1991 740 non turbo regina fuel system approx. 200k miles. This morning I repositioned my car for a car wash. She sure is pretty , when cleaned , wheels all shiny , just looking great. So an hour after the fact, it was time to run errands. It started then quit after 10 seconds. WTH I thought. So my diagnostics are as follows. Swapped relays still no start. I can hear the only intank fuel pump priming even before that. Removed oil cap check before and after position of cam lobe....timing belt good. Removed coil from amplifier . Resistances appear acceptable .Cleaned all contacts there and tightened all bolts for good ground. At this point I am awaiting a fiend to come by so I can do a crank to see if there are sparks at the plug. Checked for resistance at the rpm sensor. I got like 190ohms there. There are three tabs one is a shield. I take it crank sensor is good. I had changed that a while back.
So now I am thinking what is it I did differently while washing my car and here it is . I opened the fuel door , not remove fuel cap.. ..I wouldn't do that! , and usually it is black and gooey , so I soaped up the area with the rag and then washed away all the suds while by spraying in the area....NOW is it remotely possible for water to get by the cap gasket and into the fuel tank? My aviation experience tells that the water would be at the lowest part of the tank where the fuel pump is and so I am pumping water into the system?...I wonder
I there a fuel tank bung?

Well my friend came over and we did a spark test . There was no spark from the secondary coil wire. There was 12v to the assembly. We are somewhat optimistic that the Ignition Module assembly is bad as the coil itself tested good. I am still open to opinions .

Can you connect a known good wire from the ignition coil secondary output directly to an external spark plug that is firmly touching grounded metal ? To do it safely stay away from the intake manifold and fuel distribution.

If you have spark under that condition then the problem is in the distributor cap or rotor. Caps / rotors / wires can become waterlogged or carbon tracked and short out the ignition voltage.

If no spark then it could be a coil or ignition amplifier problem.

I would not crank the car with secondary wire disconnected from the coil. Under that condition the secondary voltages go higher than normal and could damage something.

Did any water go under the hood during the car wash ? The distributor might get wet if the rubber seals at the rear hood - firewall upper edge are loose.

Mike

Mike ,
Thanks for your excellent suggestions. I used a spare spark plug for the test. However I did not think of trying another coil wire as I thought it tested good? The distributor did not get wet at all. However I did remove it and replaced with another that I had as a spare and seemingly in better shape. I ordered an ign. Module with new coil scheduled to arrive soon. I hope this is the fix. Will update

Still waiting on parts to arrive

The Coil assembly arrived today Friday 26th . I got it from eeuroparts part number 1367438 , original Volvo , Siemens as opposed to Bendix. When I ordered the part on the 17th I opted , at an additional cost , for it to arrive today the 26th. However it took longer than expected for eeuropart to get it from their source which means that , if shipped as opted for , would arrive next week.I needed to have this car fixed! So what did eeuroparts do...they sent it next day delivery by fedex! Kudos Eeeuroparts and thanks to Josh , Eric and Bryant for their excellent communication with me. Well , did the part work? YES!
My 740 is running again!!! New coil ( old one still good and is now a spare)the ICM was bad, .So the old ICM lasted 23 years....wow

Glad to hear it's fixed, but I always wonder, on these "new part" fixes, if maybe something got "fixed" in the replacement process (by unplugging/replugging coil or connectors).

If it was mine, I'd try plugging the old coil and ICM back in, just to verify the problem source. I think the cabling is slack enough to reach without unbolting anything. And the combined unit does NOT need any special grounding*. So it should be fairly quick and easy to do.

* Mine worked OK while unbolted and in a plastic bag.



--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Bruce,
I did exactly that , reinstalled the old assembly after cleaning up and tried starting after a couple days while waiting on parts to arrive Still did not work. Even prior to installing the new assembly I again tried .No start. I also installed a new air box thermostat and the two inch diameter aluminum hose from over the exhaust to the intake box . This was way overdue! Hope that fixes the rough idle during the winter months in S. FL..
Paul

Glad to hear it's fixed, but I always wonder, on these "new part" fixes, if maybe something got "fixed" in the replacement process (by unplugging/replugging coil or connectors).

If it was mine, I'd try plugging the old coil and ICM back in, just to verify the problem source. I think the cabling is slack enough to reach without unbolting anything. And the combined unit does NOT need any special grounding*. So it should be fairly quick and easy to do.

* Mine worked OK while unbolted and in a plastic bag.



--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

If you are talking about the ignition amplifier / power stage and it has failed you should have wet spark plugs and no spark.
Dan