Could it be my fuel pump again?

RockDog

RockDog

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Joined
Sep 16, 2020
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Athens, Georgia
Hey guys! Not sure what the problem is. Would appreciate any thoughts! When I got my TJ a few years ago, my check valve was bad in my fuel pump assembly. It would start the second try if the Jeep had been sitting for a while. I quickly diagnosed the problem as the check valve. I replaced my fuel pump assembly last year, and I have had first-attempt start ups ever since... until last week.

However, this time it’s a little different. If the Jeep has been sitting overnight or for a longer period of time, it starts up first try. If I drive it, turn it off, and immediately turn it back on, it also starts up first try. However, if I leave it off for 30 minutes-2 hours or so it only starts the second try. I’m pretty certain that it’s not the battery or starter- it sounds almost identical to when my check valve was bad. Do you have any ideas?? It’s so weird that it doesn’t start first try if it’s been sitting for 1-2 hours, but starts fine if it’s been sitting overnight or if it hadn’t been sitting at all.
 
RockDog said:
Hey guys! Not sure what the problem is. Would appreciate any thoughts! When I got my TJ a few years ago, my check valve was bad in my fuel pump assembly. It would start the second try if the Jeep had been sitting for a while. I quickly diagnosed the problem as the check valve. I replaced my fuel pump assembly last year, and I have had first-attempt start ups ever since... until last week.

However, this time it’s a little different. If the Jeep has been sitting overnight or for a longer period of time, it starts up first try. If I drive it, turn it off, and immediately turn it back on, it also starts up first try. However, if I leave it off for 30 minutes-2 hours or so it only starts the second try. I’m pretty certain that it’s not the battery or starter- it sounds almost identical to when my check valve was bad. Do you have any ideas?? It’s so weird that it doesn’t start first try if it’s been sitting for 1-2 hours, but starts fine if it’s been sitting overnight or if it hadn’t been sitting at all.
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Same exact issue I am going through. What pump did you replace it with?
 
RockDog said:
I don’t exactly remember. At the time I was working at a Tires Plus, and we ordered it through the store. Probably whatever Advanced or Autozone carries that fits.
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If that's the case, it stands to reason it's going bad. Those crappy store brands tend to fail in a matter of several years, so I honestly wouldn't be shocked if it's slowly going bad.

Replace it with a Bosch unit if you can find one, or a Delphi if you can't.
 
Chris said:
If that's the case, it stands to reason it's going bad. Those crappy store brands tend to fail in a matter of several years, so I honestly wouldn't be shocked if it's slowly going bad.

Replace it with a Bosch unit if you can find one, or a Delphi if you can't.
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So it sounds like the fuel pump to you even though it starts first try both overnight and immediately?
 
RockDog said:
So it sounds like the fuel pump to you even though it starts first try both overnight and immediately?
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I honestly can't think of what else it would be. I mean I want to call it a fluke, but if it does it like clockwork each time the conditions are right, it certainly could be the fuel pump failing.

You can always cycle the fuel pump when it's been sitting for 1-2 hours. Use the key to prime the fuel pump 3-4 times, then start it. If it turns right over without hesitation, you'll know it's the fuel pump.
 
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Have you tried diagnosing the aftermarket fuel pump?

Do you have a fuel pressure gauge?

Chances are that it’s a quality issue that commonly plagues cheap pumps/parts.
 
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