Coils are pretty easy to test. Do you own a 12v test light? Key on, there will be power on the positive terminal. Electronic ignition, there will also be power on the negative side. Crank the engine, and the test light should flash on the negative side. No flash means no trigger from the module. Flash and no spark means the coil is weak or dead.
In reply to procainestart :
Thanks for all your thoughts on this - you're more familiar than I with the intricacies of the C900. I went ahead and ordered the Accel coil I linked above this morning, so I'll throw it in and see what happens. I've got a copy of the factory diagnostic procedure for the crank sensor, but I haven't had a chance to delve into it. I also have the Bentley and most of the factory service manuals, but again, no time to dig in. If the coil doesn't solve it I'll move on to other things.
In reply to Streetwiseguy :
Amazingly, no. I've always relied on a DMM. I really should get a test light.
I should add, if you have power on the positive side, and none on the negative side with no engine rotation the coil is open, the points(in the olden days) are closed, or the ignition module is shot.
OK, the coil showed up before the test light, so I threw it in - nothing. I could smell fuel, so I figured maybe the plugs were fouled. Pulled them out - they were wet, but not dirty - cleaned, and reinstalled. Looked at the cap and rotor next - both a bit dirty, so those got a little emery cloth and wiped down. I had no real hope of this solving anything, but I turned the key, and on the second try, it sprung to life. Let it run for ten minutes, all OK. Shut it down and restarted - again, OK. Going to test drive in a bit and see if it behaves, but at least I'm less inclined to believe that the Hall sensor is at fault. Fingers crossed.
Edit: Test drive complete. Drove for 45 minutes, varying speeds, throttle, climbing some steep hills, and it didn't hiccup once, so I'm cautiously optimistic. Of course, the exhaust is blowing again.
Nice. Good to here it's running again.
Meanwhile, are you referring to the manifold gasket?
No, it's the pipe behind the cat, before the first muffler. The exhaust on this car is pretty cobbled together. I put new Starla muffler sections in last year, and the downpipe is OK, but someone cut off the flange to the cat. Between is straight pipe, an aftermarket cat, and a muddle of rust, clamps, and bad welds. I plan to simply measure the whole thing, get a new section of pipe, weld in the cat, and then slam it in. I did the manifold gasket and studs when I had the head off, so that end is good.
And it won't start again. Plugs are wet with fuel when I try, so it's got to be spark (which I think was already established). This car usually required a fairly long crank to get going, but now it's not working at all.
Did the test light checks on the coil. Power to both sides, but not much, if any, flashing on the negative when cranking, which points to the Hall sensor. There's voltage to the Hall at the harness connector, but the ground doesn't seem great. I have to trace that wire and see where it goes. I'd love for it to be something as simple as bad ground, but I'm not optimistic.
Need to locate the EZK ECU. Not sure if that's the same as the Bosch box on the left side inner fender, or somewhere else.
You have a hall effect switch in the distributor, a power stage, which is Bosch's fancy word for ignition module, and an ignition computer.
Hall effect switches fail occasionally. Ignition computers from Bosch are pretty much bullet proof. When I was working on 700 Volvos, I used to stock a power stage.
Just sayin'
Now, the other clue I just realized is, your plugs are getting wet, so that means the injectors are pulsing, so that means you are getting a signal from the hall switch, and the ignition computer is still functional enough to send a signal to the ecu about firing the injectors, which probably means its sending a signal to the power stage, which is probably not triggering the coil.
In reply to Streetwiseguy :
I was just reading something over at Saab Central that suggested the same thing. I have to get the p/n off the one in my car and see if I can find one.
Struggling to find the correct ignition amplifier. All the ones I find are either an eight-pin stand-alone part, or the four-pin that my car has integrated with a coil and a bracket like this one (these are all listed as Volvo parts, but I suspect they are similar to the Saab parts). I have no visible part number on mine, so I'm sort of flying blind here. Having just bought a coil I'd rather not throw money at another one, but right now it looks like that's the only way to get any possibly suitable amplifier.
