Derision

Okay, I've done a bunch of searches and I have a general theory of what might be going on, but I figured I'd seek out a few opinions just in case.

'93 XJ with the 4.0. 224,000 miles. She's run beautifully until yesterday.

Now, when I go to start it up, it just cranks. I can keep the key turned indefinitely, it turns over and cranks away and tries to start up but never quite gets there. If I put the gas pedal to the floor, it'll start to sputter and, after maybe 30 or 40 seconds, will catch, run like crap for five seconds, and then even out and run great.

Once started, there's no problems, no hiccups, nothing... runs great. If I shut it down and start it back up within a few minutes, there seems to be a 50/50 chance that it'll start right up.

My first thought was the check valve in the fuel pump. Subsequent searching online seemed to back that up. I figured I'd seek out a few more thoughts before I go through the adventure of trying to get at that thing.

Thanks in advance!

Parsnip

What about idle air controller? If you have to hold your foot to the floor it sounds like it'd flooding then once the mixture evens out it runs rough until its back in spec...could be fuel related as well

ahell

your going to need a fuel pressure gauge.....autozone's loan a tool kit works nice.or about 50 bucks for a cheap one.

1)check fuel pressure.should have 40 when you turn on key. should hold, but chance the check valve is gone like you said. ...key it on and off a couple times, should build up to 40 psi. and fire up pretty quick then.

32 at idle with fpr hooked up. up hook FPR should have 40.

shut jeep back off, get a pair of clamping pliers, clamp off the return line at the fuel tank. the line that's NOT going to the fuel filter. key the jeep back on,to let fuel psi build. mine shot up to 70psi....I bleed it off to 40 psi.....let the system stay under pressure for 15 min. more than a lbs or two loss, may have leaky injector(s).


After about 45 min I lose pressure in my injectors,*down to 10 lbs*yet still runs fairly well for 265,000 mile and starts up easy if I double key the fuel pump

if you have the cermaic ballast block for the fuel pump, worth a test too. yes they are suppose to get warm, one side should have 13v and the other about 9v at idle. 9v side should go up as rpm increases.

also check your FPR, pull the vacum line and see if it hold's suction.

Next I would look in to the ign system ,cam and crank sensor,and coil. testing of the cam and crank sensor can be a real PNA as you have to catch it while its acting up.

if your a one man band, a timing light works great to check for spark

check your vacum line to your map sensor as well.

rojowe

I was having the SAME EXACT PROBLEM, I cleaned my TB and IAC thinking it probably wouldn't do anything, now she starts just about every time first try.
Give it a shot, just be careful with the MAP sensor.

Derision

Thanks for the suggestions! I had actually cleaned the throttle body a month ago or so, but I hadn't touched the IAC. I did have an extra IAC that I'd gotten a while back in case I wanted to change it. This morning, I cleaned out the throttle body again and replaced the IAC with the new one I'd gotten (Duralast AC320).

As soon as I'd replaced it, the idle was waaaaay high. I don't have a tach, so I can't say exactly what the RPM was... but I was hitting 50 without touching the gas. I know what everyone's thinking, but I checked the vacuum lines and they were good. Either way, I hadn't taken the throttle body out anyway, and I made sure the O ring was installed with the IAC.

I disconnected the battery for a while to reset things, and then drove around for 40-50 miles to see if the computer could relearn things. The first two times, it started up right away and I was pretty jazzed. I drove a while, stopped to get a drink, and when I came back out, it was back to not starting. This is with a brand new IAC and a freshly cleaned throttle body.

After 40-50 miles, it hadn't relearned anything, so I got it home, cleaned my original IAC up nice and put it back in. Started out idling high, but quickly adjusted and went back down to normal, so I dunno if the IAC I had was faulty or what, but... meh, if the original works, I'll leave it at that.

Still starting like crap, though, so onto the next theory...

Thanks for the info! I'll start doing that later today if the weather holds.

AJH

Derision

I've been trying to get a video of this thing failing to start all day. Of course, every time I point a camera at the thing, it starts right up.

This is the worst it's been since I've been trying. Mind you, I stomped on the gas the moment it started having trouble. Stretch this sequence out to four or five minutes of hard cranking, sputtering, and more cranking, and that's what I've been dealing with for a few days.

rojowe

Damn reading through you post I really thought the IAC was gonna win! Good luck on sorting it out, keep us updated, I'm sure someone with more knowledge will pop in eventually and give some helpful advice.

