Why do i change fuel pumps more than my oil?? - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 04-10-2003, 11:14 PM Thread Starter
 
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Why do i change fuel pumps more than my oil??

I have had three fuel pumps in my jeep in the last four months. 78 CJ 5, 258 w/ mechanical fuel pump. All of them have been from autozone, so i dont know if they are just bad pumps or what. I did replace the tank, sender, all metal fuel lines, and all rubber fuel lines before i started driving it 4 months ago. I am pretty sure the line coming from the tank to the carb is 5/16. That line is fairly smooth but there is a little kink in it at one of the bends. From my view though it doesnt look like its enough to cause a fuel flow problem. Any ideas? Thanks- Tim
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post #2 of (permalink) Old 04-10-2003, 11:29 PM
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Re: Why do i change fuel pumps more than my oil??

I don't really know, but what brand pump are you running?
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post #3 of (permalink) Old 04-10-2003, 11:38 PM
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Re: Why do i change fuel pumps more than my oil??

1. I'd be bettin' something is taking out the fuel pump.
2. But you've got clean lines and a clean tank.
3. I's possible that the lines are leaking,
4. And causing diaphragm damage.
5. It's also possible the fuel is taking out the pumps.
6. Are you using extra gas additives?
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post #4 of (permalink) Old 04-11-2003, 12:32 AM
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Re: Why do i change fuel pumps more than my oil??

How are the pumps "dying"? Are they all suffering the same fate? Could you be replacing the pump, but temporarily fixing another problem? Some times it's a knee jerk reaction to replace a fuel pump. Doesn't always mean it was bad.


Nothing is really jumping to mind, but three pumps is a lot. Maybe just switching brands would fix the problem. An electric pump might be a permanent fix, but I'm thinking you have issues somewhere else. Perhaps a jam of some sort in the carb? Causing the pumps to overwork?

Do you have a fuel filter installed? I like them just for a "checkpoint" in the fuel system. They are cheap, and can save you money.

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post #5 of (permalink) Old 04-11-2003, 12:58 AM
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Re: Why do i change fuel pumps more than my oil??

Is it vapor locking? Fuel pumps can't pump vapors. Check to make sure your lines aren't getting to hot. I mounted an electrical pump back next to the tank and that solved that problem, but with an electrical pump, if you decide to go that way, you should put a kill switch in the feed line. Either a toggle switch or a oil pressure cut out switch.



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post #6 of (permalink) Old 04-11-2003, 03:45 AM
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Re: Why do i change fuel pumps more than my oil??

I had a similar problem with an '80 and though I never verified the problem it seemed to be a wear issue on the cam lobe that operates the pump. I swapped over to an electric and had no more problems. Later I swapped to a TPI Chevy so I never took the 258 apart to verify the cause.
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post #7 of (permalink) Old 04-11-2003, 08:23 AM Thread Starter
 
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Re: Why do i change fuel pumps more than my oil??

The fuel pumps all be dyin the same fate. They slowly go out, almost like a seal inside the pump starts to give and they lose their ability to suck. I can tell because it takes progressivly longer for the engine to start once i start cranking it.

*No fuel additives.
*Autozone in house brand, not sure of the manufacture.
*The fuel line runs on the passenger side and the exhaust on the driver side so i dont think its getting too hot.
*Fuel filter installed and "clean".

*I would have no idea how to check the cam lobes or a clog in the carb. My guess is it would be it would be easier to install an electric pump than to fix either one of those. Thanks - Tim
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post #8 of (permalink) Old 04-11-2003, 08:38 AM
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Re: Why do i change fuel pumps more than my oil??

Your comment about it taking longer to start each time, is puzzling me. It should start on what's in the float bowl even if you've tossed the pump into the woods.

Do you know for sure that the pumps are bad? Has AZ tested them or just replaced them? Have you hooked up a fuel pressure gauge when you suspect that the pump is on the way out?

Maybe you've been barking up the wrong tree.
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post #9 of (permalink) Old 04-11-2003, 08:44 AM
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Re: Why do i change fuel pumps more than my oil??

Where is the fuel filter located? Is this the stock carb? Maybe this is just an issue of the carb not "holding" onto the fuel? Sometimes a fuel filter installed near the carb will keep the fuel there, to help on re-starts. The fuel pump really doesn't start working until the engine is running.... but I don't know how swapping pumps has helped you out, IF this is the problem.


.... just thinking out loud......
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post #10 of (permalink) Old 04-11-2003, 09:15 AM Thread Starter
 
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Re: Why do i change fuel pumps more than my oil??

No i have not tested the "bad" pumps I have simply replaced them. The engine takes longer and longer to start until one day the engine does not start at all. It turns over and i have spark, but no fuel. By no fuel i mean when i disconnect the fuel line by the carb and crank the engine no fuel spurts out. So i have been replacing the fuel pump. I turn it over again to check that fuel is coming up through my disconnected line, and it does. So i put the line back on and the jeep fires right up. That is the test i have been using. And after i switch the pumps out the jeep will fire and run right away for a few weeks. Then it starts to take longer to start all over again. Thats my story and im stickin to it! - Tim
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