6.5 help - Diesel Bombers



Chevy/GMC 6.2L and 6.5L Discussion of Chevy and GMC Trucks with 6.2L and 6.5L Diesel Engines

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  #1  
Old 12-02-2012, 11:14 PM
Diesel Fan
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Default 6.5 help

ok it all started when the truck started to die if i left it sit, so i thought it was air in the lines and i tried to bleed it, it had in them and i thought it fixed the problem, now i take it down the street and it sputters as im driving it and wont go over 30 most of the time. so i bring it back to the garage and crack the bleeder valve and theres air in them again. how is this happening????, did i bleed them wrong or something, or could the fuel filter be the issue? it had a new pdm about a year ago, the lift pump works fine, i checked it by hot wiring it. the pdm has been relocated also. i can sit at an idle and it runs great , until i got to drive it. please help me figure out whats wrong. thanks.
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Old 12-03-2012, 06:30 AM
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sounds like you have a bad/rotted fuel line. look at the lines coming out of the sender. there will be a steel crimp that goes to a steel line, 90% of the time that is leaking.

check your fuel filter housing as well, that could be cracked
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Old 12-03-2012, 11:25 AM
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whats the sender where is it located? and thanks for your help
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Old 12-03-2012, 01:19 PM
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the sender is in the tank, and the lines come out form the top of the fuel tank
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Old 12-03-2012, 06:36 PM
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so i have to drop the tank to look at them
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Old 12-04-2012, 07:02 AM
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nope, just follow the line from the lift pump that goes toward the rear of the truck and follow it all the way up, the return line should be next to it and you can see wether or not if its leaking
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Old 12-04-2012, 10:37 AM
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It is tough to find a leak on the suction side of a fuel line because it is not under pressure to force fuel out.If it is at a lower portion of the line it may leak at shutdown when fuel is laying in the line though.

First thing to try to be sure air in the lines is the problem is to replace the IP fuel return line with clear diesel rated line.
Then with the truck safely parked,watch the line for bubbles while the engine idles.

Bubbles indicate air intrusion between the fuel level in the tank and the LP.

Another source for air to get in and cause hard starts is the WIF sensor and fuel heater O-rings in the filter manager.

There could be a plugged last ditch screen in the filter manager,a bad fuel cap with plugged vent or blocked IP inlet screens?

---AutoMerged DoublePost---

On a 95 the LP is powered by the OPS when the engine runs,you know it works with direct power-do you know if it works with OPS power?

With the engine idling open the WIF T-valve and observe what happens-truck dies,LP not operating-diagnose.

Last edited by racer55; 12-04-2012 at 10:37 AM. Reason: Automerged Doublepost
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  #8  
Old 12-06-2012, 09:41 PM
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if i open the t valve its a lil fuel comes out then truck dies?? is that supposed to??
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Old 12-07-2012, 04:20 AM
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That is telling you that the lift pump is not working.

You now have to figure out why?
Is is the LP itself that is bad or is the OPS bad and not powering the LP?

OPS is a common problem and should be replaced with AC Delco ONLY.
An additional update/repair that can be added is "OPS relay mod"-google it for long term reliability.

If the LP is to be replaced with a stock type LP,then AC Delco ONLY and from a 93 is the best choice.

Airtex or FASS are much more expensive LP options.
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  #10  
Old 12-07-2012, 04:50 AM
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i never here the lift pump run if i get under the truck and its runing it feels like the lp has a hartbeat and if i hook a wire to the lp relay fuel comes out of the bleeder and i can here the lp run but thats the only it ill here it the truck runs fine to i take it do the road the it starts messing up when im seting a light old presser drops to like 20 but when im runing it stays about 30 40 as soon as i let off back down to 20
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