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Firing order

NCSUcherokee

NAXJA Forum User
Location
North Carolina
follow up thread to this one:
http://www.naxja.org/forum/showthread.php?t=61445

I just got back from vacation and started to work on the jeep again. It was recomended in the last thread that i check the distributor re-indexing/spark path to try and fix my problem.

I am satisfied with the distributor index, and the firing order i had in the hayes manual was correct 1-4-2-6-3-5.
But... the firing order cast into my intake manifold is 1-5-3-6-2-4.

The engine wont start at all with the cast-in numbers.

It will start and idle poorly with the hayes numbers, but it wont rev up at all. Throttle change does nothing. another interesting condition is that unplugging sensors (IAS, TPS, CamPS) does nothing at all.

I am puzzled. what is the correct sequence? why does the engine running seem to be running sensorless. BTW it is a 1990 xj with an 88 block
 
1-5-3-6-2-4.is correct.
If the CamPS in the distributor is not working the ECU will start the engine in an emergency operating mode, it won't run right but it will get you home.
 
Last edited:
NCSUcherokee said:
follow up thread to this one:
http://www.naxja.org/forum/showthread.php?t=61445
I am satisfied with the distributor index, and the firing order i had in the hayes manual was correct 1-4-2-6-3-5.
But... the firing order cast into my intake manifold is 1-5-3-6-2-4.
All in line six cylinder engines ever made have the same firing order of 1-5-3-6-2-4.

The reason for this is because it is the ONLY way that the engine will be harmonically balanced effectively.

Lord only knows how the Haynes manual came up with their order........
 
AZ Jeff said:
All in line six cylinder engines ever made have the same firing order of 1-5-3-6-2-4.

The reason for this is because it is the ONLY way that the engine will be harmonically balanced effectively.

Lord only knows how the Haynes manual came up with their order........


It is an old version that for some reason listed the firing order counterclockwise.

The problem still isnt gone. it will still run in its same crappy-ness in 2 dist. positions. I even tried switching out the distributor. still no dice.
 
I already tried the closest positions before and after on both distributors that i have.

If the CamPS in the distributor is not working the ECU will start the engine in an emergency operating mode, it won't run right but it will get you home.

I know it isnt in limp mode because its barely running at all.
 
Spark seems good. i am still not sure that i have the timing right since when i open the throttle, the engine will backfire through the intake, and as i understand it, timing is almost always the cause of backfire.

I just got in from another try, and a different method yeilded the same results. I tryed setting the distributor directly to post 1 with the engine 17.5 degrees before TDC. Still ran the same. though the closest i could get was about 2 or 3 degrees away from the post.

I wish somthing i did helped or hurt the way it ran so i know i am heading in the right direction. I guess i will try making an adjustable distributor.
 
The firing order of almost all inline 6 cyls is 153624 (only exception to this rule is 55 IH flathead 6 which runs 123654), BUT take the cap off and make sure it's spinning the right way! The harmonic balancer can slip if the rubber in the middle is bad, so don't trust it!
I pull #1 (or #6) plug and with a skinny screwdriver determine where TDC is (both are TDC at the same time, but one is on the start of the intake stroke and the other is on the start of the firing stroke) then (if you have the valve cover off) make sure the valves are at their overlap point at TDC. (#6 or #1. The opposite one will be firing) and you'll have determined the timing chain didn't jump.
A CPS or TPS on it's way out will act like this too. Clogged fuel filter or too low of fuel pressure (clogged open pressure regulator or bad pump) or possibly a melted CPS wire harness (they sell new ones because of it). Low alternator output will mess with the computer as well. It'll have enough power to crank and barely run till the battery goes dead or the computer dies from running too low of voltage. Jumper cables to a running vehicle will check that easy enough.
Of course, there's always bad fuel too. I tapped into the fuel line with another tank (lying on the ground under the back with connectors jumped to the body as well) with known good fuel when all else failed, and sure enough, the motor ran fine!
 
