Leaking injector?
Thread Starter
On The Tree
Joined: Feb 2011
Posts: 118
Likes: 4
Leaking injector? I was doing a fuel pressure test on my 5.7 LS1 and got a reading of 63 lbs while running. When I shut it off, it did not immediately lose pressure, but it slowly dropped. After about 10 minutes it was down 8 lbs. I wasn't finding anything exactly addressing this in my search, but would a slow leak like this point to a leaky injector? Or something else? Or is a slow leak somewhat normal? Thanks in advance.
Joined: Nov 2001
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From: Schiller Park, ILL Member: #317
I don't necessarily see any problem with those results. Losing 8psi after 10 minutes of shutdown isn't alarming to me at all, and 63psi under all running conditions is excellent (should be 58-60psi at all times with engine running, but the gauge might be reading a little high).
What initial concern prompted you to start a diagnostic process?
What initial concern prompted you to start a diagnostic process?
Joined: Nov 2001
Posts: 34,663
Likes: 2,597
From: Schiller Park, ILL Member: #317
Well, 63psi is technically a little high. If your gauge is extremely precise/high end, and that's a correct reading, it really shouldn't be more than 60psi (58-60psi is normal and proper for an LS1 application) so that might be contributing slightly to a rich condition. But that shouldn't really matter unless you're on a base tune for a given injector size. If it's been dyno tuned then it shouldn't matter unless something changed with pressure after the tuning.
Thread Starter
On The Tree
Joined: Feb 2011
Posts: 118
Likes: 4
Ok. I’ve got a 222/226 cam, ported heads, Walbro 255 fuel pump, upgraded injectors, and it is tuned. Would any of this account for the pressure being too high? And my gauge is not high end at all - rental from AutoZone
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Joined: Jul 2022
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From: Alaska
Rental gauge is lucky if it has %5 accuracy, so don't worry about the number: You know you have fuel pressure, call it good.
WALBRO255 are fairly well known for bleeding down pressure through check valve in tank... as long as it PRIMES and starts relieably: You do not have a problem there.
WALBRO255 are fairly well known for bleeding down pressure through check valve in tank... as long as it PRIMES and starts relieably: You do not have a problem there.
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Staging Lane
Joined: Oct 2025
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Question is the source of the slow leak down. If it’s the pump check valve slowly leaks. Not a problem because your pressure always come back for start up. If it’s an injector. Start to see if one or more spark plugs are darker from being over rich. Safe way is to remove the injectors and have them tested. In the machine they can apply fuel pressure and not fire them to see if they leak. The backyard way is to pull the fuel rails with pressure still in them to see if they drip.
Have to catch any leaks so you don’t have a fire.
Have to catch any leaks so you don’t have a fire.
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