Engine/Transmission (1998.5 - 2002) Low Fuel Pressure

[whogan]

Ok. I've tried two new stock lift pumps, changed the fuel filter, calibrated the fuel pressure sending unit and gauge,changed the overflow valve and checked pressure readings at the lift pump (12psi idle)and injection pump (11psi idle,5psi WOT no load). Any ideas as to what the problem may be???



Thanks

 

[whogan]

I should have added--



Absolutely no symptoms, truck runs great.

 

[DSeamans]

Stock pumps just suck. I finally broke dow and bought the Airdog. Best thing I've done. 19psi at idle and cruising, 15 at WOT. Best $500 I've spent in a long time.



Dave

 

[KLockliear]

11-12psi is on the low side of the idle spec. I got two brand new lift pumps in a row from Cummins that were bad. The 3rd one finally performed as it was supposed to.



Not sure what's in a stinger kit, but with an EZ for fuel, you shouldn't need too much more. The big fuel lines and getting rid of the banjo fittings is usually worth another 5+psi at WOT at 350hp, so maybe look into the Vulcan kit.

 

[JKinney]

Have you pulled the fuel module in the tank? That screen sure can get gunky.

 

[Ragain]

Check flow volume. Disconnect fuel supply line at VP-44 & bump the starter to energize lift pump. Cummins Tech says a minimum of 42 oz. in 30 seconds. If you are getting less, I would check the sock on the fuel tank pick-up tube.

 

[whogan]

Check flow volume. Disconnect fuel supply line at VP-44 & bump the starter to energize lift pump. Cummins Tech says a minimum of 42 oz. in 30 seconds. If you are getting less, I would check the sock on the fuel tank pick-up tube.

Is it possible to use compressed air back through the fuel line to the tank to check if the screen is clogged before removing the fuel module??



Thanks

 

[JKinney]

Dont do it you can blow the suction pick up right off inside the module.

 

[whogan]

Dont do it you can blow the suction pick up right off inside the module.

Thanks. I didn't think so but it was worth asking.

 

[whogan]

Check flow volume. Disconnect fuel supply line at VP-44 & bump the starter to energize lift pump. Cummins Tech says a minimum of 42 oz. in 30 seconds. If you are getting less, I would check the sock on the fuel tank pick-up tube.

Thanks.

I did a quick 20 second test through my fuel pressure guage line and only got 20 ounces of fuel. I suppose that I could have repeated it and divided by two but it's tooo windy outside. Now I have a reasonable indication of not enough pressure and not enough flow. The question remains, is it the pump, the p/u tube screen or both?

 

[DavidC]

The way I found a plugged screen was as follows. Get a 5 gallon fuel jug full of diesel, remove the fuel line from the pump and slip a 5 foot piece of 5/16 fuel line onto the pump and into the 5 gallon jug. Bleed the system. Start it up and check readings.



Dave

 

[JKinney]

Thanks.

I did a quick 20 second test through my fuel pressure guage line and only got 20 ounces of fuel. I suppose that I could have repeated it and divided by two but it's tooo windy outside. Now I have a reasonable indication of not enough pressure and not enough flow. The question remains, is it the pump, the p/u tube screen or both?

How big is your fuel pressure line? You gotta get a piece of hose hooked upright off the filter

 

[whogan]

The way I found a plugged screen was as follows. Get a 5 gallon fuel jug full of diesel, remove the fuel line from the pump and slip a 5 foot piece of 5/16 fuel line onto the pump and into the 5 gallon jug. Bleed the system. Start it up and check readings.



Dave

Damn, why didn't I think of that? Too close to the problem-maybe!



Thanks

 

[JKinney]

I think it is more fun to drop the tank, pull the module and put a vulcan draw straw in there. Then... cut the old feed line off run a new line purchase and after market fuel system with pump install, and yourOo.

 

[whogan]

I think it is more fun to drop the tank, pull the module and put a vulcan draw straw in there. Then... cut the old feed line off run a new line purchase and after market fuel system with pump install, and yourOo.

I like your style. If I were 40 years younger with a little more cash I would probably do just that.



Thanks

 

[JKinney]

I like your style. If I were 40 years younger with a little more cash I would probably do just that.



Thanks

Im a 51 year old landscaper who did exactly that this time last year after 4 lift pumps, including two on the rail.

 

[whogan]

The way I found a plugged screen was as follows. Get a 5 gallon fuel jug full of diesel, remove the fuel line from the pump and slip a 5 foot piece of 5/16 fuel line onto the pump and into the 5 gallon jug. Bleed the system. Start it up and check readings.



Dave

Dave,

I would like to thank you once more for this suggestion. It has served me well. The lift pump pressures did not change so it is not a plugged screen problem. I also wish to thank the others who were kind enough to provide

helpful suggestions.



Bill Hogan

 

[DavidC]

Your welcome Bill,



Dave

 

[WestTN]

I'm still using the stock style pump and have 13 psi at idle and 12 psi at full throttle with the Smarty running on #7. What is the difference? I used the Vulcan relocator kit from Geno's. That got rid of every banjo fitting in the system. They really kill the pressure with so much restriction.