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intermittent lift pump issues

ak diesel driver

ak diesel driver

6.5 driver
Messages
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Location
alaska
So I recently put a new LP on from Leroy, everything was fine for awhile. Now sometimes when it's warmed up and I go to start it the LP won't run. It always works perfectly when cold only when it's warm do I have an issue. I have a kennedy LP harness on it so I'm assuming it's not an OPS issue. I know I know OBD2 isn't supposed to need it but I know Simon had an issue with the OPS on his 98. I've been wondering about my IGN switch as a possible culprit since it's got 274k on it. Any thoughts???? I think I'll call Kennedy in the morning and see if he has any ideas.
 
ak diesel driver said:
So I recently put a new LP on from Leroy, everything was fine for awhile. Now sometimes when it's warmed up and I go to start it the LP won't run. It always works perfectly when cold only when it's warm do I have an issue. I have a kennedy LP harness on it so I'm assuming it's not an OPS issue. I know I know OBD2 isn't supposed to need it but I know Simon had an issue with the OPS on his 98. I've been wondering about my IGN switch as a possible culprit since it's got 274k on it. Any thoughts???? I think I'll call Kennedy in the morning and see if he has any ideas.
Click to expand...

I have the same Kennedy Lift pump module and works good. I would check your ground and ignition wire for the module. If it is intermittent I would check the ops that the module came with and see if it could be bad, if your ground and ignition wire is good.
 
so I called Kennedy this morning and we talked for a few minutes. He said to verify the light is on when I turn the key and get a no LP run. Didn't happen at all today but I didn't drive as much either. I'm thinking it is heat related and probably the OPS failing when hot. He also can't say enough bad things about aftermarket LPs especially the Walbros
 
Les, it could be just a bad LP. i had that once on my old 6.2, most times it ran but would quit and go at will when it felt like it

I replaced the OPS on my 98 when i replaced the IP a couple months ago when i had fuel supply problems under load.I still had the problems after so it was not the OPS or the IP causing it.
In the end it was too a high boost (caused by the waste gate being stuck closed) that made the ECM cut the fuel until boost was back below 15 lbs.(took a while before i figured that out though)
my LP is still the one that came with the truck 6 years ago
 
If it wasn't for the fact that my old LP acted just the same I'd agree. It still could be a bad LP but I'm going to verify a few things before I swap it out.
 
ak diesel driver said:
so I called Kennedy this morning and we talked for a few minutes. He said to verify the light is on when I turn the key and get a no LP run. Didn't happen at all today but I didn't drive as much either. I'm thinking it is heat related and probably the OPS failing when hot. He also can't say enough bad things about aftermarket LPs especially the Walbros
Click to expand...

With the lift pump graveyard I have I can't disagree with him too much unless he was recommending the short lived factory POS pump. The Walbro has been 50/50 for me, BUT the FRB-5 I have is still going after the bad fuel killed the other one and made me rebuild the one that is still going. Kennedy's Duramax lift pumps will burn up if you run out of fuel.

So the best Mexican wine is the Walbro. Everything else didn't make even 6 months for me.

Does the kit have a relay? Best 'keep it out of the shop' practices is to replace the relay when replacing a fuel pump. Sometimes a failing pump will burn the relay contacts or the relay was the real problem to start with.
 
So I'm pretty convinced it's an OPS issue. Got home today and checked it out while it was warm and the LP not running. JK wanted me to look and see if the red led was on when it wasn't working right, and it wasn't. Pushed the manual prime button on it and the light came on and the LP ran, so it's not getting power/signal from the OPS.
 
On my Kennedy LP harness it uses it's own OPS for power when running, this OPS works as a on/off switch when oil pressure is present. If you unplug the harness from this second OPS the system should default "LP ON" when the ignition is under power.

One time I washed my engine and the second OPS got wet and failed (not sure washing caused it, but something happened). I unplugged the second OPS to get me by until my replacement OPS arrived.

Try unplugging the second OPS and see if the pump continues to run 100% while driving, the pump will only activate with the ignition in the on position. If the pump works 100% then replace the second OPS. If the pump fails check all wiring and start looking for a spare LP or give the relay harness a good going over.

Hope it helps,

Brian
 
I have gotten excellent longevity out of the AC Delco and GM lift pumps I have bought. I'm not much for electrical aftermarket parts, unless they are an upgrade. I've probably only bought 8 lift pumps in 2 million miles.
 
So I took off the intake today to work on my LP issue and this is what I found on my DD.uploadfromtaptalk1401126642695.jpguploadfromtaptalk1401126661844.jpguploadfromtaptalk1401126680175.jpg
So I think I'm going to pull off the Kennedy LP harness and probably install it on my 94. One thing I can say is I seemed to go thru less LPs with it on there.

Sent from my Studio 5.0s using Tapatalk
 
So I decided since I have to build an extension harness to reach my new LP that I'd also incorporate a relay and utilize bigger wires.

Sent from my Studio 5.0s using Tapatalk
 
Pretty Sir it was mice looks like they chewed some stuffing out of the firewall or something . Also feathers and a piece of fabric scrap. Fuel hoses are still in pretty good shape just dusty/dirty.

Sent from my Studio 5.0s using Tapatalk
 
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