760 Strange Goings-On...Non start

[russwinchester]

Hello all,

So after several months of my 760 2.8 running like a dream, we have a no start. Would welcome any views on where to look.

Situation: car had a minor oil leak from the rear cam cover, so I put the car on front ramps initially to diagnose the leak. So car is pointing upwards....could be a clue?

Started the car in order to check I'd fixed the leak, car still on the ramps. Car started, I got underneath, then it cut out completely. No fade out, just clean cut out.

I started it again, and it ran, started to stumble and I increased the revs, it ultimately died.

It now cranks but no start. Nothing.

I'd noticed in the run up to the no start, that occasionally I'd turn the key in the ignition and the starter wouldn't initiate. Just all dead. I'd read that this can be a dying cell in the battery, so I put on a slave I have, but no change. Still say every 3-4 ignition cycles, no starter. So maybe this issue is a dicky starter and unrelated to the cutting out, but who knows.

So what I've checked so far:
1. There's fuel in the fuel rail and it's pumping on cranking. So it's an ignition issue I guess.
2. I've swapped out the radio suppression relay with the adjacent relay, no difference.
3. I've tried starting in P and N, no difference.
4. My alternator is recently reconditioned and was producing a good output.
5. Battery is good.

What I could do with knowing:
1. I know I'm getting fuel...but does a failing or poorly seated fuel pump relay impact anything to do with ignition? Haven't looked at this yet. I did recently fit a new head unit for the stereo and re-wire around the amp area, so who knows if I've moved something out of kilter whilst I was rooting around down there.
2. What could be the causes of my intermittent starter issue? Motor, earths etc?
3. I know it's odd, but would anything be related to the car being pointed nose up?
4. Are there any notorious hard to locate earths that I could do with cleaning up? Slowly working my way round the ones I can see, but I wouldn't expect a complete non start with a dicky earth would I?

No pressure but the car's booked in for some bodywork in early Feb plus it's broken down right where we charge our daily EV's so need to sort

[Laird Scooby]

Originally Posted by russwinchester

Hello all,

So after several months of my 760 2.8 running like a dream, we have a no start. Would welcome any views on where to look.

Situation: car had a minor oil leak from the rear cam cover, so I put the car on front ramps initially to diagnose the leak. So car is pointing upwards....could be a clue?

Started the car in order to check I'd fixed the leak, car still on the ramps. Car started, I got underneath, then it cut out completely. No fade out, just clean cut out.

I started it again, and it ran, started to stumble and I increased the revs, it ultimately died.

It now cranks but no start. Nothing.

I'd noticed in the run up to the no start, that occasionally I'd turn the key in the ignition and the starter wouldn't initiate. Just all dead. I'd read that this can be a dying cell in the battery, so I put on a slave I have, but no change. Still say every 3-4 ignition cycles, no starter. So maybe this issue is a dicky starter and unrelated to the cutting out, but who knows.

So what I've checked so far:
1. There's fuel in the fuel rail and it's pumping on cranking. So it's an ignition issue I guess.
2. I've swapped out the radio suppression relay with the adjacent relay, no difference.
3. I've tried starting in P and N, no difference.
4. My alternator is recently reconditioned and was producing a good output.
5. Battery is good.

What I could do with knowing:
1. I know I'm getting fuel...but does a failing or poorly seated fuel pump relay impact anything to do with ignition? Haven't looked at this yet. I did recently fit a new head unit for the stereo and re-wire around the amp area, so who knows if I've moved something out of kilter whilst I was rooting around down there.
2. What could be the causes of my intermittent starter issue? Motor, earths etc?
3. I know it's odd, but would anything be related to the car being pointed nose up?
4. Are there any notorious hard to locate earths that I could do with cleaning up? Slowly working my way round the ones I can see, but I wouldn't expect a complete non start with a dicky earth would I?

No pressure but the car's booked in for some bodywork in early Feb plus it's broken down right where we charge our daily EV's so need to sort

Pull and check fuses 30, 31 and 33 Russ. If all good, refit and test. If no improvement, pop off the drivers side trim from the trans tunnel and make sure all relays are seated correctly.

You might have flow through the fuel rail but you might not have pressure, the symptoms of it stumbling then restarting briefly match with this. One of the fuses i mentioned feeds the main (HP) fuel pump, the other feeds the in-tank (LP) and the third is irrelevant but i can't remember which is which, just it's one of those three fuses. I suspect it's the fuse for the HP pump is dirty and/or not seated properly - had it happen a few times on mine now.

[russwinchester]

Thanks Dave. I whipped the lead off the coil last night to see what was going on, no spark at all. So I’m guessing it could be my ignition amp. Have checked fuses and all seated and ok, I’ll have a look at relays in a bit too.

[Laird Scooby]

Originally Posted by russwinchester

Thanks Dave. I whipped the lead off the coil last night to see what was going on, no spark at all. So I’m guessing it could be my ignition amp. Have checked fuses and all seated and ok, I’ll have a look at relays in a bit too.

Use a multimeter to see if you have +12V reaqching the "+" terminal on the coil with the ignition switched on Russ. Check it stays as you try starting it.

If so, do you have a set of NOID lights? Put one on one injector and make sure it pulses as you crank, if not it could possibly be your CPS but i fear you may be right with your guess of the ignition amp module.

[Laird Scooby]

Any progress on this Russ?

[russwinchester]

@Dave, sorry for lack of response, ended up with Covid so Volvos went to the bottom of priority list...just started new thread...

[Laird Scooby]

Originally Posted by russwinchester

@Dave, sorry for lack of response, ended up with Covid so Volvos went to the bottom of priority list...just started new thread...

Hope you're feeling better now Russ? Also commented on your new thread, might be a useful comment for you, maybe not.