Hello, need advice.
V90-98 no issues, then suddenly after parking at home one evening it won't start.
Cranks perfect, but no spark
Checked compression, ok.
Checked timing belt and cam position. ok
Fuel pressure 3,1 bar. ok
Checked that there is 12v at the control plug at rear of head with ignition on, when cranking.
Replaced rpm sensor at crank. no start.
Replaced cam sensor. no start.
Replaced both ignition amplifiers. no start.
Replaced ect sensor. no start.
Replaced all 6 coils. no start.
Have taken these parts of my other v90-98 that runs perfect. It continues to run with the swooped parts.
Can someone suggest anything else to check, I have run out of idea's.
Peter Johansson

 

how did you determine there's no spark? does your model have a fuel injector relay (ie are you getting pulses to the injectors?)

Anything going on with key switch and the immobilizer? Scan for codes?

 

The way I checked for spark after all other attempts was like the pictures

Connected all coils on the chassie side together with a rod and clamped it to the head, did the same with spark end. At random attempts to start there will be a single spark on a 2-3 plugs, both banks.
I have no movement on tach, I have no injector pulses, Can't smell any fuel in the cylinders even after several evenings of trail. The car has relay for injection and ignition, I have replaced them with relays out of my other car, all parts that I have taken from that has been replaced with assumed faulty, but that one still starts and runs with these parts. The ground connetion under the air pump has been redone, also the 3 ground wires under plenum and the one between head and fire wall.
I have no OBD11 codes, that to me should suggest that no revs are counted from fly wheel, right? I don't know how to check the immobilizer, but are assuming that it should not allow any cranking at all if that was at fault. Have turned the ignition on, and by hand triggered the crank relay and that automatically triggers the relay for ignition and injection.
Anu thing else you all need to know?
Peter

 

Here's some diagrams - Do you have 12v (battery voltage) at the green w/red stripe wire going to the coils? 12v @ green/black wire from main relay to control unit?, Fuses B1, 3, 4, 5, and 7 for the coils are ok? There is a Ignition coil relay 2/46 that powers the coils listed in the wiring diagram - 2/32 is the main fuel system relay, 2/23 is the fuel pump relay and 2/46 is the ignition coil relay. Have you swapped the Motronic control unit and the 3 pertinent relays?

 

Thank you Hoonk. That was some info to take in, I will spend some evenings to go through all your info and return with the result.
Meanwhile thanks for the delicate circuit diagrams. As for the ecu, i haven't replaced that yet, don't know what will happen to the immobilizer system if I do. Have tried to get info of how to "reset" the immobilizer if tripped. Haven't got confirmed if it will damage the system or, if the immo system are standalone.
Peter

 

The picture of the trans tunnel relays - c-f double relay area is for 2/28 the alarm relay OR 4/19 the immobilizer relay if equipped. Does your car have a antenna ring around the ignition key cylinder? Either way the engine control unit does not have a direct connection to the alarm or the immobilizer. I guess the alarm or immob prevents the start function.

I've never seen a 1998 Volvo in my part of the US that had a chip in the key - needed for the antenna ring to scan and let the immobilizer allow the car to start. Perhaps they adopted immobilizers in the Swedish market a few years earlier than in the US.

Or Maybe they just never broke - so didn't investigate that.