Engine/Transmission (1998.5 - 2002) Fuel pressure problem 99 2500

[BajaBuilder]

Hey guys thanks for taking a look at this. Im hoping someone has solved this problem so here goes: Replaced the injection pump on dodge, have a fass direct replacement lift pump. Also have tried a brand new commins lift pump and pressure initially is 14 psi. With any throttle given pressure drops to 7-8 pounds and proceeds to drop to zero pounds pressure if its driven a mile or so. Liquid filled gauge is giving me accurate reading and it has done this with fass pump, original pump and new cummins pump. At some point the engine will start to run rough............i have checked the power side of the fuse and ran a new line from just under fuse when intermittent electrical issue was found. Ive checked the lines to the tank and lifted the bed and checked the sending unit from fuel tank. There did not appear anything wrong with the sending unit. Ive ran it without fuel cap and the same things happens.

At this point in time i literally have no idea what to check. It is not throwing any codes. 14 year+ fed x mechanic and i are completely stumped.

Your help would be greatly appreciated ive posted here before but have misplaced my info so had to start over. Thanks again and happy new years

 

[DavidC]

I had a similar problem as pressure would be fine until I drove a few hundred feet then a nose dive. The screen in the tank had a vaseline type coating on it which was slowing down fuel to the pickup. I wound up cutting that screen out and installed a in line screen from Fleetguard.

Dave

 

[gtwitch]

I think that I have a similar problem as my Fuel Pressure drops on cold days ( -10*F) to about 8 psi on WOT pulls but most of the time FP is OK in the 12 to 14 psi range, so come spring I will pull the truck box off and take the tank pickup/guage unit out and take the screen out and put a larger pickup tube (drawstraw kit) in. I hope that this is what I fiind when I get to the project "warmer weather". Dave , do you have a part number to get the Fleetguard inline screem??
gtwitch in wyoming

 

[BajaBuilder]

I had a similar problem as pressure would be fine until I drove a few hundred feet then a nose dive. The screen in the tank had a vaseline type coating on it which was slowing down fuel to the pickup. I wound up cutting that screen out and installed a in line screen from Fleetguard.

Dave

hey Dave thanks for the suggestion. we actually lifted up the bed and inspected the sending unit and could see no problem with the screen. something we can look at again i guess. the inline filter sounds like a good idea regardless. thanks.

any other suggestions are really appreciated. i literally have no direction to go for this solution. thanks guys

 

[DavidC]

I think that I have a similar problem as my Fuel Pressure drops on cold days ( -10*F) to about 8 psi on WOT pulls but most of the time FP is OK in the 12 to 14 psi range, so come spring I will pull the truck box off and take the tank pickup/guage unit out and take the screen out and put a larger pickup tube (drawstraw kit) in. I hope that this is what I fiind when I get to the project "warmer weather". Dave , do you have a part number to get the Fleetguard inline screem??
gtwitch in wyoming

Best 9 bucks I ever spent

https://www.genosgarage.com/product/ff5079/fuel-filters

Dave

 

[gtwitch]

I will get a couple of these, are these just a screen to get the large stuff? I have a NAPA screw on filter on a frame mount bracket in line after my frame mounted pump which is a Holley (noisey) and there is no question weather or not the pump is running! I think I will replace the Holley with an Airtex the next time I need to rebuild the Holley (rotor kit only $9.95) and it will be #3 rebuild in 120K so it is as good as the Carter but noisey. I had the stock Carter (1 origional and 2 NAPA/Carter replacements in 110K.

gtwitch in wyoming

 

[klcammie]

This may sound dumb, have you checked/changed filter? Also check line from pump to filter to vp for restrictions. Sounds like a clog in a line somewhere. Not quitw the same but I was having trouble with water to my house good pressure at start then drop to nothing. Found that the line between the filters was clogged to soda straw size.

 

[DavidC]

I will get a couple of these, are these just a screen to get the large stuff? I have a NAPA screw on filter on a frame mount bracket in line after my frame mounted pump which is a Holley (noisey) and there is no question weather or not the pump is running! I think I will replace the Holley with an Airtex the next time I need to rebuild the Holley (rotor kit only $9.95) and it will be #3 rebuild in 120K so it is as good as the Carter but noisey. I had the stock Carter (1 origional and 2 NAPA/Carter replacements in 110K.

gtwitch in wyoming

Yes on the screen. It is supposedly cleanable, probably air pressure and maybe a solvent if it is that bad. There is no real restriction to the suction side of the pump.

Dave

 

[Shelby Griggs]

I have one of these between the tank and the DDRP, well actually one I bought at NAPA. Recommended by FASS.

 

[JR]

It does sound like you've got a restriction on the suction side. If I remember correctly there are 2 screens on the modules without the in tank lift pump.
Is your fuel pressure gauge before or after your filter?

 

[BajaBuilder]

Initially i had the west tech gauge on the middle port of the filter so i believe that is after the fuel has been filtered? To double check the westec guage i hooked up my fluid filled gauge and ran the hose inside the cab through the window. Both gauges bought from geno's. Same results. Initially startup pressure is 14 psi. And in gear it drops to 7-8 then down the road a few hundred yards drops to zero.

Thanks for the replies and ideas guys ill be lifting the bed off tomorrow and taking the screen off the sending unit and installing an inline filter as one person suggested. Ill post results from that. Happy new years to all

 

[JR]

Does fuel pressure drop if the truck sits and idles? Are you still pulling power through the ECM? The circuit has proven to be somewhat unreliable over the years which is why most aftermarket lift pumps would prefer you to run their pumps off of the battery and only use the signal from the ECM as a trigger. The only other thing it could be aside from restriction on the suction side is if the pump isn't getting the proper voltage. I'd probably verify that before pulling the bed again just to be sure.

 

[BajaBuilder]

Thanks jr, ill run that info by my fed ex mechanic friend before pulling up the bed. Info much appreciated

 

[hcole]

Baja, do this. Run a hose from the inlet on your fuel pump to a 2-5 gallon can in the bed of your truck. This will tell you if you have a restriction on the suction side of pump. It will pump a lot of fuel back to your tank through the return line but it will tell you if you have a blockage in the suction side.

 

[SAndreasen]

Did we ever find the problem

 

[BajaBuilder]

well here is what got my dodge back on the road. even though we inspected the sending unit once ( clear screen, no apparent clogs etc) when we lifted the bed the second time we replaced the sending unit with a pusher pump model from Kragen/Orielly's (lifetime guarantee). the pump is small in the sending unit but it has a consistent 12 psi going down the freeway. under heavy throttle it will drop to 7-8 psi for a couple seconds then back up to 12psi. i still do not know what was wrong with the original sending unit. but am happy that the dodge is once again on the road.

thanks again to all who offered suggestions on the fix. hopefully this will help someone in the future.

 

[samsonite01]

I had the same problem. Lift pump would fire up just fine when starting (15psi). Soon as a little load on motor psi would drop erratically. Went through the fuel system replacing lines and pumps and still had problem.

Turns out the lift pump voltage (that runs directly through the ecm) was at fault.

To eleminate that being a possible problem you could wire the lift pump direct to a power source temporarily and drive the truck see what it dose.

 

[BajaBuilder]

thanks for that suggestion. we had done that earlier and eliminated the ecm from the equation. turns out it was the sending unit. pusher pump in sending unit solved the problem. thanks again

 

[samsonite01]

Glad shes running good for you!