[Jeepertrav]

Quick back story, owned my jeep for almost 10 years now. Has had a 2.5 in it for 98% of its life. Going on about 6 months of my 4.0 swap and I have pretty much 1 last problem that is getting the better of me. I’ll try to make this reading as easy as possible.

When I start the jeep it sometimes has a long hard start with a hard knocking/starter kickback noise and will either start and idle/run very bad or not start at all. I can then turn off the key, try to start it again and get the same results or it starts up like it’s brand new and runs fine.

Every sensor on it is new, starter, alternator, dostributor, coil, plugs, etc. all new due to the swap process. Used ECU with the new capacitors and new harness. Fuel pressure reads high if it’s running good or running bad. I’ve taken the fuel line off the return side of the rail and ran a hose into a gas can and my pressure drops to somewhat normal with a working regulator. Regulator has no change in pressure when the return line is hooked up. Bad start problem still occurs in either scenario.

I’m at such a loss I really have no clue what to look for next. I might try to check the fuel pump this weekend but it was working fine before the swap. Any ideas or any one have any similar problems? It’s my daily, and still gets me around but I’d like to fix the issue.

 

[armyvet25]

Both issues(hard start/runability) sound like a possible timing issue. Could be separate, starter/starter solenoid going bad/weak battery combined with running issue, definitely get the fuel issue sorted. Don't over think it, at first I'd pull the starter and have it bench tested, inspect the flywheel, then go from there, pain in the ass, but better than throwing money away. The pressure increase with return line hooked up normally might actually be normal, not positive.

 

[Jeepertrav]

I've checked the timing multiple times at the distributor. When I first put everything together I was 180 out but since then it's been ok. The starter is brand new, but I know new parts can be bad out of the box. Most everything was bought new when doing the swap. The battery was the same one in before the swap and I never had this problem but again that doesn't mean anything. Flywheel is brand new bought for a '95. I will pull the battery and starter this weekend and have them tested at my local parts store. I might drop the tank as well and check all my lines and run some tests on the fuel pump to make sure it didn't crap the bed.

 

[armyvet25]

sounds like a good plan, also, even though you have the dist in right now, double check the timing while running.

 

[Jeepertrav]

Will do, the thing that is really stumping me is that it's not a constant problem. So I can't really mess with 1 thing until the problem goes away cause the problem isn't always there. Hard to diagnose when I cant knowingly recreate the problem. Frustrating. Thanks for the tips.

 

[armyvet25]

Good luck, let us know what you find, and welcome to the forum from Ohio!

 

[Luckymac]

Welcome to the Forum @Jeepertrav

The fact that when you're having your problem, the engine finally starts buts continues to run poorly makes me think of three things.

1- Problems with starter engaging and/or the Bendix drive not releasing....Make sure the starter bolts and the power wire to the starter are tight. If not, tighten them and try to start the Jeep. If they're tight, remove the starter and closely examine the Bendix drive teeth and the flywheel teeth. if they're buggered up at all, there's your problem. If they're not buggered up, reinstall the starter. As stated above, since you have the starter off, you might take it in to where you bought it to have it tested. I don't have a lot of faith in parts store diagnostics, but if you take the starter back to where you bought it and they find it's bad, they should give you another one. Since both the starter and flywheel are new, the teeth on each one should be pristine.

2- Timing-I believe your timing is controlled by your PCM (computer). You state your distributor is new. Is that new OEM, new aftermarket or rebuilt? I'd start by pulling the cap, and closely examining the 6 contacts inside the cap for having contact with the rotor tip and check the rotor for secure fit on the shaft. I'd also check the pointer on the rotor for looseness-it shouldn't move at all.
Make sure the distributor hold down bolt is tight. I don't think the proper distributor for your setup should have any adjustment.

3- Fuel regulator...Fuel pressure is high all the time and drops a bit when vacuum hose is removed. Do you have a vacuum gauge? (They're not expensive) Test the vacuum at the regulator vacuum hose. Do you know someone that might loan you a known to be good fuel pressure regulator?

You state you have a coil. Did you get your engine from a '87-'90 Cherokee? I think '91-'95 4.0 engines had direct injection, thus coil packs. I'm not sure. I have a 4.2 with a carb so I haven't paid a lot of attention to FI Jeep issues.
With an intermittent issue, especially on an older vehicle, I'd suspect a faulty electrical connection or a single faulty component that has moving parts.

