Fuel starving 84 GTI

[BlueStreak]

I'm having some mysterious fuel problems with my ITB car, a 1984 Rabbit GTI. Long flat right hand corners, with a quarter tank of gas, no problem. Long flat right hand corners with a half tank of gas, big fuel starve problem.

Car is still using the stock tank, with an inline pump mounted at the tank. This problem didn't show up at MidOhio, but it sure did at Memphis, in turn 1 and turn 7.

Also, possibly related, car is hard to start when the engine is hot.

Any ideas?

Thanks
Eddie

[Dave Zaslow]

Eddie,

Starving on right turns is classic Rabbit behavior, but usually worse with less gas in the tank, not more. Many people have faced this issue. One of the first to diagnose this was Eric Steinel who was driven around Nelson Ledges while looking into the tank (!). The fuel pick-up is in a small well/surge box directly below the tank access plate. From there a rubber line takes fuel to the outlet that connects to the fuel pump. From the fuel pump you then go to an accumulator and finally to the filter and fuel distributor. The in-tank rubber hose gets pinpoint holes in it and sucks air rather than fuel from the surge box. To change the hose you basically have to invent tools or cut the tank open. One alternative is to buy/build an external surge tank as was done for the A2 cars. It is possible to take the whole A2 assembly and mount it in the spare tire well. The stock pump will then serve as the lift pump to the surge tank and that tanks pump will send fuel to the engine.

The hot start problem is most likely a bad check valve in the fuel pump (common) or the accumulator not holding pressure (also common). To check this you need to test for your lines holding fuel pressure.

While there are probably other causes of your problems, the issues listed above are the usual suspects.
Here is a link regarding surge tanks:

http://www.sdsefi.com/techsurge.htm

Somewhere out there is a Ford Bronco commercial site that sells a surge tank made from a NAPA fuel filter that looked interesting and cheap....

Have fun,

Dave Z

[Bill Miller]

Eddie,

Dave has outlined it pretty well. This is a well known problem among those of us that race/have raced these cars. IIRC, it's actually documented in Greg Raven's book "Watercooled VW Performance Handbook".

Unfortunately, new stock tanks are not an option. I've heard stories of people having the stock tanks cut open and fixed, but I don't have any first-hand experience w/ it. Supposedly you can get it done at a good radiator shop. The external surge tank is usually the best solution. As Dave mentioned, you can get one off a Golf II, but you can also get one from a Fox.

Good luck!

[JohnRW]

I've seen old propane torch bottles (Bernzomatic, etc.) used as surge tanks. Won't win any 'bling' awards, but they're the right size and shape...and FREE !!! (once you're done with fixing the plumbing in Aunt Martha's house). Just one of many reasons why racers should own...and know how to use...a MIG welder.

[BlueStreak]

Thanks for the suggestions! I really appreciate everyone's input.

Eddie

[racer_tim]

Summit also sells a surge tank, that I had modified to utilize a fuel cell when I converted from IT to Production.

Summit P/N SUM-300101 and had the other fittings done @ my local race shop.

Here is what I did.

http://linerud.myvnc.com/racing/2002/

bottom 2 pics are of the surge tank, top photo's are of the well cell and cover.

Won't win any "bling" awards, but it works.

Configuration of the 3 lines at the top:

1 input from fuel cell via facet fuel pump
1 input from FI return system
1 output back to cell

1 outlet at the bottom goes to the stock fuel pump

I can hear the facet put start to suck air (ticking) when I get low on fuel, but since there is still a quart of fuel in the surge tank, I don't get the starvation that I got before.

[Dave Zaslow]

http://bcbroncos.com/store/product_info.ph...products_id=119 (http://bcbroncos.com/store/product_info.php?cPath=27_51_108&products_id=119)

[Bill Miller]

That's pretty novel Dave, I'll give you that, but it looks like you could probably make it for about half of what they're selling it for.

[msogren]

The fuel accumulater is most likekly the problem if you have hard hot starts and lose fuel pressure on right turns. You can also connect two accumulaters together to extend the fuel draw. Just check pressure hold for ten minutes , like the book says.
MM