Car has never missed a lick starting or running. Doesn’t miss, runs smooth.

After an evening driving from point-to-point, the car just died while driving about 35mph on clear dry roads. One cough and dead. Cranks fine, no thought of kicking over. Thought it was out of gas, but that was not the case. Towed it home.

No spark condition on each plug, so here is what I did, following the Bentley and Haynes diagnoses for no-spark.

Replaced plugs, wires, cap and rotor on general principles.

Checked main fuse..OK

Checked voltages at coil..OK.

Checked coil..OK.

At the ignition control unit plug, checked the LH load, ground, feed, RPM sensor..all OK.

Checked the voltage at the ignition amplifier in front of the battery. OK.

Now here is the step I don’t understand: Checked the voltage change at the Amplifier plug during cranking. Hooking the multimeter across the No. 5 connection to ground and cranking the engine results in a voltage change of 0.7 to 1.7. The manuals say to look for a voltage between 0-2 during cranking. If the test is positive, then it could be bad, and replace it. What does this mean relative to my results? Has anyone ever performed this diagnosis before?

The next step is to replace the amplifier ($60-80) and/or have the ICU diagnosed, which can’t be done off the car. A local Volvo shop points out that these do not go bad often and I may have missed the diagnoses. Now I am feeling worried.

A new ICU is about $850 discount, $1,100 sucker price. I unfortunately don’t know anyone with a 1990 240 to swap ICUs with.

Any ideas or where I may have gone wrong here?

Replace the crank sensor on the right back of the engine, this is what send the signal to the dist to fire the spark, they go bad all the time. If your still has one with a part number that ends in 399 it's junk. Ecm do go bad in these cars, however the normally loose the fuel side. Did you check the on board diagnostic? Call me if you need a used computer. Brian

you missed one of the first steps. Check/Replace/Swap the main relay. passanger side, inside, behind glove box, remove the black fabric cover to get at it. good luck....Mr. Tool....i highly doubt it's the icu

Ha! I really missed one of the first steps. The first thing that occurred to me when it died was that the timing belt snapped. I pulled the plug from the cover and checked the belt on the road when it first happened, then pulled the cover and checked it after it was towed home. It must have been snapped on the bottom somewhere...I had it taken to a mechanic, who found it in less than 30 minutes. Oh well. Better than a new ICU. Thanks for the response anyway.

The way I know to see if the amplifier module is working is to put a test

light on the side of the coil that it switches (-)and see if it flashes the

test light. If not, and the unit is getting a signal from the ICU then it's bad. I only had to trouble shoot this system once. In my experience

with electronics you always consider the items that get the most stress in

the system first. That would be the rpm sensor, and the amplifier. When I

had to trouble shoot the 90 wagon in our family the rpm sensor was the culprit. They can be intermittent so personally the rpm sensor is always

the first part I would suspect. I haven't ever heard of a bad ICU. I guess

it could happen but judging by the price it's obviously rare that they

go bad.

I recommend putting dielectric grease in every connector you can find

on the motor. It will keep the corrosion at bay much longer.

Dave 82 242ti