Jeep engine "tune"

[ShadowsPapa]

This is sort of Jeep related - it's a Jeep engine, and it's in a 4x4..........
1994 Jeep ZJ 4.0 liter engine, pulled from a totaled ZJ with 100,000 miles and rebuilt by me about 2010.

Since building the egine and getting things 95% squared away, the thing has run great - easy starting, smooth running no matter the temperature. No misfires. Then I decided that since the injectors had about 120,000 miles on them a couple of years back, I'd swap out injectors. I know they wear and so on and with all else being new, it was time. However, the only injectors I could find were "cleaned and rebuilt" on eBay. So I figured what the heck. It was never as smooth as with the originals but still ran ok.
A few days ago while moving things around to prep the car for a show (and making room to store my lawn tractor inside with the big grass catcher and cart), I found it was misfiring. I could feel it. A single cylinder. Started and ran fine (other than the jerking under load.
By now the engine has 35,000 on it since the rebuild and that means the plug wires have 135,000 miles and the plugs have 35,000 on them.
I figured I'd give it a thorough going over, new injectors (Benny helped me find the only set of OEM injectors in the country) new plugs and wires.

I found a fair amount of corrosion inside the #3 wire where it goes onto the cap, otherwise the wires "looked physically ok". Still, it's a lot of miles (135,000) and 32 years on the stock original plug wires.

I was hoping to take it to a Jeep/4x4 show but will miss that.

The plugs looked pretty normal as I pulled them, but #6 looked different - rich - in reverse order, starting with #6

6

5

4

3

2

1

While digging through my parts tub loaded with ignition stuff, I found 2 NOS (New Old Stock) original distributors and caps I had from Kenosha.

Sponsored

 

[ShadowsPapa]

The injectors arrived. Supposedly the last at any dealership in the country.

Waiting on the plug wires, etc. now.
At least I can pull the fuel rail and get the injectors swapped out.

And that means carefully pulling a few other things - as this engine was built for show with a lot of parts freshly powder coated, the fuel rail zinc plated and more.

 

[rharr]

dodge neon or some sort of ford injector were the big swap for the 4.0 back in the day. Those injectors used a 4 hole design, i believe now there are like 6 or 8 hole injectors that can be used for the 4.0. Theory being the small holes mist fuel better then the old oem injectors shooting a stream of fuel.

Also if you are going to play with distributors take the time and index the distributor. It will make a difference.

https://www.cherokeeforum.com/f2/ig...um=button&utm_campaign=share&utm_content=post

Here a basic example, i sure you can figure out how best to do it.

 

[ShadowsPapa]

dodge neon or some sort of ford injector were the big swap for the 4.0 back in the day. Those injectors used a 4 hole design, i believe now there are like 6 or 8 hole injectors that can be used for the 4.0. Theory being the small holes mist fuel better then the old oem injectors shooting a stream of fuel.

Also if you are going to play with distributors take the time and index the distributor. It will make a difference.

https://www.cherokeeforum.com/f2/ig...um=button&utm_campaign=share&utm_content=post

Here a basic example, i sure you can figure out how best to do it.

There's talk of that "indexing" all over the web, for decades. I have yet to have one that was actually off or had any issues. Looking at the cap and rotor, it's pretty much jumping at or near center. And ironically, the talk is against what people used to do years ago, whiich was to put spark gap devices in line with the wires to FORCE a bigger gap. So I don't mess with the indexing - especially when there's no issues. (the article mentions RENIX - yuk, glad I don't have that systemj, plagued with rough idle and so on)
With the wild swing timing can have, I bet people are missing the idea that to have the indexing perfect, it has to be after the post at idle in order to be at or still near it during full advance.
Does anyone bother - with older engines - giving full vacuum and mechanical advance and checking that, too? No.
Half of the chatter out there about it is a solution looking for an issue. I use a scope, and I carefully check out the patterns of the rotor and cap posts. Never had a trouble.
And I think the inedexing talk is for non-engine people. If you put the dumb thing in correctly, it can't be wrong. These also must go in just ONE WAY or the injectors will misfire.
Engine at TDC, line up the alignment holes in the distributor, line up the oil pump (by experience you know exactly how it must look down there) drop the distributor in so the tabs straddle the bolt hole. Done. Any other way, it won't start or run correctly. And frankly, there's almost no reason to ever pull the distributor out of an OBD I 4.0
Trying to "inedex" a 94 will simply throw injectors off. Don't do it.


