Fuel pressure issue

redbullet

redbullet

YJ Enthusiast
Joined
May 11, 2021
Messages
338
Location
San Jose, CA
I have a 1993 yj 2.5 auto. The other morning I went to start it and while the engine will turn over, it would start for about three seconds and then die. I fully charged the battery. Then I checked the fuel pressure at the rail and it showed zero, except that it blips up to around five while I’m turning over the key. The fuel pump is cycling on (I can hear it). I checked the relays for fuel pump and auto shut down, as well as the fuel system fuse and they all were good. Previously a few years ago I also had my PCM rebuilt so I don’t actually suspect that. Here’s where it gets a bit funky. I started by replacing the fuel pressure regulator and the gasket on the nipple of the old fuel pressure regulator stayed inside the rail so when I put the new pressure regulator on there, there was a small gap. I then went to start my vehicle and fuel shot out like crazy. This tells me that plenty of pressure is coming right to the point of the start of the fuel rail. Does anyone have any suggestions on what to check next?

No AI answers or guessing by keyboard warriors please.
 
your use of "keyboard warriors" is a insult to forum members, no matter what a member says they are only trying to help.
 
Scott_db said:
I had the same issue as you, and it turned out to be a crack in the hose inside the fuel tank that connects to the fuel pump
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Thanks for the info. I’m about to use a NOID light to check for signal coming to the fuel injectors and I also changed the fuel filter this morning. Almost time to drop the tank and have a look at what’s going on in there. I’ll keep an eye out for the issue you mentioned. Thanks
 
So far I changed the fuel filter, which was overdue and swapped in a known good cps. Next up I will test that the signal is getting to the injectors…I like the idea of pouring fuel in the TB, but I am a bit worried about fire as the Jeep is in my garage.
dieselearl said:
how is problem coming along? did you find out what was wrong?
Click to expand...
 
If you're getting low fuel pressure but the pump is turning on (per the description in the original post), you probably have the busted hose that Scott mentioned.

The fact that it shot fuel at the rail could just be the lack of resistance. Once the regulator is installed and the system is closed again, then the resistance builds and fuel seeps out the cracked hose.

This is all assuming you have one of the junk aftermarket fuel pump assemblies, as those are the ones where the hose busts. Factory fuel pump assemblies don't do that.
 
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machoheadgames said:
If you're getting low fuel pressure but the pump is turning on (per the description in the original post), you probably have the busted hose that Scott mentioned.

The fact that it shot fuel at the rail could just be the lack of resistance. Once the regulator is installed and the system is closed again, then the resistance builds and fuel seeps out the cracked hose.

This is all assuming you have one of the junk aftermarket fuel pump assemblies, as those are the ones where the hose busts. Factory fuel pump assemblies don't do that.
Click to expand...

Thanks for the suggestion. I have had a few auto parts store fuel pumps bail on me over the past four years. I actually ordered some used OEM fuel pumps from a wrecker and will try one of those out this time.
 
redbullet said:
So far I changed the fuel filter, which was overdue and swapped in a known good cps. Next up I will test that the signal is getting to the injectors…I like the idea of pouring fuel in the TB, but I am a bit worried about fire as the Jeep is in my garage.
Click to expand...

Well, it looks like the fuel injectors are getting a pulse from the computer. Now I will see about dropping the fuel tank. Good thing I just fueled up. 😜

IMG_8288.png
 
I dropped the tank and sure enough the hose from the sending unit had a split in it. Thanks everybody for the help. I’ll be back in business soon. I’m going with a Delphi from Napa this time around which comes with a decent warranty. Hopefully it lasts that long. my last one, which was from autozone and lasted 3.5 years.

IMG_8327.jpeg
 
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