Author Topic: Fuel Starvation: UPDATE (Read 1049 times)

Meyer65 · « **on:** July, 01, 2009, 07:19:46 PM »

Okay, here is the issue I am having.

When I really put my foot into the throttle (like getting onto the highway) I get serious fuel starvation, Violent stumbling, a sort of "grrrrr" that happens when there is not enough fuel. I am 99% sure that the issue is fuel-deliver related. Then what happens is I'll be on the hwy, and I can't put my foot in the throttle for a little while. But if I put it in neutral for a little (or just back of the peddle) I can regain power (it's like the carb is refilling with gas, which I can then use to get up to 6k rpm before the whole process repeats). If I drive normally, there does not seem to be any issue (i.e. light footed, shifting at 3-3,500 rpm)

The first thing I did was replace the fuel filter (the one right before my Holley Red electric pump, which is in my engine bay {which I know is not where it should be}), and spray some carb cleaner on and in the carb.

This did not fix the problem. So if I'm right and it is fuel delivery, that leaves the a)the fuel line, b)the electric fuel pump, or c)I suppose something with the carb.

Does my Edelbrock 650cfm carb also have a fuel inlet filter that needs to be replaced?

Where should I start with this job? How do I go about testing/eliminating all of the possible culprits I listed above?

I have had problems with the fuel pump in the past (i.e. it died once or twice) so I suspect it most. But I don't want to shell out $120 and not fix the problem, you know?

Also I should note that in my tenure with the car, the fuel line, sending unit, and gas tank have not been replaced. However, I think that the gas tank is fairly new. The carb, fuel line, and fuel pump are all about 7 years, 15k miles, give or take.

Starfury · « **Reply #1 on:** July, 01, 2009, 10:04:23 PM »

I'd check the float level first, and make sure the needle seats aren't obstructed. The carb doesn't have an inlet filter.

Next I'd pressure/volume check the fuel pump. Pressure check would obviously require a gauge, and a volume check would require filling a container to a specific volume and comparing the time to the Holley spec.

Why an electric fuel pump? Mechanical pumps work just fine for most carbureted setups.

silverblueBP · « **Reply #2 on:** July, 02, 2009, 04:10:21 AM »

Will it starve out if you are sitting still, just revving the engine? If so, shut it off as it starts to starve and then check the fuel bowls. As Tad said, then check volume/flow into a gallon jug.
Sounds like line blockage or pump dying. You could also clean out the lines by disconnecting at the tank and pump and use compressed air.

daveSanborn · « **Reply #3 on:** July, 02, 2009, 10:27:10 AM »

All good advice thus far....

If it were me... I'd re-locate the electric fuel pump to the rear of the car. Electric fuel pumps are designed to "push" fuel from the tank forward to the engine, not "pull" it. Is this your problem? I dunno, but I'd move the pump to where it operates most effectively before I started anywhere else.

Meyer65 · « **Reply #4 on:** July, 02, 2009, 11:27:14 AM »

I've given it a lot of thought and I think you're right about moving the pump dave. I did a lot of reading about the pump last night and I know believe that because the pump was so far from the tank and not being gravity fed, coupled with the fact I drive the car infrequently, that the pump just worked too hard over its life and sucked in too much air.

So I'll clean this one, move it to the back, and check the float level, but I'm betting I will end up replacing the pump.

First off, any idea on where to get a bracket to mount the pump (and where exactly should I mount it)

And B) how do I check the float level on my Edelbrock performer 650cfm? (I read the directions, which were way too vague for someone who has never disassembled a carburetor before)

silverblueBP · « **Reply #5 on:** July, 02, 2009, 11:38:15 AM »

Does the Edelbrock not have sight screws on the side of the bowls? I've never had one of those, always have used Holleys.
If it has the screws, remove them and you should have fuel just starting to dribble out.