Are you certain that the distributor isn't 180 degrees off? Remember, the engine goes around twice for one revolution of the distributor, which means that each cylinder comes up twice in one rotation of the distributor. Putting #1 at TDC is only half of the equation -- you have to ensure that it's at TDC on the compression stroke, not the exhaust stroke.
 
if you have the dist in 180 out and the wires moved to run, the cam sensor will be 180 degrees out and fuel shot in at the wrong time.
 
carnuck said:
The firing order of almost all inline 6 cyls is 153624 (only exception to this rule is 55 IH flathead 6 which runs 123654)

Diversionary question here---if that Binder engine had that firing order, how in the hell did they make that thing run smoothly? I KNOW they did not have counterbalancing shafts back then. In fact, fully balanced crankshafts were a fairly new thing at that time.

The basics of harmonic balancing was known LONG ago, way before 1955. If the 153624 pattern is used, a straight six is balanced naturally thru the third order harmonic. (So I remember from my class in Internal Combustion Engine design 25 years ago.)

Using any other pattern results in balance thru less levels of harmonics.

I wonder how bad that engine shook..............just curious. Now back to the question at hand......................
 
Eagle said:
Are you certain that the distributor isn't 180 degrees off? Remember, the engine goes around twice for one revolution of the distributor, which means that each cylinder comes up twice in one rotation of the distributor. Putting #1 at TDC is only half of the equation -- you have to ensure that it's at TDC on the compression stroke, not the exhaust stroke.


I have the plug wires in the right place, and it is on the right stroke. I originally had the wires right, in backwards order counterclockwise which is correct with the rotation of the engine.

If the distributor was 180 out (my original problem), it wouldnt run at all. the engine just runs indescriminatly bad no matter what i change. i wish i could talk to the original owner and ask her what she did to this thing.
 
A CPS or TPS on it's way out will act like this too. Clogged fuel filter or too low of fuel pressure (clogged open pressure regulator or bad pump) or possibly a melted CPS wire harness (they sell new ones because of it). Low alternator output will mess with the computer as well. It'll have enough power to crank and barely run till the battery goes dead or the computer dies from running too low of voltage. Jumper cables to a running vehicle will check that easy enough.

Unplugging the CPS and TPS do absolutly nothing, which i find odd. I am getting to the point where i will turn my attention to the fuel because that is the last unchecked area. I have been running it jumped off another vehicle so i know it's not the battery
 
NCSUcherokee said:
If the distributor was 180 out (my original problem), it wouldnt run at all. the engine just runs indescriminatly bad no matter what i change. i wish i could talk to the original owner and ask her what she did to this thing.
Not sure, but I think if the distributor is 180 degrees off it will run, but it'll run like crap. However ...

Another possibility: Do you have the number 1 spark plug wire going to the correct terminal in the distributor cap? Don't forget that in addition to the CRANKSHAFT position sensor on the flywheel, there is also a CAMSHAFT position sensor inside the distributor. For everything to run smoothly they have to be in synch. If you set the number 1 piston to TDC on the compression stroke, toss in the distributor any old way and then start attaching wires using the terminal at the rotor as number 1 and proceeding from there ... you won't be properly indexed with the cam position sensor. Unlike an old points-and-condenser distributor that you could set up in any orientation at all so long as you had the order correct, with these engines there is only one terminal that you can use as number 1.
 
Eagle said:
Not sure, but I think if the distributor is 180 degrees off it will run, but it'll run like crap. However ...

Another possibility: Do you have the number 1 spark plug wire going to the correct terminal in the distributor cap? Don't forget that in addition to the CRANKSHAFT position sensor on the flywheel, there is also a CAMSHAFT position sensor inside the distributor. For everything to run smoothly they have to be in synch. If you set the number 1 piston to TDC on the compression stroke, toss in the distributor any old way and then start attaching wires using the terminal at the rotor as number 1 and proceeding from there ... you won't be properly indexed with the cam position sensor. Unlike an old points-and-condenser distributor that you could set up in any orientation at all so long as you had the order correct, with these engines there is only one terminal that you can use as number 1.

I have the number 1 terminal at the 5 o'clock position when standing on the pass. side of the jeep. I think that is what the manual shows. I will double check tommorow.

I think i will start on the fuel system tommorow since changing the spark hasn't helped any. Maybe if the fuel is the problem i can cure the main portion and then fine tune the spark.
 
This may help some.
firingorder.jpg
 
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