Railguy

I was going to a show about 50 mile car runs fine.I'm just about there when going up a hill it starts acting like it's running out of fuel not just missing but almost shutting off.Like if I didn't have it up to speed it would have shut off.Then it straightened out.When I got to the show I knocked on the tank and it sounded empty.I thought that must be what it is.I know the gage is off.I filled it up the first station I saw.It took over 15 gal,I didn't think it held that much.So I'm thinking that has to what it is.We took different route home which takes us over some mountains,well no sooner then we start up the mountain then it started doing it again.so we take the truck route which goes around the steep part of the moutain and sure enough as soon as we start down the moutain it straightened out I even steped on it a few times and it ran fine.But every time we hit a hill it sarted to miss if it was a small hill it would do it till we where over the hill but then it was fine.No backfireing so it,s no electrical right?When it was missing if i put it to the floor it just shut off.I.m going to check the boul floats first but I don't think thats what it is or it would do it on start outs.Power valve maybe?oh yeah it's a Holley.Please help.
railguy

MDchanic

I'm not familiar enough with Holleys to comment on the carb., but I'd check the fuel pump - if possible, the easiest way would be to put the car at the angle it was at on the hill (jack up the front pretty far), then crank the motor and see what the pump puts out.
If output is low, I'd check all rubber hoses between the pump and the tank for cracks, and all the steel lines for pinholes (may be easiest to put an air line on it and see if it holds pressure) - a way for air to bleed in on the suction side will cause this sort of problem even if the pump is good.

- Eric

Erinyes

Any chance the tank is rusty? I had symptoms like that, had to replace the filter, the fuel pump, rebuild the carb, and clean and seal the tank - not necessarily in that order...

MDchanic

Yes, that's actually a good one, too.

Rust or gunk in the tank that floats up against the pickup in a certain position.

- Eric

Railguy

I bought it new 5 or 6 years ago it's not rusty on the outside.
Good idea about jacking up the front end.I even have a hill i can park it on when it drys up a little.But about the air be drawn in through holes or leaks in the line that doesn't explain why it's just on hills wouldn't do it on take offs too?And wouldn't it leak fuel through those same holes when the engine was shut off?
Thanks railguy

MDchanic

No, and No.

A quick press of the gas pedal will use fuel that is in the float bowl, but will not immediately call for more.

A longer run uphill will deplete the float bowl, and require the fuel pump to put out more fuel in order to keep it full.

A small leak (or a number of them, such as through cracks in the hose) on the suction side will not allow fuel to leak out, or at least not to drip - it will often skin over with a thin film of fuel that you can see if you look for it.

A small leak like that can let in just enough air under suction that the pump will be able to pump a certain amount of fuel, but if it pulls harder, it will pull in disproportionately more air (air is easier to pull through the cracks than fuel is to pull from the tank, especially uphill), and output will decrease.

- Eric

oldcutlass

The float level is easy enough to check on most Holley carbs. A fuel pressure gauge with a long temporary hose can tell what your pressures are while your driving. I also would not rule out the rubber fuel lines at the tank.

Railguy

I started to adjust the float this morning,it's raining and it didn't take long for the fumes to strong in my garage .I took it at least a full turn and still no fuel out the sight hole.After I shut off the car I realized if there is a pressure problem it would take a while for the bowl to fill.There's a place for made on on my fuel for gauge.Just screw out a plug and screw in the gauge.I think that will be my next move.
railguy

rjohnson442

You can manually fill the bowls to prime them through the vent tubes on the top. I use a plastic small syringe to fill em. If you prime it slowly you can watch the float rise and stop. Now remember if you put to much down the vent it will pour out also, so don't set the float height that way but its a good start to being close.

Railguy

After chasing this fuel pressure problem around for half the summer.I think I finly got it.MDchanic you where the closest.First I replaced the pump which did't take long but work was really good this spring and summer so time was an issue.But after replacing it it still fluctuated.So I siffined the fuel out and started to take the tank out.Not knowing what to look for.Thats when I noticed that the rubber fuel lines that connect the tank to the stainless lines that run to the pump don't have any clamps on them.All of this is new tank,lines,hoses everything thats why I dismiss your idea about the hoses,and it's never done this before just recently.Well Not sure if this was the problem or not.I thought might as well go ahead and take the tank out.so I took the tank out and removed the pick up didn't see any thing wrong so I put it back togeather,thinking it has to be the lines not having any clamps on them. I started it up the pressure still bounced around.So I figured maybe it takes a while for the air to get out of the line,went for a ride came back, still same thing.Letter that night it hit me.The stainless fuel lines came in 2 peices .Were they put togeather with a hose?And did that hose have clamps?I got underneath it today and sure enough nope.Put clamps on and the presure is at about 4 lbs at a fast idle with a stock pump.Please don't any body tell me thats not right!
I guess the reason it didn't act up when take off from a light was because it had time to fill the bowl up while coasting to a stop and setting there a while.But when using fuel faster then calling for more.....thats when it started to miss.Plus when the power valve opened up I think it was pulling in air through an almost empty bowl.
railguy

MDchanic

HA! Leaks on the suction side can drive you nuts.

Glad you fixed it!!

- Eric

oldcutlass

x2.

Octania

Wow, NO clamps.

I hope you used the proper springy ring clamps.