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Crank no spark. 7 months of hell. Please help

You say this all happened after swapping the trans and it bump starts and runs fine. It has to be something you did.

Park it on a hill? Sorry. I gotta stop.
 
ZVOLV said:
Something gives me a feeling you aren't getting the engine to crank fast enough, or possibly the voltage is dropping too low. I remember my buddy had an 850 that would slow crank. It always started, but there was something wrong.

I am curious how you did your voltage drop test. You should do the positive cable too. Was the manual transmission corroded that you installed corroded? Like east coast junk?
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Hmm. It sounded like it was cranking fairly well. Though crank sensor is on the low end of the spectrum I think it produces. About 0.3V AC…

Transmission was west coast. Looking back at the pictures, honestly, they don’t look too terrible.
 
bobxyz said:
As a disclaimer, I have zero experience with 850s and Motronic 4.3, but the "ALWAYS starts when you bump start it" is a pretty strong observation.

Do you remember how it used to crank before the manual replacement? Is it about the same, or more labored?

The starter causing electrical noise could be from it mechanically binding, or from a damaged/shorted coil winding. Maybe try loosening the starter bolts, and re-tighten them with the starter shoved away from the flywheel as much as the mounting holes allow. Starter electrical noise causing a hard start / no start is a pretty uncommon failure.
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Before the transmission was replaced it fired up in a second or two. Now it’s about 30-60 seconds. I will order some ground straps and install them next Tuesday.
 
ZVOLV said:
You say this all happened after swapping the trans and it bump starts and runs fine. It has to be something you did.

Park it on a hill? Sorry. I gotta stop.
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Wouldn’t be the first time I’ve done that! My first car was a 85 MR2! I drove it to work with a dead starter motor. Bumped it at a top of a hill where I lived and had my coworkers bump start me home 😂
 
Try two batteries and a jumper cable. Seriously. I was only joking about the battery in the trunk part.

You could also try running a redundant ground with a jumper cable. You could even run a redundant positive with the positive side of the jumper cables too.
 
ZVOLV said:
Try two batteries and a jumper cable. Seriously. I was only joking about the battery in the trunk part.

You could also try running a redundant ground with a jumper cable. You could even run a redundant positive with the positive side of the jumper cables too.
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Trying that actually does get the car to start quicker. It starts in about 10 seconds instead of like 30. Then again, the starting has also been sort of random. I did a best of 4 start attempts. 3 of 4 it did it 10sec. First one was closer to 5
 
I had a similar no start, 10+ years ago. 95 855.
All sensors working, bios (basic In/Out signals), voltage all checked good

It’s a quick test to cross whichever wires signal/send current to computer.
Because changing alternator required a day, bolts under intake-hell
 
h20ham said:
I had a similar no start, 10+ years ago. 95 855.
All sensors working, bios (basic In/Out signals), voltage all checked good

It’s a quick test to cross whichever wires signal/send current to computer.
Because changing alternator required a day, bolts under intake-hell
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When you mean cross wires what are you referring to? Unfortunately my voltages coming from my computer don’t appear to be correct. My crank sensor only puts out 280mv. I’m thinking about reversing the polarity on the crank sensor since this car was manual swapped at some point in the previous owners life.
 
I don't know if there are factory specs, but 280mV from a VR crank sensor during cranking is OK. Have you checked that the new Bosch cam sensor is generating a good signal either at the ECU or at the sensor connector? It's probably the middle pin on the connector. I'd also inspect both sides of the cam and crank sensor connectors for any signs of damage or corrosion.
 
bobxyz said:
I don't know if there are factory specs, but 280mV from a VR crank sensor during cranking is OK. Have you checked that the new Bosch cam sensor is generating a good signal either at the ECU or at the sensor connector? It's probably the middle pin on the connector. I'd also inspect both sides of the cam and crank sensor connectors for any signs of damage or corrosion.
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Upon looking more, I have also noticed this car was originally an automatic. My crank sensor polarity is technically wrong. I’m not sure if that’s a major issue or not. I believe the flex plate was very similar but I don’t know as that was down before I owned the car. It started his fine before I put the new clutch in.

https://imgur.com/a/PrryrJK
This is the cam sensor and crank sensor on my mini o scope. It shows a 12v square wave while cranking on terminal no.2.

Glad to know the crank signal is right. Not sure about the polarity now though. It shows I’m using auto trans wiring for the polarity….
 
The crank sensor polarity might make a difference - it depends how picky the Motronic 4.3 ECU is with the missing tooth section. When you replaced the transmission, did you remove or swap the flywheel? I'm not familiar with 850s, is there a bracket for the crank position sensor that could have shifted or been bent?

For your crank waveforms, you need to zoom in - set the volts per division to 100mV or 200mV. Here's the CPS signal from a 60-2 flexplate on a LH2.4 240 at idle:
CPS idle1.jpg

I don't have cranking waveforms, but idle is ~800rpm and cranking is ~200rpm, so the cranking amplitude will be ~1/4th what's shown above.

Since you have a scope, take a look at the powerstage spark signal from the ECU. Is it nice and even, or does it skip around and/or drop out?
 
I swapped the polarity and now she fires right up! No hesitation whatsoever! I had no idea this car was manual swapped when I bought it. The owner said it was factory stick shift. Then I was told they didn’t make a manual 95 turbo….

I have NO idea how the car ran when I bought it with the polarity swapped. I’m scratching my head on how it was possible given how it refused to work now.

The flywheel was not swapped during the process. Same flywheel different transmission.
 
The swap on those cars to put a manual in does require reversing the polarity on the sensor. They change from leading to trailing edge, so flipping that around makes perfect sense. Glad you got it dialed in!
 
gsellstr said:
The swap on those cars to put a manual in does require reversing the polarity on the sensor. They change from leading to trailing edge, so flipping that around makes perfect sense. Glad you got it dialed in!
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The 7 month hell is finally over! Hooah! Thank you for your guys help though! Still is strange that the car used to run with the old manual transmission?! I’m not gonna question it! Just accepted the fact it’s running great now 😂
 
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