I did try the 4 hole type (Ford) a few years ago - zero difference in "feel" as far as power, in fact, if anything, not as smooth. It wasn't quite as easy to start and definitely wasn't as smooth idling.

There's a lot of "butt dyno" chatter about them, but so far, no one actually did any true dyno testing, and of course, when you are replacing older, worn and/or dirty injectors with clean 4 hole, you are going to see a difference just because they are new and clean. But I have challenged a number of people who made HP gains claims to put new OEM injectors in, dyno it, then swap out injectors for the 4 hole and dyno it again - I only got "I know it's better" comments back.
In my testing of the 4 hole Ford injectors -
I found no gain in MPG at all, it took a couple extra spins of the starter, and not quite a smooth an idle with the 4 hole, so they sit on a shelf.

I suspect part of the issue is that different injectors are made for different durations and fuel pressures and so on.............. so it's a bit of a craps shoot. I didn't feel like doing a lot of swaps to experiment. (and injectors get expensive - avoid the "I took them apart and cleaned and repaired them" types on eBay)

I also have a different cam and higher compression - so it's non-stock in those respects.
Comp xtreme 4x4 cam, 0.025" off the head, H-S aluminum roller rockers.
I know I can hit mid-to high 20s MPG with the stock worn injectors and it's smooth so I figured going back will get me to where I was in 2010 with it.

 

[rharr]

Figured you had it covered. On my 95 4.0, doing the 4 holes and indexing did improve idle and quicker start. But that could also be related to swaping used parts with new fresh parts and that was the improvement. I also did the 2001 intake and a Doug Thorley exhaust header. The header made the biggest but dyno differance.

I have a friend who has a edelbrock aluminum head that is getting ready to swap that on his XJ, he is doing it as more of an experiment in MPG's then performance, 37" tires and 1 ton axles on a XJ drink a lot of fuel.

 

[ShadowsPapa]

Figured you had it covered. On my 95 4.0, doing the 4 holes and indexing did improve idle and quicker start. But that could also be related to swaping used parts with new fresh parts and that was the improvement. I also did the 2001 intake and a Doug Thorley exhaust header. The header made the biggest but dyno differance.

I have a friend who has a edelbrock aluminum head that is getting ready to swap that on his XJ, he is doing it as more of an experiment in MPG's then performance, 37" tires and 1 ton axles on a XJ drink a lot of fuel.

If this engine ever gets torn down.......... I have an experimental head, one of 3, that Clifford Research looked into. I got the head, found someone in a Jeep forum talking about a weird head they found, and the box mine was in said Clifford Research, so I called them. Yeah, it was one they were working on. They later sold their info to Edelbrock. They said they had 3 of them made, and dropped the project. The valve cover rail is taller to support the rockers like I use (one of my rockers just barely touches the inside of the VC)

I checked the CC of the head - totally stock at I believe 56cc? Can't recall now, whatever stock was.

 

[ShadowsPapa]

The joys of having an orphan car with an obsolete engine and no parts available..........
The air filter box I am using came out of a 1990s Dodge Caravan or similar. It was about all that would fit in the spot I had in the engine bay. It's got a cheapy STP air filter in it- beyond time to change it. So I tried to look up a quality filter like AC Delco and so on, and nothing. All I can find is cheap stuff. Nothing on Amazon for it!
Maybe the STP brand is ok for filters, but I know the AC Delco filters are high quality. Hoping to have something land here tomorrow but I guess it's not going to happen.

