New fuel pump, new regulator, still has fuel pressure issue..

Threads so long now, reinerate. 1995. Cherokee. 4.0 auto. Inline6 ho. 247k miles.

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Intellect said:

So much food for though.. guess ill see where psi is at in morning and go from there. If psi is good ill start diagnosing the ecm, relay female on the box, ign switch.

Mines a 1995 btw. And yes i did mention ac issues (fixed) issue was at relay on fuse box under hood.

I did have my blinker switch go out, i replaced it months ago.

My blower motor does go out sometimes, nothing a good wack on the dash doesn't fix LOL.

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LOL, yep, that too is another early sign of a sick XJ ignition switch. Ever smell burning insulation when the AC blower is on Max? Plastic insulation, contacts and phenolic board parts get roasted by undersized headlight and AC Blower contacts on the Ignition switch. Over time they get loose, and make poor contact, resulting in iffy connections. A good whack only works for just so long.

May not be your only problem. But will get worse!!! The switch is only about $20. The bad contacts on the Ign switch, accelerate the failure of head light, and AC Blower switches, etc.

On the 1995 year, sounds like yours has the 1996 fuel pressure, in a 1995 OBD-I rig for new readers.

Long? LOL, :laugh3: you should read some of my old threads, like the RenX Files, LOL.

" I know its electrical... But never seen an ELECTRICAL issue that is only persistant on a COLD engine. .. florida... "Cold"....."

Electrical issues can often be temp sensitive, as the materials in the connections shrink and grow from temp swings.

Change the Ign Switch :laugh3:, LOL. Or heat up first every day :laugh3:

Jeeps from 1984 to at least 1995 are known to frequently have the ign switch crap out, not on the cranking circuit, but on other power paths. You have multiple signs of one that is on its last legs. It is possible it is causing the power to the ECU and thus to the fuel pump on start up to fail when cold.

Also " i give it constant gas until it has a steady stream (from the bleed down) or gas issues in general. "

How are you doing this, as the ECU ignores the TPS sensor location during cranking except at WOT, and then it cuts off the fuel 100%. All you are doing at partial throttle is giving it excess air. If you have low fuel pressure, which you had, then you have poor atomization, and can flood it I guess from repeated no starts? I always us zero gas peddle for starting. If it fails to start and floods, I use WOT while cranking tell it starts, or tryies to.

Glad you dont consider my threads super long. Was making sure i wasnt annoying. Im taking every bit of knowledge in.

So im hearing throw money at an ingition switch? Eh my ignition and driver door key dont match , so i guess it would be cool to get a door/ignition set up. (Replaced drivers door, old door was scrapped before i got a chance to swap cylinders)

And my bad, guess i learned something new about electrical issues and weather.

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And my peddle to the metal to get it to crank after sitting... Bleedoff +electrical issue... I guess i never knew that. I had a different mindset. I know it isnt the same logic as carbed (boy do i wish this jeep was carbed lately) but i just had the mindset... Jeep wants to crank and has no fuel, so ill give it fuel.

Maybe this explains why it would "backfire?" pop like a gunshot through exhaust if i tried cranking it after a long sitting cold start, before i learned 20 key cycles would help it crank, or if i was in a rush, id turn the car over and hold the gas down and rpm would 0-8k spike and it would run like utter dog poo for 3 ish minutes. Than popping and spiking would stop and i knew jeep was ready to behave for the day. Or usually id have that backfire mess for a minute. Let off gas. Jeep turn off. THAN try again. And in hein site, it worked, cause , at that point the fuel pressure was up, and the electrical grimlens where warm.


Hard to describe... But i learned, to avoid neighbors thinking im shooting off a gun at 10pm, or 7am, just to cycle my key a crap tone, while also waiting for my fuel pump to whuuuuur, was a lot easier.

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Question... I know you were kidding.... But hypothetically... I could wait a day, than take a blowdryer to my ignition switch. As a diagnostic?


Im really against/done throwing parts at it. Link to a good ign switch? Or a brand. Ive learned cherokees are temperamental with the brand of parts.... I like my pony, buy motorcraft and call it a day LOL.

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Another bit of random info

When i half cycle the key, then uncycle it. Not to run, or acc, but off off. Theres a eeeer. Noise. Im 90% sure in the column. Ill try to get it on video.

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Yes buy and install an ignition switch.

It is not the lock and key mechanism.

It is way under the dash on top of the column half way to the firewall. It is a slide switch operated by a rod that is moved by the lock-key mechanism. Costs about $20 at local parts houses. I use cheap Chine parts. And try to replace just the bad part, LOL.:laugh3:

There are old threads and you tube videos on replacing it.

