960: no start - no spark, no fuel, no communication via OBDII port?

[crashtest]

My 96 960 suddenly won't start. Motor cranks but won't start.

There's no fuel pressure after cranking. No spark and 0V dc at the fifth red/white wire at the back of the coil pack harness.

Plugged in the ODB scanner and it can't detect the car. Checked the scanner on my V70R and it worked fine. I checked the ECU relays and fuses in the engine bay, left side fender box. Is there another relay/fuse I'm missing? How can I check the ECU itself to see if this is the root cause?

Thanks all.

[93Regina]

My 96 960 suddenly won't start. Motor cranks but won't start

Here's a Volvo Wiring diagram...trace fuel relay with OTC 3631 Heavy-Duty Logic Probe Tester at GN-SB wire at relay's plug...is that terminal grounded when engine cranks? Check fuse 4.

[crashtest]

Can this test be done with a multimeter - I don't have that tool.

I've swapped all the relays in the engine compartment with a known good relay, and no change.

Biggest mystery is why isn't the scanner detecting the computer.

[93Regina]

Can this test be done with a multimeter

Download and save this wiring manual. On PDF page 70, there is a component listing.

One can use a multimenter, but a logic probe is a choice tool. Working on electronic based vehicles, its the main tool I use.

I don't have time right now to sort this out, but I'd check to see if computer is getting power, starting at the battery. I have no idea where all relays are on this vehicle, but the fuel pump relay is in the interior space, and the fuel system relay is in engine compartment. I'd slowly examine those first ten pages.

[crashtest]

OK - still don't know why the computer isn't communicating, but I did determine I'm not getting voltage to the fuel pump relay. 0V with ignition on. The 50A fuse is good, swapped with another good one to be sure, and checked for continuity.

That means the wire from the battery over to the relay is severed somewhere - right? I couldn't get the relay box free enough to check the backside.

edit: got the box out - I saw the white wire which runs from the relay to the battery. Was in place and intact.

So that problem may be unrelated to the dead ECU? Would a broken fuel pump circuit cause the computer to not respond? Is there a way to check the computer alone?

[93Regina]

...voltage to the fuel pump relay...

Looking at these newer diagrams is something new for me, so look at PDF page 16:

At Fuel Pump Relay (in vehicle in center console), the ignition switch and the ECU (computer) fires up this relay, so on pin-86, check voltage when key is switched on. On pin 30, it is only hot when 2/32 Main fuel injection relay has been turned on, and it is controlled via ground from ECU; at main fuel relay, check for power on terminal 30. If there is not power there, this means your ECU is without supplied power.

[crashtest]

Excellent - thank you. Pin 30 is not hot with ignition on. So either ECU is not getting power, or ECU is dead. I'll troubleshoot the connection at the ECU inside the car next.

[93Regina]

Pin 30 is not hot

2/32 Main fuel injection relay - Pin 30 should always be HOT

At main fuel injection relay, both Pin 30 and Pin 86 should be hot. Fuse 4 near battery (or where ever) must be blown.

[crashtest]

I checked Fuse 4 - it's good. I even swapped for a known good fuse.

If the ECU is dead - would pin 30 in the main fuel injection relay 2/32 be dead? Or is it hot whenever the ignition is on?

[93Regina]

If the ECU is dead - would pin 30 in the main fuel injection relay

Diagram shows a direct connection between battery, fuse, and pin-30

Go to fuse-4, is there voltage on one side? If true, then disconnect battery, and ohm spec from other side of fuse to pin-30