Old points ignition problem

shane038, Oct 21, 1:10am
Ok guys am working on a 73 Vauxhall Viva. Installing a newly recoed engine. The problem is this: We have no spark on number 4 cylinder. Have tried, different distributor cap, rotor, and lead. It has a very weak spark whilst cranking over but disappears when engine starts. The shaft bushes are worn but still so so. Its not rocket science I realise but I am stumped on this one. Like I say I have tried to eliminate the obvious, any help greatly appreciated.
Once this is sorted then we can get the engine reconditioner to fix the leaking head gasket and cracked sump that they didnt get right .

lyonruge, Oct 21, 1:14am
are all the other leads showing a good spark!

shane038, Oct 21, 1:16am
Yep the rest have good spark.

lyonruge, Oct 21, 1:16am
how are you testing it! to know it has spark cranking and not when running!

lyonruge, Oct 21, 1:17am
are you using a dummy plug!

shane038, Oct 21, 1:20am
First I pulled the leads off 1 at a time to isolate while it was running, then changed all the above metioned, then yes used a good dummy plug as well!

lyonruge, Oct 21, 1:22am
OK, so swap the number 3 and 4 lead at the cap and test it, if you have good spark on 3 leads and weak on 1, its the cap or the lead.

lyonruge, Oct 21, 1:24am
heres an out there possibilty, if there is play in the dist shaft, at the point where no. 4 should be firing, the spring on the points may be causing the shaft to move, and therefore the points gap to change!

lyonruge, Oct 21, 1:25am
maybe decreasing the points gap might help to show a sign!

shane038, Oct 21, 1:27am
tried swapping 3 and 4 lead still nothing on 4 , havent used the dummy plug on any other lead as they are all working, engine runs on 3 good as gold! just #4 causing the problem, like I say have tried different leads cap and rotor!

lyonruge, Oct 21, 1:28am
try the dummy pug on all and compare the spark, maybe too big a gap for an old engine!

shane038, Oct 21, 1:31am
That is the only thing I havent tried, I do know that sometimes in the old days with vauxhall stuff closing the points gap helped but really thought it was more for curing surging

crzyhrse, Oct 21, 1:54am
It can only be the cap or the lead or the plug or a worn lobe on the distributor shaft.

crzyhrse, Oct 21, 2:00am
Nothing wrong with that! Just need to fit combustion chamber under the distributor cap.

mrfxit, Oct 21, 3:46am
If this is a spare/ unknown dizzy, then yep very likely a worn rotor tip or oval shaft bush

Real easy to check the shaft play / turn engine over by hand to point the rotor at each cap contact/ give the dizzy shaft a push in all directions/ repeat on all 4 lobs & check the points gap each time

bob.moss, Oct 21, 9:51am
The centre of the breaker plate is worn, to repair it put a socket through the hole in the centre and another socket over it on the back of the plate. Squeze the two sockets together in a vice to expand the centre thereby removing the play. I hope this makes sense to you but its dificult to describe. The breaker plate is the part the points are attatched to.

bigjerry, Oct 21, 11:04am
Its points gap. strip it down, clean it up and start again. Check the gap on the plugs aswell. Its the old points technology getting the better of ya mate haha.

rlr29, Oct 21, 11:53am
If it's gone out of straight then the rotor might be missing the disturbutor all together.

lovemore_mbigi, Jan 10, 3:15am
There's a guy in Christchurch who rebuilds points distributors to as-new condition - qualityrebuilds.com.

I've used them and the quality and service is first rate.