Google is crazy - in one check they gave a AC Delco number that was the equal - and then again later results said no, that number isn't even close. Confusing results from Google. I think Google's AI has a headache or something

I'm in big trouble if the coolant recovery tank I used ever goes bad - I have no idea what I pulled it out of way back then! I know it was a foreign car, perhaps an old Toyota but I can't say for sure.
The one time I said "I'll make note of that later", and I forgot to make note, and it will bite me in the butt someday.

 

[Rusty PW]

Off subject a little. Seen a Pacer on the highway today. It was in good shape. When I seen it. I thought of you.

 

[ShadowsPapa]

Well, now I have to dig deeper. Yes, the injectors were old and problematic. Yes, it appeared #6 plug was very different, likely rich and #6 injector looked like an issue. Yes. 35,000 miles on the plugs and 135,000 miles on the wires - time for a change.
The bad news........
It all made no difference.
So now I need to run compression checks and so on, maybe connect my vacuum gauge and dig deeper. Still have the miss.
The bad thing is that if it's physical, engine related and not that an injector isn't firing due to a wiring issue and so on, I will have to find a person who can work on and under it without doing damage.
You can't even pull the valve cover off without disconnecting the AC lines. So now it gets expensive and as I can no longer work UNDER a vehicle (everything went in from the BOTTOM), I'm totally screwed. Two cars sitting, last shows of the season and I can't work under them any more. Maybe time to sell it all.

 

[RudeJeepin]

Well, now I have to dig deeper. Yes, the injectors were old and problematic. Yes, it appeared #6 plug was very different, likely rich and #6 injector looked like an issue. Yes. 35,000 miles on the plugs and 135,000 miles on the wires - time for a change.
The bad news........
It all made no difference.
So now I need to run compression checks and so on, maybe connect my vacuum gauge and dig deeper. Still have the miss.
The bad thing is that if it's physical, engine related and not that an injector isn't firing due to a wiring issue and so on, I will have to find a person who can work on and under it without doing damage.
You can't even pull the valve cover off without disconnecting the AC lines. So now it gets expensive and as I can no longer work UNDER a vehicle (everything went in from the BOTTOM), I'm totally screwed. Two cars sitting, last shows of the season and I can't work under them any more. Maybe time to sell it all.

That's sucks. I was just thinking that it's good to read your working on stuff again.
Guess you and yours are doing better, atleast to some extent. Since you are doing some work again.
That damn meniere's disease sucks. I get short term similar issues from my allergies, usually last for a few days to a week once or twice a year. My dad was diagnosed with meniere's a few years ago and I've read that some think it'd hereditary or atleast it raises your risks.

 

[ShadowsPapa]

That's sucks. I was just thinking that it's good to read your working on stuff again.
Guess you and yours are doing better, atleast to some extent. Since you are doing some work again.
That damn meniere's disease sucks. I get short term similar issues from my allergies, usually last for a few days to a week once or twice a year. My dad was diagnosed with meniere's a few years ago and I've read that some think it'd hereditary or atleast it raises your risks.

I was diagnosed with Meniere's 20 years ago when I literally collapsed out of a chair at work. (the ringing in the ears, loss of hearing and occasional dizzy episodes and they finally decided I need a more special specialist LOL)
More recently, vestibular migraines, dizzy frequently and collapsing to the floor at home, and getting sick laying down working on things, they did a more specialized specialized special test. Lay on a table wearing these funky electronic goggles and they shoot water jets into your ears. Besides meniere's - over 50% loss of inner ear function on the left side. Eyes tell me one thing, right inner ear says something else and my left ear says hold on there, you are both wrong.... it takes everything agreeing to be a modern human capable of what modern humans do.

Anyway, I need some tips, advice, whatever, on this Eagle from the expert experts here - and I hope that fellow who calls himself Hootbro is listening...........

