1st Gen fuel starvation

[jake7140]

For the first time in four years I started having fuel starvation under hard braking, right-handers only
- full to 3/4 tank of gas
- I did notice that the tank was becoming pressurized (when loosening the gas cap, big outgoing whooosh)
- when filling up at the pump, loooots of gurgling gas in the tank for minutes on end,
- I removed the charcoal canister (yes it was still on!), the tank pressurization went away, but not the starvation.
I'll start with a new fuel filter, but am I on the right track? Plugged vent/fuel line? Bad fuel pump? Other possibilities?

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Steve
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[Mike Guenther]

It could be your float level. If the level is too high you will have overspill and sputter coming out of the corner. If the fuel pressure is too high the float will not properly shut off the flow and the bowl will overflow and you will get sputter. This usually happens after braking. A bad spring in the jet or a dirty ball if you are using gross jets will also effect the shut off ability of the floats and allow overspill when the jets should be closed. If the jets don't close properly due to dirt or overpressure the result is over filling the float bowl leading to overspill and sputtering when you get back onto the throttle. I've been fighting this and a similar phantom problem for years. Mine seems to be worse on hot afternoons.

[rx7chris]

When i was running i had the same problem in turns 17 and 1 at sebring on the 12hr course. turned out i had way too much fuel pressure. I set it to 2-2.5 and the problem went away. Later i developed the same problem but it was happening all over the course. Turns out my header had split on the top of the second tube allowing exhaust gas to heat up the carb and cause vapor lock.

Hope this helped,

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Chris
PowerTrip Racing
http://www.geocities.com/ptripracing/

[jake7140]

Thanks for the thoughts guys. Seems like fuel pressure / float could be an issue. I'll poke around in that direction. I am running a stock pump (i think, if it ain't broke don't fix) with no press regulator. It was a pretty hot day too though.

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Steve
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[Dick Elliott]

Why are you running a stock pump. They can't hardly put out enough fuel for a stock "REX" on the street. Put something better like a Carter plus a regulator.21/2 LBS is plenty pressure. Wrap the header with header wrap to lower the under hood heat. Then look for your problem after knowing its not the fuel supply. DICK

[bcarter]

Had the same problem couple years ago. I run the oem Carter pump, so I'm getting about 2 - 2.5lbs pressure.

The pressurization of the tank was my problem. Terrible stumbling, mostly in right handers. I tried drilling a tiny hole in the gas cap. Stopped the pressurization, but nearly killed me with the fumes. There are three lines from the tank to the front. One fuel to the carb, one fuel back to the tank, and one for air. I have that one going up into the aircleaner, inside the filter, so the fumes go into the carb, and keep the tank from pressurizing. Never had a problem since.

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G. Brooke Carter
Wheat Buckley Racing
# 10 Challenge Car
2002 Class Champion
Calgary, Alberta

[rlekun]

i chased this ghost for years. Final resolution was lower fuel pressure to about 2. Checked on the dyno and got a beautiful Air/fuel ratio curve.

[jake7140]

Thanks all. I removed the char canister which relieved the pressurization issue, but still had the problem. I have replaced the fuel filter and have a dentist mirror handy to check float levels. I also have a carb rebuild kit, carb cleaner and grosse jets, but no more time, so we'll see how it goes this weekend I guess.

A Carter fuel pump and press regulator has been on my list for a couple years now, but my $3.95 budget hasn't allowed, and besides, I didn't have any probs. Maybe I do now, we'll see. Happy rotoring to all!

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Steve
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[Jim Susko]

Rex, I wouldn't wrap the header. That and a slightly lean mixture can brings the temps in the pipes up to over 2000 degrees. The header will literally melt and its life will be considerably reduced. Also it changes the exhaust density and consequently the torque drops off.

I'd wrap the fuel line instead. Having said that, I don't have mine wrapped and I have no problems with fuel. The comments on fuel pressure and float level are correct. I'd also be careful to retain the recirculating system to prevent vaporization in the lines. Don't dead head the system. With the carter pump and a recirculating system you'll be fine.

Jim Susko

[jake7140]

Originally posted by Jim Susko:
.... Don't dead head the system. With the carter pump and a recirculating system you'll be fine.

Jim Susko

Jim,
Please explain "dead head the system"? By the recirculating system, I'm assuming you're talking about the stock fuel return line which should bleed off excess fuel from the carb back to the tank? So does "dead head the system" mean to run only the main fuel delivery and capping off the return line?

I have removed the charcoal canister, vented the canister 'in' line from the tank to a catch tank, and plugged the 'out' line that goes into the rat's nest. That combined with changing the fuel filter seems to have cured my probs, ran fine at M-O.

Thanks all again. But I think I still might "have a problem" that "requires" a new carter and press regulator. ;-)


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Steve
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