Fuel Pump Problem?

[Garage Hound]

I have a Holley Blue pump mounted under the fuel cell at the rear of my car. I have the regulator mounted on the inner fender well, directly across from the carb (Holley 750 DP). I am using 3/8" blue fuel line, which I believe is plenty large for my SB355 (450HP). My problem is this, when I first start the car, the regulator reads about 7psi. After the car is run down the track a couple of times and is hot, however, the regulator will drop to nearly zero, even the car is running. But, sometimes it will cut out off the line like it is running out of gas. The plugs look like the engine is running lean. Should I be looking at a fuel pump problem? Seems like I heard somewhere that you can up the GPM of the Blue 110 by replacing the springs or something. Any thoughts on what I need to do to richin' this baby up? I don't want to increase the jet size in the carb unless that is going to solve the pressure problem, and I don't think that will do it.

Thanks.

 

[LS6 Tommy]

Does your fuel tank/cell have a vent? It may be going into a vacuum. it may also not have anything to do with the cell, but the fuel is just getting vaporized from heat.

Tommy

 

[Garage Hound]

It is vented Tommy. I have a separate line running out of the top of the cell, then down through the trunk. I have noticed that the cell itself has imploded slightly since I installed it 3 years ago (slightly dented downward on the top). It doesn't look bad though, and I have never heard any sucking noises when I remove the cap from the cell.

 

[barnym17]

make sure a mud dauber hasn't built a nest in your vent line they like to do that.

 

[shotgun]

What is the holley flow AT THE PRESSURE YOU RUN?

Not talking the pie in the sky, free low number.

 

[Garage Hound]

What is the holley flow AT THE PRESSURE YOU RUN?

Not talking the pie in the sky, free low number.

I'm not sure really. I think it shown in my book, but I will have to look it up.

 

[Supe]

Is your pump gravity fed by the fuel cell, or is it mounted higher than the fuel cell ouput?

 

[Garage Hound]

Is your pump gravity fed by the fuel cell, or is it mounted higher than the fuel cell ouput?

It's gravity fed Supe. The cell is mounted inside the trunk and the pump is mounted underneath the car on the side of the spare tire extrusion. Since the fuel cell outlet is below the trunk line, I would guess overall that the pump inlet is about 1" lower than the cell outlet. I am going to confirm that however since I have never actually measured the difference.

 

[cutlass389]

Once again I'm no rocket surgeon but a few things come to mind here. First off, liquid filled fuel gauges will read fine WHEN THEY AND THE FUEL IS COOL. Once either of them heats up, the gauge will read low and be unresponsive(in the reading) to any changes you try to effect. Secondly, where is your fuel filter and how old is it? Is it large enough to move enough volume? An electric pump is a puller so the filter should be before the pump. A mechanical pump is a pusher so the filter should be after the pump. Also, generally, the feed line TO THE PUMP should be one size larger than the downstream diameter. I've also learned that electric pumps of all brands and types in a deadhead configuration will live a shortened life. What type of feed line do you use from the reg. to the carb? I've had starvation issues with a single feed line that makes a 90* turn for one bowl. Do a flow test to determine the capacity of the pump.

 

[Garage Hound]

Once again I'm no rocket surgeon but a few things come to mind here. First off, liquid filled fuel gauges will read fine WHEN THEY AND THE FUEL IS COOL. Once either of them heats up, the gauge will read low and be unresponsive(in the reading) to any changes you try to effect. Secondly, where is your fuel filter and how old is it? Is it large enough to move enough volume? An electric pump is a puller so the filter should be before the pump. A mechanical pump is a pusher so the filter should be after the pump. Also, generally, the feed line TO THE PUMP should be one size larger than the downstream diameter. I've also learned that electric pumps of all brands and types in a deadhead configuration will live a shortened life. What type of feed line do you use from the reg. to the carb? I've had starvation issues with a single feed line that makes a 90* turn for one bowl. Do a flow test to determine the capacity of the pump.

Regarding the heat issue, that is exactly what I am experiencing. When the car/fuel is hot, and the regulator reads zero, no adjustment makes any difference. Regarding the other questions, I have a Summit inline filter (those annodized barrel types that are about 2' in diamter) mounted less than 6" downstream from the fuel cell outlet, which puts it about another 6" before the pump inlet. The line size is the same on both sides of the pump, and I use that same line again (the hard blue stuff) out of the regulator up the Holley pre-made dual-inlet line into the carb bowls.