The internet is an amazing tool for info, but........

[Rescue Diver]

I had another reminder to take everything you read on the net with a grain of salt recently. Shirley just purchased a 2001 Cherokee Limited with only 77,000 miles. It runs great other than it's hard to start. You have to cycle the key several times before cranking it to get it to fire up. I decided that was unacceptable so I took to the net to see if I could find the cause. It turns out that her new Jeep has a very common problem. Either her fuel pressure regulator has a bad drain back valve, or there's a bad o-ring in her fuel pump assembly. This allows the fuel to drain completely out of the fuel rail and fuel line, all the way back into the tank immediately after shutting it off. It should hold at least 25 lbs of pressure at the fuel rail for five minutes after shutting it off, but hers drops to zero lbs withing a couple seconds. The fuel pump as designed only runs for a couple seconds to pressurize the system when the key is first turned on, so it takes two or three cycles of the key to move enough fuel to fill and pressurize the line all the way from the tank to the fuel rail. I've now proven this beyond a shadow of a doubt using a fuel pressure tester and a pair of vice grips to clamp off the hose back at the tank. To find that testing info, I had to wade through countless threads in all kinds of different forums where user after user kept spewing nonsense. One guy said his hard starts were due to a bad O2 sensor when the O2 sensor doesn't have anything to do with the initial start. Another said it was the crank sensor, but if that were true, it would not run smoothly once started. Another guy said it must be leaking injectors, but if that were the case, it would be blowing black smoke when you start it from all the pooled gas in the intake, and it wouldn't take as long to presurize the line because it would still be full all the way to the rail since the injectors are higher than the fuel line and gas tank. Not one of these guys ever reported back that thier problem was fixed after replacing whatever part they said was the problem. These guys would have you replacing good parts repeatedly, in a blind attempt at fixing it before finding the true cause.

Diagnosing a problem is like putting a puzzle together. It's even harder when you're getting your info on the net, because that's like putting a puzzle together where you have pieces from 10 other unrelated puzzles mixed in! You have to sort through all the pieces to find only the ones that fit your exact same circumstances, make sure they're legit, and then put them together. It's really frustrating to constantly read posts where a guy comes off as the ultimate authority on something he's never had his own hands on because he read someone on some site saying it's so.

Do your homework. Remember that anything you read might not be accurate, or it might not fit your exact problem. Trust factory info and service bulletins more than Joe Schmoe on the net(myself included). Get the right test equipment. O'Reilly and others loan lots of really good tools for free with a deposit, if you don't want to buy them. And last but not least, look for ways to isolate the problem and eliminate other possibilities before just replacing parts.

Have a nice day!

 

[2lostspace]

I agree with you that there is a lot of miss information out there. For me it sometimes takes a couple of days to get thorough all the information (sometimes just want to toss the computer out the window). At that point I just stop looking and just come and relax on this site.
In a day or two I will get back on the endless search on the net.

 

[Rescue Diver]

I agree with you that there is a lot of miss information out there. For me it sometimes takes a couple of days to get thorough all the information (sometimes just want to toss the computer out the window). At that point I just stop looking and just come and relax on this site.
In a day or two I will get back on the endless search on the net.

I've probably got about 5 hours of pure searching and reading through lots of uninformed nonsense to learn what would have taken 5 minutes to read so I could learn how to isolate Shirley's fuel system problem. It gave me an excuse to buy a fuel pressure tester, and watching what it read, along with seeing the pressure not drop with the hose pinched back by the tank. I know for certain that the cause of the problem lies at the tank, and there are only two things that could allow the fuel to drain back, the regulator's drain back valve, or a bad o-ring. I love it when something can be proven that well. The new regulator is on order. I'm looking forward to seeing the smile on her face when she hears her new Jeep fire right up on the first turn of the key after that.

 

[2lostspace]

I've probably got about 5 hours of pure searching and reading through lots of uninformed nonsense to learn what would have taken 5 minutes to read so I could learn how to isolate Shirley's fuel system problem. It gave me an excuse to buy a fuel pressure tester, and watching what it read, along with seeing the pressure not drop with the hose pinched back by the tank. I know for certain that the cause of the problem lies at the tank, and there are only two things that could allow the fuel to drain back, the regulator's drain back valve, or a bad o-ring. I love it when something can be proven that well. The new regulator is on order. I'm looking forward to seeing the smile on her face when she hears her new Jeep fire right up on the first turn of the key after that.

