voodoosporko

1985 GSL, i bought it a couple weeks ago. I've replaced the fuel filter, plugs, changed oil, cleaned the carb...took it to the shop and had them fix a solenoid valve, which was resulting in a large vacuum leak...I still get terrible gas mileage though, i am getting around 11mpg, the car runs great other than that, does anyone know what might be causing this? should i replace the fuel pump? if so, what model pump should i buy?

monad

I have the same problem with my 84 gsL It got so bad that I had to park it.

FDreaming

keep your foot out of it for two seconds.

Forcus

If it runs great otherwise, check for fuel leaks or fuel vaporizing.

LongDuck

Put cardboard under your car overnight after you've filled it all the way up and see if it's leaking out.

Fuel tanks will develop leaks quickly in areas that have snow/ice and/or salt. A pinhole may have developed in your tank, or under your tank straps, which is slowly leaking fuel out and it's evaporating into the passing airstream. This may show as no obvious leaks around the car, but the cardboard should trap the lubricants and colorants in the gasoline and help you to find a slow drip. May need to leave it parked like that for several days to see if it's a VERY slow leak.

Also, when you perform this test, let the car run for a few minutes with the cardboard under it so that if it's a leaky fuel pump or fuel filter, you'll know right away.

Get it fixed. I'm getting about 20mph highway, 18 city with my SE, and that's with mods. HTH,

voodoosporko

Tried what you said long duck...there doesnt seem to be anything leaking from the filter/tank/pump area..maybe its got something to do with my carb? i dont know jack about carbs..

Also..my car ALWAYS has to be choked and sit for 4-5 minutes before it will idle, is this normal? even when its hot outside it does this..

I also am getting around 12mpgs now driving very conservatively..

LongDuck

Thinking back to my 80LS days (12a carb), I had a problem with the float bowls overfilling and dumping raw fuel down the intake barrels (primary and secondary) because the needle valves and seats were worn. When this happens, the fuel pump causes enough pressure that it overpowers the seats and the fuel is constantly pouring into the bowls until they fill up. Once full, they overflow and the fuel dumps over straight into the carb throat, resulting in an overly rich mixture and difficulty maintaining smooth idle. This can also be caused by collapse of the internal metal 'wall' that restricts fuel pressure coming out of your pump. When this fails, fuel pressure goes up considerably, and the carb gets too much fuel - same symptoms.

Some things that you can do to remedy this situation;

1) Get a good quality fuel pressure regulator (FPR)- install this on the feed line going to your carb. A pressure gauge would help to identify the problem, but is an expense that you may not need. The FPR will restrict total fuel flow, so set it at 3psi and see if the problem still persists - if so, try 2psi and see what happens. The lower the pressure, the higher the likelihood that you're going to lean out at high rpm which can cause additional (and more expensive) problems down the road. This is truly only a temporary work around.

2) Carb rebuild to include new needle valves and seats - this will likely fix the fuel overflow problem, but all that work could end up not fixing it if your pump pressure is too high, so see #1, above.

3) Borrow a clogged fuel filter from one of the guys on this board that changed theirs recently - the more clogged up it is, the better. (I'm just kidding on this response...)

Poor fuel mileage is normally caused by an improperly tuned carb or EFI system if not an outright leak that you're not seeing. If you don't see any leaks anywhere, then it's definitely going through the engine in one way or another. If it's overfilling the float bowls, they are designed to dump into the carb throats to prevent spillage and a potential fire risk (carb is right above the exhaust system, recall...). Good luck, and report back.

As a point of comparison, I have intake and exhaust mods on my EFI car, and I'm getting 17.5-17.9 mpg very consistently for mixed highway/city driving. This is outstanding, since the car was originally quoted by Mazda at 16/20, city/highway. HTH,