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

[Intellect]

So i have an issue that has gotten worse and worse.

1995 4.0 4wd jeep cherokee 4.0


Present day - if it sits for over a day, it takes multiple trys to get it to stay running. As in, i crank it, it dies, so i flood it with gas, the second i let off gas it dies. I have to force feed it gas for 1-5 minutes, to get it to stay on.

Once this has been done, i can drive it for HOURS in the woods..highway.. etc.

It has done this for ages. But started as, having to prime the key twice.. than having to prime 3-4 times... than it moved to, having to have it turn over twice ( turn key and try to crank, stop, turn key and try to crank again ) .. than turn over 4-5 fimes (same as last parenthesis) . Than present day, its a miracle to get it to stay on. After flooding it with gas and a few times, itll idle beautifully, AND can uncrank and recrank with NO issue.



Im on my way to be ase certified, so i know a bit about vehicles. Ive swapped a few mustang motors, had a foxbody growing up, etc... So this jeep is REALLY a puzzle.


I do NOT have a fuel gauge set, but will rent one if itll help me determine something new, as i already am pretty sure its fuel.


Things ive checked, iat, iac, tps, cps, map(3 different brands)

Fuel pressure regulator (tried 3 different ones, from different companies)

Fuel pump ( 2 offbrands, now a bosch)

Fuel filter (2 times, forget brand)


If the jeep sits for a day, i can take a screw driver to the schrader valve, and get air, and no gas. Maybe a drip.

This leads me to think a fuel issue/fuel bleed off issue/leak.

Ive checked this xj up and down, do not see a gas leak.

The fuel pump and fuel regulator are the only spots that have check valves, both parts ive replaced at LEAST 3 times, thinking "oh maybe bad out of box, or bad brand"

Ive been chasing this issue for a while, but now that it has gotten worse, i NEED to figure it out.


The jeep has 247,000, rebuilt transfer case. Engine runs smooth as butter (when it finally isnt fuel starved) , can tell pevious owner did some top end maintenance. Ive had the jeep last 10k ish.


Random facts, the battery is good, it reads good with my multimeter, its only a few months old as it is.

New alternator, oem spec.

Newer o2 bosch.

Newer cap, plug, wires, etc

Jeep is not a daily, but it isnt a mud bogger, its a weekend grocery getter, that sees an offroad event once a month if that.

Who knows, maybe im nuts, maybe its NOT fuel, maybe i am WAY OFF, this is why im asking in here.


I have had 2 Jeep techs of 20 plus years tell me they are clueless after hearing my story in depth, yall got the short version.

I will be forever grateful to anyone who helps me pinpoint this issue. Its only initial start up, once shes up and running, she is fine. Its the getting her running thats a b&t$h.

Starter is good. Spark is good. Ignition coil is good. Oil pressure is good.

Ive always went with the old... If it walks like a duck, and quaks like a duck... It's probably a duck, saying. Thats why i am led to think it is a check valve, fuel pressure being held, issue.


The only thing NOT new, are injectors, but a bad injector to my know should cause these issues, ive had my fair share of bad injectors, and these seem fine (granted i plan to change them for good measures, if my jeep starts behaving soon)

So i know i sort of rambled some, but i figured the more information the better.

1995 4.0 inline 6, automatic, 4wd, 246-247,000 , 5.5" lift, 35"s, 1 ton steering, and other goodies (if i didnt have so much into it, id just start fresh, but $6k+ later ... Lol)

I am newer to forums so i apologize if i didnt follow proper ediquiete, if your seeing this on fb than ignore the last sentence.

In the end, jeep takes 2-6 cranks, holding the gas peddle to the floor, to get it started, and that use to be it, once started it was fine, but now i have to CONTINUE to hold the gas, at 4krpm constantly for a few minutes, to get it to idle without dieng.


The kicker... INTERMENTANT issue.

Could go out tomorrow and crank it up no issue, or have to play with it for 25 minutes of gas flooding.


Excuse any typos.

Added info, i get no codes. Once a code 13, but that went away.

Also, i never replaced the the fuel pump ASSEMBLY, only the actual pump.

The pump doesnt always whine when i first turn the key to accessory, sometimes it takes a few seconds, sometimes it takes a few key cycles, this is with any pump i put in there... Electrical issue? But once i get the s.o.b running. I can sit there and uncrank and recrank it non stop, as if it was a new jeep.


Im scratching my head so hard over here.

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[Intellect]

So i have an issue that has gotten worse and worse.