Derision

You know, I'm really kind of baffled by this. After I replaced the IAC, I drove it and when I stopped for a minute, it wouldn't start. When I got it home, I put the old IAC back in. Since then, I have tried to get a video of the thing not starting. I figured maybe someone might look at it and go, "Well, that sounds like bla bla blabity bla" and then I'd have somewhere to look.

The fuel pump shows as having proper voltage. I've been unable to check the pressure, but I'd think with awful pressure, it wouldn't run or would run lean, whereas I don't see any such issues.

Either way, in the past three days, I have tried to take at least 30 videos of this thing not starting and each and every time, it has started right up. At most, it cranks for a second or two, as in the video I posted before, but it still starts up and runs fine. The THREE times that I did NOT try to take a video, the damn thing wouldn't start.

There doesn't seem to be any significant trend in when it does and doesn't start. I thought maybe it was a heat thing -- a few of the times it wouldn't start, I had been driving for a while and was in a parking lot on a 77 degree day. Of course, I have since repeated this and had no issues.

I just drove my normal Sunday morning commute, 180 miles from Maryland to New Jersey, and stopped three times. Each time, it started right back up. I get to work here, park it, drop off the dogs and go back out to run to the store real quick... and it took forever to start. Of course, I wasn't trying to take a video of it.

So yeah. I'm thinking... plugs? Wires? Distributor cap? Maybe still the fuel pump? I really, really hate throwing money and parts at things hoping to hit a run when I have no leads and I hate like hell to take it to a garage to get it diagnosed for some preposterous sum of money only to have it not do what I'm saying it's doing while they've got it, which is inevitably what will happen. Maybe I should just try to take a video every time I start it? That seems to be working pretty well so far.

Turbo X_J

Without actually checking the fuel pressure (takes less than 1 minute) your just shooting in the dark.

kjc

The CPS can cause the hard start symptoms you have. They often go out gradually over time but never get better on their own. Also, flooring the go pedal won't help if you have a fuel injection system. The PCM is on break when cranking, so the signal from the TPS won't make it supply more fuel, and there's no 'pump' like in normally aspirated carbs. I'd check the CPS.

belvedere

+1 to check fuel pressure, both while it's running and after it's shut down.

Derision

Okay, I've tested the fuel pressure. When I turn the key on and the fuel pump kicks in, I get 38psi, which I imagine is within acceptable limits. After starting, I get 32psi at idle. Following the instructions above, the injectors don't appear to be leaking.

I've checked the vacuum line to the MAP sensor; I've also run over just about every other vacuum line I can find.

I guess the ignition system would be next on the agenda. Any further advice would be greatly appreciated! This is really starting to give me agita. At least the thing DOES always start up, eventually... it's just a matter of how LONG it takes to start. And I'm mildly paranoid about it deciding finally to NOT start up, probably when I'm in the middle of Maryland farmland or something.

Again, thanks everyone in advance for any more thoughts you can lob at me.

AJ

Derision

I figured it out!!

After checking the fuel pressure at the rail yesterday, I was looking under the hood. After closing everything up, I noticed that the car was starting right up again, like nothing was wrong. Drove it home, and then today, it was running even worse.

Now, it was having trouble starting and then it would sputter and choke out for at least a good minute and a half before finally catching and running fine. I even took it to a garage just to get an opinion from the mechanic on duty; he had no idea, but suggested that maybe I try tuning it up.

I thought to myself, when I had the hood open yesterday, could I have touched something and made it run okay temporarily? I popped open the hood and started moving around vacuum lines and spark plug wires.

And then...

The wire that goes from the distributor to the ignition coil was not actually plugged into the ignition coil. The boot was over the plug, yeah, but it wasn't actually snapped in place. I pushed the thing on, and shazam... instant starting, no more problems.

Facepalm.

So that's been the problem. I guess that when it's running, the spark is able to arc from the coil to the wire because they're close, but when I'm cranking it and it's running off the battery, it just doesn't have quite enough to get it going for a while.

Either way... crisis averted!

Thanks everyone for the suggestions and general help! And I learned some new stuff, like how to check fuel pressure and adjust IAC valves.

AJ

Derision

My final update on this one.

Today, I replaced all the plugs and wires. When I pulled off the plug that goes from the coil to the distributor cap, the insides of the plug just disintegrated in a puff of dust. Eesh.

Since replacing them, she runs like a new car. So yeah... that's what it was.