Help! - HT leads order on the distributor cap

[dukeofpeckham]

Guys - following on from my query at the end of the last thread about firing on three cylinders...

I had a good old poke around and found one of the HT leads hanging off the distributor cap. Aha I thought - easy fix. But having double-jointed my wrist to get in there I dislodged a couple of the others... obviously also a bit loose! Put them back but now I'm certain I'm firing on four but in the wrong order - rough as hell, spongy and seeming down on power. I've tried swapping them but now am TOTALLY CONFUSED!

I guess the best thing is to take 'em all off and make sure they're right. then I'll know if a lead is dodgy etc.

BUT... Anyone know the correct order? say, clockwise or anti-clockwise from the lowermost socket on the distributor cap...

Thanks in advance.

[Steve C]

The distributor runs anti-clockwise, the firing order is 1-3-4-2 ...

To set it correctly, I'd set the engine to the TDC timing mark and make sure the dots on the cam pulleys line up ... this is #1 TDC. If the dots are at their furthest apart, you are at #4 TDC so will need to rotate the engine I whole crank revolution.

Pull off the distributor cap, look at where the rotor arm is and put lead #1 on at that place, then work anti-clockwise with 3 4 and finally 2...

It's may be possible to determine where #1 is by looking at the dot on the aux pulley but I've never used it ....

[dukeofpeckham]

You're a star Steve!

Would you normally do this with airbox, carb in situ or do I need to start taking things apart? It's all quite tight down there but if it's do-able I'll persevere for laziness sake.

[Steve C]

Yep, I'd leave most of it in place. Just open the airbox to remove the outer part and air filter to get a bit more clearance.

It can be a b1tch of a job getting the dizzy cap on and off ... if you can't get at it, I can look up the alignment "dot" for the aux shaft in the manual tonight and we might be able to guesstimate which cyl is #1.

Also, assuming at least 1 lead didn't fall off, you could work from that anticlockwise in the 1 3 4 2 order ...

[dukeofpeckham]

Mm - that sounds a tempting option - i think there's one that is right - maybe some trial and error called for

[Steve C]

I've just thought of another option ... pull #1 spark plug, connect a lead to it an turn the engine over ... if it fires the plug about 10 degrees before TDC when the cam pulley dots are aligned, you know that socket on the distributor is #1 - if it first half a crank turn later, it is #3, if it fires a whole crank turn later it is #4 (TDC but cam dots furthest apart), if it fires 1 1/2 turns later it is #2!

.... you can then work out the 1-3-4-2 sequence anti-clockwise from that ...

[r08813]

Be careful of the Dizzy clamp, if too loose, the dizzy jumps out of place, it's a real pain to get back in again - can be done, but really needs the airbox off first

[Redexcel]

Or...
Whip no 1 plug out. Turn the engine with the crankshaft pulley. You will be able to feel each compression as the crank gets harder to turn and you will hear the gases escaping past the piston rings. When you reach no1 compression stroke there will be no resistance, stop at about 10deg BTDC.
Take the dizzy cap off and the rotor arm will point at No1 . Install the other leads in order anti-clockwise and refit no 1 plug. Job done!

All this assumes you have good compressions of course.

[dukeofpeckham]

Thanks for all the tips on isolating the misfire.

Yep - badly fouled plug on cylinder 3. Not sure why that one should be more fouled than the others but a clean with vinegar and we are rocking on 4 again. Being London-based my car suffers from lots of pootling in town - maybe 3 was the first one to get too fouled to spark.

Good thing I am taking it to Le Mans in a fortnight - that should clear things out a bit! Anyone else going?

[Steve C]

I had the same problem on my lawnmower ... cleaned the air filter and plug, running better than ever

[r08813]

Cylinder 3 is always the one that becomes a problem, On mine, I noticed that the exhaust valves had much more carbon on them than any of the others (Just done my head!). It was actually keeping them slightly open and lowering compression.

I don't know a reason why, but I assume it's something to do with the shape of the exhaust manifold. But then I may be wrong there as I didn't really try to investigate, just tried to cure the problem.