Switching fuel pressure regulator from tank to rail?

I don't see why this wouldn't work but I'll run it by you guys anyway.

Can I remove and bypass the fuel pressure regulator (I'll abbreviate it FPR for ease of reading) in the tank and switch my fuel rail to the kind with an FPR on the rail?

Why would I want to do this? Try to find me a new 96 jeep Cherokee "in tank" FPR anywhere lol I cannot find one.

Specs: 96 xj with the returnless fuel rail with no regulator on the rail its in the tank.

Your 96 runs around 50 PSI of fuel pressure. Depending on the year, the ones with the external fuel regulator run 10-20 PSI lower and regulate on the return line. You'll have to do a little research.

An adjustable external fuel regulator is kind of pricey, most all start at a round $100+ and go up to around $350 for the name brands.

How is a fuel rail pressure regulator going to work without a return line? It can't.

I don't honestly know. There is one on my 96 sending unit though. I thought that maybe the fuel pump has the ability to pump more than 51 psi and the regulator keeps it from pumping too much.

The problem is I cant find a sending unit or a regulator for a 96 online. I will have to really start digging deep I guess. I really don't want to buy a used one and deal with this failure again.

Ah. Welcome to the club.

I have been where you are, and I have good news for you: The fuel pressure regulator on a '96 is not any different from the ones used on the earlier HO years. I don't know how far back you can go. I expect the Renix years are another ball game, but I am running the readily available FPR in the tank of my '96 and it gives me the required 49 psi at the rail. From what I can tell the difference is the lack of a vacuum line. There is no vacuum line to connect to the FPR in the tank, whereas there is on the rail. My read is that Chrysler simply stuck with the existing part and modified the fuel maps to compensate.

I did a bit of a write-up on the subject. You can see it here: http://www.naxja.org/forum/showthread.php?t=1107991&highlight=1996+fuel

If someone knows something different I am all ears, but this is working fine on my XJ.

Anak said:

Ah. Welcome to the club.

I have been where you are, and I have good news for you: The fuel pressure regulator on a '96 is not any different from the ones used on the earlier HO years. I don't know how far back you can go. I expect the Renix years are another ball game, but I am running the readily available FPR in the tank of my '96 and it gives me the required 49 psi at the rail. From what I can tell the difference is the lack of a vacuum line. There is no vacuum line to connect to the FPR in the tank, whereas there is on the rail. My read is that Chrysler simply stuck with the existing part and modified the fuel maps to compensate.

I did a bit of a write-up on the subject. You can see it here: http://www.naxja.org/forum/showthread.php?t=1107991&highlight=1996+fuel

If someone knows something different I am all ears, but this is working fine on my XJ.

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That is awesome, I will try that. I really appreciate you chiming in because I finally found a sending unit from factory Chrysler parts....for a bit over $500 :shocked: I will try this as soon as I can get the part ordered and will post my results.

Please do share what you find. All I have is my own experience and what I have managed to gather from my research, but none of that research was particularly authoritative.

The price for the whole sending unit is just nuts. At that price a person might as well step up to one of those fancy high capacity tanks that use a '97+ pump/sending unit assembly.

Best of luck.

:greensmok

Agreed. At the price of a new sending unit and being that a new gas tank is on the to do list I would probably opt for a fuel cell and external pump, regulator etc. (I would probably have cash to spare as well.)

Edit: For those wondering about that decision on the fuel cell, my xj is nowhere near practical anymore considering I use it to get down tight trails to fishing spots in the northern counties of FL.

Anak said:

I have been where you are, and I have good news for you: The fuel pressure regulator on a '96 is not any different from the ones used on the earlier HO years.

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What? The earlier years had the FPR on the fuel rail with a return line, not on the tank.

And, the fuel pressure was not static. It varied based upon "engine load" which is to say manifold vacuum. I will take the FPR in the tank any day of the week.

When I supercharged a '93 YJ, I found out about the FPR on the fuel rail. It was impossible to tune the fuel on this installation. We had to install a GM external regulator in order to resolve the fuel issue.

IMO, the in tank installation is best by far.

Talyn said:

What? The earlier years had the FPR on the fuel rail with a return line, not on the tank.

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in '96 they moved the FPR to the tank.
You can see the vacuum nipple just poking out...

No one makes a replacement as it wasn't designed to be serviced. It is different from the one on the rail as the output pressure is higher.


Crown makes a replacement OEM tank module part # 5003869AA if all else fails...

Digger87xj said:

in '96 they moved the FPR to the tank.

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What did I say that was contradictory to that?

You can see the vacuum nipple just poking out...

No one makes a replacement as it wasn't designed to be serviced. It is different from the one on the rail as the output pressure is higher.

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I now understand what he was saying. However, as you said using the earlier FPR will not give the necessary 49 psi as the earlier regulator is 39 psi.


However, I recalled someone using a FPR from a Chrysler minivan for the rail version to raise their fuel pressure. A quick google found that FPR has a higher pressure rating, ~50 psi. OEM # 5277829, Standard Motor Products # PR211.. might be worth looking into it.

Digger87xj said:

No one makes a replacement as it wasn't designed to be serviced. It is different from the one on the rail as the output pressure is higher.

