940 stalls at Hwy speed - 2 quick questions

macs70GLT · Post by **macs70GLT** » 13 Dec 2011, 08:12

Our 940 died at hwy speed (55 to 60 mph) twice on Saturday with my son driving. Car suddenly lost all power, few seconds later all dash trouble lights came on. I experienced very similar symptoms some years back with a 240. By the way, the car started up again within minutes. Full tank of gas, level road, car warmed up.

I started reading the page on Matthew's site regarding cars stalling, have more to go yet.

My questions - will the diagnostic system on a 95' 940 store any codes related to ignition problems? (no check engine light set that I can tell).

Secondly, since it is a sudden loss of all power (I didn't see if the tach dropped to zero but imagine it did), doesn't this most likely point to ignition/electrical as the source? Including fuel pump relay if suspect on these models.

(I'm assuming not a mechanical fuel problem like filter or pump because the car did not bog - just completely shut down).

I have new cap/rotor/plugs etc, just got the car 2 weeks ago.

Thanks for the help

Mike

Post by **billofdurham** » 13 Dec 2011, 12:06

The OBD system will read and store ignition codes. Socket 2 is used for the fuel system and socket 6 for the ignition. Some codes do not illuminate the check engine light.. Full instructions for the OBD are pinned at the top of the forum. Usually a total loss of power without engine coughing and spluttering does point to an electrical or ignition problem. Usually if the pump relay stops the engine will cough as it dies as it is, in effect, being starved of fuel.

Check for codes and let us know what you find.

Bill.

macs70GLT · Post by **macs70GLT** » 13 Dec 2011, 20:57

Thanks Bill,

No codes on Fuel or Ignition - both displayed 1-1-1 only, nothing else.

I read elsewhere about the ignition power stage (Ignition Amplifier) being a potential cause for stalling when car is warmed up. I'll have to check to see if that looks suspect.

Do you know of any checks for this? Is it also known as the Ignition Control Module?

Thanks

Mike

Post by **billofdurham** » 14 Dec 2011, 11:59

The attached shows how to check the ignition amplifier or control module:

940 ignition amplifier check.pdf: (200.29 KiB) Downloaded 270 times

Bill.

Post by **Fish stick88** » 14 Dec 2011, 12:05

Its not a bad idea to just check all the ports. Often times the CEL light will get burned out and not work at all anymore. If it comes on on start up then that is how you will know if it works.

macs70GLT · Post by **macs70GLT** » 14 Dec 2011, 17:50

Thanks for the ignition amplifier check sheet Bill.

I won't have a chance to look at it until this weekend, I'll post the findings when I do.

Thanks

Mike

macs70GLT · Post by **macs70GLT** » 14 Dec 2011, 17:53

Fish Stick88 - good idea, I'll have to watch next time I start the car. I don't use it very often, my son will drive it daily after the holidays - provided I get it running stable.

Thanks

macs70GLT · Post by **macs70GLT** » 15 Dec 2011, 08:01

Bill - took a second look at the Ignition Amplifier check pdf. That's good for checking the wiring harness, is there a way to check the amplifier itself?
Particularly the ground connection to the heat sink? (maybe it's grounded through the amplifier case itself). I'm asking because I suspect it's a heat related issue, as the amplifier gets warmed up it loses the ground.

Thanks

Post by **billofdurham** » 15 Dec 2011, 12:05

Unfortunately I can't find any reference to testing the amplifier itself. However, it is vital that the amplifier is securely fastened as it needs to lose heat through the mating surfaces. Remove the amplifier from its mounting, clean the mating surfaces thoroughly and smear a small amount of thermal grease to both the amplifier and the body. Radio Shack sells Heat Sink Compound, which is what you need, at a very reasonable price. In the US you are lucky to still have Radio Shack as our outlets were all closed some years ago and finding things like this compound can be frustrating.

Bill.

macs70GLT · Post by **macs70GLT** » 03 Jan 2012, 12:50

Bill,

I checked the wire harness to the ignition amplifier - mine is wired backwords from the pdf (seems strange but it does match the wire diagram in Haynes).
Anyway all wires checked OK.
I bought some pricey thermal compound at Radio Shack & followed the directions (designed for CPUs).
The car has not stalled since that one day, although I didn't do the amplifier until a couple of days ago. Also installed new plugs, cap & rotor & air filter.
Another issue the car has is a hunting idle. I have tried finding a vacuum leak, swapped out plug wires individually with some old ones but can't find the culprit.
This car had very limited use for several years, I'm wondering about the injectors, fuel filter & in-tank pump.
I have a Bentley book for my old 240, Love Bentley - wish I had it for the 940. I see the EZ 116 Ignition system in Bentley - can I assume mine is the same?
Anyway, car runs just not smooth at idle.