So, I bought a suzuki samurai with a vw 1.6td swapped in. For some strange reason my stock samurai tach doesn't work...

I have found off the factory floor the volkswagens used the "W" wire from the alternator as a signal to the car's tach. I suppose I could tear into the samurai alternator and modify it for a "W" wire and get a mysterious black box to hook up to the factory tach, but the whole process appears to be inherently inaccurate.

So, what else is available as a tach on a diesel motor?

Optical pickup? Might get fowled by dust and grease....

Magnetic pickup? Might fly off or throw the balance off whatever I put it on...


How was the first gen cummins set up?

 

AutoMeter sells a clamp-on alternator tach. Works fine once you calibrate it.

1st gens didn't have tachs from the factory.

 

Technically true but Dodge did sell a dash-mount add-on tach for the early 1st gen. Cummins.



They had a magnetic pickup that mounted near the balancer and a magnet that glued to the balancer. I installed one for my boss back in 1990.

 

All I did when I installed the tach in my '93 was drill a couple holes in the dash to mount the guage and pluged it into the pigtail provided....
All the rest of the stuff was done from the factory.

Magnetic pickup on the harmonic balancer eh?
Might have to send the wife in to visit the parts department at her work....

Then again, the vw doesn't have a balancer.... might have to find another spot for that magnet.

 

By '93, the wiring was already in place for the tach - Just install and plug it in. Same on my '92. Back in '89 & '90, you had to mount the pickup, glue the magnet, run the harness and all.

Wonder if you could attach the magnet to the flywheel and have the pickup read thru one of the holes in the bell housing. Alternator pickup is still probably easiest.

 

This has me intrigued... How big was the magnet? if I set that on the flywheel would it throw it out of balance?

Easiest, yes.... accurate, no.... Belt slipage, error in calibration etc, etc.
I'm not looking for a digital readout here but it would be nice to know with a fair bit of confidence that it's going to be and stay roughly in the ballpark.

 

Now you're asking me to test my memory from an install about 16 years ago. My recollection was that the magnet was about 3/4 the width of the balancer (1/2"?) and about 3/4" long and about 1/8" thick but I may be wrong. I've slept since then.

One difference to consider is that the VW pulls higher RPMs than the Cummins does so balance will be more critical. Might have to have a machine shop re-balance the flywheel if it's going to see lots of high-rpm use.