Post lockdown problem

[clandyuk]

Hi everyone, my ancient 940 2.3 LPT (97 MY) has been sitting idle for these past month(s).
Started it yesterday and whilst it started on the button, it's only running on 3 cylinders! Natch, it was running fine before lockdown.
Pulled leads and it's #1 that's doing nothing.
Checked for spark - yes, good spark.
I pulled the injector plugs on #1 and #2 and tested for voltage on the 2 pins with ignition on. #1 showing 11.98V on one and 0.48V on t'other. #2 is showing 11.98V on both.
So from that I assume something is amiss but I have no experience on Fuel Injection and am a bit unsure how to proceed now.
Any suggestions, please?
Thanks.
Andy

[TonyS9]

The fuel ECU pulls the ground side down to zero to actuate the injector, the 12V is permanent (via the radio supression fuel relay).

All the injector leads are connected in paralell, they should all show identical voltages, and should both show close to 12V if you have at least 1 injector coil still attached.

Seems you have a faulty loom.

[Chooch84]

Swap the injectors about, you might have a blocked injector. It's a bit of a messy job, especially if the fuel rail is still pressurised (release the pressure using the valve found at the bottom of the fuel rail). You could also check the resistance of each injector. Assuming you have the original 0 280 150 804 injectors, resistance should between 2-3 ohms per injector.

If you're going to remove the injectors, it would be worth flashing a torch into the tops of them to see if the filter basket looks clogged.

[clandyuk]

Originally Posted by Chooch84

Swap the injectors about, you might have a blocked injector.

Thanks for that. Will check wiring first as it seems it might be a more fruitful avenue given the history.

[clandyuk]

Originally Posted by TonyS9

The fuel ECU pulls the ground side down to zero to actuate the injector, the 12V is permanent (via the radio supression fuel relay).

All the injector leads are connected in paralell, they should all show identical voltages, and should both show close to 12V if you have at least 1 injector coil still attached.

Seems you have a faulty loom.

Ah, that might be the problem. You've just jogged my memory that I had to throw out a pesky field mouse from BOTH of my Volvos. Chucked him out of the bonnet lining on the 940 and the cheeky s*d moved into the V70.
I left the linngs out and then had to suffer clouds of steam from water evaporating on the bonnet when it rained and I was stopped in traffic.
Will investigate with a torch. He/She might be back as a result of the lockdown.
Just to clarify - should both injector plug wires show the same Voltage when grounding them via the Voltmeter or at least the same Voltages for each separate lead wire IYSWIM?

[Laird Scooby]

Originally Posted by clandyuk

Ah, that might be the problem. You've just jogged my memory that I had to throw out a pesky field mouse from BOTH of my Volvos. Chucked him out of the bonnet lining on the 940 and the cheeky s*d moved into the V70.
I left the linngs out and then had to suffer clouds of steam from water evaporating on the bonnet when it rained and I was stopped in traffic.
Will investigate with a torch. He/She might be back as a result of the lockdown.
Just to clarify - should both injector plug wires show the same Voltage when grounding them via the Voltmeter or at least the same Voltages for each separate lead wire IYSWIM?

Do this simple test - find a short length of wire and bare the ends. Remove injector plugs #1 & #2 and feed one end of the jumper cable (the one you've just bared the ends on) into the grey connector on #1 and the other end into the grey connector on #2 then refit the plugs on the injectors.
Start it up and see if it's back on all 4 pots. If so, there's either dirt on the connector inside the injector plug on the one with the low reading or a break in the cable.

It will help you narrow down the problem more quickly anyway.

[clandyuk]

Originally Posted by Laird Scooby

Do this simple test - find a short length of wire and bare the ends. Remove injector plugs #1 & #2 and feed one end of the jumper cable (the one you've just bared the ends on) into the grey connector on #1 and the other end into the grey connector on #2 then refit the plugs on the injectors.
Start it up and see if it's back on all 4 pots. If so, there's either dirt on the connector inside the injector plug on the one with the low reading or a break in the cable.

It will help you narrow down the problem more quickly anyway.

I'm liking that idea - brilliant (and easy to do). Will give it a go tomorrow.
Thank you.

[Laird Scooby]

Originally Posted by clandyuk

I'm liking that idea - brilliant (and easy to do). Will give it a go tomorrow.
Thank you.

You're welcome, hopefully it gives a few ponters as to where the problem lies.

[clandyuk]

Originally Posted by Laird Scooby

Do this simple test - find a short length of wire and bare the ends. Remove injector plugs #1 & #2 and feed one end of the jumper cable (the one you've just bared the ends on) into the grey connector on #1 and the other end into the grey connector on #2 then refit the plugs on the injectors.

Simple to say but impossible (for me) to do, I'm afraid.
What was easier was to make my own little Noid light!! Worked on #2,#3,#4 injectors but nothing on #1.
With ignition on, I then checked the unplugged #1 lead for voltage on Grey wire (+probe to socket; - lead to engine block) - 11.98V.
So from all this I deduce that it's the Green wire that's the problem. Am I correct?
If so, if I bridge connect #1 & #2 Green wires, is that going to blow anything up?
From looking at the wiring diagram, all Greens seem to meet together anyways after the injectors. Also, from what I understand (which I admit is v.little) from reading the Volvo Club FI FAQ, it seems that the injectors are all firing together anyway.
What I need to do is get the car temporarily mobile so I can empty it of all the garden waste in the back before getting it into the garage for a "proper" look around under the bonnet.
Can anyone tell me where the green wire goes after it disappears into the loom that goes down between the inlet manifold and round the gearbox??

[Laird Scooby]

Originally Posted by clandyuk

Simple to say but impossible (for me) to do, I'm afraid.
What was easier was to make my own little Noid light!! Worked on #2,#3,#4 injectors but nothing on #1.
With ignition on, I then checked the unplugged #1 lead for voltage on Grey wire (+probe to socket; - lead to engine block) - 11.98V.
So from all this I deduce that it's the Green wire that's the problem. Am I correct?
If so, if I bridge connect #1 & #2 Green wires, is that going to blow anything up?
From looking at the wiring diagram, all Greens seem to meet together anyways after the injectors. Also, from what I understand (which I admit is v.little) from reading the Volvo Club FI FAQ, it seems that the injectors are all firing together anyway.
What I need to do is get the car temporarily mobile so I can empty it of all the garden waste in the back before getting it into the garage for a "proper" look around under the bonnet.
Can anyone tell me where the green wire goes after it disappears into the loom that goes down between the inlet manifold and round the gearbox??

Link the green wires then between #1 and #2 injector plugs, i should have perhaps added that last night.

They are Full-Group injection or batch-fire as it's also called so all 4 injectors fire at the same time.
Top marks for making your own NOID light, good diagnostics.

As for where they go, they go to the RSR relay, usually on the drivers suspension tower or passenger inner wing.