timing jumping = impossible to set (type 4)

[marcw]

Hello,

Well at my wits end again. I have now done everything I can think of on my distributor. It is impossible to set correctly at this time and the car is therefore stuck in my garage. (Type 4 2 litre, CJ, 1976.) She is missing with every so often when at idle but seems fine-ish. When I push to 3000 rpm she starts to splutter.

The timing line (the white one showing up in the strobe) if set to 7 degrees BTC the line looks stable with a flash of a shadow at about 12 degrees BTC. At 3000 rpm the problem is much more noticeable. The main line is at 28 - 30 degrees and then there is a ghost line at around 20 degrees and another at around 35 degrees. (I wish I could take a picture but its all too fast.)

What I have done.

I have put in a completely different distributor. I have two complete distributors; one is electronic points one is manual points.

They both do the same thing, but the range of degrees is higher on the electronic one.

I have mixed and matched the rotor, the cover, the coil. I have put in a new set of points and condenser. I have set the valve clearances, the points gap and even rewired the entire ignition loom in the engine bay. I ended up taking a line from the positive of the battery straight into the coil to check that there was nothing iffy in the wiring to the key.

I stripped both distributors and checked that the springs and weights were all in place and working smoothly. I oiled and greased everything so that it was clean, shiny and smooth. Nothing changed, still jumping.

The engine is 1000 kms from a main bearing seize. New bearings all round (main, big end, top end) heads checked and new valve guides put in, new rings as well.

I cant figure this one out. Any ideas?

Marc

[Tony Z]

have you attached your timing light to #3 to double check that it isnt the lead on #1?
What is your end play? Too much might affect the timing if the crank moves around

[marcw]

Thanks Tony - I will connect to all the wires today, good idea to eliminate anything easy to reach and outside the distributor. For all I know it may even be a spark plug.

End play is another story all together

Marc

[marcw]

OK so the timing jumps for all the cylinders. I did notice however, that the jump only starts once the engine is hotter, about 3 minutes in. So expansion makes it worse.

From what I can see the following may be wrong: in order of pain and suffering

(1) Both of the distributors I have are not good - I don't think so as they are pretty much solid with no noticeable sideways movement on the drive arms

(2) The distributor drive washer fell out when I put in the distributor drive - means taking out the engine

(3) The end play is wrong however, I did check that it was in spec - I got it to 0.9 with the shims at hand - also means taking out the engine

(4) The distributor gear is worn or the distributor is worn or both - as with (2) this means taking out the engine



I suppose I will check the end play as best I can in car - pull and push on the fan - is this doable with the engine in the car?

Next I will have to pull the distributor drive out and "hope" that the washer/shim stays in place if it is there. (Hope is, I have always found, not a strategy.)

If the washer/shim falls in then I have to take the engine out. If the washer/shim is not there I will have to take the engine out. If the washer/shim is there and I can put it back properly, then I have to take out the engine as its deeper in.

Are all these thoughts correct? Is there anything else that I can check before I check end play or take out the distributor drive?

Marc

[fig]

While excessive end float will make the timing float, I think it's negligible, especially with the end float you measured, which is barely out of spec. I've had type1 engines with 5mm end float that ran sweetly and smoothly.

I have noticed that there is some timing float on almost all my engines when I put a timing light on them, and I don't have misfires or spluttering above certain revs. Maybe the timing float is not the cause of your problem, or maybe the cause of timing float is something we haven't thought of yet.

Have you confirmed where TDC is on your engine? I find the plastic degree gauges fitted on type4 engines can't be trusted. If you can be certain where TDC is on No1 and mark the fan accordingly, then you can use your timing light to accurately dial in full advance.

Also, have you properly checked your distributor advance? No vacuum leaks to the vacuum can? No pinholes in the diaphragm? Have you had a distributor technician check that the centrifugal advance is working properly (are the springs maybe worn or incorrect?)?

