Totally Stumped with the XJ!!!

[Cobia]

Hi,
I wish I could make the announcement that Streomind made but I'm not that lucky this week.
Here's the deal, after a thorough cleaning of the carbs and adjusting the floats, we installed them and with a little coaxing started the XJ. But it was running rough. After much troubleshooting BikerPhil and I found that cylinder #2 was not firing. We discovered it but spraying water on the manifold after it ran for a while. We pulled the plug and found that although not totally wet it was somewhat black and damp, unlike the others that exhibited the correct color. We checked the coil impedances an found that the coil for 2 & 3 did not meet specs either on the primary or the secondary sides.
I ordered two coils and two sets of wires from MikeXS on Saturday and installed them this morning...... IT MADE NO DIFFERENCE in the behavior of the problem !!!!
I once again checked the plug and it was wet but not drenched, and I noticed via the spray-the-manifold method that cylinders 3 and 4 evaporate the water instantaneously whereas 2 not at all and 1 does it more slowly than 3 and 4.
I did check my compression across all cylinders again and although I forgot to open the throttle all cylinders came in at 120 psi.
I then removed the wire from plug #2 while the engine was running and it did not change how the engine ran.
What is more troubling is that I took the # 2 plug out, connected it to the plug wire, rested it on the engine and I could see it sparking when I turned the engine over!!! WTF????
And because the intake manifolds are pretty (or ugly) cracked I sprayed WD40 on them while I held the RPMs at 1.5K with the cruise control and heard no difference. In a move of desperation I then sprayed starting fluid (straight ether) on them and it made no difference.
While the carbs were out I checked all the manifiolds very thoroughly to make sure the cracks did not go through to the inside, they didn't.
I also re-seated the connectors for the coils primary leads back at the Ignition Control Unit and even opened the ICU to visually inspect for possible damage. NADA!!
So, here's where I stand, totally stumped, I got fuel, I got compression, and I got spark and still #2 refuses to cooperate.
Does anybody have any ideas that can help me get over this? They will definitely be appreciated because other than this issue the engine sounds terrific. (I haven't run it yet so I don't know about the tranny, but we won't go there yet.)
Please HELP....and THANKS

[egsols]

What is more troubling is that I took the # 2 plug out, connected it to the plug wire, rested it on the engine and I could see it sparking when I turned the engine over

Is it sparking strongly? Did you check spark on 3 to see if its stronger. Could the plug be cracked or bad?

Did you tap the carbs while it was running, just in case the float on 2 is stuck/binding?

It almost sounds like it wants to go, (wet but not drenched) and its some but not enough fuel and or spark.

[Cobia]

We tapped the carb.

We tapped the carbs but have not compared strength of spark to the other cylinders.
I did find that the PO had old and mixed spark plugs in it, one resistor plug and three non-resistors.
I went ahead and installed the ones I took off my standard when we cleaned the carbs on that one. They weren't bad I just wanted to start with a new set after the cleaning. and I switched plugs 2 and 4 this AM to see if it would make a diff. It didn't. But let me go compare spark strength now. Be back in a few.
Gracias.

[vincer]

#2 cyl

Make sure the fuel lines are connected properly.
When mine did this i realized that I had the fuel lines from the petcocks plumbed wrong. Are you still using the octypus?

[Cobia]

Removed the octy

Vincer - I removed the octy, capped one side of the petcocks, and verified that I had fuel flow.

Egsols - The spark is as strong as at least #4.
But if you could verify my info:
The coil with the orange and red/white stripe primaries is for numbers 1 and 4 cylinders.
The coil with the gray and red/white stripe primaries is for numbers 3 and 4 cylinders.
Is that correct? Because the diagram for the '80 and '81 in the Clymer manual shows the secondaries, the plug wires going from one coil to 1 and 2 and the wires from the other coil going to 3 and 4??? And of course, they don't number the plugs in the drawing. Does that make sense?

[Cobia]

Stumped!!

And BTW, what it really sounds like is like if it's way out of timing!!!?? Is there a timing adjustment or is my firing order totally off??

