760 V6 getting closer to scrapyard...help!
 

Hello all. So I bought my 760 a while back as it looked like an easy project. First mistake!

This car has been fighting me at every turn, every bolt is stuck, I have no skin left on my knuckles, it has almost broken me. I'm interested if there are any pearls of wisdom before I give up.

So car has been off the road for 10 years. Was running when it was put away (apparently).

Initial diagnosis: Main fuel pump. Replaced. Still no fuel to engine.
Swapped out a spare fuel pump relay (as in the green one). No change.
Replaced Crank position sensor as a precaution at this stage. No change.
Swapped out the fuel pump relay with the fan relay (radio suppression). No change.
Found slave fuel pump inop. Now replaced. Fuel getting to engine! Hurrah! Fuel gauge now reads full all the time, but this is the least of my concerns.
Third issue: 5 out of 6 injectors gummed up. Now all refurbed. Fuel spraying!
Still no start.

Checked spark and there is one, albeit yellow at the plug and a bit weedy.
Bought a Power Stage Amp, swapped out and no difference.

Noted that when engine cranks, tacho does not move (noticed it move on one start attempt a while back, dead since). Understand this signal comes from the coil.

Did test the coil off the car and behaved OK I thought, but have just bought a new coil as it's a cheap swap but not sure if it will do anything.

Before I throw any more time and money at it, have I missed anything?

I am not an electrical expert by any means hence why I've swapped out parts, thought this would be a simpler fix.

Any support / encouragement / ideas would be more than welcome!

Hi :)

There will be plenty of people more knowledgeable than me...

A few things - a decent penetrating fluid/oil will help with the stuck bolts. And heat, where you can do it. I've got a blowtorch for that reason.

It may be worth checking you still have a spark. If you don't have one, an automotive multimeter will help track down the faults - and allow you to check for things like ignition dwell - often easier than removing a plug to check.

If you are getting only a yellow spark that indicates a fault somewhere. If you chuck a small amount of fuel (maybe a milk bottle cap full) down the inlet with the air filter removed, does it attempt to fire?

Good luck :)

Have you looked at the distributor cap and rotor arm? Replacing mine today as both were severely worn and causing weak spark, poor ignition. I'm also waiting on a new fuel pressure regulator. Do you have an electronic ignition module on your car? My 940 does.

I thought if the car has a crank position sensor that is where the signal for the rev counter comes from. Did you definitely get the right one for your car? I expect the 760 V6 is different to the four cylinder Volvos. My only experience is with 940s though, so I may be wrong.

+1 for the comments about penetrating oil and patience when it comes to seized fastenings. I have also found cordless impact wrenches and drivers invaluable when it comes to car restorations. They can be a bit of a gamble on smaller fastenings but I have had more break loose and undo than I have had snap off, even down to 10mm head bolts. The repetitive impacts are less inclined to break or round off bolts than sustained high torque.

Take all the plugs out (don't mix up the firing order on the leads!), clean them and gap them ot 0.65-0.7mm after pouring some engine oil or ATF into the plug holes.

Let the oil soak in then cover the plug holes with rags and spin the engine on the starter to expel excess oil.
Refit the plugs and HT leads and try starting.

Also inspect the long plastic trunk between the throttle body and the concertina hose on the end of the MAF. The CTS is on the thermostat housing, make sure that some numpty hasn't wrapped PTFE tape round it and squirt contact cleaner into the 2-way multiplug that goes onto it, put the plug on and off a few times, final squirt of contact cleaner then refit and try again.

Check fuses 30, 31 are pushed fully home in the fusebox and also clean the blades on those fuses with a soft wire brush or similar.

If you're still no nearer getting it to start, remove the plastic shroud from the dizzy cap and unbolt the dizzy cap. Check the contact segments inside are clean and bright and not covered in verdigris or aluminium oxide (white powdery corrosion) and that the central carbon brush is intact (about 10mm long) and springy then clean the contacts on the rotor arm as well. Refit and test.

If you're sure you're getting fuel at the injectors you can probably skip the next test but worth doing just for completeness.

There are two relays mounted just in front of the coolant expansion tank. Unplug one of them (should be the one nearer the oustide of the car) and find the two large contact tubes inside the plug. Get a piece of thick wire and bare the ends then link the two large tubes together - if the cooling fan starts, you have the wrong relay, refit the plug and remove the plug from the other one and link it out. Try starting again.

When you fitted the new ignition amp module (power stage :rolleyes: ) did you use heatsink compound on the back of it? If not that's a job for once you get it running but needs doing. Follow the loom from the ignition amp until you find the earth lead from it, somewhere near the suspension turret. Remove the screw and clean the ring terminal and the mounting point and screw then refit.

When you fitted the new coil did you observe the polarity? Should be blue to + and white or red/white to - on it. Also check the earth connection (bracket and bolts into the bodywork) on the coil. Also remove and refit the king lead several times on both ends (coil and dizzy cap) to ensure it has a good connection.

Hopefully by now you should have a running engine! :thumbs_up:

I'm pretty sure that's true for LH2.4 cars.

Older cars often use the coil for the rev counter - but I don't have any experience of 760s to know which is correct for them :)

The rev counter impulse comes from the coil. The CPS feeds in to the EZK unit then to the fuel ECU and from the EZK unit, a pulse is sent to trigger the ignition amp module to fire the coil.

With relatively few 760s surviving it would be sad to see another go for scrap.

I am presuming from the previous responses that this is a facelift car with the B280 engine, either E or F. The F one being for cars with a catalytic converter.

Do you have access to, or even aware of, the Volvo 'green' books?
These are the genuine Volvo books for servicing etc. the cars, and many include fault finding data. (They are known as 'green' books due to the colour of their covers.)
These books have checks for the fuel system (LH-Jetronic 2.2) and Ignition system (EZ-115K)
Most checks only involve the use of a multimeter, and carried out at the connectors to the control units. If all checks appear OK, it is possible that a control unit is at fault (the checks are carried out with connector removed from unit).

If you have not located them, the units are behind the trim panel forward of the A post and below the dash on driver's side i.e. near your right foot when on throttle pedal. (There are 3 units behind this panel; fuel system, ignition system and ABS system).

Thanks all for the useful advice. I'll run through the tips above and report back...with a Bank Holiday weekend I might get some time on it. I whipped off the dizzy cap since the post and there's a bit of corrosion on the contacts and arm but nothing significant, I'll clean it up as a precaution. New coil arrives tomorrow so that will be a quick swap out and test.

Would be a great shame to break it, the shell has no corrosion (couple of tiny bits on the door frames) so it would be a last resort...plus the seller wanted to see it on the road again so there's an emotional element to all this :confused_smile:

PS the car is a B280E non-cat.

I'd try the coil only as a last resort, it's very rare they fail. More likely to be the corrosion in the duzzy cap, it doesn't take much to kill HT voltage with a bit of corrosion! :nah:

I'm sure we can get it going, at least it's the full-fat 170bhp version so will go well once it's running! :thumbs_up: