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View Full Version : Sigh, No RPM Signal


EricF
01-22-2007, 05:57 PM
Sorry for the flurry of threads... But it seems there's a new issue at every turn that I can't resolve by searching or talking on AIM.

I realized that it isn't my MS that can't read an RPM signal, it's the fact that there just isn't a readable signal in the first place.

The car is getting spark (last time I checked), but the negative terminal of the coil doesn't produce anything that either the MS or tach can convert into anything but 0 RPM. I'm using an MSD 6AL with the mechanical distributor, just bought a brand new Accel coil today. I've tried using the little stock Volvo box, but still can't get a signal.

I considered the possibility it's a grounding issue, and added some more ground straps to the engine bay today (block-alternator, head-strut tower), and have an excessive amount of grounding wires now, my setup also has the main ground going to the engine block.

The tach's an autometer, and I had it on my 244 turbo where it worked perfectly fine. It still switches on, hasn't been dropped or anything since then so I assume it is still good. I assume the MSD is fine as it produces spark, and the same problem existed with the Volvo stuff (I tried it both ways after I got the new coil as well)...

Any ideas? I'm totally stumped. Have been working on this largely myself, so haven't been able to check spark in the last couple days but don't see why anything would have changed since then.

This car oughta be running! Thanks for any help.

linuxman51
01-22-2007, 06:03 PM
take a close up pic of the ms board (from the top) and post that.

Hank Scorpio
01-22-2007, 06:29 PM
Eric you HAVE to pull tach signal from the tach out on the MSD box, NOT the coil

EricF
01-22-2007, 07:19 PM
Eric you HAVE to pull tach signal from the tach out on the MSD box, NOT the coil

I've tried it both ways with no success... We have found though that the stock tach and the autometer both get an accurate signal from the positive terminal. Go figure. MS still doesn't get one from anywhere so I'm starting to lean towards a firmware problem... Trying to figure out how to update as we speak (any advice or links for an idiot like me?)

Kenny, camera doesn't work, what would you be looking for? I check plenty of boards at work for faults and the board seems intact, the diode for the D8 slot is correct (what the crucial rpm-related one is for the different board variations, right?). What else should I look for? Nothing is burned, no solder accidentally reaching across to another component or circuit.. All the external wiring is secure and correct.

linuxman51
01-22-2007, 07:32 PM
jump d8, and make sure the jumper for xg1-xg2 is there. if not, jumper that, try again.

EricF
01-22-2007, 08:23 PM
jump d8, and make sure the jumper for xg1-xg2 is there. if not, jumper that, try again.

You're a king amonst men.

EricF
01-22-2007, 09:08 PM
BTW it runs. When the rain stops I'll take it for a drive.

240Psycho
01-22-2007, 10:57 PM
BTW it runs. When the rain stops I'll take it for a drive.
on your way over?

Oh and congratulations

~Kyle

i also have no RPM signal. damn crank sensor