I have a 94 850 with a 96 engine I installed three weeks ago. After installing, I tried to start but the coil was arcing to itself so no spark. I replaced the coil and it started right up. Ran great for 5 days and then died in our driveway as my son pulled up to park. Cranking but no start. Also, the battery was losing charge over the 5 days. Here is my status:
- when the battery is connected the ecu and the idle motor both heat up and stay that way, even with the key out.
- The fuel pump will not pressurize when the key turns, nor run as I turn the engine over.
- If I remove the ecu, fuel pump will pressurize and idle motor does not heat up, but injectors will not activate (even with the ecu in) I have spark and pressure with ecu out but no injector activity.
- I have replaced the ecu twice and no luck ( as well as the fuel pump relay)
- I tried to pull codes from no.2 socket but get nothing (other sockets are working)
- With the ecu out, I pulled one injector out and let gas splash its way into the inlet - the engine would fire on that one cylinder.

Any ideas would be incredibly appreciated!!!!

 

Did you reconnect all the engine ground wires good?

 

I am pretty sure but I'll go and re-check right now. It helps to know that's apossibility.
Thanks!

 

volvos are electrical nitemares if you swapped the engine you may have broken the ground to the ecu , look for broken wire in engine compartment

 

checked all grounds and all are intact - also no broken wires......

 

It has to be wiring somewhere the trick will be to find it.
Do you have 3 wires on the starter post?
Any way you might have 2 plugs reversed?

 

That sounds like a possibility - anyways, I'm getting the idea that wiring is the culprit... I'll check all again.
Thanks!

 

OK - checked and re-checked all connections. No difference. Still baffled by this (along with everyone I know with Volvo experience)

 

ask a tech where the MAIN ground is , maybe near or on the motormount ? its the main central maybe in the engine comparment had this prob with a pontiac also have them send you a pic ! i will NEVER own another volvo NEVER !

 

Will do - I love my b230 Volvos (I have two 940s and a 240) but this 850 has certainly been a nightmare!
Thanks

 

If the engine you swapped in ran fine before you put it in, it has to be electrical. I swapped an engine (even adapted it to accept EGR). When I turned the key, it started right up.

It has to be electrical.

 

What are the odds of a wiring harness replacement fixing this?!?

 

If you can isolate by logic which wires in the existing harness to check for continuity, you can possibly trim some labor.

However, it may take you much longer to chase the electrical issue (short - or worse - intermittent short) than to swap the harness. Just make sure the donor car ran fine before the harness was removed. Can you take photos of another car with the same harness as your to compare with?

 

So...I have replaced the wiring harness and it at least solved one problem - the ecu and Idle Air Control don't heat up anymore. But still no start! Just cranking. One thing that is also different is that the main relay buzzes loudly with key in position II. I tried three different relays and all the same. Also, I get a code in A-6 (Ignition ecu) that indicates no signal from injectors. Does any of this mean anything to anybody??

 

Did the wires in the relay plug happen to fall out?
Maybe they are in the wrong slots.

 

Actually, the old wiring harness had that problem - but I made sure this one was intact when I plugged it in.

 

Cam sensor good?

 

I have tried two different ones, but they are both used. It's just the odds of both of them being faulty seems unlikely. I'll procure another just to make sure.
Thanks!