Fuel Clog or Pump Failed

[seely]

Hey Bronco experts, I was driving my 75 Bronco the other day and it quit on me. After a bit of diagnostics, I figured out that there is no fuel going to the carburetor (bowl was empty and so was the fuel line when I pulled it from the fuel pump). I reconnected the fuel line to the pump and removed my inline fuel filter and used my mouth to blow down the line to try and clear a potential clog and heard bubbling in the tank. After putting in a new fuel filter (in case it was clogged) I couldn’t get fuel to come up the line even when using starting fluid down the throttle when cranking to get the fuel pump primed.

My question is, if the line is allowing air to go through and bubble at the tank, does that rule out a clog, or could air pass through but a clog prevents fuel from travelling the other direction up to the fuel pump? I’m thinking if it’s not a clog, it might be the fuel pump, although I just replaced that a little less than a year ago. Any help from you all would be much appreciated!

 

[SteveL]

If the pump came from an oriellys or auto zone type stores I wouldn't be surprised

 

[EPB72]

If you have a vaccum/fuel pressure gauge , you can test the pump by hooking up the gauge to the inlet side of pump and cranking you should see 4-6 inches of vaccum and relitivly steady ,, low no vaccum or large needle bounce theres a pump issue,,,, as far as the line to the tank you could still have a crack ed hose ,bad selector valve something that will allow air to be sucked into the line losing the fluid pull..,, If you have a gas can you could try to pull from that set it on the fender/ or cowl with a hose to the pump and as mentioned I've seen pumps bad in the box so .....

 

[seely]

Thank you, I will definitely try all of your suggestions. I have a vacuum gauge and gas can and could easily do those tests this weekend when I have a chance. I’ll let you know how it goes!


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[DirtDonk]

Is your bronco a daily, or almost daily driver? If it sits for long periods of time, or even just occasionally for a month or more, the chances of your pump being bad go up exponentially.
Modern pumps versus modern gas, the pump usually loses.
This is a far too common problem to assume that because it’s a year old it’s still good. I’ve seen pumps with less than half an hour of use on them go bad after sitting for a few months.

 

[73azbronco]

I was also going to say half hour is my record for worst ever fuel pump. there I said it..

 

[dmoses42]

If you have the plastic fuel line going from the tank to the carb, check to see if you have cracks in it in the engine bay. I chased fuel issues for a long time before finding mine was brittle and cracked, presumably from being baked by the headers. I found it by accident when I was replacing another fuel pump and the rubber hose from the hard line to the pump when part of it broke off in my hand It had several cracks all the way back to where it exited the engine bay. That was on the '73 I sold a couple of years ago.

 

[seely]

Is your bronco a daily, or almost daily driver? If it sits for long periods of time, or even just occasionally for a month or more, the chances of your pump being bad go up exponentially.
Modern pumps versus modern gas, the pump usually loses.
This is a far too common problem to assume that because it’s a year old it’s still good. I’ve seen pumps with less than half an hour of use on them go bad after sitting for a few months.

I used to drive it about once a week, but my other car has had some problems lately so I’ve been driving it daily for about a month before this problem came up. I am noticing there are quite a few sections of fuel line, rubber hose, plastic, and metal line leading from the pump to each of the tanks. I am going to keep that in mind for tracing problems if it ends up not being the fuel pump.


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[bmc69]

In addition to the premature failure of the little rubber check valves in the pump, getting even a small piece of crud from an old fuel tank stuck in one of the check valves will cause a failure as well.

 

[seely]

Everyone who said fuel pump should get a nickel. I wouldn’t have thought it could have failed so quickly, but I decided to get a more expensive part from Napa, so hopefully that will last a little longer, but who knows. Thanks again for all of your suggestions and help!


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[seely]

In addition to the premature failure of the little rubber check valves in the pump, getting even a small piece of crud from an old fuel tank stuck in one of the check valves will cause a failure as well.

I have a feeling that is what happened. I will need to work on clearing out any gunk at the bottom of my tanks. In yall’s opinion, do the fuel system cleaners work, or is the only way to drop the tank and totally clean it out.


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