Can the fuel pump arm wear down the cam lobe and how can i tell? I replaced the fuel pump, checked the carb, the line coming from the tank to the pump, and that was all fine. But the carb is still not getting gas. I was told that the arm does not ride on the cam and the part that it rides on is replaceable. Any help on this would be great. Thanks

 

So you have gas from the pump to the carb line? If so pump is working. Does your carb. have the little fuel filter in it? Maybe it is clogged. If gas is coming out of line to carb. then the problem lies with carb. unless I misread your question. Some info on your truck could be helpful.

 

No sorry I wrote that wrong, I do not have gas from the pump to the carb.

 

I have also had to prime fuel pumps in order to get them started. I've not seen an eccentric wear out, probly pretty rare.

 

No, it has a 2 piece eccentric & it can't wear down.

 

On some engines you can miss the eccentric when you install the pump. I would take the line off the carb and use rubber line to run it to a can and see if you get gas while cranking. If no then take the line off the pump and see if it's clear.

Also it may take a while to prime a new pump. Have your tried priming the carb? You can squirt some gas into the bowl vent.

 

Thats what I do I just put gas in a spray paint cap and pour it in to start it then the fuel pump will usually take over from there.

 

Never seen an eccentric wear out but have seen the bolt come loose that holds it and then it won't work. I always use lots of lock tite on mine when I install it.

 

It's not completely impossible that a new fuel pump isn't bad too. Just a thought.

 

Thanks, the info on the eccentric really helps. How do I "suction" gas up from the tank to the fuel pump? Can I use air pressure in the gas tank to push fuel to the pump? Yes I have primed the carb and it has started then stalled.

 

Can't help on the priming question, but I did have a related question.

When I bought my truck it had an electric fuel pump on it. The mechanical pump is still there, but not hooked up. I'm wondering why someone would add an electric fuel pump rather than replacing the mechanical pump.

Are there advantages to an electric pump over a mechanical pump. All things being equal, I'd rather install a new mechanical pump since it would be one less set of wires to worry about.

Rick

 

Check the rubber hose that goes from the tank, to the metal fuel line that extends the length of the frame rail. You mentioned the line, but not the hose that connects it to the tank. It's about a foot long, at the back of the truck, coming off the tank. This is overlooked many, many times. If this has a crack in it anywhere, the pump will suck in air and not draw fuel. Sometimes the fuel pump is replaced when this hose is really the problem. This hose takes heavy chemical abuse and should not be ignored.

Also, crank the motor with the distributor cap off to make sure the rotor is turning; that way you'll know you didn't lose the timing chain or anything catastrophic like that. The camshaft of course will not rotate if the timing chain is gone.

I'm thinking that investigating those two things will nail your problem.

For your question - the main advantage to an electric pump is that it can be shut off at anytime, whereas a mechanical pump only stops pumping when the motor cuts out. For example, you can wire an electric pump to an oil pressure cutoff switch. This shuts fuel off to the motor immediately if the oil pressure drops, which prevents extensive bearing damage. In the case of EFI vehicles, the pump can be wired with an inertia shutoff switch, to cut off the flow of fuel in the event of a collision. Lastly, some performance engine builders eliminate the cam eccentric to reduce rotating weight, and instead use an electric pump. However, I've also seen people install an electric pump when the mechanical pump dies, simply out of laziness.

 

Thanks I will try that advice next. I will let you know how it works out.

 

Just to add... Try to avoid smoking a cigarette afterward