Intellect said:

So im hearing throw money at an ingition switch? Eh my ignition and driver door key dont match , so i guess it would be cool to get a door/ignition set up. (Replaced drivers door, old door was scrapped before i got a chance to swap cylinders)

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It works as a diagnostic for testing ICM-HV coils and CPS sensors, as does hot or ice water on the CPS. Doubt it is useful on the Ign switch.

Intellect said:

Question... I know you were kidding.... But hypothetically... I could wait a day, than take a blowdryer to my ignition switch. As a diagnostic?


Im really against/done throwing parts at it. Link to a good ign switch? Or a brand. Ive learned cherokees are temperamental with the brand of parts.... I like my pony, buy motorcraft and call it a day LOL.

Click to expand...

Intellect said:

Another bit of random info

When i half cycle the key, then uncycle it. Not to run, or acc, but off off. Theres a eeeer. Noise. Im 90% sure in the column. Ill try to get it on video.

Click to expand...

Sound like arcing, hissing at the ign switch? Or a vacuum leak in the AC Vacuum lines?

Backfiring is usually caused by loss of the MAP vacuum in my experience, or a distributor not indexed right or going bad.

Granted i made the video before i received pur latest reply.. figure it may help? Or have no impact lol. Anyway..

https://youtu.be/gJXzelDrZHE

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It's not a vacuum noise. May not even be related to this entire issue. But figured a video would help.

I'll look into the ignition switch. I researched it. For $30 and some torx screw 30 minutes job it's worth it.

As you see at start of video, first key cycle when the pump/check engine light takes a minute, the abs/ebrake/radio is on just fine. Idk if that means anything.



Im also back to 0 psi after 4 hours.


Cycling the keys starting to seem better and better each day...for the bleed off... Heck when the gauge tool is hooked up and the pump is electrically behaving, 2-3 cycles has me way over 49 psi. If pump aleays electrically behaved im thinking id never worried about the pressure, cause a single prime might be all she needs.

If i didnt have $7k+ into her id just get another at this point LOL. What's sad is if it would learn to behave, i planned to surprise it with a rebuilt motor next year. But boy are those plans cancelled. Im putting my efforts elsewhere, the ungrateful turd LMAO

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Im writing off the pressure as a leaky pressure regulator, the o ring. Since the rail had to be masaged back strait where it sits.

WHO KNOWS


Like i said earlier, maybe the pressure has always bled off and i just didn't know cause the pump was electrically fine and primed it right up.



If ign switch doesn't fix it, hotwire a switch to pump as a primer switch? Lmao

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Im reading a lot of ignition switch forums... To clear up earliers terms I used...

When i turn key half and the pump delays and check engine light delays, i can still attempt to crank vehicle. (Starter works, flex plate spins etc) it just has no gas because... Well mr pump is late to the party.

I only mention this because the ignition switch posts are all saying people had no crank situations where not even the starter would engage, basiclaly a bad ignition immitates a dead battery, which isnt my case. The plate gets spun, the system just has no fuel.


Id hate to throw money at an ecm/pcm, and radioshack died so i cant just replace caps.

Why oh why mr jeep

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Every jeep ignition switch I replaced, and many others on this forum, was due to stuff other than the crank starter not running. Usually stuff like dead blower and dead windshield wipers was the part of the Ign switch that died. I have seen them so fried and loose and sloppy, etc, that I have no reason not to believe that it is a contact in the switch or wire that goes to power the ECU that then powers the fuel pump that can be your intermittent problem. You already know the HVAC blower power is dropping out at times.

Warning folks, ignor the first 6 minutes of his video, unless your bored stiff with nothing to do, LOL, the noise finally happens near the end of it. Sounds like a noisy buzzer in the dash, no idea what it is.

There are better online electronic parts sources.

Intellect said:

Im reading a lot of ignition switch forums... To clear up earliers terms I used...

When i turn key half and the pump delays and check engine light delays, i can still attempt to crank vehicle. (Starter works, flex plate spins etc) it just has no gas because... Well mr pump is late to the party.

I only mention this because the ignition switch posts are all saying people had no crank situations where not even the starter would engage, basiclaly a bad ignition immitates a dead battery, which isnt my case. The plate gets spun, the system just has no fuel.


Id hate to throw money at an ecm/pcm, and radioshack died so i cant just replace caps.

Why oh why mr jeep

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Ecomike said:

Every jeep ignition switch I replaced, and many others on this forum, was due to stuff other than the crank starter not running. Usually stuff like dead blower and dead windshield wipers was the part of the Ign switch that died. I have seen them so fried and loose and sloppy, etc, that I have no reason not to believe that it is a contact in the switch or wire that goes to power the ECU that then powers the fuel pump that can be your intermittent problem. You already know the HVAC blower power is dropping out at times.