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Incorrect.

Rockauto lists the same part number for the '96 and all HO regulators before it.

Anak and his link are correct. The only difference between the '96 setup and the '91 - '95 setup is the location of the regulator (obviously) and the vacuum line. In the '91-'95, the pressure in the rail is regulated by vacuum, in this case, 39 psi at full vacuum (engine idling). At wide open throttle (no vacuum) the rail gets the full pump pressure that it is capable of with a max of 49 psi. This is why Anak got the 49 psi at the rail in his installation, no vacuum (or vacuum line) going to the regulator. Simple really...

I agree with O-Gauge. Living here in the desert, and at the time having a badly cracked exhaust manifold, the fuel would come from the tank, get slightly heated when entering the engine compartment, then whatever fuel that was not used in the rail and was bypassed by the regulator on the rail and returned to the tank, picking up more heat from the return from the engine compartment, then dumped into the tank. On any hot day, this cycle would happen constantly and it would get to the point that the fuel pump would be screaming and the tank would be extremely hot to the touch and oil canning sounds would be coming from the tank. I would have to shut the Jeep off, and carefully take the gas cap off to relieve the pressure, and let it cool down for about an hour. It really sucked. Bypassing in the tank is so much better.

Warlock1 said:

Incorrect.

Rockauto lists the same part number for the '96 and all HO regulators before it.

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If you look at rockauto's listings they specify on the rail, not in the tank for the regulators. "Located at Fuel Rail" with the exception of the airtex part, which is a pos anyhow and doesn't list location.

39 psi at full vacuum (engine idling). At wide open throttle (no vacuum) the rail gets the full pump pressure that it is capable of with a max of 49 psi.

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Wrong. The fuel pressure should be 39psi using the earlier FPR on the rail with the vacuum hose disconnected, 0 vacuum. With the vacuum line connected it is lower.

Try this one: http://www.jeep4x4center.com/fuel-pressure-regulator-53030001.html

It is listed for '91-'96. Also fits Wrangler and Grand Cherokee. I have no idea whether those are in the tank or on the rail at the head.

I think the only difference is whether or not a vacuum line is connected.

At atmospheric pressure that regulator will give you 49 psi. Add a vacuum to it and the psi will drop according to the vacuum. If you were to add positive pressure to it (regulated air pressure or a set screw) the pressure would go up in correlation with the applied pressure. I think that is the only difference in play here.

And I think recognizing that difference could save owners of '96s a lot of headache and cash.

Its interesting that all those vehicles it is listed for have a fuel pressure of 39 psi.. but magically it jumps to 49 psi.

Talyn said:

What did I say that was contradictory to that?

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I don't know why I quoted you

Warlock1 said:

Incorrect.

Rockauto lists the same part number for the '96 and all HO regulators before it.

Anak and his link are correct. The only difference between the '96 setup and the '91 - '95 setup is the location of the regulator (obviously) and the vacuum line. In the '91-'95, the pressure in the rail is regulated by vacuum, in this case, 39 psi at full vacuum (engine idling). At wide open throttle (no vacuum) the rail gets the full pump pressure that it is capable of with a max of 49 psi. This is why Anak got the 49 psi at the rail in his installation, no vacuum (or vacuum line) going to the regulator. Simple really...

I agree with O-Gauge. Living here in the desert, and at the time having a badly cracked exhaust manifold, the fuel would come from the tank, get slightly heated when entering the engine compartment, then whatever fuel that was not used in the rail and was bypassed by the regulator on the rail and returned to the tank, picking up more heat from the return from the engine compartment, then dumped into the tank. On any hot day, this cycle would happen constantly and it would get to the point that the fuel pump would be screaming and the tank would be extremely hot to the touch and oil canning sounds would be coming from the tank. I would have to shut the Jeep off, and carefully take the gas cap off to relieve the pressure, and let it cool down for about an hour. It really sucked. Bypassing in the tank is so much better.

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No sir, you are incorrect and so is rockauto.
All repair information, as well as the FSM all say the regulator in a 96 is a non-servicable part.

FSM said:

The Fuel pressure regulator is part of the fuel pump module and is not serviced separately. If the regulator is defective, replace the fuel pump module.

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As far as fuel pressure goes... the 91-95 fuel pressure spec is 39psi with the vacuum line disconnected and 31psi connected. I just verified this in the FSM as well.

96+ specs are 47-52 psi. Using a earlier model regulator designed for in-rail applications in the 96 will result in low fuel pressure and possible driveability problems.

Anak said:

Try this one: http://www.jeep4x4center.com/fuel-pressure-regulator-53030001.html

It is listed for '91-'96. Also fits Wrangler and Grand Cherokee. I have no idea whether those are in the tank or on the rail at the head.

I think the only difference is whether or not a vacuum line is connected.

At atmospheric pressure that regulator will give you 49 psi. Add a vacuum to it and the psi will drop according to the vacuum. If you were to add positive pressure to it (regulated air pressure or a set screw) the pressure would go up in correlation with the applied pressure. I think that is the only difference in play here.

And I think recognizing that difference could save owners of '96s a lot of headache and cash.

