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Ecu weirdness... intermittent no spark no start

T

toby2tongues

New member
Joined
May 5, 2021
So I am new to Volvo's but not new to old cars with complicated electrical systems, I'm a big fan of Jaguar XJS's.

So I picked up a nice 92-240 wagon. Everything was going well and I was really only focused on cosmetics suspension and brakes given everything else was working nicely then I took it out for a drive and all the sudden I completely lost spark.

I fiddled with it for a while it finally started out of nowhere and was able to get it home. I started to look things over and I realized that the coil was on its last leg as per the specs from the Bentley manual and then it started to start again and then immediately die.

I unplugged the MAF sensor and it would run but poorly I cleaned the MAF sensor things got much better then it started to die again and not want to start... No spark

I started to delve into the ECU only to find out that it is a 25-pin ECU which to my knowledge means it's an LH 2.2 which is rather odd given that it's a 92. Also the MAF sensor is a Bosch 016 which is supposed to be for the 2.4, just an FYI there are six pens on my m a f sensor and five on the plug.

When the car will start I have 5 volts on pin 18 on my ECU FYI there is no wire going into that port. When the car does not want to start there is nothing there... As I'm typing this I just realized that when I tested the fuel relay it was working but the car would also start I have not tested the fuel relay while the car won't start maybe that's an issue, but I have typed so much here I will finish.

I can't read the serial number on the motor it's too worn but obviously (?) the ECU and wiring harness are not meant for this car as far as I can tell and the MAF sensor does not match the ECU.... So what would you all do?

I am thinking given the failures I may have a multitude of problems happening at the same time maybe a power issue from the ignition or maybe just a really bad ECU that's not even supposed to be in the car connected to a wiring harness that's not even supposed to be in the car. So should I just get the car running sell it and let somebody else deal with it or plug in a new ECU and MAF sensor?...I do not see alot af jankie butt splices and the like, so if this was a harness swap, it was done well(ish)...everything "looks" stock, I also have a ton of receipts...they paid >$450 on 3 separate occasions to replace the MAF sensor over 4 years...so money didn't seem like an issue and they were not doing it themselves.

I promised I looked before I asked...thank you in advance.

Toby
 
Got a test lamp? Unplug an injector, peel back the boot, and backprobe the lamp between the two pins. Got fuel injector pulse?

Got power to the MAF blue/yellow wire, when it is a no start?


The most common no start on these is the crank sensor at the top of the trans.
 
When my vovlo doesn't start, I immediately do these two things:
1. Spin all of the fuses in the fuse panel. These are always corroding and causing issues. You can clean them and apply dielectric grease and that seems to be the end of it.
2. Grab the relay above the ECUs and feel/listen for it to click on when you turn the key to start. If it doesn't, unplug it and plug it back in. If that doesn't solve it, give it some taps.
You really should have a known good or brand new OEM ECU relay as a spare. These fail all the time.

Those two failure points have been 99% of the no start issues I've experienced with most 240s.
 
ZVOLV said:
Got a test lamp? Unplug an injector, peel back the boot, and backprobe the lamp between the two pins. Got fuel injector pulse?

Got power to the MAF blue/yellow wire, when it is a no start?


The most common no start on these is the crank sensor at the top of the trans.
Click to expand...

Getting fuel...wet plugs
Will need to test MAF
For what it's worth, the crank sensor is noticeably new
 
culberro said:
When my vovlo doesn't start, I immediately do these two things:
1. Spin all of the fuses in the fuse panel. These are always corroding and causing issues. You can clean them and apply dielectric grease and that seems to be the end of it.
2. Grab the relay above the ECUs and feel/listen for it to click on when you turn the key to start. If it doesn't, unplug it and plug it back in. If that doesn't solve it, give it some taps.
You really should have a known good or brand new OEM ECU relay as a spare. These fail all the time.

Those two failure points have been 99% of the no start issues I've experienced with most 240s.
Click to expand...

I'm with ya on the fuses, very first thing I did was sand, grease, replace every fuse....had a 67 bug

I have a mess of relays on order from ipd just to have...that is after finding this forum
 
The powerstage is a common source for a no spark.

I assume you don't have a test lamp of any type.
 
A Z suggests. Get a test lamp. You can use it to troubleshoot the ignition. No spark is tested at the ignition coil. You should have 12v on terminal 15 and when cranking terminal 1 should flash as the ignition triggers. If there is no flashing you work back toward the ignition amp in the left inner fender near the batter where it gets corrosion from the battery. Check that the connector is clean and tight. Back probe the connector using the refence in the Bentley for testing for power and the trigger circuit from the EZK computer. Use a meter to measure the fluctuating voltage signal used to trigger the amp. If there isn't a trigger then it's either wiring, the EZK computer itself or the engine speed sensor.

