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NVRL8TE
01-16-2022, 03:26 PM
Hello team,

I recently purchased a 58k mile 1990 ZR-1.

Haibeck chip and a ported top end are the only mods.

It was running great until the other day it started to run rough under light load, and it seems to continue, the higher I take the RPMs.

I ran codes, and it gave me a DTC code 55 "Fuel Monitor Lean".

I have a fuel pressure gauge hooked up, key on engine off, and the pressure goes from 42 PSI, to 20, inside of 30 minutes.

Is this common? I hope I'm looking at fuel pumps as opposed to injectors...

What is the next direction I should take?
Figure8it
01-16-2022, 05:03 PM
I had my fuel pressure regulator fail. One way to check it is to remove the hose to the plenum and see if there is any fuel coming out when you pressurize the system.


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NVRL8TE
01-16-2022, 05:13 PM
I had my fuel pressure regulator fail. One way to check it is to remove the hose to the plenum and see if there is any fuel coming out when you pressurize the system.


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

I?ll give that a shot.
NVRL8TE
01-17-2022, 12:29 PM
No fuel leaking from the fuel pressure regulator, when pressurized (key on, engine off).
Figure8it
01-17-2022, 02:02 PM
No fuel leaking from the fuel pressure regulator, when pressurized (key on, engine off).

Here is an old post that may help: http://www.zr1.net/forum/showthread.php?t=25016

Best of luck!
NVRL8TE
01-17-2022, 04:29 PM
Here is an old post that may help: http://www.zr1.net/forum/showthread.php?t=25016

Best of luck!

Thanks, amigo!!!

My days of parts cannoning are done, I want to know EXACTLY what it is. Lol
NVRL8TE
01-19-2022, 09:26 AM
If anyone has had this code, I would like to know what it was in your case.
aafc
01-24-2022, 02:24 PM
Check out my post "code 55 still" Look at what I have done. At this point I
think code 55 is gone, of course it my need more testing. Rear brakes and
WOT at the track. Right now I'am having some work done on my headers. Will
do a full report when everything is back together (small header leak)
Try and see if any of the things i've done will help you.
John
1990 white/black # 2546
one of a few 4l8OE EQ ZR-1's