I would have gone nuts sitting on the net that long looking for infromation. It is good that you found the problems on the Jeep. Now just have to fix it.

 

[Rescue Diver]

It is good that you found the problems on the Jeep. Now just have to fix it.

That's the easy part. It'll take me an hour to drop the tank and install the new regulator and o-ring. I love my air tools!

 

[jeffgtoman]

Ok, I'm no Jeep expert, just asking. Is the regulator in the tank? On Fords, it is usually at the back of the engine. That way you only have one pressurized line running to the tank. It's also easier to change the regulator.

I love the way you LEARNED what's possible and what is not. The people that can not do this should just take their problem to a mechanic. I read many posts that I want to help the person but I can tell they would not be able to sort thru all of the variables that come up while diagnosing.

 

[Rescue Diver]

Ok, I'm no Jeep expert, just asking. Is the regulator in the tank? On Fords, it is usually at the back of the engine. That way you only have one pressurized line running to the tank. It's also easier to change the regulator.

I love the way you LEARNED what's possible and what is not. The people that can not do this should just take their problem to a mechanic. I read many posts that I want to help the person but I can tell they would not be able to sort thru all of the variables that come up while diagnosing.

On the later model fuel injected Jeeps like the 2001 Cherokee, the regulator actually snaps into the top of the fuel pump assemble on top of the tank. You have to drop the tank to replace it, but you don't have to actually remove the fuel pump if you don't want to. I plan to remove the fuel pump assembly because I'm replacing an o-ring in the assembly that had a service bulletin on it. The bad thing about this design is that the regulator is also the one and only fuel filter. That means to replace the fuel filter(a regular service item) you have to drop the gas tank!

Here's a good view of how it all works.

WJ Fule pump fix TSB:1400201 - North American Grand Cherokee Association

 

[Petescj]

You spend to much time on the computer. :laugh: I had to dumb down your post to save time for others.

I've probably got about 5 hours of pure searching and reading through lots of uninformed nonsense to learn what would have taken 5 minutes.

 

[Rescue Diver]

You spend to much time on the computer. :laugh: I had to dumb down your post to save time for others.

Maybe I should report this post!

 

[kickitandholdit]

Were all fighting the computer chair technicians lol

my dads jeep does this and i found so much different on the net i just said screw it and let dad hit the key a few times every time he drives his jeep :laugh:

 

[Rescue Diver]

Were all fighting the computer chair technicians lol

my dads jeep does this and i found so much different on the net i just said screw it and let dad hit the key a few times every time he drives his jeep :laugh:

There's a seller on ebay that lets brand new regulators go for $45 with free delivery. They don't come with the package, but they're new. I'm guessing they bought them bulk without individual packaging. It'll run your dad over $100 for one from Advance or any other auto parts store. After I ordered Shirley's, there were 8 left.

 

[Old Dog]

I agree, most of the info you get on the net is worth exactly what you paid for it.
Funny story, when I got my ford 8.8 I asked a couple questions about it
on some ford sites and got no good answers. I finally got my question answered correctly on a jeep site.
I guess jeepers know more about them than the ford guys.

 

[Petescj]

Duly noted.

Maybe I should report this post!

 

[2lostspace]

You know if it was me I would change the fuel pump seeing that the tank is out. If you dont you know what will go out next.:dunno: You know how it goes.

 

[Rescue Diver]

You know if it was me I would change the fuel pump seeing that the tank is out. If you dont you know what will go out next.:dunno: You know how it goes.

The pump costs about $140. The current one only has 77,000 miles on it and it's making a solid 49 lbs of pressure. And it's not that hard to drop the tank. I'll take my chances.

 

[jeffgtoman]

On the later model fuel injected Jeeps like the 2001 Cherokee, the regulator actually snaps into the top of the fuel pump assemble on top of the tank. You have to drop the tank to replace it, but you don't have to actually remove the fuel pump if you don't want to. I plan to remove the fuel pump assembly because I'm replacing an o-ring in the assembly that had a service bulletin on it. The bad thing about this design is that the regulator is also the one and only fuel filter. That means to replace the fuel filter(a regular service item) you have to drop the gas tank!

Here's a good view of how it all works.

