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

My bracket left, new one on right.
27025ce869b5bdf2587482cf99d6192e.jpg


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Update on fuel issue... I went to the junkyard for an electrical piece today, and noticed that the fuel pressure regulator bracket looked different than mine... I snagged it and just got home, swapped it with mine, and low and behold at idle i went from 30psi to 50psi.... probably still have a bleed off issue knowing my luck this week.

Umm...

30 psi is closer to where a '95 should be. Unless you have the vacuum disconnected, and then it should be 39.

50 psi is more in the range of where my '96 and later models are supposed to be.

:dunno:
 
Umm...

30 psi is closer to where a '95 should be. Unless you have the vacuum disconnected, and then it should be 39.

50 psi is more in the range of where my '96 and later models are supposed to be.

:dunno:
To add to the mystery, if i undo the vacuum line on the regulator it holds 30 when off...

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I got nuffin...
Gosh darn cherokee lol. Well ive decided whats the worse that can happen? Ill cycle the key a bunch and hope for the best. Once on its perfectly fine. Now something i noticed. Sometimes the second i turn the key on i get the whuuuuur. Sometimes it takes up to 15, seconds. But that shouldnt have to do with it HOLDING fuel, correct?

If that is correct than after my event, if my jeeps behaving good, im giving her new injectors and if that fails, the bmw inline check valve. (Return style fuel system) so should be ok. Plus *nock on wood* i carry a fire extinguisher.




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I got nuffin...
Not to beat a dead horse, but back at the fuel issue. It drove fine this weekends 400 mile round trip. With plenty of offroad fun. Only gave me an issue when it sat overnight. I got a nice fuel pressure set (returned the cheapo to autozone).

It dawned on me, i have a return style fuel set up, i was told to clamp the return line. But neverthe feed line. When i clamped the return line i had the fuel bleed off still, but i didnt know if it was a leak in feed line/pressure reg/or injectors.

Today as i cleaned the dust off her i ran a few pressure tests. But this time i clamped the supply AND return line. It drops 10psi within 30 minutes like clockwork. Ive tried countless pressure regulators so i doubt thats it. So im ordering new injectors. (As much as i hate the "throw parts at a problem" method) , because with both lines clamped. It is 100% isolated to the rail alone (i would think). Only thing that gets me is how when i removed the rail and laid it on paper towels, i didnt SEE any gas leakage? Maybe its so minoot that a human eye cant see it? Or internally in the injectors?


Aure your tired of this thread as long as everyone else here..


But a lot of food for thought.


I ordered some motocraft ev1 4 hole upgrades from a guy online. Whatever the 91-95 injector styles are called, i forget. But there motorcraft or bosch i forget, but he rebuilds them and gives them lifetime warrantys. And even threw in a free extra for my trail bag. So lets see if these solve the issue... (Knowing my luck, probably not)

I plan to keep this thread alive till i resolve the issue.. i never give up!

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It's a start.

Leak down with both lines clamped pretty much points to injectors. Especially if there is no sign of external leakage. Make sure to clean the injector holes in the intake with a bore brush of some sort, and use a small coating of engine oil or bearing grease on the o-rings when installing. (Dont use silicone based greases or sprays due to oxygen sensor damage.)
 
It's a start.

Leak down with both lines clamped pretty much points to injectors. Especially if there is no sign of external leakage. Make sure to clean the injector holes in the intake with a bore brush of some sort, and use a small coating of engine oil or bearing grease on the o-rings when installing. (Dont use silicone based greases or sprays due to oxygen sensor damage.)
New injectors... She DOES idle better, and seems to have more umf in her step. But as soon as i key off the ignition she drops to 30 psi, than ten minutes later is now at 20psi... Ill keep you updated but this Jeeps driving me nuts. Remember i isolated it to the rail... So new injectors, countless new pressure regs, and still bleed off! Ive inspected up and down and no leaks ANYWHERE.... Im going crazy over here.

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A slow pressure down to 20 psi is OK, and even something like 10 over night IIRC. -Pressure can change with fluid temperature, and very very slow check valve leak seems to be OK. But If it dropped under 10 psi in 24 hours I would look for a remaining issue. IIRC you want it be at least 20-22 psi after about 20-30 minutes of being off IIRC.

Is the original problem gone????


I had a defective brand new vacuum hose like your bad fuel hose you found. It was not round inside.
 
