jordanandrewkay

ok well i had first thought my injectors were bad but now idk....i put a performance filter (removed stock routing) on her two days ago and as long as i have more than half a tank of gas she runs perfectly now (no more idle jumping or stalling while idling)if she sits at around a quarter of gas the differance is night and day. what could that mean?? fuel pump? i know these cars have probs at high heat conditions and i live in houston so that aint changin.lol. any help or opinions would be greatly appreciated.

b4ccamaro

It might be the rubber hose between the pump and the fuel line in the tank. If it is cracked you will lose pressure there.

jordanandrewkay

so a loss in pressure in the fuel system would make it do that?? because i think my filler neck has a leak. im not exactly sure of the construction of the filler neck for i have put off dropping the tank. but if i top the car off it leaks gas. so there is probably a loss of pressure there.

ASE doc

A leak in the filler neck wont cause a loss in fuel pressure but it isnt safe. The rubber hose from the pump to the hard line in the tank is probably cracked and bleeding pressure. When submerged, the pressure loss is slightly less. Thus its more noticable below a half tank. A marginal fuel pump can also cause this symptom. You will want to drop your tank. Repair the fill neck, its probably the grommet thats leaking, or replace the tank if unrepairable. Then remove the sending unit and replace the pump and the rubber line. Be sure to use fuel injection fuel hose (high pressure).

jordanandrewkay

ok thanks. im just gonna buy everything then do it all at once (hopefully repairable.) but another question is my gas guage is pretty weird. if i put like 3 gallons in my tank it will show like 3/4 tank from empty....i have a 12 gal. tank which i realize is not big but 3/4 tank seems kinda inflated. the only thing that throws me off is that if the guage IS off i can get it down to the yellow around empty and it still runs. so is it more accurate when it gets empty. ? now my question is....when i drop the tank is the guage censor in the tank? or on the sending unit? or located somewhere else in the car. (not much fuel experiance). also what part do i exactly test to see if the resistance is off??

ASE doc

Sending unit is in tank. Gauge sender and fuel pump are together on an assembly that installs in the top of the tank. Be careful removing and installing this unit that you dont damage the float arm or sending unit or pinch wires. Also the fuel sock can be tricky on these as the sending unit is long and the tank is odd shaped. Resistance of the sender is 90 ohms at full and zero ohms at empty. As the fuel gauge gets old it loses its dampening. This is evidenced by the fluctuation of the needle as you accelerate/decelerate or go up/down hills. I understand that this can be cured with the installation of a capacitor across the fuel gauge circuit but Im not sure what size cap. I will be doing this on my 87 IROC at some point. BTW, I believe that our 3rd gens have 16 gallon tanks.

ASE doc

Also, what do you mean by "removed stock routing"?

b4ccamaro

ASE thats great info! If i get to 1/4 tank i'm on fumes and always wondered if it was my sending unit or the gauge. Thanks for the info to check!

jordanandrewkay

uh...must have been thinkin about my honda lol....but i mean i went with an open element filter and removed the black plastic thing (air filter housing to throttle body.) cant think of an 'correct' name for that.....


also what would be the best way to relieve fuel pressure and pump excess fuel out of the tank??

ASE doc

Jordan, Im sorry for not keeping up with your thread. To relive fuel pressure, pull the fuel pump fuse. It should be in a black plastic case by itself on the inner fender close to the battery. Then start the motor and let it run til it dies.

As far as removing fuel from the tank, good luck. I made my own fuel evacuation system using an old carter fuel pump and a 20 gallon drum. There is a "fuel caddy" you can buy for big bucks, but aside from that I dont know of any easy way to empty a fuel tank.

You can try the old school way of syphoning with a hose. And hey, gas tastes sooo good. Ive done it many times and hated it. I ask customers to run as much fuel out as they can before having me drop a tank. Of course, when the pump goes its not like they have a choice. Good luck

jordanandrewkay

oh dont worry bout it to much.i feel like i have been neglicting the site lately lol. but yeah thats kind of what i figured....me and my dad have done that too many times lol. and good info on the fuse. never would have thought of that. thx for the info though.