Warning folks, ignor the first 6 minutes of his video, unless your bored stiff with nothing to do, LOL, the noise finally happens near the end of it. Sounds like a noisy buzzer in the dash, no idea what it is.

Click to expand...

Hmm you only had to say wipers 3 times for me to remember my wipers only work on high.

Or thats a seperate issue, it never bothered me, just MORE food for thought.


Im buying an ignition switch and going from there i guess. Psi keeps dropping to 0 overnight. But if the pump kicked on normally i dont think the psi would be an issue.

A problem thats always been there but gradually has gotten worse over the span of a year sounds electrical. Ah i remember when it was just a double crank. Turn engine over a few seconds. Let off. Try again, vroom! ... Boy do i miss those days about now.

Thank you for all of your help, its been most useful, folks had me chasing cps/tps/iac/map/ etc. Lets just say, all my sensors are in working order. I knew from that point it was fuel related. Than a purchased a gauge kit. And chased the entire fuel bleed off. Never looking back to realise the pump/check engine light thing till 2 ish weeks ago. (I always thought i had crappy lemon pumps, until i just happened to be starring at the check engine area as i cranked cold one day)

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Wipers, there is solid state timer delay black box right under the kick panel of the dash near the steering column shaft, and of course the column selector multi switch as well. But lets see what all a new switch does first.
While under there inspect all the wiring for any burned or melted connections, connectors. Don't frget to check that rubber vac hose between the MAP and the throttle body. If it is on its last legs, it could cause the code 13.

Do this:

With engine up to temp with fuel pressure gauge connected. Find the return fuel line where it is rubber and is accessible to clamp with flat blade pliers. Start engine, read gauge, clamp return line. Pressure should jump up to 70>90 psi, turn engine off with line still clamped. If pressure drops fast it will indicate fuel pump check valve. If it stays up or drops a small amount it will indicate regulator or injector leak, if it steadily drops it will be injector.

Ecomike said:

Wipers, there is solid state timer delay black box right under the kick panel of the dash near the steering column shaft, and of course the column selector multi switch as well. But lets see what all a new switch does first.
While under there inspect all the wiring for any burned or melted connections, connectors. Don't frget to check that rubber vac hose between the MAP and the throttle body. If it is on its last legs, it could cause the code 13.

Click to expand...

Ive been under this dash a few times recently. Everythings good. Nothing melted or out of ordinary.


UNRELATED: One time the headlight delay module white wire with black stripe, the rubber got rubbed off the wire and the copper touched metal.. little smoke and check engine light stopped working that entire abs/brake/cel section. BUT. All i did there was run a new wire from delay module to fuse under dash and that fixed it no problem. This wire controls all of the power to that area. Had a tech help walk me through it.


Im doing an ignition switch today and reporting back. $30 autozone with lifetime warranty. So why not.

comanche91 said:

Do this:

With engine up to temp with fuel pressure gauge connected. Find the return fuel line where it is rubber and is accessible to clamp with flat blade pliers. Start engine, read gauge, clamp return line. Pressure should jump up to 70>90 psi, turn engine off with line still clamped. If pressure drops fast it will indicate fuel pump check valve. If it stays up or drops a small amount it will indicate regulator or injector leak, if it steadily drops it will be injector.

Click to expand...

Ill try this, but im at my wits end for the pressure issue. No matter what it hits 0psi eventually. After 4-5 hours.

I figured ill chase the electrical grimlen instead because ahen the pump DOES turn on just fine, and i have my gauge hooked up, a single half turn or two gets it to pressure. So ideally if i solve electrical or whatever makes the pump delay. All ill have to do is half turn the key, wait 3 seconds. Than crank er over. Which is what i do with ALL my vehicles anyway, maybe im crazy but even a healthy system sill last longer if your gentle with her, let the pressure build. Same logic as i let them sit if cold. :dunno:

comanche91 said:

Do this:

With engine up to temp with fuel pressure gauge connected. Find the return fuel line where it is rubber and is accessible to clamp with flat blade pliers. Start engine, read gauge, clamp return line. Pressure should jump up to 70>90 psi, turn engine off with line still clamped. If pressure drops fast it will indicate fuel pump check valve. If it stays up or drops a small amount it will indicate regulator or injector leak, if it steadily drops it will be injector.

Click to expand...

Ps - even where the return lines "rubber" it is hard plastic underneath. I HAVE clamped off the return line and it still loses pressure. Somewhat slower. But does happen. Probably the rail where the pressure reg sits, BUT once again, its such a sloooow bleed that a single prime gets her where she needs to be. Maybe 2 primes.