Hey there volvo forums. First time poster but I've used the forums for a few problems successfully and I was wondering if I could have a hand.

A few months ago, June I believe, while having my car jumped the ICM was burnt out because the jumper cable leads were put on incorrectly. I didn't know what the problem was so I took it to a non-dealer volvo specialist who gave a "good" used one for $500. Within 20 minutes of getting down the street I could already tell the "good" he had written on the ICM was generous because the car would now "hiccup" at random times. During the "hiccup" the car acts as though the key has been turned to the off position: the radio cuts out, the engine stops, the lights turn off if on fully, the horn and turn signals stop working. Sometime it would happen so fast that it only seemed like the radio station messed up and other times it would happen for 5 minutes at a time. It happens at any speed, any gear, any RPM, any power demand.
I repalced the ICM within two weeks with another used one found on eBay and everything was fine for about 3 months but the problem came back last Friday. This ICM isn't having the hiccups as frequently or as strong as the other "good" one was but it is happening again and getting progressively worse.
Is this ICM issue a common problem where I should just order a new or remanufactured one or could something else in the system be killing them?

Any and all help is welcomed

 

I don't know any scenario where an ICM failure would affect the radio.

the radio is powered via a 'load shed relay', which is controlled by the ignition switch, such that the radio and other auxiliary systems (headlights, etc) are shut OFF when you turn the key to START

 

Then could it be the ignition switch that's going bad and affecting everything?
The way the car loses power is in the same fashion of turning the key to the off position and taking it out: only the door lights and hazards work. If they system is off for more than about 6 seconds it comes on like the key was just turned, the seatbelt light comes on, the chime rings, and all the gauges go back up to where they should be.

 

hard to say, but yeah, could be. It also could be some fried wiring, your 'jumped backwards' would lead me to suspect that first.

on the left fender, there's a metal relay bracket and on that is a thin black 2x3" or so box with a snapped on plastic cover, and a BUNCH of red wires coming out. I'd pop that cover and look for any sign of melting, overheating. thats your 'positive terminal', its wired directly to the battery, and virtually everything in the car that needs electricity comes off that.

a couple wires from that positive terminal go to the ignition switch. another 1-2 go to the fuse panel for the strip of always-on fuses.

 

Unfortunately those are all good. I saw a schematic with a breaker unit coming from the ICM. Where is that located? It could possibly be tripping there maybe?

 

different year 240's have different ignition systems, and the wiring varies widely. 87-88 are nearly identical, with LH 2.2 fuel injection, and Chrysler ignition controllers, using Bosch coils and distributors The definitive source of info is the Volvo 'greenbook' TP31099-2, 1987-1988 240 Wiring Diagrams....

afaik, there's no circuit breakers on these cars, just fuses, and the ignition system is NOT fused.

red wire from said positive terminal goes to ignition switch pin 30. blue-yellow wire goes from ignition switch in 15 to the input side of fuses 11-12-13. blue wire goes from input side of fuse 11 (NOT going through the fuse) to coil pin 15, so this should always be +12 when the car is turned on. blue wire goes from coil pin 15 to ICU pin 2.

remaining wires on Chrysler ICU:
1 - grey wire to coil pin 1 (and on to tachometer)
3 - green wire to hall sensor +
5 - yellow wire to hall sensor 0
6 - brown wire to knock sensor
7 - orange wire to full throttle switch
8 - green wire to LH ECU
9 - black wire to hall sensor -
10 - black wire to chassis ground.

thats it, the whole thing. when the ICU grounds the pin 1 grey wire, the coil fires, you get spark. the hall sensor signals provide the timing. if the knock sensor triggers, it retards the timing to prevent knocking. full throttle probably tells it to run as hot as it can.

 

The device on this schematic labels the full throttle switch as the breaker unit that I was talking about. All the wiring visible up to the ICM and fuse box and ignition switch still looks top still so on Sunday I'm going to pull out the distributor for a new one and trace all the ICM wiring to make sure it didn't burn up somewhere in the middle.
Do you know where the full throttle switch is so can check that also?

 

the full throttle switch is part of the same assembly as the idle switch (which goes to the ECU), on the side of the throttle body opposite the throttle control rod.

the car would run 100% fine with that full throttle switch completely disconnected.

 

Is 87 in the the years of the bio-degrading harnesses, or had they solved that by this point?