Starfury · « **Reply #6 on:** July, 02, 2009, 12:27:41 PM »

Nope. Nothing under the fuel line to leak:P

It's easy enough to check float level with a couple drill bits. Hell, I do it by eye.

blue65coupe · « **Reply #7 on:** July, 02, 2009, 12:38:37 PM »

I'm having the same problem. I haven't been able to go after it for the past couple weeks (already replaced all the ignition stuff btw) but I was given another thing to check. Fuel lines...make sure none are collapsing. If you find your problem soon, let me know.

johnpro · « **Reply #8 on:** July, 03, 2009, 05:01:34 PM »

Quote from: daveSanborn on July, 02, 2009, 10:27:10 AM

All good advice thus far....

If it were me... I'd re-locate the electric fuel pump to the rear of the car. Electric fuel pumps are designed to "push" fuel from the tank forward to the engine, not "pull" it. Is this your problem? I dunno, but I'd move the pump to where it operates most effectively before I started anywhere else.

+1

Put everything where it's supposed to be, then start diagnosing the problem if you still have one. I have never attempted to run an electric pump in the engine bay, and the reason is that I've always been told it would cause the problems that you're experiencing.

johnpro · « **Reply #9 on:** July, 03, 2009, 05:11:36 PM »

Quote from: Meyer65 on July, 02, 2009, 11:27:14 AM

First off, any idea on where to get a bracket to mount the pump (and where exactly should I mount it)

And B) how do I check the float level on my Edelbrock performer 650cfm? (I read the directions, which were way too vague for someone who has never disassembled a carburetor before)

Just make an "L" bracket out of heavy metal. Drill 4 holes in it, 2 on each plane. Two should match the pump's mounting bracket, and the other 2, drill 2 holes to match in the trunk area, forward of the fuel tank, and bolt it there. That's the easiest way. This pic will show where mine is mounted on Scary (look past the tail pipe), although I don't have any good pics of the bracket or it's mounting.

To adjust the float bowls on an Edelbrock, you have to remove the air horn, similar to the Autolites. I doubt that is your problem. I've never had to adjust the float levels on any of the Edelbrocks I've had.

Meyer65 · « **Reply #10 on:** July, 05, 2009, 01:10:25 PM »

Thanks Johnpro and all others.

I have decided my course of action:
I will get a bracket and purchase a new fuel pump. When I have everything apart I will blow air through the fuel line to make sure it's clean, and I will then mount the new pump in the proper location.

From what I have read it is very bad to mount the fuel pump where I have it. Because it is not being gravity-fed, coupled with the infrequency of use, the pump has sucked a lot of air over the past 7 years, which is apparently very bad for the pump. What's funny is the issue started only going uphill, and now it has worsened to include the flats. What this says to me is that the pump, when it was just starting to go bad, was unable to pump enough fuel and overcome that much gravity. Now the pump has worsened. It also does not sound the same as when it was new.

Anyway, I'm optimistic this course of action is the easiest way to solve my problem, and prevent it from happening in the future.

I am also considering installing a fuel pressure gauge in the engine bay. I had one briefly when I had a Barry Grant Demon. Thoughts/suggestions on this?

daveSanborn · « **Reply #11 on:** July, 06, 2009, 06:45:13 AM »

Quote

I am also considering installing a fuel pressure gauge in the engine bay.

Great idea IMO. Along with the guage, buy one that is also a fuel pressure regulator (FPR). FPR/gauge combos are pretty compact and cheap.

Meyer65 · « **Reply #12 on:** July, 06, 2009, 10:29:14 AM »

Will first off, I already have that Barry Grant 15 psi liquid filled fuel pressure gauge (it came as part of a carb fuel line, but the gauge itself just unscrews) so I found a $6 part at summit that will allow me to adapt the gauge to the 3/8s hose I'm using. I'm only running hose from the side of the engine bay to right around the water pump, where a hard line runs all the way to the carb. Any suggestions on where to put the gauge?