Here's how I'd begin.
I'd start my diagnostics at the distributor, looking for loose connections especially where a terminal is connected to a wire. Make sure the terminals are secure in the plug and are making good contact with each other between the male and female halves of the plugs. If the clip that holds the plug halves together is not working properly or is missing, you can use a small wire tie to hold the two halves tight together. Always put a dab of dielectric grease in the plug when putting it back together.
If all looks good at the distributor, I'd move on to the coil checking the same things, Then to the starter solenoid and relay. If the terminals are ring terminals, make sure the nuts are tight and that there's no corrosion on the studs or ring terminals. If the terminals are push on. make sure that there's no corrosion and that they grab the tab and aren't at all loose. if the push on terminal is even slightly loose, pinch it with pliers so that it stays tight when connected. A dab of dielectric grease on any electrical connection that you touch will go a long way in preventing future corrosion.
I'd for sure check the battery connections at the battery and especially the ground cable where it attaches to the block. You state the flywheel is for a '95, so I assume your Jeep is a 1995 model. Check where the (+) cable attaches in the PDC. I doubt the issue is with your battery, but as an outside chance, I'd make sure the battery posts are clean and shiny as well as the inside of the battery cable ends. If there's any sigh of corrosion where the cable connects to the cable end, replace that cable. If the terminals aren't able to tighten properly replace the terminal or better yet, the entire cable.

Kind of a long read but hopefully I've given you some direction. Let us know what you find and don't be shy about asking for any more suggestions.

Good Luck, L.M.

 

[Jeepertrav]

Thanks for the long reply, gives me a lot to read and think about!

1. I will check everything you mentioned when I remove the starter. Starter was from RockAuto so return is possible but a pain with shipping.

2. Timing is PCM controlled, so set it to baseline and let the computer take over. New aftermarket distributor with new plugs, cables, etc. I will double check all those you mentioned in this as well.

3. FPR is new. When I have the fuel return line unhooked from the fuel rail and a hose hooked up to it to reroute fuel into a gas can the fuel pressure regulator does change with vacuum hooked up or unhooked. With the fuel line connected back it runs high at about 39-42 PSI. Differs slightly every time I check. So I know somewhere in my return line there is a kink or blockage. But the hard start problem is there even when the fuel return line is unhooked.

Jeep is a '95 YJ with a 4.0 swap. It's got a single coil, multi port injected. I've checked all my electrical contacts and grounds on a few occasions but 1 more time won't hurt. And I use dielectric grease everywhere there is electrical contact made.

I have been wanting to replace the cables because they do show some signs of corrosion and get some good terminals with ports for accessories such as my winch. That might be a project this weekend along with these test and checks.

Thanks again for the long reply, I'd rather get to much information that not enough.

 

[JimHansen77]

Hello @Jeepertrav

1993 YJ, 4L, automatic

I went through a recent phase of intermittent difficult start or no start, occasional hard knocking when it did start, and occasional rough running if it did start and didn't knock. But it was intermittent. Most of the time is started and ran great. Very, very long story short it was the PCM. I went through WranglerFix.com and got a new-to-me PCM and it's now running fine. Your milage may vary, of course.

Jim

 

[Jeepertrav]

Thanks Jim, I've been tossing around the idea of it being the PCM on mine as well. I've got a few things to look at this weekend before I start throwing parts at it.

 

[JimHansen77]

Thanks Jim, I've been tossing around the idea of it being the PCM on mine as well. I've got a few things to look at this weekend before I start throwing parts at it.

One of thing things I tried to convince me it was the PCM was to disconnect both battery terminals and touch them together to discharge the PCM when it wasn't starting or was running rough. Each time I did that the Jeep started up great when I reconnected the battery cables. Good luck!

 

[Jeepertrav]

Copy, I may add that into my list and see how it reacts. Thanks again.

 

[Luckymac]

Copy, I may add that into my list and see how it reacts. Thanks again.

If you think your issue may be with your PCM, check out Wranglerfix. They're a preferred vendor on this forum. If you type "wranglerfix" in the Search Community box at the top of the page you'll see what other forum members have to say about them.

Good Luck, L.M.

