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Discussion Starter · #1 ·
Jeep died on my way home the other night. 1989, 2.5L, standard.

Didn't hear the fuel pump prime, so I assumed it was that, after swapping the relay's I had replaced recently, to make sure it wasnt that.

I replaced the fuel pump, but it still didn't prime. I cut out what seemed like a bad fusible link, which turned out to be good. it was a terminal near it.

So I went to start it, still nothing. Swapped relay's and it finally started pumping!!

but then it didn't stop... I put more gas into it. Still didn't stop. I even went as far as to swap my old fuel pump back into the tank. now that one isnt stopping either!

I know my automatic shutoff relay is bad, but everything else seems to be fine. It just won't build any pressure. Whenever I go to try and start the thing it just cranks.
 

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Discussion Starter · #3 ·
Could a fuel pressure regulator stuck open be causing my Jeep to not start? It would make sense that it would keep it running, constantly trying to build pressure, right? But would that really stop it from firing?

Im stumped.
 

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Can you get a pressure reading at the fuel rail? You can rent a fuel-pressure gauge from Autozone. Hook that up and see what you have at the rail. It should prime up to around 30 psi and then stop. I don't know if the ASD waits to get to a certain psi and then shuts off, so there could be a clog somewhere in the system or the FPR is stuck open like you said.

If they ASD doesn't require a certain psi I would think that there is something electrically going on to keep the pump running continuously. I had installed a brand new fuel-pump relay and the relay turned out to be bad, so it kept my pump running continuously but the Jeep would fire. Also, can you get the Jeep to fire with an Ether shot down the TB? Maybe you have an ignition problem going on at the same time. First try to confirm that you have the correct psi getting to the fuel rail, it'll eliminate the regulator / a clog / ignition from being the issue.
 

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Discussion Starter · #5 ·
Hey, I was looking at some of your topics earlier trying to figure this out.

but yeah, I bought two new relays, those arent the problem. and it's an 89, so there's no fuel rail, it's single point injection.

I havent tried to get a reading on the pressure yet, im gonna do that tomorrow. But my father today tried starting it by putting some gas directly in and it wouldnt start. So it looks like I also have no spark...

Bad ECU? Bad crank position sensor?
 

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Discussion Starter · #6 ·
Im thinking it might be the ECU, even though it's only two years old. Cause I remember when it was in the process of dying, the voltage gauge was freaking out. It would go from 0 to normal level and back down very rapidly, over and over again.
 

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Discussion Starter · #7 ·
So if my fuel pump wasnt kicking on, I would say it was the Crank position sensor. Because I've read that that stops the spark and stops the injectors.

However, my fuel pump is constantly pumping.

Maybe a mix of a bad fuel pressure regulator and something causing it to not get spark?

bahh...I just want my Jeep back.
 

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Discussion Starter · #8 ·
I doubt it's the CPS, because I checked it with a meter. It's supposed to have 200 +- 75 ohms HOT. I checked COLD, and it had ~225. Even though I didnt check it when the engine was hot, because I can't, it's still in the normal range.

but then again, I read it's a fairly common problem. and it can cause the voltage gauge to not display properly, which it's fine at the moment, but when it was dieing it wasnt. My fuel pump is also acting odd, and it isnt getting spark at the plugs.

it might be a mixture of issues too. The act of something going bad caused my fuel pressure regulator to get stuck open?

Im gonna check for fuel pressure when I get home tonight. Is there any way to adjust the fuel pressure regulator? or do I have to just buy a new one?
 

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Discussion Starter · #9 ·
The stupid fitting I had to test my fuel pressure was hitting when I tried to screw it in, so I have to buy a new one before I can test tomorrow.

Im also gonna pick up a CPS and try it out and at least rule it out as a possibility.
 

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The CPS should not have anything to do with it, that is an output sensor that tells the ECU to fire the coil and injector...
It sounds like either the ECU or Ignition Switch. just above the relays are two test connectors, you want to look at the PINK wire, 12v switched from the ECU, it should gl dead after the Ign is turned off. This powers a ton of stuff on the engine. I will check my refference materials when I get home.
 

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Discussion Starter · #11 ·
I ended up using a Diagnostic/troubleshooting flowchart, it pretty much immediately brought me to "replace ECU and restart the test".

Took out the ECU, popper her open, and sure enough, one of the pieces is all melted.

So on my ride home, I had a melted wire going to my fusible link, blew my relay, and damaged my ECU. Causing no spark, and no fuel pressure.

But I got the new ECU ordered, hopefully the thing fires right up.
 

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Discussion Starter · #12 ·
Thanks for the help too, Peety. I wish I saw your post before I picked the CPS up this morning. But whatever, I got a good backup now.
 

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I did an external work around on mine. I added a relay powered and switched by the YELLOW wire coming from the Ignition switch and plugged the PINK in as the output to feed the components on the engine.
Glad you have it sorted.
P
 
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