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A slow pressure down to 20 psi is OK, and even something like 10 over night IIRC. -Pressure can change with fluid temperature, and very very slow check valve leak seems to be OK. But If it dropped under 10 psi in 24 hours I would look for a remaining issue. IIRC you want it be at least 20-22 psi after about 20-30 minutes of being off IIRC.

Is the original problem gone????


I had a defective brand new vacuum hose like your bad fuel hose you found. It was not round inside.
Well 4 hours later it started first try. So lets see what it does after sitting overnight. Will report back. Thank you. Was mislead. Was told it shouldnt drop no where near 10psi.

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Not so much miss led.

95-96 was when the operating fuel pressure and plumbing changed, from 30/39 range to 49 psi, and the return line was deleted. Which reminds me, the FPR on the older rigs with the vacuum line can leak fuel into the vacuum line too!!! I think yours has the vacuum line at the FPR???

But you have a new FPR now, so that is no longer an issue. I was diagnosing an endless gremlin on mine where I monitored the FP for days about 3-4 months ago, and IIRC a group of us finally decided that the Factory FSM FPR test was only in the 10-30 minute range after shut down, and did not say what the pressure should be 6 hours later or overnight. I think mine stopped at 20 psi in 30-60 minutes and as low as 10-15 overnight. I forget, it may have been lower, but it was not a problem, and not my problem.

Mine was a distributor gear with a role bin breaking that held the gear in place, and it was changing the location of the rotor as it stuck in different spots. It finally got so bad it took WOT to hold 500 rpm while it shook and backfired. Then finally it was a never will start anymore. I was about to pull the head, when I checked the dizzy guts one last time. At that point I could rotate the rotor by hand 360 degrees :scared:

The rig now runs better than it ever did in 13 years since I bought it, 297,000 miles on her now. Never gave the fuel pressure another thought. But it got a hard look and discussion as I searched for gremlins to blame.

Well 4 hours later it started first try. So lets see what it does after sitting overnight. Will report back. Thank you. Was mislead. Was told it shouldnt drop no where near 10psi.

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Not so much miss led.

95-96 was when the operating fuel pressure and plumbing changed, from 30/39 range to 49 psi, and the return line was deleted. Which reminds me, the FPR on the older rigs with the vacuum line can leak fuel into the vacuum line too!!! I think yours has the vacuum line at the FPR???

But you have a new FPR now, so that is no longer an issue. I was diagnosing an endless gremlin on mine where I monitored the FP for days about 3-4 months ago, and IIRC a group of us finally decided that the Factory FSM FPR test was only in the 10-30 minute range after shut down, and did not say what the pressure should be 6 hours later or overnight. I think mine stopped at 20 psi in 30-60 minutes and as low as 10-15 overnight. I forget, it may have been lower, but it was not a problem, and not my problem.

Mine was a distributor gear with a role bin breaking that held the gear in place, and it was changing the location of the rotor as it stuck in different spots. It finally got so bad it took WOT to hold 500 rpm while it shook and backfired. Then finally it was a never will start anymore. I was about to pull the head, when I checked the dizzy guts one last time. At that point I could rotate the rotor by hand 360 degrees :scared:

The rig now runs better than it ever did in 13 years since I bought it, 297,000 miles on her now. Never gave the fuel pressure another thought. But it got a hard look and discussion as I searched for gremlins to blame.




So i let it sit overnight... Issue is still there. BUT a tidbit of information...

The first key turn to accessory doesnt always make the pump whuuuur. Itll take EITHER multiple half turns of the key. OR i can half turn the key and wait 30seconds - 2minutes. That leads me to wonder... Two issues here? Or maybe it was an electrical grimlin ALL ALONG.

(Its NOT a bad fuel pump, ive put 2 offbrands in and 2 bosches before starting this mess. ALSO 3 DIFFERENT new fuel pressure regulators, 2 relays, new injectors, fuel filter, new injector hose clamps on pump lines. I did attempt the usuals. Also ran many pressure tests.. it bleeds off overnight still)

But what im wondering.. is , is the internal check valve maybe electrically driven? (Built into pump on my 95) , What im asking, is when the pump is suppose to hold pressure ...is it an ELECTRIC internal check valve that has a very low low current draw?

If so than maybe the pump loses electric current and cant hold the gas.


If it has nothing to do with electrical current ignore that theory, im just thinking of anything possible at this point.


Another side note...

When it takes the pump a minute to "wake up" the check engine light also takes a minute to "warm up" BUT the abs light comes on first key turn no problem.

Im Just giving as much info as i can.. maybe itll lead to an electrical conclusion?