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highlighted section is incorrect. Adding pressure to the vacuum port of the FPR will not raise the fuel pressure

The part# you quoted, 53030001, regardless to what the aftermarket says, is NOT for a '96. it is 91-95 only.

I also just verified this in the factory parts manual.

Did you verify after replacement that you actually achieved 49 psi at the fuel rail? edit: just read your thread. interesting result.. was the part number printed on the old regulator?

Digger87xj said:

No sir, you are incorrect and so is rockauto.
All repair information, as well as the FSM all say the regulator in a 96 is a non-servicable part.

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I might be incorrect, but it apparently is serviceable for some. And apparently, it DOES work.

Digger87xj said:

As far as fuel pressure goes... the 91-95 fuel pressure spec is 39psi with the vacuum line disconnected and 31psi connected. I just verified this in the FSM as well.

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Ok, I didn't check with my FSM, and my memory is a little bad and I'll admit that. But the important thing here is that he got 49 psi, which is what he needed. I would guess that the '96 fuel pump delivers a higher pressure and might be where the higher pressure comes from. Just a guess.

Digger87xj said:

96+ specs are 47-52 psi. Using a earlier model regulator designed for in-rail applications in the 96 will result in low fuel pressure and possible driveability problems.

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Yes, with the older style pump.

Digger87xj said:

highlighted section is incorrect. Adding pressure to the vacuum port of the FPR will not raise the fuel pressure

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You might be correct, but have you actually tried it? The regulator was also not supposed to go any higher than 39 psi. Hmmm.......

Digger87xj said:

The part# you quoted, 53030001, regardless to what the aftermarket says, is NOT for a '96. it is 91-95 only.

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Who cares? If it works, and without any modification, why not use it?

Digger87xj said:

Did you verify after replacement that you actually achieved 49 psi at the fuel rail? edit: just read your thread. interesting result.. was the part number printed on the old regulator?

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Probably should have read the whole thread, just saying...

Man, so many people always ready to jump down peoples throats around here. If it is a clean install, solves a problem, uses factory parts, is more cost effective, and does the job properly, who the hell cares? Would most hard core Cherokee owners do the WJ knuckle/brake upgrade if possible? Probably yes. Is it a factory XJ part? No. Are you bitching them out also? Man, just stop with the constant bitching and whining. Open your mind. If someone does it for themselves, and is a safe, clean install, good for them. If you don't like it, then don't do it to your rig. That's why they make more than 1 flavor of ice cream, not everyone like vanilla. I for one applaud Anak for finding another good parts swap that will save a crap load of money and and do it correctly. Rant off.

Warlock1 said:

Man, so many people always ready to jump down peoples throats around here. If it is a clean install, solves a problem, uses factory parts, is more cost effective, and does the job properly, who the hell cares? Would most hard core Cherokee owners do the WJ knuckle/brake upgrade if possible? Probably yes. Is it a factory XJ part? No. Man, just stop with the constant bitching and whining. Open your mind. If someone does it for themselves, and is a safe, clean install, good for them. If you don't like it, then don't do it to your rig. That's why they make more than 1 flavor of ice cream, not everyone like vanilla. I for one applaud Anak for finding another good parts swap that will save a crap load of money and and do it correctly. Rant off.

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I agree 100%
Also, sorry if I came across as bitching.. not my intent. Correcting misinformation is.

As a professional my first instinct is to question and verify every single aftermarket part out there. I have been burned too many times not to question their information and cross reference it with factory parts, using factory manuals.

Running a 4.0 or any engine lean can lead to other unintended consequences. Some of them catastrophic to the wallet.

If it, in fact works, Great! save some money and go for it.

As for myself, or a customer's vehicle, I'd replace it with the module unit from crown. Why? The fuel pump is as old as the regulator, and why do the job twice? Plus you get a warranty if it fails. If you replace just the regulator, there is a high probability that the pump will fail soon after, and you are doing the job twice, wasting your time. I've seen it too many times in the past not to mention it in this thread.

Who knows who will see this thread... it may help someone to make an informed decision in the repair they choose.

Correction of misinformation is a good thing. At no point have I claimed that I have the final answer. But I do think I have found an answer which will serve a number of folks well.

From my own experience I am not convinced that the FSM is correct in calling the '96 FPR a non-serviceable part. I suspect someone didn't want to take responsibility for the required prying on the tabs to release the FPR. Besides, there's more money to be made selling complete assemblies. How many times have you found that you needed a plastic doo-hickey to fix a problem only to have the dealership tell you that no, you can't buy that plastic doo-hickey all by itself, it only comes as part of a sub-assembly? I swear the longer I live the closer they are getting to the point that the replacement sub-assembly is a new model vehicle.

Speaking for myself, I can gently pry a few plastic tabs in order to release a part. I swear it was easier than opening any number of retail packages. I didn't even have to risk slitting my own wrists with a box cutter.

I would love to get feedback from other owners of '96s who have been down this road. Perhaps my situation and experience was unique. I really don't know.

However, I will say, to paraphrase George Bernard Shaw, "Man who say it cannot be done should not interrupt man who is doing it."