I thought I had been noticing something funny, but tonight I know I did. When my truck dropped from 2 into drive and the RPM dropped, it acted like it was starving for fuel. Let off the throttle and picked it right back up, and it was fine. IS that a lift pump symptom?

Also, I've had some issues with it not wanting to start. When I open my filler cap it sucks in a bunch of air. Is the tank vent plugged? How difficult is it to get to? I've noticed when it is over a half tank, parked nose-down at the curb, if I loosen the cap before I shut it off it starts better in the morning.

 

I'd change the filter before I replaced the lift pump.

It does sound like the tank is not venting properly, but it also sounds like you are getting air in the system somewhere.

With it being a '90, all the rubber lines are suspect, as well as the fuel heater gasket.

 

The heater has been leaking since I got it. Just haven't got to fixing it. I've been opening my cap, then shutting it off. It seems to be starting better since I started to remember to do that. I think I am going to pull it in the boss's shop, pull the bed and tank, and run new lines. If I can find another tank, maybe re-route the exhaust and put another tank in, too.

 

I would think you could loosen your fuel cap on a nice day to see if the tank vent is the problem. The gasket for your fuel heater is cheap somewhere around $2.00 if memory serves me. Sort of a pain in the rear to change though. Good luck Mike

 

I loosened my cap slightly yesterday morning and it started a lot better. Of course I messed with it after I got to work. But I think a lot of it is the vent being plugged.

Now to plan my attack on repairs. I'm aiming to visit back weast at the end of February. Do I get the gasser fixed while driving the Cummins, and take it, or fix the gasser and hope I can get the Cummins fixed to take it? Not sure, but I need to drive one while fixing the other. ARG!!!

 

So is it bad when you open your tank filler cap and you can hear it hiss with air? mine does that plenty and sometimes it drops rpm when i put it in gear also.

 

It means the tank isn't venting and the lift pump has to pull the fuel up against a vacuum, too.

 

so do i need a new filler cap? wonder if mine is just old and doesn't vent anymore.

 

hmm, mine does this as well sometimes.

 

I think it vents through the top of the sending unit in the tank, not the cap, a cheap/easy fix would be to buy one of those diesel venting caps the old chevy's require.