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Firing Through The Intake :)

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A_Work_In_Progress

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Discussion starter · #1 ·
OK, so this “simple Jeep swap” has turned into a nightmare.

Started with a “simple swap”... which I have never done one on a Jeep.

I’ve had a **** ton of input from the best of the best on this forum. But I can’t seem to seal the deal…

So here we go… I got the firing order off of here… And I got the manual off of either here or Pirate 4x4… Any who since the 1998 Engine has a different distributor connection; I used the old engines dizzy. Its looks identical, so I’ve matched the 0 degree mark on the crank, both times (lined up and flipped 180)

and yet it’s still firing through the damned intake… what the hell did I do wrong.. I’m going to do some more digging tonight finding maybe another firing order diagram… but I’m literally stumped…

this project has spanned 2 moves. One tree through my shop, and a fire… It’s pretty much the only thing I have left hahah, and its stealing my sanity every time I look at it. I’m scheduled 55 hours this week, so any input would be amazing. I just want to get this done!!!!!

Thanks in advance guys, this site is pretty much my only source of jeep sanity.
 
Discussion starter · #3 ·
Sorry guys, guess I left out some information

The jeep is a 1997 Grand Cherokee 4.0
The Engine is a 1998 4.0 from a Grand Cherokee
Im using the 1997’s dizzy because the connections different, and I didn’t want to try to splice it
I have a chilton, a Haynes, and ALLDATA Labor and Install Program


Its firing through the intake, ive set the crank at the 0 degree tick mark, and repositioned the dizzy to point at the number one cylinder. Tried it and fire out the intake yeay

set it 180 degrees to the 0 degree tick mark so the dizzy was pointing to the number six cylinder removed the dizzy and pointed it at the number one cylinder again…. Hoping that maybe I didn’t have it at TDC. Turned it over again, and fire through the intake…. I don’t know what im missing or what else I should do. Ive followed each of the manauls religiously, and still nothing . what else should or can I do? Im totally stumped
 
#5 · (Edited)
There are only 3 things that I can think of that would cause the motor to backfire out the intake on cranking.
1. The ignition timing is off and spark is occurring when the intake valve is still open, or
2. The valve timing is off, either was set up wrong, or the chain has stretched and slipped a tooth or two on the cam gear causing the intake valve to still be open when the correct ignition timing fires.
3. A stuck open or bent intake valve on a motor that is pretty worn out or was abused.

If the motor was running good before you did your distributor swaps then of course you would suspect the ignition timing.
Double check the rotor under the cap and all of the routing of your plug wires.
You can also check to find TDC of #1 Cyl by removing #1 plug and using a compression gauge. This should verify that you have compression near where your timing mark on the crank is telling you that you are just before TDC of #1.

Here is the 4.0L Firing Order again:
 

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Discussion starter · #6 ·
Thank you, im almost positive i have the firing order correct.. like i said three manuals worth haha...

But never the less thank you, the engine was pulled out at the dismantlers. i turned the jeep over before they ripped it apart and i ran rather well. no engine codes no knock no nothing, it actually sounded better than the jeep were swapping it into before the mishap. But, thank you, again. i have the day off in about an hour. so it will be checked the second i get some sleep. ill post back the second i know anything.

And if i remember correctly ill have to take off the ac condenser again to get the compression tester in there... goody :) ahah
 
#7 ·
Sometimes you can look at something several times and not notice that something is wrong. It would be a good idea to have a friend double check the position of your Distributor at TDC #1 and also the routing of each plug wire from where it is suppose to be in the distributor cap to the correct plug and cylinder.
It's easy to overlook something or think that it is correct when it's just one click off. :)
 
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Discussion starter · #8 ·
Ok, so yet again I’m here posting a failure. I found TDC using the chopstick test, The dizzy is on number one, everything is set “correctly”. But when I found TDC I noticed that the tick mark on the harmonic balancer is no-where near the 0 on the timing pad thing attached to the block…. It’s about 2 or 3 inches past? I have a massive gut feeling that, that means something wrong… I’m going to recheck the firing order again. But, here is the strange thing. It fires through the intake for one pop and then turns over normal… It’s like every time I turn it over the first time it pops through the intake? It never does it again for as long as I’m actively cranking it over… Any input/ideas??? I’m almost thinking cam timing sadly…. Please tell me it isn’t so!
 
#9 ·
A_Work_In_Progress said:
Ok, so yet again I’m here posting a failure. I found TDC using the chopstick test, The dizzy is on number one, everything is set “correctly”. But when I found TDC I noticed that the tick mark on the harmonic balancer is no-where near the 0 on the timing pad thing attached to the block…. It’s about 2 or 3 inches past? I have a massive gut feeling that, that means something wrong… I’m going to recheck the firing order again. But, here is the strange thing. It fires through the intake for one pop and then turns over normal… It’s like every time I turn it over the first time it pops through the intake? It never does it again for as long as I’m actively cranking it over… Any input/ideas??? I’m almost thinking cam timing sadly…. Please tell me it isn’t so!
Click to expand...
Let's start over.
Crank the motor over, by hand with a breaker bar on the harmonic balancer nut if you have to, until the pointer on the block points to about 10 deg before TDC on the timing strip on your harmonic balancer.
Check the position of the rotor in your distributor, it should just be about to point directly at the #1 plug wire contact in the cap. If it is not pointing more at the #1 than anywhere else then you have your distributor in wrong.
I'm "old school" so I'm a little disadvantaged here, but the last time I replaced a distributor, it would start into the hole, make contact with it's drive gear on the cam shaft and would turn slightly as you pushed it down into where it needed to be. So you would have to anticipate just how much it would turn at the end and allow for this when you started it into the mounting hole. Always double checking that when it was seated that the rotor was pointing at the #1 plug wire contact in the distributor cap.

