Fuel delivery question
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Fuel delivery question
I have a 1986 f150, 300ci, carb, DS2 motor. After a 20 minute drive it began to bog down like it was flooding the carb until it stalled. Then it would crank but not start. I took off the fuel line and it was dry, apparently not pumping gas. When I put my thumb over the hose to get some suction it began pumping gas. I hooked it back up to the carb and she started right up but then began to bog down and stalled once again after a couple of minutes. I'm thinking fuel pump but would some other opinions. Thanks in advance.
FTE Legend
Joined: Jul 2010
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From: Northeast, OK
Do you have a mechanical or electric pump? In other words, do you have a pump on the side of the engine?
In either case your pump may be failing. Or, you may have a poor connection upstream of the pump, meaning between the pump and the tank. Any leak upstream can allow air in and kill the pump's ability to suck the fuel in.
In either case your pump may be failing. Or, you may have a poor connection upstream of the pump, meaning between the pump and the tank. Any leak upstream can allow air in and kill the pump's ability to suck the fuel in.
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Thank you for the response.
The fuel pump is on the side of the motor. I'll check the fuel line back to the tank.
When I pull the fuel line off of the carb and crank the motor, should it pump fuel by itself, without the need of creating suction by covering the hose with my thumb?
The fuel pump is on the side of the motor. I'll check the fuel line back to the tank.
When I pull the fuel line off of the carb and crank the motor, should it pump fuel by itself, without the need of creating suction by covering the hose with my thumb?
FTE Legend
Joined: Jul 2010
Posts: 32,875
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From: Northeast, OK
Yes, it should pump strong squirts of fuel when you crank. And with a mechanical pump you may still have the steel fuel line and rubber hose joining the segments of the line. If so, check each and every hose as all of the trucks I've seen had rotten hoses on them. With the rubber connector hoses there's one from the tank to the steel line, one from the line to the switching valve if you have dual tanks, one from the valve to the next line, and then one from the line to the pump.
Also, make sure the vent line is open. It runs up the passenger's side to a charcoal cannister below the battery. If it is plugged you will pull a vacuum on the tank and the pump won't be able to do its job. One test for a vacuum on the tank is to pull the gas cap when it quits pumping. If there is a sound like air rushing in then you have pulled a vacuum on the tank.
Also, make sure the vent line is open. It runs up the passenger's side to a charcoal cannister below the battery. If it is plugged you will pull a vacuum on the tank and the pump won't be able to do its job. One test for a vacuum on the tank is to pull the gas cap when it quits pumping. If there is a sound like air rushing in then you have pulled a vacuum on the tank.
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