TheSamba.com :: View topic

Mon May 09, 2016 4:29 pm

Got the dwell tach today and it seems squirrelly . Bounces around so it is unreadable. Red wire to coil ,distributer , and black to bat neg. any ideas what is going on? Name is standard digital multimeter. Thanks Dan

Mon May 09, 2016 4:46 pm

Ah the eternal question: is your dwell/tach screwy or is your distributor nice and worn out?

Mon May 09, 2016 5:34 pm

Try it on another engine.

Tue May 10, 2016 4:42 am

It dosen't appear to have excessive wear . What would I look for ? I had the tach close to the engine. Could I be picking up noise from the plug wires?

Tue May 10, 2016 9:39 am

If your dwell meter is digital, it certainly could be interference from ignition. I had that problem with my old set of plug wires, couldn't get steady voltage, rpm, or any other readings on digital equipment. New set of plug wires and everything was fine.

Tue May 10, 2016 2:10 pm

Yes digital....Sineometer ut100. Company makes a bunch of these so I guess it should be fairly reliable.
I've looked at the blue wires in the dark and can't see any leakage but old eyes play tricks n me too.
Any way to check for noise?

Wed May 11, 2016 8:22 am

Well if you get a lot of static on the radio and it changes with RPM, that is always an indicator. The wires could be non-suppression which would cause the same issue.
As suggested, check the dwell on another vehicle to verify the meter is good.

Wed May 11, 2016 2:23 pm

Don't have a radio or another engine with points. I wonder if I can put a resistor inline with the meter to settle it down? What size resister?

Tue May 17, 2016 4:41 am

As per Ken's advice I put new bosh wires in and that solved the tach jumping around problem thanks
However the tach reads steady at about 325 but by ear it seems to be idling about right for a vw if memory serves me. But it's been about 30 yrs since I worked on one.

Tue May 17, 2016 8:48 am

bad wires will do that. affected my voltage measurements on the generator for me.
Is it possible the tach has a 4,6,8 cylinder position and it's in the 8 position or do you need to double the reading for a 4 cyl?

Tue May 17, 2016 3:20 pm

Yes this one has 3,4,6,8 and it is set on 4. It is a puzzle but I learn with every challenge . I'll try the 8 setting and see if there is any coralation between the two.

Tue May 17, 2016 9:46 pm

I used an analog dwell meter and had no problems.

I referenced Rob and Dave's tune up procedure:

http://vw-resource.com/tune_up.html

Although kind of lengthy, it explained everything I needed to know. I just printed out the whole thing so I could reference it while at the engine.

Rebuilding the carb at the same time made a huge difference when I did the full tune up. Everything ran very nicely since the whole system was refreshed and worked on as a whole.

Mark

Wed May 18, 2016 5:39 am

I have Rob and Daves printed out too. I've cleaned the carb and replaced o rings and gaskets. I'm going to try to set the fast idle with a feeler gauge today. Can't do it by eye and get it accurate and from what I read that is critical to do the other two adjustments right.
Finding "stuff" here in northern Maine is a pain. Will a dashboard tach work? I may be able to find one of them