Well .... here it goes....


About 15 years ago I built a 1986 Ford ranger with a 5.0L (non high output).


Truck has been really fun, and has had its fair share of issue...


But this one has me scratching my head....


Last summer I started having fuel delivery issues. I figured I had a bad pump.


So I parked the truck till this summer. Put in a new carter 4070 electric fuel pump... and still a fuel delivery issue.


Figured maybe a bad pump, although it bench tested fine. Only real concern that made me think it was a bad pump was that the pump was heating up, and transferring the heat to the fuel lines.


Ordered a replacement pump... installed it.... same issue.


When I would start the truck up, the filter element would fill right up. After running for 10 minutes or so you could literally see the fuel disappearing from the filter.... I figured I had some severe vapor lock. I have the spectre style clear fuel filter at the front of the engine. You could actually see the fuel level get less and less in the filter.




so....in an attempt to get the fuel away from the engine I redid the fuel lines from the pump to the carb and checked all the fuel lines for blockages. Nada.


start her up... fuel pump and lines after pump heat up.

 

As a starting point you need to know fuel pressure also consider that to big or different size fuel lines will cause this same issue. I see this is a 4 to 6 psi pump so i take it that it has a carburetor.do you have a return line hooked up or an inline pressure regulator. Also figure for how close the fuel lines and pump are to the exhaust if at all and fuel tank venting.

 

Everything is the same as it was built originally.

Same fuel line... Same carb...

Never had a pressure regulator nor return line.

Fuel lines before pump are nice and cool.

Fuel lines after pump and pump are hot.

Brackets for pump are all cool to the touch.

Haven't ran it with the gas cap removed, but one would think the fuel line before the pump would be hot too if it was a venting issue.

 

Have you done an electrical check on the pump to be sure their is no resistance at the pump or its circuit. If theirs no blockage or pick up issue then it only leaves the pump circuit the pump or a venting issue or at least these are the most likely causes and a good starting point.

 

I'd run a return fuel line back to the tank. "T" off the supply line just before the carb. That should keep the fuel in motion. I'm wondering if the fuel pump is keeping the needles on the seats too much causing back pressure on the supply line and causing the pump to heat up. A return line would probably eliminate that possibility.

 

I just spent the morning playing with this....


engine running I am getting 14.5 volts to the pump.

 

Yeah I agree that a return line would help keep the fuel flowing, however up until last summer I never had any issues with this truck. I drove it year round when I first built it. There were no changes to the fuel system.


I had noticed that the fuel pump was heating up so I assumed that I had a bad fuel pump. Changed that out..... still heating up.


assumed I might have got a bad pump. returned that one... tried another.... same heat issue....

 

so.....


Today I disconnected the fuel line from the fuel pump at a steel line junction under the hood.


Grabbed the old fuel pump off the shelf, and Plumbed some rubber and steel lines together in between the fuel pump and carburetor. Clamped the fuel pump to a 12 ton jack stand. Then ran the inlet from the fuel pump into a 5 gallon plastic gas can


Grabbed a fully charged battery and the battery charger. Hooked the fuel pump to the battery and turned on the charger to simulate the truck running.


Figure this way I will be eliminating the trucks charging circuit and fuel delivery completely.


I power up the pump, start up the truck ... and wait.


I keep touching the steel fuel line and the carburetor to check the temperature. As I monitor the temp I can feel the pump heating up.


I am having the same heating issues with a stand alone fuel system.


Just to make sure I don't have a bad pump on the test mule, I disconnect the fuel line going to the carburetor and dump it into another 5 gallon gas jug.


Turn on the pump.... now I can feel the pump motor cooling down and the line going into the 2nd gas jug getting cool.


The eliminates the fuel pump, tank and lines form my issues as well as the charging circuit.


I know the timing is good, checked that a few times.


Truck could use a tune up. (plugs and wires) but I find it hard to believe that a tune up would fix this issue.


I guess I could have a bad carburetor, but how does the carburetor heat the fuel pump??