Introduction Volvo 850T no spark no injector pulse

[flyingsquirrel]

Hi All,
I recently acquired a 1995 850 Turbo sedan. I think it's a pretty cool car and I would like to get her running. The guy I got it from had just put a good used engine with low miles in it. The problem is that there is no spark and no injector pulse.
I have gone down the rabbit hole of the internet trying to figure it out. I have done every test I can with a multi-meter, the guy before me replaced all the usual suspects, cam and crank sensors, coil, the relay above the fan is good. I even have a box of extra ECUs and TCUs he got from junkyards,
I was able to retrieve a few codes from both the obd2 and the blinking codes after cranking for the engine for a while. They were related to throttle position sensor and temp sensor.
I even took it to a local shop and paid them $100 to basically tell me what I already knew. They did suggest that I check the timing marks, and look for a broken wire, as that would be their next step.
So I guess that's what I'll do, but if anybody has some voodoo magic knowledge, I'd love to hear it. I'll update as I get further into it. Thanks!

[greg850r]

I chased one just like that for over a year and it turned out the bolt on the positive cables at the solenoid had stopped turning before it bottomed out and the wires there were loose. Check that there are 3 wires there, the battery cable and two others, one big, one small.

[misha]

Ect and tps codes will prevent the car from starting.
Start with those.
Grey relay is main fuel injection relay and it runs the injectors and all sensors.

Could be just an immobiliser issue.
It also will prevent the car from starting.

[flyingsquirrel]

Thanks for the replies.
I’m curious about the immobilizer, would it still allow the engine to crank but no spark/pulse?
Update, I found the intake cam was off one tooth (advanced). The PO replaced the timing belt before the engine install.
Obviously I need to get the timing right but I can’t imagine it would actually prevent the engine from running (albeit like cr@p).

[misha]

Yes....it would allow cranking but will disable ignition and fuel system.
Does the car have aftermarket alarm system or factory setup?
Note that Ect and tps codes will also prevent the car from starting.

[flyingsquirrel]

I just had the battery checked out, and it is bad. It holds enough voltage to crank the engine a few times but then the battery dies and I need to charge it. Would a bad battery cause a no spark even though it still cranks strong? I don't to waste money on a battery if it won't help the problem.

[abscate]

Yes, it will. These cars use electronic ignition systems and ECU control, and a low input voltage can cause many failures of bizarre nature.

Borrow a good battery from another car to save your dollars for testing

[misha]

850 have cap & rotor abscate.
It's not DIS system like Me7 on '99+.

But...yes.Weak battery will prevent the car from starting even if it would slowly crank the engine...because all voltage goes to the starter and not enough voltage remaining for fuel injection system and ecu...also there is not enough voltage to energize the injection relays.

[flyingsquirrel]

New Battery, no luck.
I do have one other clue, I had someone hook up a fancy scan tool to the obd2 port and was able to communicate with the ECU, but as soon as I turned the key to engage the starter, the scan tool would lose connection and get booted out every time the starter was enaged.
I wonder what this would indicate? Why would the scan tool lose connection every time the key is turned?

[abscate]

Monitor the voltage while cranking. If the starter is defective, it could pull the voltage too low

You also could have a faulty ignition switch, electrical part. That’s a common failurecpoint on P80s. Expected life , about 150k miles