Now you said that it would fire back up the intake and then turn over normal.
If you can turn it over normal without a lot of intake firing then you should be able to hook up a timing light and use it to verify that you indeed have the timing set correctly.

If you do all this and verify with a timing light that the timing is set correctly and you still have this problem, THEN it is time to suspect other things such as the valve timing or a stuck open intake valve.

I hope this helps, I am not very familiar with the new electronic ignition systems so I may have overlooked something here and I hope someone younger and smarter than me can jump in here and help.

Woody
 
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Discussion starter · #10 ·
It turns but doesnt start im sorry wrong terminology... Sadly the timing light is a no go. it burned up with most of the stuff i couldnt stick in the jeep when my shop burned down....
but ill go ahead and try the 10degrees before tdc thing you were describing.

as for the dizzy being in there wrong? how would that happen? it has a slot for the bolt to line it up with the mounting plate and bolt hole. maybe im misunderstanding. but thank you AGAIN AGAIN

Oh and the firing order was exactly the picture you posted. i was sure i had something right ahah

and im almost about to pull the valve cover to see that the valves are relaxed at tdc, and to see if there is any damage thats noticeable; if any.
 
#12 ·
I would go buy or borrow another timing light and a compression gauge.
The compression gauge will help determine if the valve timing is correct and which cylinder has the problem.
If the basic mechanical stuff is correct then there are sensors such as the crank position sensor that could come into play.
I'm not too savey on the sensor stuff so hopefully someone else will jump in at that point.
 
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Discussion starter · #13 ·
So I pulled the valve cover off and had a buddy of mine spin the crank with the 19mm socket…. Andddddd the rocker closest to the radiator dips before the one before it? If that makes sense…. And I maybe wrong… but I’m assuming like with all engines. The rocker/valve nearest the exhaust is the exhaust side…

So now my question is why is the exhaust activating before the intake every time… I thought it was weird so we did almost 9 revolutions. And it’s the same every time… and it almost seems that the intake side fires once every two exhaust… but this is the case on ONLY the number one cylinder. Or it’s the only one I noticed it on. Either way this strikes me as odd..

 
Discussion starter · #14 ·
As for sensors and electrical. Almost all the sensors have been replaced. CrankPS, Neutral Sensor, Oil pressure. the only thing that is stock is the cam sensor... other than that, im the only one out of my friends that spins wrenches, i don't think any of them know what a timing light is or more so how to use one. so i'm thinking its off to a local harbor freight to see what i can or cannot find, replacing tools is hard. especially if you amassed them all in a 9 year span. Thank you for the speedy replies, it makes the coping process easier ahah.
 
#15 ·
If you are turning over the motor the same direction that it runs, then the exhaust stroke will always proceed the intake stroke and the camshaft actually keeps the exhaust valves open past the point of opening the intake valves so that the escaping exhaust gases will help draw in the intake fuel charge (overlap).

I see from an earlier post that you replaced a broken Crank Position Sensor. Re-check the CPS. Also recheck the fuel pressure at the fuel rail. If it has fuel and spark and the timing is correct, it should at least start even if it runs rough.
What other sensors did you change that could cause a non start and why did you change them?
So many things have been changed or modified on this swap that it is hard to pinpoint just what is causing your problem.
You say that this new '98 motor was running good before the swap, so maybe you need to backtrack to take another look at all that you changed.
Is it really that difficult to wire in the '98 Distributor that came with the motor instead of using the '97, as you said, I don't know why that would make a difference but at this point you try to go back to what was working.
 
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Discussion starter · #16 ·
I changed the crank position sensor because of the not turning over issue. I have replaced the stock module and still nothing. I was just afraid to start modifying the distributor and I have no idea why. Ill replace the dizzy from the 1998 and splice the connections tonight and try again tomorrow. Other than the crank position sensor that's the only thing that would keep it from starting.

Anddd they pulled the engine a day after they ran it for me. So I've no idea what and or if they had done anything but I doubt it. I think its just me. Anyways thank you so much! Your bearing with me and I really appreciate it
 
#17 ·
Might check for any changeovers in the ignition from 97-98. For example the coil rail from an 01-04 will not work for the 99-00 even though they look alike except for the plug pointining in a different direction. If you use one in place of the other, it will want to fire 180 deg off and backfire through the intake similar to what you're explaining.
 
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Discussion starter · #18 ·
There you are Red. I think I need to set up a beacon for you guys; bat man had the bat symbol... I need the jeep logo....

Anyways, new developments yeay...

Here we go...
I spliced the dizzy connections on the 1998 to the 1997, and nothing...
I got two distributors from Kragen, (1997 & 1998) thinking the same thing that REDLEG had brought up... nothing…
And then I fried the started YEAY!!!!
I had the CPS tested and it read shitty... much like the stock and the new replacement… SO this paycheck (tomorrow) I’m picking up another new CPS, Some grounds, Some Band-Aids, and a new starter. Sorry for the late reply, work is kind of screwing up my jeep time :(

but thank you all, again….
Ill post more when I’m done.
 
Discussion starter · #19 ·
Here we go again

New starter new cps....

Same cranking and non fire....

is it my timing?

ive done literally everything ever written about setting timing. will any of you give me a write up so i feel less ignorant...

and by write up, i mean piston setting and dizzy angle. and keep in mind the timing tick on the jeeps harmonic balancer is about 25 degrees off... so i cant just point it to 0.
 
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A_Work_In_Progress
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