[bikerphil]

coil wiring

Hey Cobia, I just checked the manual, orange= left coil, plugs 1+4, gray/white= right coil, plugs 2+3. Double check them. The other day we set the float level to 23mm just like we did to your 80G carbs. I wonder if that is correct for the 82XJ? Mabye someone with an XJ will chime in?

[egsols]

You mean ignition timing? Not that familiar with XJ's but I think their timing is fixed?

[stereomind]

it sounds like you might be dumping way too much fuel into that cylinder for proper ignition...

you said the #2 plug looked wet. did it smell like gas?

make sure the float valve is operating properly on that cylinder and float height is the same as the others. make sure the enrichment valve on that carb doesn't have any crud in it that would hold it open.


just my 0.02USD...

Vlad

[79XS11F]

If your firing order was off it would not likely run at all. Sounds like your running too rich on #2. That means checking the carbs again. I know it's a pain in the behind but if you have spark across all cylinders and the times is close then your likely flooding #2
Rob

[79XS11F]

OH by the way i always leave the air box off when doing carb work. It's a lot faster to re&re the carbs with the air box off. Once the engine is firing on all 4 then reinstall the air box.
Rob

[Cobia]

Stumped

Stereomind - I almost think that there may not be enough fuel coming into that cyl. Since you have an XJ and you cleaned and set the carbs, what do you set the floats to?

Egsols - Yes, I believe the timing is set but if the timing chain jumped.....?? I will be checking that tomorrow AM first thing.
Thanks, please keep your ideas coming.

[AlanB]

Hi Cobia,

I have just read the first post, so will start there!

Coils link the cylinders 1-4, and 2-3. Fuel links the cylinders 1-2, and 3-4, so straight off, we are probably looking at fuel, not ignition.

You can confirm this by swapping the plug leads over on the same coil; swap 1and 4, and swap 2and3. if the same two cylinders are hot, it proves that the coils are good on all four leads.

If the fault moves, you have a coil issue.

You then need to check whether the plugs are firing in the cylinder; this is NOT the same as sparking in the open air!... I would pull the two non-firing plugs and spin the motor over to get rid of the unburnt fuel in the pots. Either clean the "dead" plugs thoroughly, or (preferably!) replace 'em. Put the two "cold" (cleaned or new?) plugs in the two cylinders which you know run.
Put the "HOT" plugs which were just running those cylinders into the cylinders which were NOT running, so you have "guaranteed" plugs, on tested coils in those cylinders.

If it still doesn't run on those cylinders, you have a carb problem!

Once you have it all sorted out, you NEED to change the plugs; the ones which have been fuel-soaked in the dead cylinders will never be 100% again (unless your fuel is a LOT different to ours!!)

If the cam timing is out enough to bend some valves, NONE of the motor would run. Ignition timing can't be out unless something is broken.

back to the carbs......

Hope some of this helps!

AlanB

[stereomind]

Cobia -

I did not mess with the float levels. They appeared to be "stock", and they were all dead even (the PO has never had the carbs apart, which corresponded with the amount of sediment in the bowls). When the carbs were upside down, the floats rested in such a way that the flat surface on the floats was close to being parallel to the carb body... maybe 0.5-1mm higher on the far end from the float hinge pin.

On yours... since the other 3 seem to be ok, I think it would be safe to set #2 exactly the same as them. I'd look over the float valve again and make sure it closes properly, and make sure the enrichment valve is spotless.

Alan brought up a good point though... swap the plug wires from #3 to #2 and see if the problem follows. And definitely replace that fouled plug.

although it would seem strange to have the same issue even with brand new coils and wires.

[TopCatGr58]

Hey Cobia,

The XJ uses the same float valve seat design, and so it has that O-ring that can leak, which could contribute to too much fuel in that carbs bowl....did you replace the float needle seat O-rings when you cleaned the carbs??

Secondly, the manual only describes the use of the float bowl clear hose for setting the float height...PITA, they are the same as the 80-81 carbs settings of 23mm as per BikerPhil's settings!

I agree that if the plug is wet, it's flooding somehow, cause with new coils and wires, it's very doubtful that it's not firing properly!
T.C.