I know, it sounds weird but I had a post on here last night about what I thought was a failing trailing coil. Start the car and it turns sluggish and acts like it is missing, may catch and run but the tach is dead. Today it got more interesting in that it starts though much more sluggish but the tach works. I thought about pulling the egi fuse and unhooking the crank angle sensor and seeing if it still turned sluggish,,,,, misfirish. If so then I can rule out ignition and look at the starter. Does that sound like it would work??? If the engine is turning over too slowly can it cause the tach to occassionallly not work? Or could I just have a flaky trailiing coil??
Thanks,
Rob
87 Turbo

 

I'd start by checking the battery & its primary cables & connections.

Measure the voltage at the battery when cranking.
Compare to the voltage at the alternator when cranking.

They should both be steady at near 10 volts.

The coils may have an unrelated problem.

 

I am showing 12.75 volts at the battery with engine off. About 14.2 from alt. when running. While cranking the battery should still be at about 10 volts?? I will check it and see. I always thought starter failure was either working or totally dead.
thanks,
Rob

 

True.

At this point I'm thinking cables or connections.
You must have bright shinny metal to metal contact.
The battery ground clamp can look good on the outside and be corroded on the inside.
To test- with the engine running & the headlights on:
Measure the voltage drop from the alternator frame to the battery (-).
A good primary ground will show zero volts.
While you’re there measure the voltage drop from the alternator output post to the battery (+).
That should also show zero.

The tach could be a weak connection anywhere between the coil & the gauge solder joints.

 

Well, turns out it was a starter going bad. Totally dead now. Good voltage, no crank, hear the pump running but nothing else. Also blew my heater hose under the oil filter on the way home to fix the starter so ended up having it towed off the highway. They brought it to me at 2:15in the morning. I WAS sleeping pretty well. Gotta get some 5/8 heater hose (thanks Kevin) and then a new starter from Advance possibly. Should be good to go then. Thanks for all the advice and if you have any hose tips send em my way.
Rob