Starving for Fuel

[Phil P.]

I own R2585 which is an R2 w Auto trans.  Beginning last summer, under full throttle the engine began running out of fuel. I changed the fuel filter and it was some better. Later, it began

to starve for fuel almost every time it was under any load at all. After disconnecting fuel line to carburetor, fuel pump delivery appeared weak, at this point I had the pump rebuilt by one of our reputable rebuilders. I also found that a previous owner had added another filter above the rear end at the line from the tank. After installing the rebuilt pump and changing the filter and checking the delivery from the electric pump under the driver's seat, the fuel delivery will support low load gentle driving. As soon as I get aggressive, it seems to starve probably as soon as the float bowl runs low.  At this point the see thru filter bowl between fuel pump and carb will be empty. It's as if pressure from the carb inlet is pushing the fuel back towards the fuel pump, which can't seem to overcome the pressure and deliver a steady supply. Also, the 1/4 in. line from the supercharger to the fuel pump appears to be working.  I'm out of ideas, has anyone experienced this problem? 

[Dunkin]

I don't have one these, but it almost sounds like a tank vent problem.

 

[Gunslinger]

It could also be a gas tank full of debris...as soon as it's under load crud clogs the fuel pickup.  

[mfg]

I  agree with Gunslinger....just the fact someone added an extra fuel filter at the tank outlet makes me suspicious!

[Ron. Strasser]

If it was my problem; I would install a fuel pressure gauge on the output of the flue pump and run the gauge into the car. Then go for a ride to see what is going on

Ron

 

[Phil P.]

Is there any scenario or defect that would allow pressurized intake air from the supercharger to enter the float bowl. It almost seems as though fuel is being pushed toward the fuel pump from the carb as I advance the throttle by hand while watching the clear fuel filter. 

[Kodjo]

21 minutes ago, Phil P. said:

Is there any scenario or defect that would allow pressurized intake air from the supercharger to enter the float bowl. It almost seems as though fuel is being pushed toward the fuel pump from the carb as I advance the throttle by hand while watching the clear fuel filter. 

Should not be possible as the float bowl has an air vent above the fuel line.

2 hours ago, Ron. Strasser said:

If it was my problem; I would install a fuel pressure gauge on the output of the flue pump and run the gauge into the car. Then go for a ride to see what is going on

Ron

 

I'm with Ron. Check fuel pressure while driving. If to low, it is probably the fuel line from tank to pump clogged-up.

Did you check/change the float level in the bowl?

[Phil P.]

I have not checked or changed the float level. 

[64studeavanti]

Are you sure that the boost reference line from the S/C to the fuel pump is connected and functioning properly? 

How about the electric pump restricting the flow. The electric pump should be set a little high on pressure and a regulator should be used with a boost reference line.

 

[Phil P.]

The line from the s/c is unrestricted and connected. Beyond that I wouldn’t know how to check it. Without the engine running The electric pump will push fuel thru the mechanical pump and up to the fuel filter. With engine running (and both pumps) volume produced is more than the engine could use under any load. I will check the pressure at the carburetor next. 

[DaytonaR2]

The back seat upper cushion has likely crushed the rubber vent hose flat.  That is what mine was...   Easy to check

[Ntenna]

Easy test is remove gas cap. Watch fuel bowl. Carb is of course under pressure but vent is too - so  it is possible to have rising blower pressure reduce fuel flow. Of course, pressure line from blower to Jet-Thrust manual pump is intended to overcome that. It will not help if main fuel line is plugged, or has a pin-hole reducing vacuum.

You may want to consider a close look at all steel line for tiny rust holes especially under coil spring protected areas and rubber hoses by the electric pump and rear filter. Tiny cracks there will do what is happening to your car. And finally check tank output elbow, add fuel screen if not equipped. Fuel will not necessarily be visibly leaking and the line can still fail to allow full suction.

Edited January 4, 2022 by Ntenna