fuel pressure question

Project 77 · Apr 3, 2004

I have a question for you guys...My cobra has the newer 86 roller motor in it, so it has an electric fuel pump. Now this electric pump is one like i have never seen before, all the ones I have seen are located under the rear bumper area, like the Holley red and blue pumps. This one is small and sort of square shaped, says Purolator on it, and it's mounted under the hood, on the drivers side fender. When i get in the car I have to throw a switch for the fuel pump before i start the car, well when i do the car fires up and runs real nice for like 10 seconds, then it loads up and wants to shut off. tonight I fired it up, and when it started to load up and miss I threw the fuel pump switch off, and after about 5 seconds the miss and loading up went away and it ran fine for a few seconds before it shut off. there's maybe 12-18 inches of fuel line between the pump and where it comes into my carb. Could I be putting too much fuel pressure into the carb? Anyone think I could fix this with a fuel pressure regulator? I was supposed to buy a motor but if this fixes my problem I could save alot of money. Thanks guys!

Power Surge · Apr 3, 2004

Put a fuel pressure gauge between the pump and the carb, and see where you are at. You shouldn't see more than 7 or 8 psi of fuel pressure. Any more and you'll unseat the float valves and flood the motor. You might need to put a regulator inline after the pump. Some electric pumps are self regulated, but definitely check the fuel pressure anyway.

Blue Thunder · Apr 4, 2004

You should be sure your primary and secondary float bowl levels are set correctly. If you have one or both set too high, fuel will flow up and through the vents at the top, then dump into the intake manifold.

If both float levels are correct, or the levels are too high and are unresponsive to adjustment:
Like CIIL said, 7.5 psi is the most a carb will deal with.
Many performance pumps are factory set at 10+psi, and are intended to run with an inline fuel regulator.
Install a regulator in the line just before the carb, and be sure to also install a fuel pressure gauge. If you're running anything close to a stock 302, a fuel pressure of 5psi should be sufficient.

LedZ 5.0 · Apr 4, 2004

Sounds like one of the small aftermarket pumps you can buy at Auto zone or Advance. Like CobraIILover said, check your fuel pressure to get a reading. If you get a good pump pressure reading than like Blue Thunder said, set your float levels with the motor warmed up and choke open. Be careful when setting the float levels fuel will run out of the top adjusters. Stuff a rag under the bowl area to catch any fuel. Just move the adjustment screw a little at a time until the fuel just starts to seep out the sight plug area on level ground. That's where the float level is parallel with the bowl. Also set your idle mixture screws to get the smoothest idle. You can start with 3/4 turn out from the lowest setting. The most you should have to turn the mixture screw out should be about 1 turn only for any Holley 4 bbl. You'll have to experiment. It's not that complicated and Holley's are very easy to tune for the street. My double pump runs best at 3/4 turn of the mixture screws. Hope this helps some.

zwhitr · Apr 4, 2004

Blue Thunder said:
You should be sure your primary and secondary float bowl levels are set correctly. If you have one or both set too high, fuel will flow up and through the vents at the top, then dump into the intake manifold.

If both float levels are correct, or the levels are too high and are unresponsive to adjustment:
Like CIIL said, 7.5 psi is the most a carb will deal with.
Many performance pumps are factory set at 10+psi, and are intended to run with an inline fuel regulator.
Install a regulator in the line just before the carb, and be sure to also install a fuel pressure gauge. If you're running anything close to a stock 302, a fuel pressure of 5psi should be sufficient.

Before quoting pressures, the question we must ask is. Is it EFI -- he said new roller block

Blue Thunder · Apr 5, 2004

zwhitr said:
Before quoting pressures, the question we must ask is. Is it EFI -- he said new roller block

"there's maybe 12-18 inches of fuel line between the pump and where it comes into my carb. Could I be putting too much fuel pressure into the carb"

Unless he's confused and misindentifying an 86 CFI unit, it's a carb.

LedZ 5.0 · Apr 5, 2004

Correct, It is carbed. I saw the car. Real sharp too

zwhitr · Apr 8, 2004

Blue Thunder said:
"there's maybe 12-18 inches of fuel line between the pump and where it comes into my carb. Could I be putting too much fuel pressure into the carb"

Unless he's confused and misindentifying an 86 CFI unit, it's a carb.

Whoops Sorry blue it was late --plus I the red and blue holley units aren't for EFI either.

fuel pressure question

Project 77

Power Surge

Blue Thunder

LedZ 5.0

now you have my pea brain going in circles

zwhitr

Blue Thunder

LedZ 5.0

now you have my pea brain going in circles

zwhitr

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