So to paint a picture.. SOMETIMES after sitting, i half turn key, and pump takes ages to turn on, but when it does as soon as i hear whuuuuur, the check engine light illuminates, BUT the abs light/radio/ turn on instantly.

(Abs is on cause i swapped to a beefier rear axle and clipped the abs dana 35 lines, dont need them, and check engine is on for code 12 because i disconnected my battery within last 50 cranks, plus the check engine light always flashes on any car when you first half turn the key)
 
You need to get a helper, one turn the key, one under the hood checking spots for voltage when the key is turned to run (1/2 turn as you have called it). There is no electrical-fuel check valve.

Your ignition switch (not the key lock part, but the electrical start-run acc slide switch buried deep under the dash on top of column may be going bad, and the wires/contacts attached to from over heating over 2 decades....

Or it may be a dirty weak electrical connection anywhere between the battery, the computer and certain relays. But it sounds like the computer is getting a rand late pre start signal voltage that makes me suspect the ignition switch first. The fact that turning it to run and it taking 1-120 seconds to power up the timed 3 second power to prime the pump must be a low wandering voltage signal to the computer that powers and times the fuel pump relay. It would not fuel pump or fuel pump relay wiring as the late power up means the computer is sending fuel on signal late!!!! So it has to be the ECU or power to the ECU like the ignition switch. Also check for any loose corroded fuses!!! Check the ignition switch first or just replace it, they are cheap. Also make sure there is power to the ECU at the fuse when you turn the ign-switch!!! To both sides of the fuse, when the fuel pump does not run right away!!! You need to low or missing voltage in the path to the computer at times when the fuel pump fails to cycle on right away. When you do you will know what path has a bad connection to the ECU, or the Ign-switch, or you will know of the Ign-switch or ECU is bad.

If it was me I would buy an Ign-switch and swap it, after testing the fuses and contacts in the fuse boxes that power the ECU. The ECU is what times and powers the prime!!!! Since the timing is variable, it is a power at the ECU issue (wiring, corroded contacts, intermittent contacts) or the Ign switch IMHO.

Nothing after the ECU could change or delay the fuel pump prime on start cycle, and it never restarts a prime cycle till you turn the ign switch off!!!

Any remaining bleed off, if it is even an issue, is not related to your prime power to the pump problem!!!

It is possible the prime timer chip, wiring, electronics in the ECU is going bad, But I'd bet on it being dying, burned, corroded contacts in the ignition switch that powers the ECU, before any thing else.
 
You need to get a helper, one turn the key, one under the hood checking spots for voltage when the key is turned to run (1/2 turn as you have called it). There is no electrical-fuel check valve.

Your ignition switch (not the key lock part, but the electrical start-run acc slide switch buried deep under the dash on top of column may be going bad, and the wires/contacts attached to from over heating over 2 decades....

Or it may be a dirty weak electrical connection anywhere between the battery, the computer and certain relays. But it sounds like the computer is getting a rand late pre start signal voltage that makes me suspect the ignition switch first. The fact that turning it to run and it taking 1-120 seconds to power up the timed 3 second power to prime the pump must be a low wandering voltage signal to the computer that powers and times the fuel pump relay. It would not fuel pump or fuel pump relay wiring as the late power up means the computer is sending fuel on signal late!!!! So it has to be the ECU or power to the ECU like the ignition switch. Also check for any loose corroded fuses!!! Check the ignition switch first or just replace it, they are cheap. Also make sure there is power to the ECU at the fuse when you turn the ign-switch!!! To both sides of the fuse, when the fuel pump does not run right away!!! You need to low or missing voltage in the path to the computer at times when the fuel pump fails to cycle on right away. When you do you will know what path has a bad connection to the ECU, or the Ign-switch, or you will know of the Ign-switch or ECU is bad.

If it was me I would buy an Ign-switch and swap it, after testing the fuses and contacts in the fuse boxes that power the ECU. The ECU is what times and powers the prime!!!! Since the timing is variable, it is a power at the ECU issue (wiring, corroded contacts, intermittent contacts) or the Ign switch IMHO.

Nothing after the ECU could change or delay the fuel pump prime on start cycle, and it never restarts a prime cycle till you turn the ign switch off!!!

Any remaining bleed off, if it is even an issue, is not related to your prime power to the pump problem!!!

It is possible the prime timer chip, wiring, electronics in the ECU is going bad, But I'd bet on it being dying, burned, corroded contacts in the ignition switch that powers the ECU, before any thing else.
WOW that was informative, i did a quick read, but ill sit down and digest it later. But the gist is i more than likely have two issues at hand. Which is good..ish? To here LOL.

