Bouncing Tach

[airbur]

My tach has been working fine for the last month or so but now it bounces all over the place. I thought this might be a bad ground but it seems to be fine. I attached it directly to the neg battery terminal and it's doing the same thing. Any ideas?

Thanks.

[Viperwolf1]

Could be a sign of a problem in the distributor. What type of ignition do you have?

[airbur]

It's whatever was OEM on the 1970 year. The dizzy is a new Mallory model....

http://www.amazon.com/gp/product/B000FVZHTS

In the last year I've installed:
New battery
New Flamethrower coil
New plugs/wires
New solenoid

Has the original voltage regulator and alternator.

This just started happening about a week ago.

[Viperwolf1]

Try adjusting the points.
http://prestoliteperformance.com/Portal ... _25_27.pdf

[airbur]

So from those procedures, the point gap for a 27 series should be .022 for the dual-point? I'm not sure how to adjust this but I'll do some research. Thanks.

This seems to be a pretty good writeup.... http://thecareandfeedingofponies.blogsp ... butor.html

[Viperwolf1]

Yep. You need to get one rubbing block on the peak of the cam then adjust that one only. Then turn the motor slightly to get the other rubbing block on the peak and adjust that one. It's twice as complicated with dual points.

[airbur]

So to be clear, I use the feeler gauge between the felt pad and the cam lobe? That's what should be .022? Thanks.

[Viperwolf1]

No. the feeler gauge goes between the point contacts when they are all the way open.

[airbur]

Ok, so I checked the points, they were right on at .022. Then I checked the timing, it was off so set it back to 11. Then I changed the ground on the tach and also replaced the coil to dizzy wire. The tachometer still bounces.

One more thing now, it's running really rough, stalling and almost impossible to start without flooring the throttle after waiting 10 minutes. I'm going to change the fuel filter again but I'm now thinking it may have something to do with the mixture screws on the carb? It smells of gas horribly but there are no leaks.

Thanks.

[Moab Mike]

Ok, so I checked the points, they were right on at .022. Then I checked the timing, it was off so set it back to 11. Then I changed the ground on the tach and also replaced the coil to dizzy wire. The tachometer still bounces.

One more thing now, it's running really rough, stalling and almost impossible to start without flooring the throttle after waiting 10 minutes. I'm going to change the fuel filter again but I'm now thinking it may have something to do with the mixture screws on the carb? It smells of gas horribly but there are no leaks.

Thanks.

Fouled plugs?

[airbur]

I checked the plugs and they looked ok. They are pretty new.

[Shawns Fords]

I would say the coil could be going bad. Its nice to have a known good working coil to swap out and verify. Do you have an ignition ballast on the coil circuit or the resister wire? Check all of your wiring connections and verify they are making good connections.

[airbur]

Well, the coil is 6 months new also...but I guess it could be bad. No ignition ballast that I know of. What would that look like?

[Viperwolf1]

The hard starting after shutdown is most likely fuel boiling in the carb. Might need a little tweeking on the mixture screws too with this warm weather. Neither of those will affect the tach though.

[Shawns Fords]

Well, the coil is 6 months new also...but I guess it could be bad. No ignition ballast that I know of. What would that look like?

The ballast originally would be in the wire itself. the hot wire to the coil. If the wire shorts out then normally a replacement wire is installed with a ballast on the firewall. But that is not likely the cause now that I think about it more. Its a simple ignition system, so if it all checks out ok you may have a bad tach but I can say I have never seen a tach that just went bad. I have to think it is a connection problem somewhere.

[airbur]

Thanks guys. I'm going to replace the fuel filter again and mess with the mixture screws. Still baffled on the bouncing tach.

If the tach to coil wire is in close proximity to any other wires....battery, plugs, alt. etc. could this cause issue?

Thanks

[Shawns Fords]

you could be getting a cross signal if there is enough amps going through the other wires. Or if there is a fray in one of the wires.

[Viperwolf1]

Or if it was running parallel to a plug wire.

[Booger]

What about a condenser problem?

[airbur]

The condenser I'd that cylinder on the outside of the dizzy right? It's new.....but it could be bad I imagine.

[Booger]

The condenser I'd that cylinder on the outside of the dizzy right? It's new.....but it could be bad I imagine.

Yup. Seen them bad right out of the box. When I used to run points I always carried a spare set of points and a condenser. Cheap insurance.

[airbur]

How else would a bad condenser show itself?

[Viperwolf1]

How else would a bad condenser show itself?

Points wouldn't last long.

You can test it with an analog ohmmeter but it's kind of tricky. I'd just swap it out.

[airbur]

Sounds good....will pick one up at Advance soon. Thanks guys.

[airbur]

New coil fixed both the bouncing tach and the stalling/stumbling problems! My old coil was only 1 year old.

[cobshane]

You never know what's going to happen with aftermarket junk!

[airbur]

Well, the bouncing tach is back again. I can't figure it out. It was fine for about 3 days after I put the new coil in, then all of a sudden it starts bouncing again and the bad performance is back. The new condenser should be here today so I'll try that. It's getting annoying.

[airbur]

My new conderser made it 3 blocks before it took a crap.

That isn't what I wanted to hear! So should I order a bunch of them as backups? Man, what a pain.

[ZOSO]

Ditch the points and go with a oem electronic ignition.

[airbur]

Ditch the points and go with a oem electronic ignition.

Would love to, but I just bought this new Mallory dizzy as a direct replacement. Would like to get it working.