I've got on my hands a 1990 Camaro Iroc-z 5.7 TPI.

at first I thought the fuel gauge was broken when i ran out of gas at 1/2 full level. when I went to fill it up, it filled 8 gallons then clicked to stop filling... I thought it was weird so I kept pumping, and a little gas leaked out the top of the fuel inlet. This has happened twice now, and I even had the fuel pump and filter replaced recently (A different matter ,they were faulty). Its not a matter of those because this happened both before and after the replacement.

Can anybody tell me why it won't use half of the gas in the tank, and how much it would cost to fix it?

Thanks alot, I appreciate it.

-Jake

 

I'd say you have a problem with the in-tank pickup... its probably broken off somehow, and no longer reaches the bottom. At least, thats my most logical conclusion.

 

The fuel pump is in the tank. the tank may be dented.

 

Are you sure you ran out of gas and don't have another problem?

 

1) The tank did not appear dented but I'll take that into consideration.
2) I am definately not out of gas. It's a 15.5 gallon tank, the gas gauge said half when I "ran out" of gas. Upon filling it up at teh station, the pump stopped at about 7 gallons. I kept going thinking it was a problem with the pump and then gas leaked out the inlet. Definately there is still half of the gas in the tank left.

 

you would have to crush the tank to make it hold 1/2 the gas. If it was crushed, it would be obvious.

 

Well it may be the fuel pickup then. but curiously it only goes at almost exactly half.

 

Here is an idea: What if the tank is not venting properly and builds up a vacuum such that the fuel can no longer be delivered at the proper pressure to the engine. It would then 'appear' that the fuel tank had been run dry when in actuality the fuel simply is not being 'delivered' properly.

One thing you could try is removing the gas cap when the car acts like it is out of gas. This would allow air into the fuel tank thus removing any vacuum. If you could start and run the car without a problem then it would indicate that excessive vacuum is building up inside the tank.

What a puzzle !!

It also seems to me that the short rubber hose that connects the fuel pump to the hard fuel line inside the tank might be about half way down the height of the fuel tank. Maybe that short hose is developing a problem (like a crack). The pressure to the engine might be just adequate to run the engine when the fuel is above that hose. When the fuel level drops down to the short hose the fuel pressure might be affected enough that the pressure becomes inadequate.

Are you monitoring your fuel pressure? If so, what are your readings?

 

Was the pump and pickup replaced properly by dropping the tank and carefully disconnecting and pulling out the assembly?

or is there a hole in your floor that the assembly got yanked through so that the pickup tube is bent as to not allow the pump to reach all the down to the bottom of the tank?

 

It may have to do with the "vaccum" thing. I remember the other day when I was "out of gas", when I returned from a gas station with the gas, the tank made a "hiss" noise of venting out when i removed the cap. It also happened later at another gas station. maybe I have over-tightened the gas cap when I filled it?

 

Considering that this was done before the new pump was installed, likely not.

 

The gas tank vents by hose to a canister behind the left headlight. sounds like something stopped up.

 

I've seen this little canister with hoses. the hoses are old looking and cracked... I'll look at it again tomorrow.

 

What? I just don't understand that reply at all.

 

Sorry, worded badly. I meant to say that the problem existed before the work with the fuel pump and filter was done.

 

Got it

OK, I'll bet then the pick up tube that the pump is attached to was already bent and still is. I bought 3 parts cars while I was putting my '89 back on the road and 2 of the parts cars had screwed up pick up tubes. In your cars case it's really the only thing that makes sense to me.

The other idea about the vent is easy to test so check that out first but I bet something is wrong with the tubes

 

How would I go about checking and possibly replacing the pickup tube?

I'm not really much of a mechanic but I'm willing to learn.

 

Jake did you have a dealership replace your fuel pump? I would expect that a dealership would have been able to recognize a problem with the fuel pickup tube when the pump was replaced.

Do you have an access panel cut in your car that allows access to the fuel pump so that you would not have to drop the fuel tank?

 

No, an auto garage did it for me, one of my friends works there, getting a little experience before going to a trade school to be a mechanic.

I dont know if I have this access panel. where would I find this?

 

There is a 'hump' or 'shelf' located right behind the rear seat. The center of the horizontal area is the area where an access panel could be cut. It would be under the rug. You could probably feel (through the rug) any cover that might have been installed if an access hole was cut then covered. You could search this forum or the TBI forum, etc. for 'access hatch' or 'fuel access hatch' or similar key words. There are pictures in some of those threads that will show you exactly what an access hole would look like so you can determine where it is located. I will nose around and post the thread I think would be helpful.

Your friend most likely dropped the fuel tank to get access to the fuel pump. I assume if the fuel pump was replaced then the small (two inch) rubber hose that connects the fuel pump to the hard line that exists the fuel tank was probably replaced so there might be no reason to suspect that as a possible problem. The hose needs a clamp on the upper and on the lower portion to hold it in place. You should find out from your friend if that coupler hose and clamps were replaced and also find out if he/she had any problems removing or re-inserting the pump assembly. Did they need to bend any hard lines?

Here is a thread: See the picture in Post #1 for a picture of the fuel sending unit and what it looks like through an access panel.

https://www.thirdgen.org/forums/tpi/...l+hatch+access

 

Thanks for the info and link. I'll take a look at it later.