I might be wrong, but I think Volvo used those 4 pin units on pretty much every 850 built, so maybe a trip to the junkyard is in your future.
No self-service junkyards around here any more. I checked car-part and there are plenty of Volvo units available, but by the time I get it here I'm pushing into the same price as new aftermarket parts. Are these the sort of parts where only OE will work properly, or are the aftermarket units decent? Also, I realize that the coil on these uses a male center post, while the Saab uses a female, so I'll have to change the coil wire (or at least the end).
I don't like aftermarket electronics at all.
All the used Volvo units I can find are (naturally) ~25 years old and likely have 200k+ miles on them - in your experience, you'd prefer that to a new aftermarket part? How much would you trust it? Given that I'd be putting it in a non-original application, would you think it would be better to move the ignition amplifier over to the Saab bracket and use that coil, or simply drop the whole amplifier/coil assembly in and use it that way?
There are plenty of Volvos in the self-serve yards around here. I can go check and pull a couple if you want me to ship them to you.
In reply to EvanB :
I appreciate the offer, but I don't want to put you out. If you happen to be going there anyway, that would be great. FWIW, I'm seeing them from $25+ on car-part, which of course doesn't include shipping. If you can grab a coil wire as well, so much the better, since I need to switch the end to fit the Volvo coil.
In reply to 02Pilot :
My main yard is about 10 minutes from me and pretty lax on pricing for little stuff like that so it would probably only be a few dollars. I'll try to get over there tomorrow over lunch and see what they have.
In reply to EvanB :
Outstanding. Thanks so much for your help.
Not many Volvos in the yard at the moment but I was able to grab 2 for $10. They should fit in a fairly small box to ship.
In reply to EvanB :
That's great, thanks! I'll PM you with shipping info and to arrange payment.
The plot thickens - maybe. While I'm waiting for the Volvo ignition amplifiers that Evan so graciously plucked from the junkyard for me, I decided to just have a quick look at the EZK ECU in case there was corrosion or something. It's in the passenger footwell, so I pulled the carpet back and found the wiring bundle coming off the ECU was being used as a load-bearing member in a mouse nest. Shop vac came out and made quick work of the (unoccupied) nest, but it revealed several chewed wires - seven in total, with insulation damage ranging from tiny, almost invisible bits of exposed copper to full inch-long sections of it; none were broken. I cut, cleaned, and rejoined each with solder/shrink-wrap connectors, so I'm confident they are now good. One of the worst was the wire that carries the ignition pulse from terminal 16 to the ignition amplifier; while there was no sign of anything shorting out, I wonder if that may have happened and in the process killed the amplifier.
The car still refuses to start, but at least now I think I'm ready to plug in the new parts with a degree of confidence that everything else is OK. I didn't test the EZK box itself, but I'd have to find a procedure for doing so. It looked like new, with no sign of corrosion or damage. Connectors were perfect.
In reply to 02Pilot :
What is the part number on your EZK box? I have several used from running Volvos. If you have damaged the amplifier, you may also have damaged the box
If the P/N is the same I will send one up on loan for diagnostic if the amp fails to start the car. PM me with number and I will check mine this evening.
Having said this before and been burned, I'm hesitant to do it again, but the problem appears to be solved. I swapped in one of the Volvo coil/ignition amplifier units Evan sent me, changed one of the ends on the coil wire to match my distributor cap, and hit the key - it fired up almost instantly. Only a quick test drive so far, but it ran well - so well, in fact, that I think I may have been down on power due to weak spark for some time. The coil wire is a tiny bit shorter than I would prefer, but I can move the coil a little closer with some minor fiddling, so I'm not bothered. Other than that, it's pretty much plug-and-play. Thanks again to all who helped out along the way.
In reply to TurnerX19 :
I appreciate the offer, and if this thing proves me wrong again, I'll definitely reach out to you. Thanks.
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