1995 4.0 4wd jeep cherokee 4.0


Present day - if it sits for over a day, it takes multiple trys to get it to stay running. As in, i crank it, it dies, so i flood it with gas, the second i let off gas it dies. I have to force feed it gas for 1-5 minutes, to get it to stay on.

Once this has been done, i can drive it for HOURS in the woods..highway.. etc.

It has done this for ages. But started as, having to prime the key twice.. than having to prime 3-4 times... than it moved to, having to have it turn over twice ( turn key and try to crank, stop, turn key and try to crank again ) .. than turn over 4-5 fimes (same as last parenthesis) . Than present day, its a miracle to get it to stay on. After flooding it with gas and a few times, itll idle beautifully, AND can uncrank and recrank with NO issue.



Im on my way to be ase certified, so i know a bit about vehicles. Ive swapped a few mustang motors, had a foxbody growing up, etc... So this jeep is REALLY a puzzle.


I do NOT have a fuel gauge set, but will rent one if itll help me determine something new, as i already am pretty sure its fuel.


Things ive checked, iat, iac, tps, cps, map(3 different brands)

Fuel pressure regulator (tried 3 different ones, from different companies)

Fuel pump ( 2 offbrands, now a bosch)

Fuel filter (2 times, forget brand)


If the jeep sits for a day, i can take a screw driver to the schrader valve, and get air, and no gas. Maybe a drip.

This leads me to think a fuel issue/fuel bleed off issue/leak.

Ive checked this xj up and down, do not see a gas leak.

The fuel pump and fuel regulator are the only spots that have check valves, both parts ive replaced at LEAST 3 times, thinking "oh maybe bad out of box, or bad brand"

Ive been chasing this issue for a while, but now that it has gotten worse, i NEED to figure it out.


The jeep has 247,000, rebuilt transfer case. Engine runs smooth as butter (when it finally isnt fuel starved) , can tell pevious owner did some top end maintenance. Ive had the jeep last 10k ish.


Random facts, the battery is good, it reads good with my multimeter, its only a few months old as it is.

New alternator, oem spec.

Newer o2 bosch.

Newer cap, plug, wires, etc

Jeep is not a daily, but it isnt a mud bogger, its a weekend grocery getter, that sees an offroad event once a month if that.

Who knows, maybe im nuts, maybe its NOT fuel, maybe i am WAY OFF, this is why im asking in here.


I have had 2 Jeep techs of 20 plus years tell me they are clueless after hearing my story in depth, yall got the short version.

I will be forever grateful to anyone who helps me pinpoint this issue. Its only initial start up, once shes up and running, she is fine. Its the getting her running thats a b&t$h.

Starter is good. Spark is good. Ignition coil is good. Oil pressure is good.

Ive always went with the old... If it walks like a duck, and quaks like a duck... It's probably a duck, saying. Thats why i am led to think it is a check valve, fuel pressure being held, issue.


The only thing NOT new, are injectors, but a bad injector to my know should cause these issues, ive had my fair share of bad injectors, and these seem fine (granted i plan to change them for good measures, if my jeep starts behaving soon)

So i know i sort of rambled some, but i figured the more information the better.

1995 4.0 inline 6, automatic, 4wd, 246-247,000 , 5.5" lift, 35"s, 1 ton steering, and other goodies (if i didnt have so much into it, id just start fresh, but $6k+ later ... Lol)

I am newer to forums so i apologize if i didnt follow proper ediquiete, if your seeing this on fb than ignore the last sentence.

In the end, jeep takes 2-6 cranks, holding the gas peddle to the floor, to get it started, and that use to be it, once started it was fine, but now i have to CONTINUE to hold the gas, at 4krpm constantly for a few minutes, to get it to idle without dieng.


The kicker... INTERMENTANT issue.

Could go out tomorrow and crank it up no issue, or have to play with it for 25 minutes of gas flooding.


Excuse any typos.

Added info, i get no codes. Once a code 13, but that went away.

Also, i never replaced the the fuel pump ASSEMBLY, only the actual pump.

The pump doesnt always whine when i first turn the key to accessory, sometimes it takes a few seconds, sometimes it takes a few key cycles, this is with any pump i put in there... Electrical issue? But once i get the s.o.b running. I can sit there and uncrank and recrank it non stop, as if it was a new jeep.


Im scratching my head so hard over here.

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Forgot to add, injectors are oem, think a leaky injector could cause all of this heart ache?

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[Anak]

Leaky injector would be the next thing to pursue. Possibly more than one.

A fuel pressure gauge would certainly be a helpful tool.

The best thing to do at this point is to get a fuel pressure gauge and a pair of needle nose vise-grips. Put on the fuel pressure gauge, get the Jeep running, check the fuel pressure, shut the Jeep down and immediately clamp off the fuel line back by the fuel filter where it is rubber and can be collapsed/shut off by the vice-grips. Now go see what the fuel gauge does.