I'm going with a Holley Red though, which is internally regulated. Do I still need an external regulator?

daveSanborn · « **Reply #13 on:** July, 06, 2009, 11:06:08 AM »

What is the Holley Red internally regulated to?

cmayna · « **Reply #14 on:** July, 06, 2009, 11:25:31 AM »

Does Derek need to get a new fuel line along the tunnel or do you route the hose from the sending unit to the pump and then back to where the fuel line end resides next to the sending unit?

Meyer65 · « **Reply #15 on:** July, 06, 2009, 02:05:29 PM »

Quote from: daveSanborn on July, 06, 2009, 11:06:08 AM

What is the Holley Red internally regulated to?

7psi

lethal289 · « **Reply #16 on:** July, 06, 2009, 05:36:01 PM »

Quote from: daveSanborn on July, 06, 2009, 06:45:13 AM

Great idea IMO. Along with the guage, buy one that is also a fuel pressure regulator (FPR). FPR/gauge combos are pretty compact and cheap.

Dave are you running one on your car? Any Pics?

daveSanborn · « **Reply #17 on:** July, 07, 2009, 12:09:16 PM »

My car is EFI and would be different that what you'd need to use.

Here are a couple pictures of the FPR with guage in my sons carbuerated '68.

The reason I asked about the internally regulated fuel pressure of the Holley fuel pump Derek mentioned is that most carbuerator manufacturers recommend that fuel pressure be set to approx. 4 psi.

Meyer65 · « **Reply #18 on:** July, 07, 2009, 01:14:35 PM »

I thought you could run up to about 8 psi before you needed to run a regulator?

What are the downsides to too much pressure?

johnpro · « **Reply #19 on:** July, 07, 2009, 04:43:20 PM »

Quote from: Meyer65 on July, 07, 2009, 01:14:35 PM

I thought you could run up to about 8 psi before you needed to run a regulator?

What are the downsides to too much pressure?

The downside of too much pressure is that it will blow the needle off the seat, fill the fuel bowls and flood the carb.

While Holley advertises an internally regulated 7psi on the Red pump, that's a bit "optimisitic", shall we say.

I am running the Holley Red on both of my cars, unregulated. The '66 has a "better than stock" 289 w/ Edelbrock 1405, and the '69 has a 408 with 416 ft. lbs. of torque at the wheels w/ Holley 750 DP. I've never had a problem with either car on the street or at the track.

A regulator is a MUST with the Holley Blue, but not really necessary with the Red.

Meyer65 · « **Reply #20 on:** July, 08, 2009, 07:03:50 PM »

So I installed a new Holley Red back at the fuel tank. I was too lazy to fabricate a bracket so I bought a Ron Morris one from Mustangs Plus for $30.

The instructions showed the pump centered, just like the sending unit. Well after drilling the hole for the bracket I realized there was no way my fuel filter was going to fit. Sh**.

So I go to NAPA and get a filter that had the inlet and outlet on the same side of the pump, with a built in bracket. Cost me $25 (pricey for a filter w/o a replaceable element) but whatever.

Ran the wiring through the wiring channel, out right above the trunk, and grounded it on the bracket.

BTW, I had a full tank of gas, so I had a nice gas-bath while hooking up the hoses. I know, I'm a moron, but it worked.

Theres a nice little maze of hoses now, but I got everything hooked up, took her on the highway and...

MISSION ACCOMPLISHED!

She's pullin' right through 7k rpm in all gears now, even uphill. It's a relief to tackle a problem and actually get it right the first time. And because I relocated the pump, I do not expect to have to do this again!

Total cost was around $190. Took me about 6 hours including a trip to NAPA and a shower :)

$110 for the pump
$40 for the bracket
$40 for the filter, new hose clamps, new hose, etc. at NAPA

Prices include tax and shipping

Anyway, thanks for all the help and advice here. I am going to install some new rear seatbelts tomorrow so I'll snap some pictures of the whole setup while I'm under there again.

WOOHOO!