850 2.5 10V - Starts sometimes. Has spark now and then

[WRITEX]

Hello.

I'll just create a new topic since we've discovered a bit more than last time.
Old topic: https://www.matthewsvolvosite.com/forums ... hp?t=72402

Information about the car: 1994 Volvo 850 2.5 10V, engine code B5252S, SIEMENS S103955403J ECU
I know that the 10V version isn't around in the US but I'll be asking regardless.

The car will start now and then. By "now and then", I mean it could start once, then run fine for half a minute until it eventually stalls by itself. It won't start again after that. There's no spark anymore.
Let the car be for like 2-3 weeks, and it will start again but only that one time. Same thing happens.

Since the last time I posted anything on this forum, I put the car at a nearby workshop. It's been their little "now-and-then-project" and they've been looking at it for almost 2 months.
They've pretty much checked all the fuses, relays, sensors, cables... The only things they haven't gone that for into is the wiring harness and the immobilizer. They don't want to touch the immobilizer.
It's a original volvo immobilizer that seems to have been retrofitted in a different way than how they are supposed to. Anyhow, it isn't connected with the ECU is all they found out.

They also said that there should be a 2 volt signal coming from the ECU to the ignition coil, but they measured 0.2 - 0.3 during the periods the car won't start. Can't get a read when the car is running because... well we have absolutely no idea when it will start.

This is what's been done with the car:
- Swapped the engine in June 2015. Same engine code (B5252S). The car ran fine for 3 weeks after this. I have no idea if the engine swap is related to the problem. The car was acting weird even before the engine was swapped (it would act up on rides where I was going to the convenience store, but when I was heading back it just wouldnt start. Seemed to be in the exact same matter as it is now when it has no spark and just cranks and cranks.)
The only thing I know about the new engine is that it came out of an automatic. The person who performed the engine swap apparently had a hard time because of this since mine's a manual. (?)

- New fuel pump
- New ignition coil, camshaft sensor and another sensor I don't remember the name of. The car ran fine for half a day after this. Later on the workshop changed all sensors and whatnot but there was no difference.
- Changed the ignition coil 3 more times as it seemed like the car was eating coils, but it didn't.
- New coil-distributor wire, spark plug wires, spark plugs
- New distributor cap and ignition rotor

- Tried with 2 other ECUs. One with S103955403C, as I was told that the letter at the end didn't matter. It would work anyway. This one was dead on arrival.
Then one with S103955403J, which is the same as the ECU the car came with. This one worked, but there was no difference. The car started up once, stalled after 30 seconds, and wouldn't start afterwards. No spark.

Also, reading fault codes isn't possible as the OBD1 thing has been torn apart.


I've tried so many tips and swapped so many parts that I don't remember all of it. I have wasted a lot of time and money into a car that isn't really worth it.
When a workshop with employees that has many years of experience on all kinds of cars can't figure out what's wrong, I really have to wonder what the problem with this car is.

I'm asking around on forums one more time before I see no other option than to get rid of it.


WRITEX

[Ozark Lee]

Is the Lambda light on?

Being able to read codes is pretty important at this point and there are ways around the the A/B boxes but they aren't particularly clean and easy.

The A/B DTC boxes are fairly generic and they have a connector on the bottom. If you could scrape up a salvage A/B box I think we could actually get somewhere with some codes to work with. A replacement DTC box will just plug into the connector and get you some diagnostic capabilities back.

Without codes all we can do is guess which typically isn't terribly productive. The codes from the Fenix ECU setup are different than the standard Bosch codes so keep reminding us that it isn't a Bosch once you get the DTC boxes going.

...Lee

[Azik09]

I had sometimes a problem with starting exactly on B5252 engines with Siemens ECU , not any other engines. I don't know basic reason of this problem, but it was solved by connecting a 15-20 kOhm resistor serially with crankshaft sensor. After this engine started and worked fine.