I decided to run a compression check.
Every cylinder was 125-130 dry. Very even.
I looked at each plug as I pulled them one at a time to run the compression test - one at a time (pulled a plug, checked compression, put that one back, pulled the next, checked that cylinder, put that plug back and so on)
All looked white and normal for as short a time as it has run since I put them in (a couple of runs, maybe a minute each) - EXCEPT #2 and it had no sign of combustion at all, as if there was either no fuel or no spark. There was spark.

So I figured perhaps no fuel to #2. Great, now what - all NEW injectors and plugs, wires, cap and so on.
Well, buttoned it all back up and WTH - it smoothed right out after acting a bit flooded for 3 or 4 seconds (cranking with injectors energized - duh)

I sort of wonder with all of the things I've done under the hood if one of these is or was possible:

How long does it take the fuel to get to every injector once the fuel rail is emptied and dry injectors put in?
or
Is there a goofy injector connection at #2? I checked every connector - fully seated and clicked, but - the wiring to the injectors along the fuel rail is from 1994 and has 135,000 miles.

Further -and I suppose I could google this or get the freakin' big fat 1994 ZJ TSM out and read - is there a simple way to check for each injector firing signal??

Today was one of those vestibular migraine days - for 30 minutes could not see, dizzier than usual, and a nice headache, but I guess I made some progress.

Finding the compression at each cylinder to be 125 to 130 DRY made me pretty happy.

 

[Rusty PW]

I was diagnosed with Meniere's 20 years ago when I literally collapsed out of a chair at work. (the ringing in the ears, loss of hearing and occasional dizzy episodes and they finally decided I need a more special specialist LOL)
More recently, vestibular migraines, dizzy frequently and collapsing to the floor at home, and getting sick laying down working on things, they did a more specialized specialized special test. Lay on a table wearing these funky electronic goggles and they shoot water jets into your ears. Besides meniere's - over 50% loss of inner ear function on the left side. Eyes tell me one thing, right inner ear says something else and my left ear says hold on there, you are both wrong.... it takes everything agreeing to be a modern human capable of what modern humans do.

Anyway, I need some tips, advice, whatever, on this Eagle from the expert experts here - and I hope that fellow who calls himself Hootbro is listening...........

I decided to run a compression check.
Every cylinder was 125-130 dry. Very even.
I looked at each plug as I pulled them one at a time to run the compression test - one at a time (pulled a plug, checked compression, put that one back, pulled the next, checked that cylinder, put that plug back and so on)
All looked white and normal for as short a time as it has run since I put them in (a couple of runs, maybe a minute each) - EXCEPT #2 and it had no sign of combustion at all, as if there was either no fuel or no spark. There was spark.

So I figured perhaps no fuel to #2. Great, now what - all NEW injectors and plugs, wires, cap and so on.
Well, buttoned it all back up and WTH - it smoothed right out after acting a bit flooded for 3 or 4 seconds (cranking with injectors energized - duh)

I sort of wonder with all of the things I've done under the hood if one of these is or was possible:

How long does it take the fuel to get to every injector once the fuel rail is emptied and dry injectors put in?
or
Is there a goofy injector connection at #2? I checked every connector - fully seated and clicked, but - the wiring to the injectors along the fuel rail is from 1994 and has 135,000 miles.

Further -and I suppose I could google this or get the freakin' big fat 1994 ZJ TSM out and read - is there a simple way to check for each injector firing signal??

Today was one of those vestibular migraine days - for 30 minutes could not see, dizzier than usual, and a nice headache, but I guess I made some progress.

Finding the compression at each cylinder to be 125 to 130 DRY made me pretty happy.

Do you have a lift pump in the gas tank? Did you check the fuel pressure at the injector rail? If the car has sat for a while. The fuel in the injectors and lines will bleed off. So it may take a few start/stops to pressurize everything. Is there anything in the manual about pressuring the fuel system?

 

[RudeJeepin]

You can check the injector pulse with a simple 12v test light. Clamp on positive and probe negative wire. A small needle can usually be inserted into the injector plug between the wire and the rubber seal around the wire.
It's been awhile, but I believe that's right. As in which way to use the probe.
I'm sure you know this, or could figure it out.

