Printable Version of Topic

Click here to view this topic in its original format

914World.com _ 914World Garage _ Weak spark with Bosch Blue Coil

Posted by: second wind Jan 3 2018, 04:43 PM

Hello gang and Happy New Year to all. My car hasn't run in weeks and I am closing in on the problem. With plugs out and cranking the spark in the spark plugs is very faint. I have a new Bosch Blue Coil to put in but wondered if anyone knows of a static test I can perform on my replacement coil (not brand new but told it came off a running car) and my old coil to compare results? Time to get back on the road. Thank you very much.
gg

Posted by: Rand Jan 3 2018, 04:46 PM

Check the braided ground wire between the advance plates in the distributor. If it's not solidly connected at both ends, you get weak spark. It's not unusual for one end to break loose where it's soldered. May not be your answer, but it's an answer you need to know either way
.

Posted by: BK911 Jan 4 2018, 08:49 AM

Check continuity between the terminals.
Haynes describes the procedure and acceptable values.

Posted by: jcd914 Jan 4 2018, 09:36 AM

A generic testing procedure, I'm not sure of the specs for a Bosch blue coil.
Attached Image

Posted by: mgphoto Jan 4 2018, 09:59 AM

Start with the battery, fully charged should measure from terminal to terminal (not clamp to clamp) 12.8 - 12.6 v if not change it to capacity.
Resistance is the next problem, that's why we measure from the terminals.
Corrosion between connectors is the main issue with a 40+ year old car.
Starter will operate at a voltage of 9.5 v, FI might but ignition will have a tough time, especially if the ignition wires have some corrosion.
Multi-meter is your best weapon.

Posted by: Perry Kiehl Jan 4 2018, 08:11 PM

Can also be the points and/or condenser