I rather agree with pierce--I think there is probably an issue in the wiring. Let's get back to the bad jump, and be sure were are clear:

Were you jumping, or getting the jump? If you were getting the jump, did you hook up directly battery to battery or hook up the red side of the battery and the negative side to the car frame? How long did you have it this way? Did you try to start it? I'm just trying to back up a bit. I have my doubts that two independently "good" ICMs would be bad... so my guess is that it may have not been your problem. Even if it is, it appears something else went bad too... so figuring out the details original incident may be the most useful.

 

my understanding is, the biodegradable wiring started in 81 or 83 (depending on who you believe) and extended through MY 87. the 1988's got the revised harnesses with better insulation, everything from 88+ is fine.

 

My thought on that comment is perhaps overheating wires that were already susceptible to bio-degrading sped up the process.

 

I was the one recieveing the jump. The ground on the alternator had been chewed up by squirrels and a sensor from the alternator to right above the oil filter had come out.
(Those were fixed the day after I got the ICM from the specialist)
Once the cables were hooked up I tried to start it once, it didnt work and then the cable began to smoke. I took the cables off and let it cool a little then tried to start it again with no luck.
The inline fuses near the battery were still good, the red wires in the little black box were still intact and the ignition coil was still good.
That's when I had it towed to the specialist who told me it was the ICM. He told me he had used one now that would work enough for now or he could order me a referbished one that could be there in a week.
I went for the one he had in house and it started up with the describes symptoms before I got home.
The one I got from eBay gave me no issues and until two Fridays ago.
The connections all still look good in all the same spots, the sensor had fallen out again but I replaced the connection with one from a new 740 so it shouldn't rot out as fast, I foliowed the path that pierce described and found no issues so I'm back to thinking its just a chance bad ICM.
The original ICM still doesn't work and the second ICM is still a lot worse and I don't have a fourth one or another volvo I compare it with.

 

I have found the connectors on those chrysler ICU's can be problematic. pull the rectangular connector straight out without rocking, and use a little pointy object (I used a very small screwdriver) to gently tighten each of the sleeves in the plug so they will make better contact with the pins in the ICU socket. don't overdo it. liberally grease the connector with silicone electric grease, and reinsert it, again straight in without rocking.

 

Still no luck so far.

Does anyone happen to know what symptoms of a dying distributor are in these cars? I know in most cars when the distributor goes the car will work for about ten minutes and then need 20 minutes before it starts again. Is it the same in these beautiful old bricks or I am I experiencing something along those lines? I believe the rotor was possibly changed once, I changed the cap at the beginning of the year and I'm pretty sure with all my 260k miles the distributor is original.

 

the only thing that dies in the distributor is the hall sensor (usually its the wiring), and of course, the cap and rotor need occasional replacement when the carbon tracks get too nasty and the gaps get pitted, usually concurrent with spark plug wire replacement.

my daughter's 240 has been having cold starting problems, which apparently were due to some sketchy vacuum lines (she's in another state, so had to go to a new mechanic).

 

I'm going to grab a hall sensor from the junkyard and test it out if they have one. If I can find a cheap ICM ill try that too.

 

I found a fresh 85 that still had the ICM in it so I cleaned it out nice and hooked it up and so far that seems to be doing the trick. I didn't hange the hall sensor out yet but I'm going to get that new so I don't risk getting a bad one from the junk yard.

 

I assume you mean the ICU, as the ignition power module is something thats not ON 85-88 LH2.2+Chrysler 240's. cars with Bosch EZK ignition have a separate ignition power module that is between the ICU and the coil.

 

You're correct sir. I was calling it a control module but I did mean control unit. Sorry about that confusion.

Has anyone ever attempted the hall sensor change out? I hear its kind of a beast to get the old one out and I don't want to destroy my distributor if I can help it.

 

Swapping out a Hall sensor isn't horribly difficult...just tedious. It's much easier to swap an entire dizzy...but they are getting harder to find as so many people with the older CIS KJet injection are swapping to LH2.2. BTW, if your "specialist" charged you $500 to reach down and unplug an ICU and plug a used one back in, you need to run...not walk...away from that shop. ICU's almost never fail (although reversed polarity can fry anything) and can be had on eBay for $20. Hopefully that charge was for a few hours of tediously tracking down wiring faults.