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Need help 85 corvette fuel pressure very weak

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Old May 12, 2026 | 12:23 AM
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Default Need help 85 corvette fuel pressure very weak

This is the fuel pressure after 5 min of applying 12v from batter to pin B at the sending unit , so far I’ve replaced fuel pumps with multiple different pumps , regulator, injectors sending unit , relay and harness? I can hear the pump prime & the relay click loud and clear when turning the key but I only get a squirt of fuel less than 1 psi. if I apply 12v long enough eventually it will build to 40psi & hold. Any ideas? I’m at a loss right now don’t know what to do
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Old May 12, 2026 | 07:13 AM
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Any history about this car? Was it sitting for a long time without being run? I'd start by testing for 12v at the pump. Don't bother with a test light or a meter, put a loan on the system with a headlight bult or two. Watch this video. testing automotive wiring with a halogen headlight bulb - Google Search
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Old May 12, 2026 | 07:27 AM
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Did you blow through the line to make sure it is not blocked? The wierd part is it eventually gets to 40 PSI and holds, that would tell me the regulator is good. It would seems strange that you have multiple failed new pumps and pump connections to the line so that that is why I suggest looking for a plug in the line that does not allow much if any fuel to pass through it.
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Old May 12, 2026 | 08:32 AM
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I would definitely try and blow out the lines.
A severe blockage would eventually allow it to reach full pressure.
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Old May 12, 2026 | 04:11 PM
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How quickly does the pressure fall after the pump is turned off?
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Old May 13, 2026 | 04:28 PM
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Originally Posted by Hiltsjr42
This is the fuel pressure after 5 min of applying 12v from batter to pin B at the sending unit , so far I’ve replaced fuel pumps with multiple different pumps , regulator, injectors sending unit , relay and harness? I can hear the pump prime & the relay click loud and clear when turning the key but I only get a squirt of fuel less than 1 psi. if I apply 12v long enough eventually it will build to 40psi & hold. Any ideas? I’m at a loss right now don’t know what to do

You need to voltage drop the fuel pump circuit from the battery to the pump.


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