Gentlemen, I need your help.

My 740' 88 (non turbo) suddenly quit on me. There is no spark.

I've another 740 '86; so I swapped Ignition coil and the coil is OK.

I checked the control unit (under steering wheel) by swapping it with my 740 '86 and it is OK as well.

Two days prior the 740 '88 started to quit without any reason but I was able to start it right away.

Now it doesn't start anymore. There is no spark from the coil. Though there is battery voltage on the coil terminal 15.

Please help.

Joseph

My ignition system manual points out that I have problem with Ignition system.

There is no spark at Ignition coil on 740 '88.

I concluded that Power Stage must be at fault so:

I swapped the Power Stage from my 740 '86 to 740 '88. My 740 '88 still will not start. But I connected the power stage from 740'88 to 740'86 and my '86 will not start either. Putting Power Stage back to '86 and the '86 starts right up. Can anybody explain this?

Both volvos '88 & '86 are using the same Bosch Power Stage.

Joseph

I

I forgot to add.

I have fuel in the tank my my fuel pumps are working.

I connected spark plug directly to the ingition coil and there is no spark. So the hall sensor should be OK.

I just need to find out why there is not spark on my 740 '88 direclty from the ignition coil.

What to check next?

Joseph

Not sure why you figure the Hall Sensor is OK by connecting a spark plug to the ignition coil, because the spark plug side (tower) is the secondary winding of the coil and the Hall Sensor is the input signal to the Power Stage.

The Hall Sensor is a common failure and you've got exactly the right symptom...no spark. Anyone who has been through this will bet money that it's the problem with your car too.

Steve, thank you for your input.

It was indead the Power Stage.

When I was doing the testing yesterday. I made a small mistake, when I was tesint the Power Stage from my '86 on my '88, I forgot to connect the Control Unit back on my '88, so there was no way it could start.

Today, I went back repet the procedure and my '88 starts right up.

It is good to have two the same bricks (for testing purposes).

Joseph