Fuel Pumps: Mechanical vs. Electrical

[5hundo]

Hey people!

I'm sort-of new but I just posted some pictures of my 67 Le Mans over on the intro page.

I had a chance to do some work on my cooling system that I had been having trouble with. I've got that working okay now. I think if I change out those decorative radiator hoses to regular ones, it should work fine.

Today though, I managed to get it on the road for about 15 seconds. The car idles great, and I can rev it up when it's sitting in park but as soon as I stomp on the gas to drive the engine stutters and spits and sometimes dies, leading me to believe that my fuel delivery isn't what it should be.

The guy had the car before me put an electric fuel pump on it but I've been hearing a lot of people saying that I should go back to a mechanical pump.

I've got a 750 Holley and an edelbrock torquer on a 455. What do you people think? Electrical or Mechanical?

...and if I go back to Mechanical, should I use a high volume pump?

Thanks everyone!!!

[NOT A TA]

Sounds like you've got other issues to take care of before figuring out what kind of fuel pump you would be best suited with. I'm no engine guru (wish I was) but it sounds like you've got timing or carb probs if it misbehaves under load.

If there's an electric pump on the car now is there a regulator and a pressure gauge? If so how many psi is the regulator set for?

[Roadrage David]

could be a ignition problem!!!!! .

[5hundo]

The engine that's in there now was just rebuilt, so I think that both of you are probably correct, there are bound to be a few more problems. I really do think, though, that I have a fuel delivery problem also...

The pump just sounds "weak" and there is a fuel pressure gauge on the rail that never shows a reading. I used to think that the gauge was broken but I'm starting to think now that it's just not getting enough pressure to give a reading.

The engine idles perfectly and I can rev it up when the car is sitting and the engine sounds great. It's just when I take it on the road, it craps out. I would think that if I had ignition or timing problems, that would mess up the way the engine idles or revs up while parked, right?

[Josh]

Difference between sitting and driving is that vacume will not change until the car is under load (driving). Vacume will effect carb fuel delivery and timing at the distributor.
Reset the timing and make sure all the plug wires are on the right plugs. After that I would make sure your idle adjustment screw was adjusted to just begin to show the idle transfer slot as seen under the carb then sset the fuel mixture 2 turns out and tweak from there.

[5hundo]

Difference between sitting and driving is that vacume will not change until the car is under load (driving). Vacume will effect carb fuel delivery and timing at the distributor.
Reset the timing and make sure all the plug wires are on the right plugs. After that I would make sure your idle adjustment screw was adjusted to just begin to show the idle transfer slot as seen under the carb then sset the fuel mixture 2 turns out and tweak from there.

Okay, I'll reset the timing. The engine runs hot too, so that very well could be part of the problem.

I don't know much about the carb either. It might need a rebuild but then again, if I'm going to go through all that, I think I might just get an edelbrock and throw it on there.

...whatever is wrong, it looks like I've got lots more work in my future.

[Josh]

A Holley 750 is a good, easily adjustable carb. Start witht the timing and see what happens...

[shizzy]

you might want to try plumbing in a fuel pressure gauge you can read while driving the car. I had a Similar problem a few years back in my Oldsmobile. it would read 7lbs of fuel pressure sitting in the driveway at idle or reving. I temporarily plumbed in a fuel pressure gauge and duct taped it to my windshield and went for a drive. Sure enough within a few seconds of me having my foot on the floor the pressure would drop to 1lb. just enough to keep the engine from stalling, but low enough to cause it to sputter and kick. Vac secondaries wont open with the car in park/neutral. If I let it Idle for a minute or two it would come back up to 7lbs and the car would drive fine as long as I didnt try to put my foot in it. Apparently the pump (mechanical) wasnt pumping enough.

[Chad-1stGen]

If it stumbles the moment you hit the gas under load I'm doubtful about the fuel pump. The fuel in the carb's float bowls should give you a few moments before low fuel volume would trigger issues.

[6'9"Witha69]

If it stumbles the moment you hit the gas under load I'm doubtful about the fuel pump. The fuel in the carb's float bowls should give you a few moments before low fuel volume would trigger issues.

Correct! I would look into timing, accelerator pump cam and adjustment and power valve.

[shizzy]

it sounds like you purchased the car with all its current parts already on it? was the car running when you got it? is this the first time out with the car?

[5hundo]

it sounds like you purchased the car with all its current parts already on it? was the car running when you got it? is this the first time out with the car?

When the car was first bought, the motor had a spun bearing. Most of the compnents on this car came with it. I've only been able to get the car on the road twice and it's done this both times. I don't know how long the carb sat around with bad gas in it, and I don't even know how old the carb is. It might need a rebuild...

I really don't think it's the timing but I'm going to check it anyway because that's really easy to rule out. Besides, if the engine is running hot, that could also be a symptom of bad timing (and it runs hot).

[shizzy]

in that case I thin the carb could use a going through.

[redhead]

ditto that, holley gaskets don't like to sit around too long.
da.

[pitts64]

I prefer a Carter mechanical pump.