740gl

[Laird Scooby]

Originally Posted by griston64

It looks cheap and shiny Dave, so is deffo a replacement . The lights stay on until you rev it and it cuts out on the odd occasion

I've yet to test with my meter so will know better then. Battery is brand new

It's a Bosch but it's a rebuilt one Mark, probably by an aftermarket such as BSX or similar. Is there a label on it anywhere stating what it is?

It sounds like you have a sticky brush in the voltage regulator or possibly a slippy belt.

When you say it cuts out, do you mean the alternator or engine cuts out?

[griston64]

Originally Posted by Laird Scooby

It's a Bosch but it's a rebuilt one Mark, probably by an aftermarket such as BSX or similar. Is there a label on it anywhere stating what it is?

It sounds like you have a sticky brush in the voltage regulator or possibly a slippy belt.

When you say it cuts out, do you mean the alternator or engine cuts out?

Engine cuts out. I'm assuming the alternator isn't providing enough power. Especially the fact that the lights stay on until you rev on initial start up

Going to try and remember to take my meter in to work tomorrow to test

Belt is new and not slipping

[Laird Scooby]

Originally Posted by griston64

Engine cuts out. I'm assuming the alternator isn't providing enough power. Especially the fact that the lights stay on until you rev on initial start up

Going to try and remember to take my meter in to work tomorrow to test

Belt is new and not slipping

Highly unlikely to be the alternator especially if it spins over happily and restarts Mark. If the alternator wasn't putting out enough juice, it would run as rough as a hatful of monkeys a-holes, might cut out eventually but you'd know something was wrong long before it did.

When it cuts out, does the tacho immediately drop to zero, even if the engine is still turning? If so, suspect the CPS and ignition amp module.

If the tacho still shows engine RPM, check the RSR hung on the coolant expansion tank, the coil king lead and the inlet manifold trunking as that looks a bit loose on the throttle body.

It'll take you about two minutes to check the brushes on the alternator seeing as it's mounted high up - you'll need a wide (7mm if i recall correctly) flat blade screwdriver to undo the two screws holding the voltage regulator into the back of the alternator. Catch the reg as it comes out and inspect the brushes for equal length and free movement within the contraints of the springs. If all is good, refit it, putting the brushes in first so they line up with the slip rings and easing it into place followed by fitting the screws.

Something else to check are the fuel pump fuses, not sure if they're 11&13 like the 940, depends what incarnation of the fuse box you have as some later 740s had a different arrangement. Make sure the blades are clean and also check the fuel pump relay is sitting fully down in the fusebox.

Also worth crawling underneath and gently tapping the cat to make sure it doesn't rattle, if it does then that could be a cause of it cutting out as well.

[griston64]

Originally Posted by Laird Scooby

Highly unlikely to be the alternator especially if it spins over happily and restarts Mark. If the alternator wasn't putting out enough juice, it would run as rough as a hatful of monkeys a-holes, might cut out eventually but you'd know something was wrong long before it did.

When it cuts out, does the tacho immediately drop to zero, even if the engine is still turning? If so, suspect the CPS and ignition amp module.

If the tacho still shows engine RPM, check the RSR hung on the coolant expansion tank, the coil king lead and the inlet manifold trunking as that looks a bit loose on the throttle body.

It'll take you about two minutes to check the brushes on the alternator seeing as it's mounted high up - you'll need a wide (7mm if i recall correctly) flat blade screwdriver to undo the two screws holding the voltage regulator into the back of the alternator. Catch the reg as it comes out and inspect the brushes for equal length and free movement within the contraints of the springs. If all is good, refit it, putting the brushes in first so they line up with the slip rings and easing it into place followed by fitting the screws.

Something else to check are the fuel pump fuses, not sure if they're 11&13 like the 940, depends what incarnation of the fuse box you have as some later 740s had a different arrangement. Make sure the blades are clean and also check the fuel pump relay is sitting fully down in the fusebox.

Also worth crawling underneath and gently tapping the cat to make sure it doesn't rattle, if it does then that could be a cause of it cutting out as well.

Not sure if tacho shows revs as I normally just quickly restart. The cutting out has only happened a few times and it's always when cold a few minutes after starting and driving off. It doesn't do it when warm. I have noticed if you rev very gently when cold the revs drop a bit so not sure what that could be.Sticky throttle body perhaps ?? I kind of assumed that if all the lights stay on until you rev the car that the alternator would be the issue ?

[Laird Scooby]

Originally Posted by griston64

Not sure if tacho shows revs as I normally just quickly restart. The cutting out has only happened a few times and it's always when cold a few minutes after starting and driving off. It doesn't do it when warm. I have noticed if you rev very gently when cold the revs drop a bit so not sure what that could be.Sticky throttle body perhaps ?? I kind of assumed that if all the lights stay on until you rev the car that the alternator would be the issue ?

Those are several good clues there Mark!

As previously suggested, checked the plastic intake hose between the MAF and throttle body, not just for security but also for pinhole leaks, splits etc and get it further on the throttle body, it's barely hanging on from what i can see in the pic further up.

As for the rvs dropping if you gently rev it, sounds like it's working perfectly!

Counterintuitive, yes?

A bit, but don't forget when you gently bring the revs up when cold, you're lifting the throttle away from the idle microswitch in the TPS so it comes off the idle control map. Chances are the ECU would be running it at say 1200rpm and you give it just enough throttle to bring the revs to 1000rpm but in doing so, release the idle microswitch - therefore the revs actually drop.

I seem to recall seeing somewhere you were planning a new 92C thermostat for it? A new 'stat would definitely help the cutting out or possibly alter your route so you go further before needing to take your foot off the loud pedal. May also be worth checking the connections to the CTS but it sounds like it's working as it should. Am i right in thinking it cuts out only when the temp guage is at about 1/8 of the way up from Cold?

You're correct in thinking when the alternator isn't charging it also brings on a few other warning lights - BFU, washer fluid, ABS (if fitted, i didn't see it in the pic), handbrake/brake fluid and one or two others.

Would also be worth checking all the earth straps on the engine including the alternator earth link, renew any that are suspect.

I'm pretty convinced the alternator sluggish response to the engine turning isn't connected to the cutting out, two separate things. Also some alternators need a smaller pulley than others, it's entirely possible the rebuilders used the "one size fits all" approach and yours needs a smaller pulley. Without knowing what the original Bosch number was (which will be long gone due to the rebuild) it's difficult to say for sure but i'd still suggest checking the brushes on the voltage regulator just to make sure.

[griston64]

Didn't have a lot of time today but the car started ( 2nd attempt ) and didn't cut out. Revs did drop a little but then ok

Checked hose onto throttle body and it's on rock solid so not that

Runs and accelerates ( as much as a 2.0 N/A auto will ) fine after starting

It's been pretty much sitting at Lukes since last October although it did have a good 350 mile blast up the M6 to get up here.

I'm going to give it a thorough look over next week and might just switch in my spare alternator to see

[griston64]

Gave her a little wash today. Not bad for 32 years old

[Laird Scooby]

Looking good there Mark!

[Ian21401]

Agreed. Wish mine looked as good as that.

[Steve 940]

Looks fantastic Mark, nice and shiny, and I love the colour, very similar to my 940.
Hope you get the odd gremlin sorted.
Thought my 940 2.0 Turbo was slow, but can only imagine how a NA is, at least you can enjoy the scenery as you proceed😀
Cheers
Steve