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91 Cherokee Won't Start

Ok I mad a big Loop right back to Fuel pressure! It doesn't hold pressure that long. When I disconnect the return fuel line by the Fuel rail its gushing out when i turn the key on. Seems like its going in the rail and gushing right out?? Doesn't build up enough pressure. Wouldn't the fuel pressure regulator control that? Or is the return line supposed to be pressureized too? But If I clamp off the return line and turn the key on I still don't get any pressure now. If the pump is pumping wouldn't it build up pressure? Maybe the check valve? If it is I am going to try the inline check valve trick first.

Thanks
 
Anyone? Does the Fuel pressure regulator hold the pressure in the Fuel rail? When I undo the return line and turn they key on the fuel is just making a round trip right back to the tank.
 
You still never post any pressure readings.
The check valve only helps if you have pressure, good pressure not just flow.
The only thing the check valve is give you faster start ups.
 
yes, the pump should be putting out more tan the required 39 PSI, the pressure regulator dumps the extra fuel/pressure back to the tank through the return line.
 
I know I have intermittent fuel pressure. But I am trying to figure out if its the pump/check valve or Fuel pressure regulator. Before it started this I did have a hard start condition, had to cycle the key twice before it would start. I am going to go buy more parts tomorrow and work on it again on Friday.
 
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after the pump cycles it wont keep pumping unless its running, from what ive seen on my 91,
im not sure if it will start the pump while cranking tho.

by the way this problem is going to end up to be something little that was overlooked,,,it always works out like that
 
Elfwizard1975 said:
I know I have intermittent fuel pressure. But I am trying to figure out if its the pump/check valve or Fuel pressure regulator. Before it started this I did have a hard start condition, had to cycle the key twice before it would start. I am going to go buy more parts tomorrow and work on it again on Friday.
Click to expand...


Ok, I am having the same problem as you are right now. I have Replaced the Fuel Pressure Regulator last night. No help. I have replace the fuel pump and fuel filter. Also Spark plugs, wires and TPS. Still no Start. My fuel pressure is doing the same as yours. When I tested the pressure it was below 20 psi. I think it was 13psi if I remember right. For the pass 2 weeks to get it to start I would have to hold the gas pedal open to get it to run. Once it started it would run great. I was thinking it was the CPS But I have spark. So I am not sure. I have thought about replacing the IAC But the last time I had it running I pulled the connector for it and the idle was all over the place. I reconnected it and it idles at 900rpm.

By the way Mine is a 92 4.0LHO with an auto.
 
When you replace the fuel pump does it come with the check valve in the unit? I wonder if that could be the problem. From what I have read.

I'll work on mine friday all day, I'll let ya know what I find.
 
No, It did not come with a check valve. It came with the pump and a new sock, and a new hose to go to the hard line in the take. Not sure where a check valve would go.

I hope you fine something, If I come across the answer I will let you know also.
 
iac is the idle air controller, but im not sure thats your prob if your not getting the right fuel pressure. You could have a bad injector that is causing your FP to drop. To test and see, put a fp guage on the rail and leave it and see if the FP drops very quickly. you can check the fp regulator by taking pliers and pinching the fuel return line and seeing if that spikes the pressure, i think all manuals cover how to test for that and give you the appropriate psi, when pinched and not pinched. i believe that you need to have around 39 psi with vacum to the fpr, but check the man. Get the FP fixed before you worry about starting it. But if it does not start with carb cleaner you have a problem other than just fuel. If your getting spark, and your getting fuel by rail or carb cleaner and your still getting no bang it is either the CPS or the IAC. They r the only 2 sensor devices that can fail that will cause a crank but no bang.

Good luck
 
Tweeternpi said:
No, It did not come with a check valve. It came with the pump and a new sock, and a new hose to go to the hard line in the take. Not sure where a check valve would go.

I hope you fine something, If I come across the answer I will let you know also.
Click to expand...
The check valve is built into the pump.
 
One thing that's been overlooked....how cold is it there right now? I remember back in early December when we had a similar severe cold snap there were quite a few problems with no starts.

It's -2*F here right now, and I have no doubt that if I were crazy enough to venture outside and try to start it, my Jeep wouldn't start. It's a cold weather thing, and I don't think there was a good fix ever found for that (unless you park it in a warm garage, that is)
 
Fuel pressure is low, BUT I cant even get it to start with carb cleaner. I pulled the distributor and it spins fine. The starter seems to have drag on it Like the battery is somewhat dead. I guess the oil pump could be causing the drag? The timing is on, valve train is moving and dist is pointing at 1 when its supposed to.
Im pretty much pissed off so I had to quit working on it.

New starter
New battery
Cap and rotor
Plugs and wires
I have spark
Fuel pressure is 20lbs {I know its low but wont even start with carb cleaner}
Tested coil its fine.

Turns over slower than normal, All grounds checked and battery cables too.
 
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Well tonight I am replacing the Coil an Cap an rotor. The Cap and Rotor look new, but I bought the XJ used and They do not cost that much. As for the coil, It looks like it has never been changed. I have almost 200,000 miles on the XJ so why not. I have spark but it does not look that strong. If it starts I will let you know.

Just for an update. I have replaced FPR, Fuel filter, Fuel pump,TPS, Wires, and Spark plugs. Tonight I am going to Replace Coil and Cap and Rotor.

If this does not work, I do not know.

Tweeternpi
 
Dude, if you have spark, by the old pull the plug and ground it method, and you cant start it with carb cleaner it is deff the IAC. Its a wierd part and somebody smater than me could explain it better, but im fairly confident that your engine is suffocating.

pull the plugs, let it sit over night

Then clear flood the motor while starting. IE Put the pedal to the floor and try starting it. Make sure the bat is good and have a buddy spray in carb clean if it does not start after the 5th cranking session

Gl
 
Yucca-Man said:
One thing that's been overlooked....how cold is it there right now? I remember back in early December when we had a similar severe cold snap there were quite a few problems with no starts.

It's -2*F here right now, and I have no doubt that if I were crazy enough to venture outside and try to start it, my Jeep wouldn't start. It's a cold weather thing, and I don't think there was a good fix ever found for that (unless you park it in a warm garage, that is)
Click to expand...

It was damn cold up here this morning at 6:45. I went out to head to work and mine wouldn't start. Just turned over. I finally got her going after 5 minutes but she was moody all the way to work.

Elf...I went through all of this during the cold spell that Yucca spoke of in Dec. Mine ended up being the battery. It cranked over fine with my battery and when I jumped it off my 01. When I tested the battery, I showed volts that were well within range and then moved on. After 3 days of no trial and ALL error, my buddy brought his computer over and checked the cold cranking amps. They were in the mid 100's. We put in a new battery and it fired right up. The computer wasn't getting enough juice and was acting like you do when you don't get a good nights rest.
 
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