[Barnzi]

Hi all,

This is not inrelation to our supras, but my mum owns a toyota landcruiser striaght 4liter 6 cylinder using the old carby and points. Now the problem is that the dwell angle must be 41degrees, which is all good. Now i adjust the points inside the distributor and with my tester i adjust it to 41 degrees and tighten up the screws that holds the points and thats it. But after a few miles/kilometers the dwell angles goes out and the engine starts to back fire due to the dwell angle being out (ie 50 - 60 degrees instead of 41 degrees). I can't seem to work out why this happens. The points have not moved!! so i re adjust it.

I have thought that maybe the coil is dieing? or the distributor is in wrong! Personally i have no idea!! I'm sorry this is nothing to do with supras but i would really appreciate your help.

A quick note my 82 supra is just about ready for re spray, i will post pics when complete.

Regards
Wayne

 

[Dave A.]

Widening the point gap increases the dwell so something is causing the point gap to increase over time. Did you replace the condenser? Is there any play in the distributor shaft bushings?

 

[Barnzi]

Thanks for the reply, i have not replaced the condensor as yet nor have i noticed any slack!

I think i will take it apart this weekend and see what i get out of it. A friend suggested that there are weights that work in a centrifugal manner which may be stuck!

I will replace the condensor anyway to eliminate that variable in the problem.

Thanks again.

Any other ideas are sure welcome.

Barnzi

 

[Dave A.]

The points could be arcing due to a bad condenser and that can damage the point surfaces and cause the dwell to change. The centrifugal weights that you mentioned are for the mechanical spark advance. The spark gets advanced by the action of the weights rotating the breaker plate as the weights swing outward. This won't, or at least shouldn't change the dwell angle as long as the shaft bushings on the breaker plate are in good shape.
HTH!

 

[Tommy]

Widening the point gap increases the dwell so something is causing the point gap to increase over time. Did you replace the condenser? Is there any play in the distributor shaft bushings?

Dave has it backwards here.
Dwell is the amount of time (measured in degrees of crank rotation) that the coil has to saturate between firings.
Ie. widening the gap DEcreases dwell angle.
But I would replace the condeser too!
Jamie

 

[Dave A.]

Yes, sure enough, I did get it backwards! Thanks, Jamie! Maybe the rubbing block on the points is wearing out prematurely, thus narrowing the point gap which will increase the dwell angle and retard the ignition timing (causing the backfiring) and also cause wear on the distributor cam surface. Did you use some distributor cam lubricant when you installed the new set of points?? Check the condition of the distributor cam and replace the cam if the surface is scored or otherwise damaged.

 

[Barnzi]

Thanks

Thankyou very much guys, i really appreciate your help. I will replace the condensor. I did not use lubricant when i fitted the points, so i will do that too and see what happens.

I will post once i have completed these options with results.

Thanks again. :wink:

Regards

Barnzi