1985 fuel pressure
Drifting
Joined: Aug 2019
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Drops quickly, or after a while? Dead give away for leaky injectors....wet plugs, hard start when hot, Chances are the check valve in the pump, or the coupling on the pump.
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Instructor
Joined: Apr 2013
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Thread Starter
Instructor
Joined: Apr 2013
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It does run after 3 crank cycles of 5 turns each it fires but roughly.Then if you turn it off it will fire up first lick.I noticed if i go on a long drive like 30 min ,stop and get gas it takes 3 cycles again to crank.
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Instructor
Joined: Apr 2013
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Tested it whilw running it holds at 40 with the fuel pressure vacuum line unplugged and 32 with it plugged in. also i sniffed the vacuum line for smell of gas didnt smell any.
Last edited by sturmmorser2000; Jun 26, 2021 at 01:01 PM.
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Drifting
Joined: Aug 2019
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If it was the fuel filter, you'd have a lean issue/drivability issue, especially when cold. Something that concerns me is that you can generate 40psi running, but only 20psi key on/engine off. I have a feeling your coupling is leaking. It's a small leak, because when the pump is running constantly, it's able to overcome that small leak.
Thread Starter
Instructor
Joined: Apr 2013
Posts: 229
Likes: 2
If it was the fuel filter, you'd have a lean issue/drivability issue, especially when cold. Something that concerns me is that you can generate 40psi running, but only 20psi key on/engine off. I have a feeling your coupling is leaking. It's a small leak, because when the pump is running constantly, it's able to overcome that small leak.
Thread Starter
Instructor
Joined: Apr 2013
Posts: 229
Likes: 2
If it was the fuel filter, you'd have a lean issue/drivability issue, especially when cold. Something that concerns me is that you can generate 40psi running, but only 20psi key on/engine off. I have a feeling your coupling is leaking. It's a small leak, because when the pump is running constantly, it's able to overcome that small leak.
Drifting
Joined: Aug 2019
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The coupling is what connects the fuel pump to your fuel feed line. Honestly, if you block the return line, it's called dead heading the pump. You will get max pressure, which should be approximately 50 psi. If you can't get that with the return line blocked, then you do have a leak either in the fuel pump check valve or the coupling.
Safety Car
Joined: Mar 2017
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From: LeClaire Iowa
The coupling is what connects the fuel pump to your fuel feed line. Honestly, if you block the return line, it's called dead heading the pump. You will get max pressure, which should be approximately 50 psi. If you can't get that with the return line blocked, then you do have a leak either in the fuel pump check valve or the coupling.
Drifting
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Thread Starter
Instructor
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I just put new plugs in a month ago didnt smell anything also it runs great. I changed the fuel filter and noticed it only had one o-ring on it? Could the pressure have been escaping from the side that didnt have one?It never leaked gas though.I'll check the pressure tomorrow.
Last edited by sturmmorser2000; Jun 26, 2021 at 10:44 PM.
Drifting
Joined: Aug 2019
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Like I said, it's probably a small leak. Right now the pump is able to overcome it while the pump runs. If it held pressure properly, it would start on the first crank. Because it loses pressure, you have to crank it a while in order to build up pressure.