 

[Jeepertrav]

Working on it this morning, distributor and initial timing are all real nice and tight. Everything has a good connection.

I was checking timing with a light while it was running and when it runs good its at about 12deg advanced. When it’s running bad it’s at about 8-10 deg retarded. But what’s also a little weird I think is that both times the timing would jump around anywhere from 8-14deg. Never stayed at a constant which I don’t think is right. Not sure what this means but it’s new info that should definitely help.

 

[Luckymac]

Since your timing is adjusted by the PCM, I think there's a possibility of a bad PCM or damaged wiring. Since the problem seems to be intermittent, I'd start with the wiring. I'd follow the wire from the distributor to the PCM. If you don't find any loose or questionable connections or perhaps a pinched wire, check the plug into the PCM. Unplug it, examine it and plug it back with a swipe of dielectric grease. Test drive the Jeep.
Following a wire through a loom can be a real pain. Perhaps a cursory exam of whatever connectors are easily accessible and a quick peek at the Ignition Control Module connectors (if a FI motor has an ICM). My 4.2 came with a ICM, but the newer 4.0s may not have one.
If you don't find any wiring problems and the condition continues, pull the PCM and open it up. Look for 3 capacitors. They'll be little cylinders sticking up off the circuit board. Maybe 3/8" tall and about as big around as a soda straw. Look at the tops. If the tops of the capacitors are bulged, they need to be replaced. They may have an X marked on the top. Because the issue is intermittent I'm more inclined to think the problem is in the wiring or connectors, but the PCM is a definite possibility and if it were my Jeep, I'd be sure to check it.

When you turn your key "on" but not to "start", your check engine light should come on momentarily and then go out. If it doesn't come on at all, that's an indicator of a bad PCM. Being that your problem doesn't happen at every start attempt if your check engine light seems to function normally, it may be that that's one time the Jeep will start and run just fine. If the CEL functions properly and the engine runs poorly, I think that the issue is elsewhere. Keep plugging away and hopefully other members will contribute their experience with similar issues.

Keep us updated on what you find.

Good Luck, L.M.

 

[Jeepertrav]

Thanks for the reply Luckymac. I put the correct bolts to the CKP this morning thinking maybe the air gap was off but that changed nothing. Have had some other things to do around the house so I haven't gotten around to checking everything on my list.

I have opened the PCM and the PO replaced the capacitors but I went ahead and redid them myself too just in case.

As far as I have noticed the CEL comes on with every turn of the key regardless of the hard start. I'll pay more attention to that though. All I have to work with now is the changing timing and the timing being different on the good/bad start. Still chuggin along checking and looking.

 

[Jeepertrav]

CEL comes on during bad and good start problems. Which may be a good sign that my PCM hasn't crapped the bed just yet.

I've got a new noise coming from the starter it sounds like. It's happened 2-3 times now. When it starts on a bad start there is a very bad ugly grinding almost sound. Maybe like some gears aren't meshing properly or something isn't working right in the flywheel/starter contact. Haven't had a chance to pull the starter yet and get it bench tested with the battery. Hopefully that will be tomorrows project.

Over on Jeep Forum a guy mentioned he had a similar problem and it ended up being a out of spec flywheel. Said he ran through 2-3 new ones and ended up getting an older used one that worked perfectly. I've got to pull my tranny back a little anyway to get my dust cover on so it may be time to give all that a check and make sure the flywheel is still torqued and at least looks true to the eye.

This is SO ANNOYINGGG!! I thought I was doing a nice thing swapping my 2.5 to a 4.0 but man it's been a battle. Besides all this I'm dealing with a transmission that has no synchronizers. UUGH

 

[Jeepertrav]

Checked the flywheel and starter today.

I manually tested the starter and the bendix pushes forward the entire way and spins good.

The flywheel had a couple knicks on some of the teeth. See pictures

 

[Luckymac]

I have an OE '95 (Cherokee) 4.0 flywheel that I took a pic of so that I could compare it to the one you have. Without counting the teeth, they look pretty much the same.
How does the starter check out?

Good Luck, L.M.

 

[Jeepertrav]

The starter looked good. Little oily from a leak at my oil filter adapter. I hooked it up to the battery off the jeep and the bendix extended very good and fast every time and the gear spun over really smooth. I didn't see any damage on the starter.