Ok fellas and ladies,

running a 4.0 HO, 98 XJ, 3" 31 tires package, exhaust/intake, upgraded 8mm wires, nothing too crazy.

I have had a long crank problem for a while now, about a year. I have just remedied it by turning the key 2 clicks to the ON position, then off, on then off again to prime the fuel pump, then she starts 2 cranks no problem.

I have spark and ignition pulse on all occasions, but like most jeeps with this problem, very little fuel pressure. (every turn of the key to the ON position would bring up the pressure at the rail up about 5 PSI) So I put a nice new expensive BOSCH fuel pump in. I also did a MotorVac cleaning ( Google it if you like) Its a little machine that you basically hook up to the fuel rail/injectors and run fuel and a cleaner through the system, while the car is running.

Now after a nice new fuel pump, and injector cleaning, I still have very pressure at the rail. Now if i just get in the car after it sits for 1 week or 1 minute, i turn it over and it just keeps cranking with no signs of starting. I let off the key, and crank it again, and she fires 2 cranks no problem. And even if I do prime the fuel pump, (like before) key on, then off, It doesn't matter I have to crank it for 10 seconds or so, then stop, and crank again to start it.

I have recently switched from Shell to Mobil fuel. and out of about 10 different start times, I have had a normal time starting 2 out of 10. I'm thinking that was just a damn coincidence.

I am totally stumped, thanks for reading hope you have some suggestions!

OHH and just put a new NSS in about 6 months ago, so that's working good.

sounds like a relay problem to the fuel pump. But I don't know TJ's. Just from your explanation, something is not telling the fuel pump to work up to the needed pressure at the rail. Go buy a chilton's book. They have good wiring diagrams and diagnosis procedures.

Ever think about changing the bad fuel pressure regulator?
When they go bad or the o-rings go bad, they can bleed off fuel back to the tank thru the return line.

Ever think about changing the bad fuel pressure regulator?
When they go bad or the o-rings go bad, they can bleed off fuel back to the tank thru the return line.

X2. Thats what it sounds like to me

Thanks for responding.

However the fuel pump/bleedback valve/ filter / everything, is all one unit, and thats the one I replaced in the tank. And there is no return line. There is only the one line going up to the rail.

I looked in the Chiltens book, and i guess I can test the leakdown of the injectors, with the pressure guage and a a special fitting i have to find, so I can connect the fuel line > guage > rail. Instead of just the guage plugged into the shrader valve on the rail.

If fuel was leaking down wouldent the cyl. fill up with fuel, and upon startup cause a little erratic operation?

Take a picture of your engine.

I know you think it will not help but facts are facts 9 out of 10 people who post a picture have gotten help. To include the guy that could not get his brakes to bleed. He had his calipers mounted on the wrong side with the bleeders down.

Now your suckin Air from somewhere, I'd wash everything really good. Then run it and then look for a wet spot. If nothing is found chances are the sending unit fuel pump pressure regulator you bought is bad IF all the o-ring seals clamps and rubber hoses are good. It could even be the seal on the gas tank. Or a leaking seal on the gas cap.

http://i97.photobucket.com/albums/l231/jeepmansro/100_0344.jpg http://i97.photobucket.com/albums/l231/jeepmansro/100_0345.jpg

Here are picts of my fuel rail. I dont really know what other kind of pictures to take. but its just the single rail, with a fuel feed line going to it. Im wondering if the injectors are leaking down into the cylinders. Has anyone had that happen? and ended up replacing injectors/o-rings?

What about a vacuum issue?

My vote goes for leaking injectors dropping fule pressure. A vaccum issue shouldn't cause a slow start that is remedied by cycling the ignition.

My vote goes for leaking injectors dropping fule pressure. A vaccum issue shouldn't cause a slow start that is remedied by cycling the ignition.

Well if there is no evidence of a leak. Start the engine to normal shut it off and pull the fuel rail. with injectors attached. Turn the key on DO NOT Crank it let the electric fuel pump build pressure. You may have to turn it off and to the RUN posistion a couple of times then look at your injectors.

Had similar problem and was my crank sensor and pulley now jeep fires within a second even at 15 below

If it was a cherokee (the only Jeep I know) I'd say it was a bad crank position sensor. That's a little electric doohickey that tells the computer how fast the motor is turning. When it goes bad the computer can't tell that the motor is cranking, so it doesn't initiate a start cycle and the engine cranks forever. Generaly cranking it again is enough to wake the sensor up if it hasn't totally fried.

EDIT: I know the guy above me just said the same thing, I'm giving some more information.

Troubleshooting is the elimination of everything that is good. What is left has a 95% chance of being the problem.

But being he does not have a scan tool or a Fuel pressure tester. I'm guessing this because if he had he would have it fixed by now. With out a scan tool that can do trips to find intermittant faults. I was helping him with trouble shooting with simple tools once you eliminate the fuel system then start buying parts. But from his discription it sounds more like a fuel problem.

Now it could be that the Crank posistion sensor maybe it works right when at normal opperating temp. But trouble shooting only works one step at a time, one system at a time.

Another thing to consider would be the condition of the fuel filter. It should not cause the pressure to leak down over time, but I have seen them cause a slow start before. Also, if you plan to pull the fuel rail to check the injectors, go ahead and get new seals for them. Make sure you lubricate them during install as well.

First, Thaks for all the help. I still have to pull the rails up to physically see if the seals are shot or injectors dripping. Its weird to see, with a pressure guage on the rail, It takes 5 cycles of the key to get it to read 40 PSI. and with the key on or off, the pressure drops like a led weight.

Second. There is no external fuel filter on this truck. Its all internal to the pump assembly.

Just a thought. I am thinking out of my arse since I do not know TJ's or have a book on them.:homer: I do understand that the fuel pump/FPR/filter is all located inside the tank as one unit. What if the FPR inside the tank is faulty? How does a FPR for these models operate? I don't know? But thinking that its a one line to the fuel rail with no return, Does the FPR operate on a check valve system? again, I don't know. But I would think that a check valve type on FPR on a non return fuel system is the only way to operate. So if its not operating correctly(floating) that could theorytically cause a flow back into the tank and not maintain pressure.

Or your fuel injectors are allowing bleed down as said before.

Again, Im talking out of my ass and don't know TJ's. Im just thinking on theory of how stuff needs to work to achieve desired operation.:homer:

another way to check for a leaking injector is to pull the spark plugs one at a time and look for one that is wet and stinks of gas. this should work if your pressure is dropping that fast. if not, i would say you probably have a bad pump.

also what is the fuel pressure spec for your engine. 40 psi sounds low. my 4.0 '98 gr cherokee has at least 45 psi koeo.

When you put the new unit in did you make sure it was sealed?

Ok time to close this post.

thanks for all your help and suggestions.

I pulled the rail off with the pressure gauge on it. turned the key 5 times to get 40psi of pressure and watched it bleed back to 5 in not even 10 seconds! and no leaks from the injectors. I WAS PISSED! I cleaned the seats and changed the o-rings cause I already got some.

After that i figured its gotta be a new bad fuel pump. It is known to have happen. Well I had it out and new one in, in half the time, and be damned, she shot up to 45psi and started every time. Within 10 min the pressure only went down to 41!! I was giddy with excitement.

motha Fing jeep... but I love her...



Thanks again everybody!