RPM Spikes - What's the cause?

DurocShark · Post by **DurocShark** » Mon Feb 05, 2007 8:09 am

http://www.youtube.com/watch?v=vhgbVnLcBFM

It shows on my dash tach too.

DurocShark · Post by **DurocShark** » Mon Feb 05, 2007 8:28 am

Oh, and the dwell spikes too. I changed the dwell all the way to 60* but no difference.

I can't help but think this is the points. but they're new Bosch bought back in August. Grrrr...

I couldn't find my spare points so I'll have to buy some new ones.

vwlover77 · Post by **vwlover77** » Mon Feb 05, 2007 10:34 am

I would think the spikes would be caused by arcing across the points as they begin to open, which your tachometer would interpret as an increase in RPM. The condenser is supposed to prevent the arcing. How old is the condenser, and is it properly connected to the points and grounded via the distributor body?

DurocShark · Post by **DurocShark** » Mon Feb 05, 2007 10:56 am

vwlover77 wrote:I would think the spikes would be caused by arcing across the points as they begin to open, which your tachometer would interpret as an increase in RPM. The condenser is supposed to prevent the arcing. How old is the condenser, and is it properly connected to the points and grounded via the distributor body?

Both are brand new as of last August. And both Bosch. The ground in the distributor is perfect.

steve74baywin · Post by **steve74baywin** » Mon Feb 05, 2007 11:15 am

Maybe your voltage regulator is causing you problems?

vwlover77 · Post by **vwlover77** » Mon Feb 05, 2007 11:28 am

Are you connecting your test meter directly to the coil? I had a dash tach that jumped around like that and it was the wiring to the tach going intermittent that made it jump.

DurocShark · Post by **DurocShark** » Mon Feb 05, 2007 11:33 am

vwlover77 wrote:Are you connecting your test meter directly to the coil? I had a dash tach that jumped around like that and it was the wiring to the tach going intermittent that made it jump.

Yes, they both connect directly to the coil.

If it was just one or the other I'd just assume it was either wiring or a goofy tach. But both my analog dash tach and my digital handheld do it.

vwlover77 · Post by **vwlover77** » Mon Feb 05, 2007 2:25 pm

An unlikely possibility is a problem with the wire from the coil to the points.

Maybe throw the old condenser on there and see what happens???

DurocShark · Post by **DurocShark** » Mon Feb 05, 2007 2:27 pm

vwlover77 wrote:An unlikely possibility is a problem with the wire from the coil to the points.

Maybe throw the old condenser on there and see what happens???

Good idea. I'll try that.

Post by **Amskeptic** » Sat Feb 17, 2007 8:26 am

Do we have a resolution for this topic?
Dr. Delete is Restless

DurocShark · Post by **DurocShark** » Sat Feb 17, 2007 8:51 am

Amskeptic wrote:Do we have a resolution for this topic?
Dr. Delete is Restless

I'll post when I have one. Between the weather and kids getting sick, I haven't tackled this yet. Plus for a while the symptoms weren't happening.

Itinerant Air-Cooled

Itinerant Air-Cooled

RPM Spikes - What's the cause?

RPM Spikes - What's the cause?