If the fuel gauge holds steady, and continues to hold steady overnight, then you will know that you are losing you fuel pressure back into the tank.

Hmm...

It occurs to me that you have a return line too. I haven't had to play with one of those yet. You might need two pairs of vice-grips. Hopefully somebody who knows the earlier fuel systems better can chime in on that front.

At any rate, isolate the fuel system components so that you can determine if you are losing fuel to the front (injectors) or rear (fuel pump).

If you are losing fuel to the injectors then you know what your next step is.

If you are losing fuel back into the tank then we need to figure out what is going on to allow that. Perhaps a loose hose inside the tank? Or perhaps a hole in the steel lines in the pump/sending unit assembly?

At this point my bet is going to rest on injectors, but you would be best off putting in some diagnostic efforts first.

 

[Intellect]

Thank you Anak, i plan to rent a gauge friday, i havethe day off friday. i thought about it today during work and have been wondering injectors myself. Since that is the only part that is oem. (At 247,000 miles).

I do not know these style fuel system that well either, i thought of the clamp before fuel filter a few days ago, but the return style throws me off, i think i have to clamp somewhere else but im not sure where?

I have an offroad event all weekend and it would be cool to solve this before that, no one has injectors in stock locally. BUT i have 4 oem ones from a friends part out free. So if i find an injectors bad, or two, i have spares to get me by.

So what i need to learn, is ....1) how to isolate the check valve (in fuel pump, and pressure regulator) from injector rail

2) if our theory of bleed of at rail is right, how do i diagnose WHICH injector? Undo rail, but keep them pluged in, and prime the system, lay down some paper towels, and see which leaks over the spand of a few hours? usually an hour is all it takes.

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[Intellect]

Anak to add icing on the cake here, my gf and friend who tag along offroad, HAVE mentioned a faint fuel smell when i pop the hood to check fluids. (Probably useless inflrmation, they are car illeterate, but when im in the woods in florida, the pollen has my sniffer out of commision LOL)



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[RCP Phx]

It a bad idea to install any injector that isn't in a "matched" set.

 

[Intellect]

It a bad idea to install any injector that isn't in a "matched" set.

Really? Ivenever heard this. I understand to not put a brand new with a set of used for obvious reasons. But ive never heard they are "sets" matched together. Because anytime you buy them at auto stores they are sold single, not matched in groups of six or 4 or 8 depending vehicle.


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[Intellect]

Leaky injector would be the next thing to pursue. Possibly more than one.

A fuel pressure gauge would certainly be a helpful tool.

The best thing to do at this point is to get a fuel pressure gauge and a pair of needle nose vise-grips. Put on the fuel pressure gauge, get the Jeep running, check the fuel pressure, shut the Jeep down and immediately clamp off the fuel line back by the fuel filter where it is rubber and can be collapsed/shut off by the vice-grips. Now go see what the fuel gauge does.

If the fuel gauge holds steady, and continues to hold steady overnight, then you will know that you are losing you fuel pressure back into the tank.

Hmm...

It occurs to me that you have a return line too. I haven't had to play with one of those yet. You might need two pairs of vice-grips. Hopefully somebody who knows the earlier fuel systems better can chime in on that front.

At any rate, isolate the fuel system components so that you can determine if you are losing fuel to the front (injectors) or rear (fuel pump).

If you are losing fuel to the injectors then you know what your next step is.

If you are losing fuel back into the tank then we need to figure out what is going on to allow that. Perhaps a loose hose inside the tank? Or perhaps a hole in the steel lines in the pump/sending unit assembly?

At this point my bet is going to rest on injectors, but you would be best off putting in some diagnostic efforts first.

Im new to naxja, relised i replied wrong at first, my mistake, my replies are bellow.




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[RCP Phx]

Really? Ivenever heard this. I understand to not put a brand new with a set of used for obvious reasons. But ive never heard they are "sets" matched together. Because anytime you buy them at auto stores they are sold single, not matched in groups of six or 4 or 8 depending vehicle.


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You could get lucky, but you also might have one cyl not running right (rich/lean). The ECU only sees the injectors as all the same!

 

[Intellect]

You could get lucky, but you also might have one cyl not running right (rich/lean). The ECU only sees the injectors as all the same!

Im not following, if its in working order its working, if its faulty its faulty, how will replacing just the bad injector hurt the others? If they are all within ohm load and spec.

When you buy them new they are single sold not biased into sets of 6

So?