The pump taking a minute to turn on happens VERY VERY rarely. So ill adress the bleed off issue for now. Im putting an inline check valve in and reporting back.

I ran another test, with a fancy gauge set I bought. Right after the fuel filter. And BAM bleed off. Im guessing faulty pump, which im tired of replacing, so check valve it is!

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I hear OEM (if it exists) and Bosch are the only fuel pumps worth a damn for our jeeps. How bad is the bleed off? There is a reason the ECU cycles the pump on for 3 seconds during the start up/pre start process. It is to restore fuel pressure as some bleed down from say 30 to 20 in about 20-30 minutes is normal. If it ain't broke don't fix it. But it does need to hold some pressure to avoid vapor lock on hot restarts, and gas vapor in the injector feeds....

I had issues with my saturn recently, the FPR is in the external inline filter on them, LOL. Mine would drop to zero in under 10 seconds when the power went off when I found the problem. And the operating pressure was about 7 psi below spec while running. May have been that way for 10 years, LOL. It got bad enough to finally throw a lean code this year which was the second clue that sent me hunting, the first clue was bad gas mpgs this year... The FPR in the filter was bad.

WOW that was informative, i did a quick read, but ill sit down and digest it later. But the gist is i more than likely have two issues at hand. Which is good..ish? To here LOL.

The pump taking a minute to turn on happens VERY VERY rarely. So ill adress the bleed off issue for now. Im putting an inline check valve in and reporting back.

I ran another test, with a fancy gauge set I bought. Right after the fuel filter. And BAM bleed off. Im guessing faulty pump, which im tired of replacing, so check valve it is!

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I hear OEM (if it exists) and Bosch are the only fuel pumps worth a damn for our jeeps. How bad is the bleed off? There is a reason the ECU cycles the pump on for 3 seconds during the start up/pre start process. It is to restore fuel pressure as some bleed down from say 30 to 20 in about 20-30 minutes is normal. If it ain't broke don't fix it. But it does need to hold some pressure to avoid vapor lock on hot restarts, and gas vapor in the injector feeds....

I had issues with my saturn recently, the FPR is in the external inline filter on them, LOL. Mine would drop to zero in under 10 seconds when the power went off when I found the problem. And the operating pressure was about 7 psi below spec while running. May have been that way for 10 years, LOL. It got bad enough to finally throw a lean code this year which was the second clue that sent me hunting, the first clue was bad gas mpgs this year... The FPR in the filter was bad.
Its bad bleed down. Its instant 30 to 20 as soon as i key it off. Than within 30 minutes 10psi, than 0psi withinan hour.


It is a bosch pump. I had this issue 3 months into owning my jeep. put an oreillys pump, solved the issue for a few months, than it shit out and made the issue happen again, i warrantied it, week later same issue, warrantied it, week later same issue, said f it, went bosch, and same issue.

So i either have extremely bad luck, or its not the pump.

But its bad bleed off for sure. I tried isolating it to rail or not rail but found out i have the hard plastic lines under the rubber outside, so the vice grip method wasnt accurate, if you seen the above post, it was faulty. Psi was still bleeding through. Reason being, Which explained why the bleed down was super super slow with lines clamped. (Gauge is at rail, fuel at rail, lines clamped, but not perfectly since hard plastic, fuel seeeped past clamped lines superrrrrr slow, leading me to think bleed off at rail, new injectors, and 3 new fuel pressure regs, before realizing its not at rail)


Earlier today i confirmed this by attaching my fuel gauge right after the engine side of the fuel filter. And priming it. The bleed off acted identical. So either my gauge attachment wasnt fastened perfect, or its on the filter/pump end for sure.


This fuel thing has had me double check so many things its unreal.


Ive had my fair share of vehicles. And worked on my fair shair. 04 mustang, 01 mustang, 05 calorado, 92 f150 ,89 mustang.. engine swaps, semi restores. Pumps, injectors, top end rebuilds, you name it.


This jeep is possessed 🤣.

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LOL, I named them Cloaked Jeep Gremlins, similar to cloaked Klingons (birds of Prey, leaving you praying they will vanish and not return), LOL, they just appear and then when you look for them they vanish.:shiver:

Good luck and have fun.

Are you 100% sure it is not still the hose/clamp issue? You could pressure test the pump and hose outside of the tank, next time, if there is one, before installing the assy.
 
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