I really don't know what the problem is, but maybe these ideas will give you something to work with.

Good luck!

[Tony Z]

thinking about this, we keep guessing and not one of us can actually see your engine and see what it is doing...
after all of your efforts, maybe you should consider taking it to someone who knows these engines inside out and can put you on the right path or fix it for you.
As fig said, 0.9m endplay isnt too bad wrt timing - its a heck of a lot past VW's rebuild spec though.
The shims under the dizzy shaft are there to save the case. As long as your teeth fit into the slots, they should be fine, but the shims are important.
All point systems will have a bit of spark floating, but usually only 3 or 4 degrees one way or the other, not 15 total.
If it happens only after a few minutes, check that your coil isnt giving up the ghost. But once again, we are here guessing and throwing out ideas without seeing the engine. It needs a good doctor to look at it.
@Bugger

[marcw]

Thank you tony - end play is actually at 0.009 - I missed a zero there.

Problem is that I cant drive her, but am thinking to take it to Primrose just keeping the revs low.

I am stumped with this one.

[Tony Z]

hire a piggy back trailer.
They cost about R300 for a day down here and given their bad reputation, I have had good success with them

[Dawie]

To re-cap, (from your previous posts):

Shortly after re-assembly of engine, some noise started to appear from rear of engine, around distributor drive area. Initially car was still drivable, but noise from distr drive area worsened until timing was jumping around so badly that car became undrivable.

"1 - there is a ting which is coming from the distributor area of the engine. This was not there when I first put the engine together and at around 200Kms started. It has been getting progressively worse."
viewtopic.php?f=4&t=36174

As a test, i would take an old distributor and remove "points mounting plate assembly". (That way we can directly feel the bottom shaft without centrifugal advance play.) Install this, then slowly turn engine through 720 degrees while stopping bit by bit, while feeling play from distributor side. Determine if and how play changes while turning engine.

[marcw]

Thank you Dawie - I will do that - it is a pity I cant drive her to Pierre and have him and Johan listen.

Here is a video of the timing jumping all over the place. As I said it is rock solid at first start when cold then after 3 or 4 minutes it starts to wander. You can also hear the ting (now a ding from the post you provide - thank you for that) in the background.

https://www.youtube.com/watch?v=zPUoR1DH4Qc

[Terry Phillips]

Have you tried using another timing light.The timing light I have is the one you can adjust so you can get 2 readings.

[fig]

... it is a pity I cant drive her to Pierre and have him and Johan listen. ...

Only indirectly related to your problem:

I would recommend that everyone who drives old cars should have AA membership. The annual fee pays for itself the first time you use the towing service. In SA today, roadside assistance can save your life. At least once a year one or other of my cars needs to be towed from my home to a mechanic's workshop. I have the peace of mind of knowing I will always be able to move non-op cars.

[fourier]

Just a thought, but do you have the spring installed between the distributor and the drive shaft. The shaft could be "floating" up and down, affecting timing...

[marcw]

On both counts. Yes I do have AA, and yes the spring is there.

Today I shall check the play on the distributor drive and then will check on how to take out the drive its self without a drive puller. That is the last resort before I pull the engine again.

Four things can happen. The washer stays with the case, the washer comes off with the drive, the washer falls into the sump, or I find out the washer has already fallen into the sump.

The first three means I still have no idea what is wrong and the last that I do know, but have to split the case.

A very sad place to be.

[Dawie]

What happens at different rpms

Could it be that, as it heats up, idle speed increases until distr starts advancing. Then with slight changes in rpm, the advance mechanism starts operating. That would be a sensitive part in it's advance curve.

What does it do when hot and adjusted to slow idle. And at 4500 rpms when advance mechanism is sitting against it's stop.

As they say: When doing fault finding, DONT ASSUME ANYTHING!

Oil pump's idler shaft backing out against the cam gear? (Could be checked by removing oil pump).

Are you sure noise is only at the very rear. Not the flywheel coming loose maybe?