posted by
someone claiming to be pittroj
on
Sat Aug 21 16:53 CST 2021 [ RELATED]
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My baby has finally developed a problem. This car has been my rock, a pretty clean NO RUST florida that I brought back from Florida. Never driven in salt. Anyway, It started out after it was running fine as usual, went to start it and it stalled. Tried to start it, no start. Waited a few minutes, and it started and luckily, got me home. I then checked the obvious stuff, fuses, swapped the fuel inj. relay, checked all connections at AMM, PSM,CPS, nothing obvious.
I then unplugged the AMM with it running and it kept running. A few times I did this, kept running. Now today while working on it, I unplugged the AMM and it stalls. Why no limp home mode? I am thinkinG AMM? I have a known good one on a 940 T and another 240 that I may swap and see if the problem follows the AMM? Any help is appreciated.
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posted by
someone claiming to be pittroj
on
Sun Aug 22 18:59 CST 2021 [ RELATED]
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Just drove the car around the block, it started and didn't stall so, hopefully I didn't do any damage with unplugging it hot. I will not do that again. Thanks for the link to the green book! And, I have not checked the codes yet. It's been 95degrees here today and no shade or garage to work under, It will have to wait a few days until it cools. I wish whatever is failing would lock in so I can figure out what is going on. If it ain't broke etc.
I will check codes on the OBD2 and swap the AMM, and referance the green book, And yes, gizmo behind battery, power stage module.I believe that when it fails, there is no spark, and it's not intermittent but has to be replaced to re-establish spark . I will also check the following:
"Have you checked for power, with a small test light, off the orange wire in the AMM.
This will let you see that the CPS side on outwards is working."
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By unplugging the AMM you're trying to find fault with the ECU and others (as AMM already out of the picture).
I could start my car with AMM unplugged, so the limp home mode is there. No I don't do hot unplugging. Unplug first then try to start.
To find fault with current AMM you must swap it with another known working AMM. And from past board experiences the type of AMM likely to fail is the one with hot air hose still connected from exhaust shield. Not just any AMM.
I suggest looking at your ignition parts first. They deliver thousands of volt every miliseconds. Big burden there. They might look well outside but there could be some internal break inside. When they fail some fail completely, some intermittently, some prematurely too. At least do continuity test with mulltimeter.
Amarin.
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posted by
someone claiming to be pittroj
on
Sun Aug 29 06:33 CST 2021 [ RELATED]
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Swapped the AMM and replaced the cap, rotor and plugs (it was due anyway.) So far it has started and ran everytime but, haven't really driven it any distance. I will report back once I get to give it a good test.
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posted by
someone claiming to be pittroj
on
Sat Sep 11 21:10 CST 2021 [ RELATED]
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*UPDATE* Hello, again, thanks for the help with my intermittent Start. I have driven it 200 miles this week and so far it has been running and starting fine. Not sure though what fixed it. The AMM or the new cap and rotor?
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Faulty rotor underneath the distributor cap. Check continuity between the center of the rotor and the firing edge of the rotor. There is a 1k Ohm resistor embedded in the rotor that can go bad. Also check the center of the distributor cap for the carbon tip in the cap's center. Not sure about your 1991 240 set- up.Just going by what I've found on my Volvo when needing repairs.
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Hi,
You could have had a simple ignition or air leak problem but messing with the AMM while it was running, sure as heck, isn't something that you should have been doing!
I think you should put the AMM in the category with Alternators and not disconnect a battery while it's running.
Luckily since you have spare meters and as long as the last three numerals match, you have saved your bacon!
You mention a PSM? Is that the gadget behind the battery that fires the ignition?
I assume you know about service it.
Have you checked for power, with a small test light, off the orange wire in the AMM.
This will let you see that the CPS side on outwards is working
Since you were dancing around with the AMM connector, maybe you wiggled a problem, in the area of the fuel injection fuse holder.
I think this year car still has one but definitely check the battery wire off the positive post and a connection block on the fender.
That wire feeds the inside fuse panel, of which, can have corrosion problems of it own, down there in the salt air of Florida. Salty humidity can cover that whole state from three directions.
As far as no limp mode, you may have not tripped it on.
This car has some capabilities of adapting or definitely self-tuning.
If you are confused, just think about it being the same way for the ECU.
The AMM isn't supposed to be totally missing "after" its running?
Engineers don't write operational programs for the near impossible happening!
You can tell this worries me!
You might try doing a hard reset.
This means taking the battery cables totally off the battery an holding them together for about 15 seconds.
Lots of cars have gone to this "catch or clear it all" method since there are so many components holding residual power for their circuit memories.
Good luck hunting.
Phil
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posted by
someone claiming to be pittroj
on
Sun Aug 22 15:01 CST 2021 [ RELATED]
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OK, point well taken. I used to work on fire alarms, and it didn't hurt to disconnect, unplug cards while powered up, you just never re-connect, plug cards back in hot. I figured the same would go for this AMM stupidity (mine). It still does start and run, albeit intermittently so, hopefully I didn't blow anything up.
I will try a good AMM and see what happens. Thank you!
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Unplugging stuff when under power (ignition on) really isn't something you want to be doing.
Did you check to see if there were any error codes stored by using the diagnostic socket?
The how-to and meaning of the codes can be found in the FAQ on this forum. It's not terribly specific about many of the possible causes, but it's a place to start and can point you in the right direction.
As always with LH2.4 Jetronic fuel system problems am I referring to TP31361/1 that can be found here. It's a Volvo service manual on the design, function, fault tracing and repair of the system and is a good document to have, even when you're not experiencing any problems. Your fault tracing can now begin. Good luck!
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