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Thread: My YJ is so close to starting up! (Help) Reply to Thread
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  Topic Review (Newest First)
09-25-2019 07:45 AM
letitloose06 FUEL SYSTEM Testing Steps from the factory service manual.

https://jeep-manual.ru/index.php?page=320
09-24-2019 05:14 PM
sequel
Quote:
Originally Posted by TSEJEEPERS View Post
You said you got a fuel pressure tester. What did it say?
Agree. Hook up a fuel pressure tester and turn key. You can even jump the fuel pump relay (pins 30 and 87) to get the pump running without the key. Just make sure you do those pins. If you get them wrong you can damage the pcm.
09-24-2019 04:36 PM
xpage Howdy fellow Ag,
I would check for proper voltage to the fuel pump, if you aren't getting enough volts a new pump or old pump will behave the same. Checking grounds on the YJ are important as it might be corroded where they ground. If it isn't shiny, get some sandpaper or a wire brush and make it shiny. Then add a tiny dab of dieletric grease and make a light coating so it won't corrode.

The others were correct to recommend to change the filter and clean the tank. How did you clean the fuel injector? I had mine professionally done $15/per injector, and found mine were off by 8-13% or so. Though my major issue was corroded relays, so be sure to check yours. That can stop a Jeep from starting or drop your volts too.
09-24-2019 02:40 PM
TSEJEEPERS You said you got a fuel pressure tester. What did it say?
09-24-2019 02:39 PM
jbolty is power getting to the pump? you are throwing a lot of parts at this without a diagnosis.

have you done anything with the parking brake? the ground for the fuel pump is attached there.
09-24-2019 02:34 PM
cullen_merchen
Quote:
Originally Posted by Siva283 View Post
There are no sensors on hte fuel system. If you have no pressure you have a very limited number of things to look at. First rent the fuel pressure tester. Second get a brand new fuel filter. Third Drop the tank and clean it. You have metal in there man that will destroy injectors but isnt from them. So clean the tank test the feul pump and replace the filter. Still no pressure check hte fuel pressure regulator. By that point you should have fuel. When the pressure reg fails it doesnt run rich it runs lean if your pump can pump enough fuel.
So far I've rented the fuel pressure tester, bought and installed a new fuel filter, dropped the tank and cleaned it, bought and installed a new fuel pump and checked the MAP sensor. I'm off to replace the regulator just cause it had bad gas in it, would that be a possible cause of my fuel pump not priming?
09-24-2019 02:24 PM
cullen_merchen
Quote:
Originally Posted by mikewiz38 View Post
One of the sensors you may want to check is the MAP sensor. It's mounted on the middle of the firewall towards the top and has a vacuum tube going to it and a plug. Here's a page on how to test...

https://www.fixjeeps.com/map-sensor.html

I forgot to plug this back in and the jeep would crank but not run because, I believe, it was being starved for fuel.
I checked my MAP sensor today using the guide that you gave me. It and its connectors appear to be working fine. I don't know why else my fuel pump wont prime.
09-24-2019 02:21 PM
cullen_merchen
Quote:
Originally Posted by jbolty View Post
why are you looking at sensors when there are metal chunk in the fuel filter.
After switching that out along with cleaning the injectors, my jeep wasn't getting fuel pressure. It has been intermittently working. I'm now trying to figure out why my fuel pump won't prime.
09-24-2019 09:57 AM
Siva283 There are no sensors on hte fuel system. If you have no pressure you have a very limited number of things to look at. First rent the fuel pressure tester. Second get a brand new fuel filter. Third Drop the tank and clean it. You have metal in there man that will destroy injectors but isnt from them. So clean the tank test the feul pump and replace the filter. Still no pressure check hte fuel pressure regulator. By that point you should have fuel. When the pressure reg fails it doesnt run rich it runs lean if your pump can pump enough fuel.
09-24-2019 06:28 AM
jbolty why are you looking at sensors when there are metal chunk in the fuel filter, or did I misread that earlier? sounds like the previous fuel pump came apart.
09-24-2019 05:51 AM
mikewiz38
Quote:
Originally Posted by cullen_merchen View Post
Yes, I actually replaced the ECM not that long ago. It died one day, but miraculously came back after a week.

No actually, I did yesterday. Something is going wrong with that, I replaced the fuel pump yesterday and it seemed to get some fuel pressure going. It doesn't seem to want to run fuel after cleaning the injectors. There may be a bad sensor or wire somewhere, any ideas on what sensors might be at play, if any?
One of the sensors you may want to check is the MAP sensor. It's mounted on the middle of the firewall towards the top and has a vacuum tube going to it and a plug. Here's a page on how to test...

https://www.fixjeeps.com/map-sensor.html

I forgot to plug this back in and the jeep would crank but not run because, I believe, it was being starved for fuel.
09-23-2019 10:01 PM
cullen_merchen
Quote:
Originally Posted by Chrisnvegas View Post
Does your check engine light come on when the key is turned to on?

Yes, I actually replaced the ECM not that long ago. It died one day, but miraculously came back after a week.



Quote:
Originally Posted by Chrisnvegas View Post
Do you clearly hear your fuel pump?

No actually, I did yesterday. Something is going wrong with that, I replaced the fuel pump yesterday and it seemed to get some fuel pressure going. It doesn't seem to want to run fuel after cleaning the injectors. There may be a bad sensor or wire somewhere, any ideas on what sensors might be at play, if any?
09-23-2019 08:36 PM
Chrisnvegas Do you clearly hear your fuel pump?
Does your check engine light come on when the key is turned to on?
09-23-2019 06:39 PM
Flyer58 Bad gas will do it but there's also a fuel pressure regulator on the fuel rail. If it fails I believe the engine will run very rich and poorly.
09-23-2019 03:29 PM
mikewiz38
Quote:
Originally Posted by cullen_merchen View Post
Howdy,
Just checked the fuel filter and some bad gas is coming out of the clean side along with metal chunks and filings. Starting to consider that there might be some clogged injectors. Thanks for the tip!
Wow, glad I could help. I've been on a roll for the past couple of days; maybe I should try the lotto!
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