Fuel pressure testing

justfixedthat... said:
I realize this is an old post. My jeep stalled a few days ago about 2 miles after I got gas. Cranks but won't turn over. Changed the CPS, IAC, MAP, TPS, starter solenoid, ignition switch, and ignition actuator pin. And checked the starter brushes.

I can't hear the fuel pump when I key it on (not sure if I'm supposed to) but I checked the pressure last night and it read 44-45 when I keyed it on each time. It didn't change when I cranked it.

I'm not sure how to interpret that. And I don't know if it would be related to the stall/no start issues.
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44-45 lbs would not create a no start condition, is the Jeep running now. Throwing parts at it is not the best approach especially if they are not oem or equivalent.
 
TJ4Jim said:
44-45 lbs would not create a no start condition, is the Jeep running now. Throwing parts at it is not the best approach especially if they are not oem or equivalent.
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No it's not running.

I'm on a time crunch so I just swapped a number of sensors because any of those could be responsible. The jeep did this a year ago and a new Crankshaft Position Sensor fixed it so I thought maybe that would be it. Another time it was having trouble starting and I kept having to replace the starter brushes. So I was just trying the things that have worked in the past. Another time it was the coil pack. So I guess that's next.

But you're saying it's not fuel pump, based on the readings?
 
justfixedthat... said:
No it's not running.

I'm on a time crunch so I just swapped a number of sensors because any of those could be responsible. The jeep did this a year ago and a new Crankshaft Position Sensor fixed it so I thought maybe that would be it. Another time it was having trouble starting and I kept having to replace the starter brushes. So I was just trying the things that have worked in the past. Another time it was the coil pack. So I guess that's next.

But you're saying it's not fuel pump, based on the readings?
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If those are your numbers then yes it's fine. The crank and distributor pickup are the 2 critical sensors that aftermarket sensors often fail. A bad crank sensor generally takes the fuel pump out.
 
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TJ4Jim said:
If those are your numbers then yes it's fine. The crank and distributor pickup are the 2 critical sensors that aftermarket sensors often fail. I bad crank sensor generally takes the fuel pump out.
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^^^THIS^^^
When you replaced the CPS, was it MOPAR? For me, it took 3 different parts store brands of sensors failing prematurely to convince me that MOPAR sensors was the way to go on these Jeeps . One of the three was no-start right out of the box.
Another thing is to THOROUGHLY check/repair the wire bundle behind the valve cover (remove anything that impedes a visual check of individual wire insulation) and the crank sensor wires themselves for chafing/ burns
 
Jablinski said:
^^^THIS^^^
When you replaced the CPS, was it MOPAR? For me, it took 3 different parts store brands of sensors failing prematurely to convince me that MOPAR sensors was the way to go on these Jeeps . One of the three was no-start right out of the box.
Another thing is to THOROUGHLY check/repair the wire bundle behind the valve cover (remove anything that impedes a visual check of individual wire insulation) and the crank sensor wires themselves for chafing/ burns
Click to expand...

When this happened last year a new CPS from Oreilly fixed it. It wasn't MOPAR. It had a 1-year warranty and it just expired so this time I got the one with a lifetime warranty. It didn't fix it and I ended up returning it and getting the same one that worked last year.

I'll put it in tonight and if it works that'll confirm the diagnosis. Then I'll order a MOPAR CPS.

So CPS is the running theory so far?
 
justfixedthat... said:
When this happened last year a new CPS from Oreilly fixed it. It wasn't MOPAR. It had a 1-year warranty and it just expired so this time I got the one with a lifetime warranty. It didn't fix it and I ended up returning it and getting the same one that worked last year.

I'll put it in tonight and if it works that'll confirm the diagnosis. Then I'll order a MOPAR CPS.

So CPS is the running theory so far?
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Worth a look in my opinion/experience
If you research, you will find that even "lifetime warranty" sensors are garbage in a TJ. THEY MUST BE FACTORY SENSORS if you wish them to be problem-free for any decent amount of time. Oreilly was the no-start out of the box for me. Got a refund for that one. Longest lasting was the NAPA brand. Lasted about 14 months. 4+yrs problem free after I tracked down and installed the MOPAR sensor (the NAPA stranded me on an easy solo camping trip and now I carry an extra MOPAR sensor everywhere).
Yes, they cost significantly more, but this is not a vehicle you can keep running reliably with parts store china crap...
edit: as far as sensors are concerned
 
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Jablinski said:
Worth a look in my opinion/experience
If you research, you will find that even "lifetime warranty" sensors are garbage in a TJ. THEY MUST BE FACTORY SENSORS if you wish them to be problem-free for any decent amount of time. Oreilly was the no-start out of the box for me. Got a refund for that one. Longest lasting was the NAPA brand. Lasted about 14 months. 4+yrs problem free after I tracked down and installed the MOPAR sensor (the NAPA stranded me on an easy solo camping trip and now I carry an extra MOPAR sensor everywhere).
Yes, they cost significantly more, but this is not a vehicle you can keep running reliably with parts store china crap...
edit: as far as sensors are concerned
Click to expand...

Tried out the new Oreilly CPS and a new evap purge valve/solenoid. I ordered a Mopar CPS.

Just to clarify, the fuel pump doesn't seem to be the issue since it's putting out 45 psi. Correct?

Should I be looking at the coil pack as well? I had to replace that about a year or so ago. Yes from Oreilly. Or Amazon...
 
TJ4Jim said:
If those are your numbers then yes it's fine. The crank and distributor pickup are the 2 critical sensors that aftermarket sensors often fail. A bad crank sensor generally takes the fuel pump out.
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Takes the pump out as in causes it not to function or ruins it?

If I'm getting 45 psi at the rail, am I not getting spark?
 
justfixedthat... said:
Takes the pump out as in causes it not to function or ruins it?

If I'm getting 45 psi at the rail, am I not getting spark?
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I check for ignition spark with one of these. Cheap & easy. 5 bucks at HF or Amazon. Slightly more at auto parts stores...but still cheap & easy

Screenshot_20220628-083110_Google.jpg
 
Waiting for the Mopar CPS. New coil pack didn't fix it. After I put the old coil pack back in, I noticed the fuel infector fuse was blown and it started when I replaced it. But, the injectors tick (couldn't hear them before) and the engine ticks (almost a small rattle) like it's misfiring and it dies after about 15 seconds, without blowing a fuse again.

I didn't try the new fuse with the new coil pack.

What else could be causing the fuel injectors to be acting up like this and causing it to stall? I assume there must be a short somewhere in the wiring harness or the coil pack or something. The ECU was giving me issues about 2 years ago as well.
 
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