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[RCP Phx]

Im not following, if its in working order its working, if its faulty its faulty, how will replacing just the bad injector hurt the others? If they are all within ohm load and spec.

When you buy them new they are single sold not biased into sets of 6

So?

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No matter what they do to try and replicate the factory results, they can't! Your old injectors are not going to put out the same, PERIOD!

 

[BCKNBLK]

Drop the fuel tank and give that assembly in there a very good look-over. You are describing the exact problem I had several years ago. Turns out the fuel pump/filter/float assembly had a leak on it. The pump worked fine, but there was a leak on the unit itself and was leaking fuel right back into the tank. Finally discovered this after taking it out again, and priming it off the vehicle. It started pissing fuel back into the tank. Thats where my pressure was going. Dropped in a brand new assembly (brand new), re-installed the tank, etc. Ran like a champ.

 

[Intellect]

Sensor "shelf life"?

Leaky injector would be the next thing to pursue. Possibly more than one.

A fuel pressure gauge would certainly be a helpful tool.

The best thing to do at this point is to get a fuel pressure gauge and a pair of needle nose vise-grips. Put on the fuel pressure gauge, get the Jeep running, check the fuel pressure, shut the Jeep down and immediately clamp off the fuel line back by the fuel filter where it is rubber and can be collapsed/shut off by the vice-grips. Now go see what the fuel gauge does.

If the fuel gauge holds steady, and continues to hold steady overnight, then you will know that you are losing you fuel pressure back into the tank.

Hmm...

It occurs to me that you have a return line too. I haven't had to play with one of those yet. You might need two pairs of vice-grips. Hopefully somebody who knows the earlier fuel systems better can chime in on that front.

At any rate, isolate the fuel system components so that you can determine if you are losing fuel to the front (injectors) or rear (fuel pump).

If you are losing fuel to the injectors then you know what your next step is.

If you are losing fuel back into the tank then we need to figure out what is going on to allow that. Perhaps a loose hose inside the tank? Or perhaps a hole in the steel lines in the pump/sending unit assembly?

At this point my bet is going to rest on injectors, but you would be best off putting in some diagnostic efforts first.

I rented a pressure gauge..

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[Intellect]

Drop the fuel tank and give that assembly in there a very good look-over. You are describing the exact problem I had several years ago. Turns out the fuel pump/filter/float assembly had a leak on it. The pump worked fine, but there was a leak on the unit itself and was leaking fuel right back into the tank. Finally discovered this after taking it out again, and priming it off the vehicle. It started pissing fuel back into the tank. Thats where my pressure was going. Dropped in a brand new assembly (brand new), re-installed the tank, etc. Ran like a champ.

I just seen your comment.. thats my next task after i do a gauge test... How do i do that on a return style fuel cherokee?

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[Intellect]

So my fuel pressure is 30psi when its on, and goes to 0 when off, there isnt even enough time for me to clamp anything its so fast...

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[four_shot]

You have a fuel leak. It should hold pressure for hours. Try clamping the return line and running the test again.If it holds, the leak is on the return side. if it drops, its on the pressure side.

 

[Intellect]

https://youtu.be/VqjuAqeMZWA

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[Intellect]

You have a fuel leak. It should hold pressure for hours. Try clamping the return line and running the test again.If it holds, the leak is on the return side. if it drops, its on the pressure side.

So I did as you suggested I clamp the return line and Prime that the system in gauge shot up to 60 because the return line is Vise grip and it slowly bled down to 40 mid-30s but stops right there which is where it should hold anyway so it isn't bleeding off at the rail since it drops from 6230 correct it only drops from 60 to 30 because it is over pressurized correct

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[Intellect]

You have a fuel leak. It should hold pressure for hours. Try clamping the return line and running the test again.If it holds, the leak is on the return side. if it drops, its on the pressure side.

WOW.. voice to text butchered that! I clamped it at the return line.. i primed it... It shot to 60 and lowered to 30-40 ish, and stays there. So im wrong for thinking the rail is the culprit correct? It drops 60 to 30-40 because 60 is over pressure ised. Am i thinking logically?


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[Anak]

Leaking down that fast does not sound reasonable for an injector. Or several. If it were injectors your oil should be full of gasoline by now. It should be simple enough to check the oil just with the dipstick. Maybe give it a good sniff too. If still in doubt you could change the oil. Then try to light the drain pan. Well, maybe not... :fuse:

I can't imagine the vehicle would even run well with injectors that didn't shut down.

I think revisiting the tank end of things is the best bet right now. The suggestion of trying to run the pump assembly outside of the tank is a reasonable one, if you can figure out how to do it safely.