Be aware that even brand new engine speed sensors fail. I've had the crank sensor become intermittent and drive you crazy thinking it's something else. I have also had bad EZK computers that don't fire the trigger signal to the amp. Don't forget to check for codes! Some codes don't turn on the check engine light.
 
dl242gt said:
A Z suggests. Get a test lamp. You can use it to troubleshoot the ignition. No spark is tested at the ignition coil. You should have 12v on terminal 15 and when cranking terminal 1 should flash as the ignition triggers. If there is no flashing you work back toward the ignition amp in the left inner fender near the batter where it gets corrosion from the battery. Check that the connector is clean and tight. Back probe the connector using the refence in the Bentley for testing for power and the trigger circuit from the EZK computer. Use a meter to measure the fluctuating voltage signal used to trigger the amp. If there isn't a trigger then it's either wiring, the EZK computer itself or the engine speed sensor.

Be aware that even brand new engine speed sensors fail. I've had the crank sensor become intermittent and drive you crazy thinking it's something else. I have also had bad EZK computers that don't fire the trigger signal to the amp. Don't forget to check for codes! Some codes don't turn on the check engine light.
Click to expand...

Edit: You have LH2.4. The 169 number on the EZK is for LH2.4. ecu. It's probably either a 561 or a 951 fuel ecu. Those are the last three numbers on the bosch part number.
 
dl242gt said:
Edit: You have LH2.4. The 169 number on the EZK is for LH2.4. ecu. It's probably either a 561 or a 951 fuel ecu. Those are the last three numbers on the bosch part number.
Click to expand...

That's why I asked him the ECU part number. I want to get him on the right train of thought as to what is really going on. Those 2 ECUs are what should be in there. Although, the 951 didn't appear in production until 1993 as far as I can tell from all the 1992 240s I've owned. It was a common replacement for a failed 561.
 
dl242gt said:
A Z suggests. Get a test lamp. You can use it to troubleshoot the ignition. No spark is tested at the ignition coil. You should have 12v on terminal 15 and when cranking terminal 1 should flash as the ignition triggers. If there is no flashing you work back toward the ignition amp in the left inner fender near the batter where it gets corrosion from the battery. Check that the connector is clean and tight. Back probe the connector using the refence in the Bentley for testing for power and the trigger circuit from the EZK computer. Use a meter to measure the fluctuating voltage signal used to trigger the amp. If there isn't a trigger then it's either wiring, the EZK computer itself or the engine speed sensor.

Be aware that even brand new engine speed sensors fail. I've had the crank sensor become intermittent and drive you crazy thinking it's something else. I have also had bad EZK computers that don't fire the trigger signal to the amp. Don't forget to check for codes! Some codes don't turn on the check engine light.
Click to expand...
<----this is what heros do

Will update Friday night sat. Morn
 
2manyturbos said:
That's why I asked him the ECU part number. I want to get him on the right train of thought as to what is really going on. Those 2 ECUs are what should be in there. Although, the 951 didn't appear in production until 1993 as far as I can tell from all the 1992 240s I've owned. It was a common replacement for a failed 561.
Click to expand...

Not a single piece of unhelpfull or judgemental advice!!!!!! :-) .I believe everything above will get me on the path I want to be on. Thanks all, will update soon.
 
Well that was kinda fun...everything came back good going through both complete ECU test sequences...except, drum roll please, the f'n crank speed sensor. Once the car heats up for a bit, nothing, once it cools off, 250ohms, which makes sense, it's only a magnet, and if the insulation is cheap, as the resistance increases, with the heat increase, the ECU does not read pulsation, therefore not allowing crank...let it all completly cool, resistance reduces, signal returns, car starts.

Only fault found...does this makes sense (the sensor is VERY new looking.)

Should I buy the expensive Volvo one, or just a dozen cheap ones and keep them in my tool box in the car...serious question.

Also, as mentioned before, the coil is on its last leg...I'm guessing go with Bosch?...this will ultimately be a 10-20 mile a day, daily, work and back/ round town/ occasional road trip daily driver.

Again, you all rock
 
In my experience the coil can be had for $10 and run forever, spend a tiny bit more on the Bougicord ($50-$60 last time I checked) so you won't have to go back and do it again next month. Congrats on an excellent diagnosis!
 
toby2tongues said:
Well that was kinda fun...everything came back good going through both complete ECU test sequences...except, drum roll please, the f'n crank speed sensor. Once the car heats up for a bit, nothing, once it cools off, 250ohms, which makes sense, it's only a magnet, and if the insulation is cheap, as the resistance increases, with the heat increase, the ECU does not read pulsation, therefore not allowing crank...let it all completly cool, resistance reduces, signal returns, car starts.

Only fault found...does this makes sense (the sensor is VERY new looking.)

Should I buy the expensive Volvo one, or just a dozen cheap ones and keep them in my tool box in the car...serious question.

Also, as mentioned before, the coil is on its last leg...I'm guessing go with Bosch?...this will ultimately be a 10-20 mile a day, daily, work and back/ round town/ occasional road trip daily driver.

Again, you all rock
Click to expand...


Just buy a bougicord sensor. The one I bought recently was $38.
 
The bougicord sensor is the OEM one. So you can also buy a bougicord branded one from FCPEuro and get the lifetime warranty. It was worth it when I had a bad out of the box bougicord sensor. I've also used the cheapo ebay ones and they have been hit or miss on the quality.
 
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