Real Time Help - Dwell Angle

[Nigel]

I'm doing the timing on my 87 fj60. I put a dwell/tach on it and the Dwell angle is 48˚. According to the shop manual, it should be 42˚. To change it, I'm adjusting the rubbing block air gap in the distributor. I've set it a couple of times, at .2mm and .4mm (both ends of the range, according to the manual), but I can't seem to get the Dwell angle to move below 48˚.

Am I doing something wrong?

Is there another way to adjust the Dwell angle?

Thanks,

 

[2mbb]

Do you have a US-spec distributor. If so, it does not have conventional points and therefore I don't think you can adjust the dwell. The spark duration is controlled by the igniter assembly (the box on top of the coil), not by points.

below are excerpts for the 2F engine manual. You can see that the dwell angle (41deg) does not apply to US vehicles. The 2F did have points in some countries (Australia, for example).

 

[Nigel]

Yes, as far as I know, it's the US spec distributor. The manual has instructions for adjusting US and for Other. Does the air gap not make any difference then?

Also, if the dwell angle is 48˚ is it going to affect the timing, or should I just move on and assume the dwell is set OK?

Thanks for the help.

Just saw the diagram. Thanks for posting. I didn't see that section. I'm going to move on to check the timing.

 

[2mbb]

Yes, as far as I know, it's the US spec distributor. The manual has instructions for adjusting US and for Other. Does the air gap not make any difference then?

Also, if the dwell angle is 48˚ is it going to affect the timing, or should I just move on and assume the dwell is set OK?

Thanks for the help.

The air gap needs to be within specifications, but it probably does not effect the dwell. The "electronic" distributor uses a magnetic device to signal the igniter to fire the spark. If the gap is too large, the distributor won't send a signal to the igniter. If the gap is too small, the rotating part might hit the stationary part and break. Just forget about measuring dwell on this truck.

 

[Nigel]

Now checking th timing and I don't see any timing marks on the fly wheel (this grainy video on YouTube shows what I'm seeing).

Can anyone offer any guidance?

 

[donny paradise]

Rotate the dizzy as your checking the timing until the marks become visible

 

[2mbb]

Now checking th timing and I don't see any timing marks on the fly wheel (this grainy video on YouTube shows what I'm seeing).

Can anyone offer any guidance?

It's often difficult to see the timing mark the first time. Underneath the bell housing, between the transmission and the engine oil pan is an inspection cover. If you remove the cover, you will get a much better view of the fly wheel. Rotate the engine over by hand until you see the timing marks on the front side of the flywheel. Then I'd recommend cleaning that part of the flywheel with a solvent (aerosol brake cleaner works good) and using white or yellow paint or some other bright marker, mark the location of the timing mark.

There will be two marks on the flywheel separated from a couple of inches. There is a straight line--this marks top dead center. Then there is a dimple or round mark (it looks like a BB). This marks 7deg before TDC. The BB is what you set with the engine running. Make sure that the truck is at idle and both vacuum lines are removed from the distributor advance and plugged.

 

[Nigel]

Thanks for the advice. Dark outside now so I'll follow up next weekend. I forgot to pull the vacuum hoses off the distributor advance before checking so that may have accounted for the missing marks.

Thanks again.

 

[grant5127]

Timing lights with advanced adjustment controls are handy for this sort of diagnostic procedures....