Engine/Transmission (1998.5 - 2002) Something is dying - FP gauge or lift pump?

[VicR]

I did a search but couldn't find anything quite like this: Last night coming home from camping I was crusing down the interstate and glanced at the FP and saw it was at zero. I was only 10 miles from the house so I figured I would just take it easy home. Got off at my exit and hit a bump and my FP was back to the same place its been for the last 40k miles since I installed the gauge.



Figured it was a loose wire and this was a good time to move the sender off of the fuel filter head where its been for 40k miles, so I got my hose and moved it to the firewall and cleaned up all of the connections. So then I started it and it took 45 seconds for the FP guage to read, but when it did it was right back to my normal reading. This delay really has me stumped.



Its the original lift pump on the truck, but I picked up a spare campaign pump last fall that I carry as a spare. I'm going on a 2000 mile trip next month.



So should I take a chance on the new pump or just order a new sender? I hate to replace a good pump and still have the problem, and I've read a lot of stories about new pumps that have troubles too. On the other hand, fixing it before it breaks sounds better then doing it on the side of the road!



-Vic

 

[GCULP]

does it always take a while to read since you moved it or just the first time? You say you used a hose, the hose may be bleeding off pressure and it just takes that long to build it back up for the sender to read it. have you checked it with a mechanical guage at the injection pump to compare?

 

[Bob Cochran]

I had mine go to zero before(it did not come back up to normal pressure though) and took out the fuel filter and bumped the starter to get the pump to run for a longer time. The LP was barely squirting fuel into the filter canister when looking inside. The LP was shoot and I am sure once I lost prime and got air into the filter canister there was not enough pressure to clear the air out with my little test!!! If you find the LP is bad I would strongly consider since you are replacing the LP to get and install the 1/2 relocation fuel kit from Vulcan. Might make the campaign pump last a little longer.

 

[VicR]

Started it up tonight and watched the guage fluctuate, so I'm pretty sure its the LP. New one is going on this weekend.



-Vic

 

[C4gan]

I went round and round with this same exact issue. replaced LP, Sending Unit over a 2 week period. kept having the same issues. I put a mechanical gauge on it and duct taped it to the windshield for a whole day of driving and FP never fluctuated or dropped below 11. 5psi. I would recomend that you do the same before you go throwing money at parts. . 100. 00 for a sending unit and 130. 00 for a LP... . I'd throw 65. 00 at a gauge and you will know for sure what the issue is... Just my 2cnts

 

[jp8819]

mine had same symptons when going out. Would run normal for a while then drop to 5 the come back normal then to 5 hit a bump come back to normal. Then it just stayed at 5 or below and I knew my problem so I ordered the airdog and been at 15 steady ever since.

 

[Bob Cochran]

You will normally find when the guage pressure is jumping around that while driving if you accelerate a little it will steady out but later will start again. By playing with the go pedal you can get it to stop until it goes out completely(dreaded zero). Then you have to change right away even on the side of the road. Of course I have a spare campaign pump and the Vulcan kit with pump back by tank on the frame so a fast and fairly easy change if not at night(mine is starting to jump around AGAIN)!!! Still trying to make up my mind what kind of pump I should go with next Waldpro or FASS.