I have a 1977 245.

Recently, it won't start (it started, stalled after a couple seconds and won't start since). The starter seems to be trying really hard, but it never turns over.

With the ignition on, the voltage seems low at the coil (I measured 6.8 V) and I don't get a spark from the ignition wires. Battery is fine, putting out a solid 12.0 V.

So my questions are:
Should I be reading 12V at the coil?
And if so, would it be safe to bypass the ignition control and hook my coil positive directly to the battery's +12V terminal?
If not, is it a bad coil? Bad wires? The distributor and rotor are new.

 

In the old days, no spark almost always meant a faulty ignition coil. I believe 1977 counts as old days. Yes, you should read 12 VDC between either primary terminal and ground at ignition "On."

Measure resistance between the primary terminals. That reading should be low (check your manual). Also check resistance between each primary terminal and center post. Those resistance readings should be similar and in kOhms. For example, the Bentley manual gives 0.6-1.0 ohms for the primary winding and 6.5-9.0 kohms for the secondary winding on the EZ-116K ignition system (240).

No spark in newer models can also mean a bad Hall or RPM sensor, or bad Power Stage. For tests on those, go to www.stepbystepvolvo.com for free guide to diagnosing no-starts on 740/940 (B230 engine).