Warm Start Issue - Resting Fuel Pressure Drops to 0 after 5 minutes

[DMC-81]

I remember a fuel cooler being one of the enhancements that Andre talked about on the 3 world tour cars. I wonder what their setup looks like?

[burch]

I remember a fuel cooler being one of the enhancements that Andre talked about on the 3 world tour cars. I wonder what their setup looks like?

I can't remember right off, but is that what the new vents on the front fenders of their cars were for?

[sdg3205]

I can't remember right off, but is that what the new vents on the front fenders of their cars were for?

That sounds familiar

[cpistocco]

That sounds familiar

How about taking the return fuel line, and adding a length of coiled line in an area where there is good air flow (yet protected from road debris). Wouldn't that act as a mini radiator? The fuel should be cooled to some extent.

[Jonathan]

In a perfect world, you would probably have the coolant running through that coil and then have it spiralled around a straight (and protected) fuel line. On our cars though, or any car really, there isn't an extra cooling loop that would have it's own heatsink and pumping ability. You could use the engine coolant on it's way back to the engine from the radiator, but the temperature of even the "cold" side would likely make matters worse rather than better with the fuel temperature.

If we have no add-on cooling loop, there could be a way to try and divert up some airflow to get at or around the fuel lines or tank. Maybe some sort of modest air scoop integrated into the fuel tank closing plate, that would let air rushing under the car up into a slight opening at the front of the plate, then down along the length of the tank, and out the back of a corresponding opening. You might be able to test an easy and simple version of doing this just by offsetting the location of the fuel tank closing plate by putting a certain thickness of washers on each bolt, between the plate and the bottom side of the frame where the bolts go. I'd have to look closer at how much the tank may rest right on the plate, to allow that air flow pathway, and maybe you reposition the pads or add a couple spaces to take the weight but still give you some cooling.

Just a thought anyway.

[cpistocco]

Thanks Guys.... You are all very generous with your time.

Two last questions.... Is there any way to determine how much resistance the pump is pushing against. I have an external check valve (and maybe a check valve on the pump). I am also unsure if the inside diameter of my fuel hoses (near the tank) is large enough. Again, the noise began with the new accumulator. Wouldn't that increase the pressure that the pump is fighting?

Also, should I check the voltage at the pump with the pump running or shut off?

[Bitsyncmaster]

Thanks Guys.... You are all very generous with your time.

Two last questions.... Is there any way to determine how much resistance the pump is pushing against. I have an external check valve (and maybe a check valve on the pump). I am also unsure if the inside diameter of my fuel hoses (near the tank) is large enough. Again, the noise began with the new accumulator. Wouldn't that increase the pressure that the pump is fighting?

Also, should I check the voltage at the pump with the pump running or shut off?

You want to check the voltage across the two pump terminals with the pump running. If your voltage reading is low, then you can check each pump terminal using the battery ground and start tracing back the circuits to find bad connections. I would guess you can check your pump efficiency by measuring how much return fuel you get. It should be a large amount of returned fuel with the engine at idle.

As far as pump buzz. I did have the spring inside my pump pickup hose and had Hervey's heat shield keeping radiator heat off the tank and still got the buzz. So buzz is not always caused by the pickup hose collapsing. I was considering making an electronic pump controller which would hold 75 PSI primary pressure. That would eliminate most of the heated return fuel into the tank. You still need the return line for the lambda (FV) return fuel.

[cpistocco]

You want to check the voltage across the two pump terminals with the pump running. If your voltage reading is low, then you can check each pump terminal using the battery ground and start tracing back the circuits to find bad connections. I would guess you can check your pump efficiency by measuring how much return fuel you get. It should be a large amount of returned fuel with the engine at idle.

As far as pump buzz. I did have the spring inside my pump pickup hose and had Hervey's heat shield keeping radiator heat off the tank and still got the buzz. So buzz is not always caused by the pickup hose collapsing. I was considering making an electronic pump controller which would hold 75 PSI primary pressure. That would eliminate most of the heated return fuel into the tank. You still need the return line for the lambda (FV) return fuel.

Thank you for your input Bitsyncmaster