Archived 1999 2500 needs help

[BajaBuilder]

Thanks for looking this over: I have replaced the injection pump, truck ran fine for awhile then it started running rough and i looked at the fuel pressure gauge and it was setting at zero psi. I had replaced the stock pump with a fass pump and it worked great for years. It will start up and show 14 psi but as soon as u drive it fuel pressure drops to zero. This same thing happens with the fass pump, the old lift pump and a brand new cummins pump. Ive lifted the bed and examined the sending unit and it looked in fine condition nothing in the filter. Problem exists with fuel cap on or off.

Any ideas or suggestions id be very grateful for them. Thanks and have a happy new year

 

[Missouri Mule]

If your tank is on the full side taking the fuel cap on or off isn't going to matter.
You can check to see if the tank vent iisn't blocked.
You mite want to check the over flow valve at vp44 it is supposed to be in the return fuel line. *I think if you took off the return line off at the vpp44 you uwould see it in the line.

 

[crabman]

Everything you need know about your VP44 & more.
https://www.bluechipdiesel.com/vp44diagnostichelp.html

 

[BajaBuilder]

hey Crabman, thank you for the information and the website. i read through it and will be giving him a call on monday. happy new years !

 

[JKinney]

I had a plastic seal from a fuel additive bottle fall off and ended up in my tank. The draw straw sucked it up like a cap. Dropped the tank and found it on the bottom.

 

[SnoKing]

Have you verified the fuel pressure with a shop gauge at the VP-44? SNOKING

 

[BajaBuilder]

ive verified the fuel pressure with a westec gauge with sending unit and also a liquid filled gauge; both from the middle position of the filter hosing. the same thing has happened with 3 different lift pumps.

 

[BajaBuilder]

i had thought about as well, something got put into the tank etc. but i have a locking gas gap and again nothing looks wrong with the stock sending unit. screen is in great shape and flows liquid no problem at all........

 

[BigPapa]

I'm not a VP expert so this is just a question.

Could the wrong woodruff key or the key installed backwards affect the timing enough to cause this issue?

 

[crabman]

After re-reading your post several times & making a list of the items that you have replaced: 3 different fuel pumps & injection pump with limited success. Please try this: Buy enough fuel supply line to run from the fuel pump to the injection pump. Supply filtered fuel to lift pump from another source other than your fuel tank. Getting all the air out of the line will take some time. This will exclude all of your current supply items.
I think that there is something that is blocking your fuel supply.
If your take a garden hose, put a valve & gauge of end of hose, open supply, you will read the supply pressure. If you close the supply valve almost all the way the gauge will read the same. Open valve & gauge will drop almost to zero, not enough supply volume. Close outlet and gauge will climb back up to supply pressure.
Pressure & volume are inversely proportioned.

 

[BajaBuilder]

after installing the new injection pump, something that the code sender specified was needed, the truck ran well for 6 weeks 2 months or more. so im guessing the woodruff key was installed correctly.

 

[BajaBuilder]

After re-reading your post several times & making a list of the items that you have replaced: 3 different fuel pumps & injection pump with limited success. Please try this: Buy enough fuel supply line to run from the fuel pump to the injection pump. Supply filtered fuel to lift pump from another source other than your fuel tank. Getting all the air out of the line will take some time. This will exclude all of your current supply items.
I think that there is something that is blocking your fuel supply.
If your take a garden hose, put a valve & gauge of end of hose, open supply, you will read the supply pressure. If you close the supply valve almost all the way the gauge will read the same. Open valve & gauge will drop almost to zero, not enough supply volume. Close outlet and gauge will climb back up to supply pressure.
Pressure & volume are inversely proportioned.

hey crabman, thanks for taking the time to reread my post and what ive done. we actually did try what you suggested. run the truck from a 5 gallon can of diesel. truck ran well np. the issue is when the truck is moving it goes from 12 psi to eventually zero as i drive less than a mile. could a sending unit cause this problem? it seems to me that all the stock sending unit is is a screen and tube for fuel to go through to the lift pump. i dont see how this could "fail" given the fact the screen is completely clean. thanks for your time and replies

 

[JKinney]

If the fuel lines are rubber they could have delaminated internally and you have a line that is blocking off the fuel

 

[BajaBuilder]

thats another possibility that i will definitely look into. thanks !

 

[BajaBuilder]

WELL GUYS AFTER ALL THE SUGGESTIONS, POSTS READ, OTHER SITES VISITED LIKE BLUE CHIP DIESEL(ONE GUY SUGGESTED THAT INFO) AND IT WAS COMPLETE FOR SURE. GOOD GUY ON THE PHONE TO TALK TO AS WELL. THE SOLUTION CAME DOWN TO THIS: WITH TRUCK BED RAISED UP WE DECIDED TO INSTALL A NEW SENDING UNIT (even though there didnt appear to be anything wrong with the original one) the new sending unit had a pusher pump with it and after some new wiring, ( you dont have to buy all the harnesses etc.) and bypassing the stock lift pump. THE TRUCK RUNS GREAT !!! LIFETIME WARRANTY FROM ORIELLYS. 12+ psi at idle and never goes below 7-8 pounds under acceleration. so happy to have it running again. thanks and happy new year to all.