WJ Fule pump fix TSB:1400201 - North American Grand Cherokee Association

Good info. I'll remember this. I have a Grand Cherokee at work that is a Security vehicle. I'll remember this if I run into the same symptoms. The vehicle is one of my favorites in the fleet due to it's reliability. Our Blazer is my least favorite.

 

[flyingbrick]

hi there.

It may be easier for you to pop into your local performance car parts store and buy a cheap adjustable fuel pressure regulator.

You can install that into the return line in the engine bay in 10 minutes and use your pressure gauge to set it up.

Could be easier, maybe cheaper

-Nathan

 

[Rescue Diver]

hi there.

It may be easier for you to pop into your local performance car parts store and buy a cheap adjustable fuel pressure regulator.

You can install that into the return line in the engine bay in 10 minutes and use your pressure gauge to set it up.

Could be easier, maybe cheaper

-Nathan

Small problem with that. A 2001 Cherokee doesn't have a return line.

I learned a lot more since I last updated this thread. Number one, the Internet bad info strikes again. There IS NO CHECK VALVE IN THE FUEL PRESSURE REGULATOR OF A 1997 OR NEWER JEEP!

Before 1997 Jeep had the fuel pressure regulator mounted on the fuel rail with a return line running from it back to the tank.

Starting in 1997, Jeep combined the regulator with the fuel filter and moved it back to the top of the fuel pump assembly on top of the tank. This eliminated the need for a return line. The check valve that keeps the fuel line and rail full of gas when the engine is shut off is located inside the plastic fuel pump assembly between the fuel pump and regulator.

You SHOULD NOT put an inline check valve in a 1997 or newer Jeep because the check valve needs to be BEFORE the regulator, not behind it!!!!

The reason for this is that when you shut off your engine and the fuel sits still in the fuel line and fuel rail, the heat still in the car warms the fuel and causes it to expand. With the fuel regulator isolated before the check valve so it cannot do its job, the fuel pressure begins increasing in the line and rail until it's so high that it will cause something to burst!!!

I know this from personal experience and I proved it.

Thanks to the many many people on the net, including ebay sellers saying the easy fix for the Cherokee check valve problem is to install an inline check valve, I installed a 5/16" inline check valve in the plastic fuel line as close to the tank as possible.

At first it worked perfectly! I was happy to see it maintaining 49 PSI in the fuel rail after shutting the engine off, and the jeep would then start with one tap of the key!

I drove it around a while and it worked great!!!

*******THEN REAILITY HIT********

After test driving it, I parked it in the garage. About an hour later we heard a loud thump. It was the newly installed check valve burtsting internally! I was back to square one with the pressure dropping to zero and the fuel running back to the tank at shut off. At first I thought it must have just been a defective check valve of flimsy design that caused it to fail. I re-did my work and installed another working inline check valve. Again it was holding pressure after shutting the engine off. I was suspicious that something else was going on besides the valve failing because it was defective, so this time I decided to leave my fuel pressure tester hooked to the fuel rail so I could watch it for a while after shutting the engine off. After about 10 minutes, the fuel pressure was growing fast! It got as high as 100 PSI from fuel expansion!!!
If the fuel regulator was after the check valve, it would have simply done its job and allowed the extra fuel pressure to relieve itself back to the tank. But on 97 and newer Jeeps, if you install an inline check valve, the expanding fuel has nowhere to go and will eventually blow something up like the check valve itself, the injector o-rings, or it will burst the plastic fuel line somewhere. It could spray gas on a hot exhaust and cause an explosion!

I had my answer, the internet bit me again by recommending that I install a check valve in line!!!

Now I get to replace the plastic fuel line I cut to splice in the check valve, and I still have to drop the tank and replace the fuel pump assembly to fix the original problem. Replacing just the pump will not fix the drain back problem because the check valve is not in the pump, it's in the plastic assembly that the pump mounts inside of.

********SUMMARY*********

DO NOT INSTALL AN INLINE AFTERMARKET CHECK VALVE IN A 1997 OR NEWER JEEP CHEROKEE!

IT WILL NOT WORK WITH THE NEW DESIGN THAT WENT INTO PRODUCTION IN 1997 WHERE THE REGULATOR IS MOUNTED ON TOP OF THE TANK!!!

IT WILL CAUSE SOMETHING TO BURST AND COULD CAUSE A FIRE OR EXPLOSION!