Runs like crap when low on gas

[streetlamp]

Well my car is a 85 Omni GLH, and has the following mods which I know of boost controller and straight 3" exhaust. I say that I know of because I bought it like this from a guy who didnt know anything about it and it has been passed around a lot. For a while I hardly drove the car so I didnt notice it but now that its my daily driver I have noticed that when it starts to fall below a quarter of a tank it runs like crap. Power loss especially from a stop, lots of backfiring and a slight bucking especially when coming into boost and occasionally idling high. I have to rev it pretty high while gently letting out the clutch to keep it from stalling. All of the problems are immediately gone if you put gas in her. Also I dont know if its related or not but the car violently bucks under WOT everytime and sometimes randomly just when accelerating hard like to pull out in traffic. The boost is set to around 14-16psi. Not sure because I only drive it to work, no reason to drive it hard and it would never make it that high anyway without bucking me or itself apart. The bucking usually happens around 5 psi. Car drives fine besides this.

[88_pacifica]

change the fuel filter and the tank is probably full of 20 yrs of crap too. Might have to drop it and clean the thing out really well too. Also you may have a lot of water and other junk in their too.

[iTurbo]

I've had this happen on my Shelby Lancer. The fuel pump pickup 'sock' wasn't snapped onto the end of the pump and when the fuel would run low, the pump would suck in air bypassing the sock filter. The sock sits flat on the bottom of the tank but the pump sits at an angle.

[streetlamp]

Thanks guys, I will order a new fuel filter now and check out that sock

[t3rse]

also if the baffle was removed from the tank you will have problems...

[streetlamp]

Sometimes when starting the car it takes 3-4 turns of the key and pumping the pedal to get it to start like its not getting enough fuel to start. Could this be related to the sock possibly coming loose? I will pull it out this weekend when I have a chance so I guess I shall find out.

[Clay]

that would typically be the check valve in the fuel pump going bad, causing the system to loose its prime when it sits not running.

[t3rse]

^yup, and if it cuts out on decel you know its the valve for sure...

[mw6886]

Hmmmm.. sounds to me like the old "2 pump cavatation" issue. Mopar had a TSB about it, and replaced the 2 pump system with a new hanger and single pump.