@Rusty PW is right on the money, I believe.

 

[ShadowsPapa]

Do you have a lift pump in the gas tank? Did you check the fuel pressure at the injector rail? If the car has sat for a while. The fuel in the injectors and lines will bleed off. So it may take a few start/stops to pressurize everything. Is there anything in the manual about pressuring the fuel system?

I haven't gone downstairs to get the 94 Jeep ZJ TSM and looked at the procedure.
I suppose I could have used the valve to release air from the fuel rail - DUH.

It's an in-tank Jeep 4.0 pump. Made for the engine.

I turn the key to on, listen closely for the pump to stop, and then crank to start (that's my all the time normal way)

It had been started and run at least 3 times, although only about a minute each time.

Last week I put in fresh, brand new out of the box OEM MOPAR 4.0 fuel injectors. So the fuel rail was removed and empty/dry, new injectors put in place and all reconnected and put back together.

Jeep/MOPAR fuel pump for Jeep with 4.0 I modified the original AMX SX4 sending unit to handle the pump wiring, etc.

New MOPAR regulator in the rail.

New injector - correct MOPAR number for this engine -

 

[Stan H]

I was diagnosed with Meniere's 20 years ago when I literally collapsed out of a chair at work. (the ringing in the ears, loss of hearing and occasional dizzy episodes and they finally decided I need a more special specialist LOL)
More recently, vestibular migraines, dizzy frequently and collapsing to the floor at home, and getting sick laying down working on things, they did a more specialized specialized special test. Lay on a table wearing these funky electronic goggles and they shoot water jets into your ears. Besides meniere's - over 50% loss of inner ear function on the left side. Eyes tell me one thing, right inner ear says something else and my left ear says hold on there, you are both wrong.... it takes everything agreeing to be a modern human capable of what modern humans do.

Anyway, I need some tips, advice, whatever, on this Eagle from the expert experts here - and I hope that fellow who calls himself Hootbro is listening...........

I decided to run a compression check.
Every cylinder was 125-130 dry. Very even.
I looked at each plug as I pulled them one at a time to run the compression test - one at a time (pulled a plug, checked compression, put that one back, pulled the next, checked that cylinder, put that plug back and so on)
All looked white and normal for as short a time as it has run since I put them in (a couple of runs, maybe a minute each) - EXCEPT #2 and it had no sign of combustion at all, as if there was either no fuel or no spark. There was spark.

So I figured perhaps no fuel to #2. Great, now what - all NEW injectors and plugs, wires, cap and so on.
Well, buttoned it all back up and WTH - it smoothed right out after acting a bit flooded for 3 or 4 seconds (cranking with injectors energized - duh)

I sort of wonder with all of the things I've done under the hood if one of these is or was possible:

How long does it take the fuel to get to every injector once the fuel rail is emptied and dry injectors put in?
or
Is there a goofy injector connection at #2? I checked every connector - fully seated and clicked, but - the wiring to the injectors along the fuel rail is from 1994 and has 135,000 miles.

Further -and I suppose I could google this or get the freakin' big fat 1994 ZJ TSM out and read - is there a simple way to check for each injector firing signal??

Today was one of those vestibular migraine days - for 30 minutes could not see, dizzier than usual, and a nice headache, but I guess I made some progress.

Finding the compression at each cylinder to be 125 to 130 DRY made me pretty happy.

As my theorizing is merely that it sounds like you might have the answer its in the wiring.
The only way I ever seen to check the injectors is an injector test rig . Where all 6 are taken out then they are put through the firing simulation and it test flow.
I am far from an expert but I seen that Guy from Dave auto trouble shooting a Chevy car and after they did everything you just explained( plus tested each injector) it turned out to be fuel beyond its usefulness. They drained the tank and filled with fresh fuel and bam it was running like a top.

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