briangbettes

Have a 2000 XJ w/ 245K miles. Runs like a champ. Recently started having a problem where it will start just fine, then I get to a destination, it will crank, but no fire. Try several times, but no fire. Not an electrical issue I don't think because everything works when I turn the key. I can hear the fuel pump pressurize, but it is like it isn't getting any gas. I can sit and try to crank up to 20 times and it won't start. Leave it sit for 30 mins to an hour, starts first try. I have had a problem with it since I bought it 7 years ago where I have to always let the fuel pump pressurize twice for it to start most times. My brother, who owns same vehicle and is a certified mechanic said he has had the same issue with his. He has replaced all the filters, fuel pump, gas lines, relays, etc. and it still does the same thing.

New battery last week, new starter 8 months ago. So it happened to me again today, and I let out a little gas through the psi valve. Started right up. But I did that once before and I still had to let it sit for 30 mins.

Searched this forum on several intermittent starting problems and none seemed to address this.

Ideas please?

BlueRidgeMark

Search here on "heat soak". It's a known issue with the later Cherokees. I think your problem sounds like what I've read.

97grand4.0

Recently I am finding out what bad injectors can do, hard start after driving is one thing. However, the classic signs you describe seem to point more to fuel pump, imo. cam and crank sensors can also cause similar probs. I would start with a $20 harbor freight fuel pressure gauge.

briangbettes

So...it happened again today. Took my wife to a class, then went off to do a couple of my jobs. After I finished, about an hour and a half later, crank, crank, crank, but no start. Like it isn't getting fire.

Like I said before, I hear the fuel pump pressurize, but now I am wondering, does a fuel pump go out slowly, or all at one time? Does a fuel pump sound like it is pressurizing, but isn't getting any fuel in the line? Reason I am asking is because, after it didn't fire after several cranks, I did what I did yesterday. I let a little bit of fuel out through the pressure sensor valve, maybe two seconds worth at the max, got in and it started right up. Same as yesterday. Does this give any more clues as to what I am looking at? Thanks!

PatHenry

Yes, a fuel pump can and often does die a slow death.

Let me second what 97grand4.0 said and suggest you check your fuel pressure. A cheap Harbor Freight special of the parts store loaner tool is sufficient. You need to read a steady 49.2 +- 5 psi to be in proper spec.

Also BlueRidgeMark knows what he is talking about so look into the heat soak thing as well.

BlueRidgeMark

Pat's right, of course. A slow death is quite normal for a fuel pump.

But this bleeding the fuel business is what has me thinking it's not the fuel pump. You are reducing the pressure in the rail and getting it to start.

Hmmm. Thinking out loud here.... Maybe the pump can't start against the pressure, but once the pressure is relieved, it can spin enough to get going?

In any case, the fuel pressure test is where you need to go.

briangbettes

Okay, thanks to all of you! I did try a search on this forum for "heat soak" and didn't come up with anything that made sense to me, but then again, I am new to this forum, AND not a strong wrench. More like a weekend hack. So maybe I did something wrong in my search?

Will try the fuel pressure either tomorrow or on Sunday when I have time (I know...taking a chance it will not die on me between now and then). Will get back to you all on it as soon as I find out. Thanks again for the info!

PatHenry

Anytime sir!

In full disclosure, I am myself a "weekend hack"... aka Amateur Jeep mechanic, aka Jeep enthusiast.
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97grand4.0

That is really the hallmark of a failing cam or crank sensor aka CPS or CKPS, respectively. No they won't throw a code only about half the time. But first you need the basic fuel pressure test.
Should come right up to 50 lbs when running, then shut it off. It should hold 25 lbs min for 5 minutes. If it bleeds right off below that you found your problem. $20 at harbor freight. Otherwise we are just guessing.

I will add that a couple years back mine was doing the same thing, ran to my destination, shut it off, go to start and just cranks. As I was using it for estimates at customers homes it was enough to p*** off the pope. Ended up being the cam sensor. Not the cranks sensor, mind you, though that was changed also. Long story short, 3 replacements...first worked for a couple weeks..second..same..third being a mopar from a junkyard that's stil in there. You want MOPAR only on that anythig else is a pure waste of time and money. Stronger magnets in the hall effect switch.

briangbettes

Harbor Freight has a Fuel Injection Pump Tester Kit - $19.99. Is that the one you guys are talking about? It is the only thing they list on their website as a fuel pressure gauge that is a tester. If so, I am going to pick it up tomorrow.

I am assuming I just hook it up on the nipple on the rail, start the vehicle, then take the readings? Sorry to ask such a dumb question, as I am sure it is, but I haven't done this before. :-P

Also, 97Grand4.0, another friend of mine was saying today that it sounded like either the cam or crank sensor. So after getting the Fuel pressure tested tomorrow, then I will go from there. Thanks for the tip on the MOPAR part. We have a U-Pull It close by, so I am sure I can find what I need.

Thanks again, Gents!

PatHenry

Yes that's the one.

A local parts store (Autozone, advance, Napa) will lend you one for free (you have to leave a deposit until it's returned) as a "Loaner tool".

briangbettes

Okay thanks. I asked O'Reiley's near me and they said they didn't do that. If it is the right one, and only $20, I just as soon own it so I have it for the future.

Thanks again!

RocketMouse

also some parts stores have these as part of their "loan a tool" programs.
Don't forget to test at idle, speed, accel, and decel too.
Let us know what the results are.

97grand4.0

The HF one I just bought last week myself. You need teflon tape to connect the hose on the gauge so it won't leak.. ..$1 at any hardware store..after that , good to go. Yep just put it on that schrader valve on the fuel rail.
Someone suggested taking readings during accel and decel, .Not sure how that would go..would you have him lean out the window with the hood up as he drives along? Also there is no book test for that that I am aware of. Only ones I know of are the key on engine off test, the running pressure, and the leak down test. Of course you can use it to diagnose other stuff like fuel injectors, if you have a pulser, they are about $100.

When the cam or crank sensor goes it eventually MAY throw a code if you try to start it half a dozen times. These items are just plain good preventative maintenance if you haven't ever done them, there will come a day when you will need to. Notorious for going out.

4WD4EVER

I agree with BRM in his initial response: It's heat soak of the fuel in the rail. This is why it will start after you release the vaporized fuel; you have a liquid present for the injectors again. Liquid fuel is required for the injectors, not a vapor. Does it make sense now?

I suspect you will need something like this:

https://www.summitracing.com/search/...at-shield-kits

2nd edit: btw, this is/was a known issue by ChryCo and a TSB was issued to resolve it by insulating injector #3 but insulating the #3 injector only didn't work for everybody. Some owners required insulating injector #4 as well. May as well do them all at that point...