his kit, is that he uses mountable relays, instead of mountable relay sockets and replaceable relays. I believe you also have to request the prime feature.
If you make your own OPS relay upgrade. Do not do it like the pictures say. Do it like Leroy does his - No wire splicing - plug and play. plug into the wires going to the lift pump and run back to the relay. Then run wires from the relay, back to the lift pump. I believe Leroy uses 14 ga. instead of the tiny little OEM wiring
On a 1995 and older 6.5 a dual lift pump relay upgrade is a good idea. It takes the load off the OPS and gives a prime feature for strarting.
Leroydiesel.com Sells a relay upgrade kit for a reasonable price. The onl;y thing I do not like about his kit, is that he uses mountable relays, instead of mountable relay sockets and replaceable relays. I believe you also have to request the prime feature.
If you make your own OPS relay upgrade. Do not do it like the pictures say. Do it like Leroy does his - No wire splicing - plug and play. plug into the wires going to the lift pump and run back to the relay. Then run wires from the relay, back to the lift pump. I believe Leroy uses 14 ga. instead of the tiny little OEM wiring
#19
11-16-2016, 06:36 PM
I have a 95 6.5 td k2500 suburban , now I have been having a ton of problems with this thing lately. I had replaced " with new " the injectors , the filter , injector pump " three times " , pmd , fuel pump relay, fly by wire throttle sensor, fuel tank , parts of the fuel lines that were rusted , crank shaft position sensor , .. Here are some things still clearly wrong with it.. The vacuum pump stopped working so I temporarily wired the waste gate shut cause around 70 mph it was bogging out , right now when key on I don't hear the lift pump prep , extremely hard to start it takes me about 10 15 minutes to start the truck, and when it does start a check engine like it on and rpm pulse and the motor sounds very very different , everyonce in a while during driving periods it will suddenly shut off for a spit second , it will run dead =" like I Jammed the breaks "run dead dead runnnn dead runnn dead dead dead , the more I hit the gas to try to get it to go and stop from dying it bogs out more to the point where it's gonna shut off and I have to pull over shut it off and restart it but still acts up , ops reads roughly just under 40 psi and I everyone in a while I have to tighten the batt cables on the batts because they come loose idk how. And also notice when it's acting up the volts gauge reads lower then normal but that's with all light on , both heaters on , and it doesn't over heat it runs about 180 / 190 ,,also I forgot to mention , when the truck is off and in gear besides neutral and park if I turn the key to start I hear the lift pump , but don't hear it when it's running, and when I open the waste valve the truck stays running and getting a decent amount of fuel coming out .. Dealerships can't find the problem and has several codes coming up all pertaining to the ip circuits , iv checked all wire plugs and did ground and lead and load tests on all the wires in the harness for shorts such.. Also idk if this is normal but when cranking it the speed gauge comes up to 10 mph and rpm come to about 3 / 500 please help me someone
#20
11-20-2016, 09:34 AM
Diesel Enthusiast
A faulty ignition switch can cause random shutoffs, but usually the dash lights will also come on and off.
Heavychevy doesn't like this, but I tossed the fuel sock and haven't looked back. I thought it would suck air when the tank was low during driving conditions, but it has never done that.
Heavychevy doesn't like this, but I tossed the fuel sock and haven't looked back. I thought it would suck air when the tank was low during driving conditions, but it has never done that.
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