V8 won't run properly, distributor question
Discussion
My 350i started to cut out the other day a I pulled the distributor cap to find that the rotor arm had risen up and was grinding away the cap.
After partially dismantling it the shaft clicked back into place and all appeared to be fine. The weights and the vacuum linkage are in their correct positions. Is there supposed to be a circlip inside the timing rotor holding it on the shaft? Mine just seems to have a plastic clip. I do have one on the outside of the shaft, but this doesn't stop it riding up about 10mm.
The car drove ok for about 20 miles it started to play up again.
So far I have changed the distributor cap, rotor arm, ht leads, - it seems to run ok for a bit and then won't idle or rev cleanly under 2000rpm.
I have checked for vacumm leaks, been through all the fuel injection tests - although I am 99% it is something to do with the ignition.
I have won a distributor, and ignition module on ebay - which I will pick up during the week. Any other ideas?
Cheers
Danny
After partially dismantling it the shaft clicked back into place and all appeared to be fine. The weights and the vacuum linkage are in their correct positions. Is there supposed to be a circlip inside the timing rotor holding it on the shaft? Mine just seems to have a plastic clip. I do have one on the outside of the shaft, but this doesn't stop it riding up about 10mm.
The car drove ok for about 20 miles it started to play up again.
So far I have changed the distributor cap, rotor arm, ht leads, - it seems to run ok for a bit and then won't idle or rev cleanly under 2000rpm.
I have checked for vacumm leaks, been through all the fuel injection tests - although I am 99% it is something to do with the ignition.
I have won a distributor, and ignition module on ebay - which I will pick up during the week. Any other ideas?
Cheers
Danny
Is it a 35DLM8 dizzy??
If so, mine does exactly the same thing. When pulling the rotor arm off, i need to use a screwdriver to hold the trigger wheel down, or the shaft pops up and the bob-weight springs, well, spring off!
Also, mine had the same idle problem (390SE) as yours, turned out to be the ignition amp on its way out. A test you can do is to hook a strobe gun up to either the no1 plug lead, or even up to the kinglead if you want, and let the car idle as best it can. If the amp, coil, or VR sensor in the dizzy are knackered (its probably the amp, as its always the weak spot), you will get a very stuttery, dim series of flashes out of the gun. Point it at the bonnet insulation or something and watch the flashes carefully.
Thats how I diagnosed a faulty amp on mine. After replacement of said amp (REMEMBER TO PUT FRESH SILICONE HEAT TRANSFER COMPOUND ON THE NEW AMP!! They overheat and die otherwise), if you repeat the test, you'll nearly blind yerself with a nice regular train of much brighter flashes.
Oh, and it'll idle properly too;-).
HTH.
Ed.
P.S. I should add that the reason the flashes are dimmer with the old amp is cos the old amp wont be giving as much signal gain as a new one (thats why you'll be getting a shitty spark), and the brightness of the flashes from the gun (assuming its an inductive pickup gun) are proportional to the electromagnetic kick given off by the HT lead.
If youre wondering why it would run ok at higher RPMs... Well, my only explanation was that at idle the alternator voltage tends to drop back towards 12 volts, and hence the amp isnt running at full supply power aswell. at 14.4 volts (i.e. higher revs), it seemed to have just about enough grunt to prevent misfires...
If so, mine does exactly the same thing. When pulling the rotor arm off, i need to use a screwdriver to hold the trigger wheel down, or the shaft pops up and the bob-weight springs, well, spring off!
Also, mine had the same idle problem (390SE) as yours, turned out to be the ignition amp on its way out. A test you can do is to hook a strobe gun up to either the no1 plug lead, or even up to the kinglead if you want, and let the car idle as best it can. If the amp, coil, or VR sensor in the dizzy are knackered (its probably the amp, as its always the weak spot), you will get a very stuttery, dim series of flashes out of the gun. Point it at the bonnet insulation or something and watch the flashes carefully.
Thats how I diagnosed a faulty amp on mine. After replacement of said amp (REMEMBER TO PUT FRESH SILICONE HEAT TRANSFER COMPOUND ON THE NEW AMP!! They overheat and die otherwise), if you repeat the test, you'll nearly blind yerself with a nice regular train of much brighter flashes.
Oh, and it'll idle properly too;-).
HTH.
Ed.
P.S. I should add that the reason the flashes are dimmer with the old amp is cos the old amp wont be giving as much signal gain as a new one (thats why you'll be getting a shitty spark), and the brightness of the flashes from the gun (assuming its an inductive pickup gun) are proportional to the electromagnetic kick given off by the HT lead.
If youre wondering why it would run ok at higher RPMs... Well, my only explanation was that at idle the alternator voltage tends to drop back towards 12 volts, and hence the amp isnt running at full supply power aswell. at 14.4 volts (i.e. higher revs), it seemed to have just about enough grunt to prevent misfires...
Edited by ed_crouch on Sunday 18th February 14:48
Edited by ed_crouch on Sunday 18th February 14:52
ed_crouch said:
A test you can do is to hook a strobe gun up to either the no1 plug lead, or even up to the kinglead if you want
Be sure to use a cheap passive strobe not a fancy active one. You can get HT test lamps that fit in line with the HT leads, but I prefer to use a cheap £1.99 timing gun perched on top of the plenum so I can see it from the driver's seat.
Ah rats! Y'mean my 75 quid Gunsons blinging chromed inductive one isnt active?!? Mind you, it just sits there all day: dun't look very active to me...
Danny, it looks like you may have found the culprit: good luck!
You can get a lucas amp for about 50 or 60 quid, or an intermotor one for 35. Lucas one will probably last longer.
Ed.
Danny, it looks like you may have found the culprit: good luck!
You can get a lucas amp for about 50 or 60 quid, or an intermotor one for 35. Lucas one will probably last longer.
Ed.
Edited by ed_crouch on Sunday 18th February 16:13
Have checked mine Danny and there is no vertical movement on the dissie shaft.
Another failure that a few people saw last year was the pickup coil inside the dissie breaking down and going open-circuit: on my car it acted like a 5300 rpm rev limiter until it finally failed.
Incidentally certain versions of the BL Metro used exactly the same ignition amp, in case you don't fancy being ripped-off for a 'Rover V8' one...
Another failure that a few people saw last year was the pickup coil inside the dissie breaking down and going open-circuit: on my car it acted like a 5300 rpm rev limiter until it finally failed.
Incidentally certain versions of the BL Metro used exactly the same ignition amp, in case you don't fancy being ripped-off for a 'Rover V8' one...
wedg1e said:
Have checked mine Danny and there is no vertical movement on the dissie shaft.
Another failure that a few people saw last year was the pickup coil inside the dissie breaking down and going open-circuit: on my car it acted like a 5300 rpm rev limiter until it finally failed.
Incidentally certain versions of the BL Metro used exactly the same ignition amp, in case you don't fancy being ripped-off for a 'Rover V8' one...
Another failure that a few people saw last year was the pickup coil inside the dissie breaking down and going open-circuit: on my car it acted like a 5300 rpm rev limiter until it finally failed.
Incidentally certain versions of the BL Metro used exactly the same ignition amp, in case you don't fancy being ripped-off for a 'Rover V8' one...
Mr Scrapyard here I come!!!
Still not sorted, changed the distributor, amp, coil, leads, cap, rotor, checked all connections (all crimps have been soldered, ran a clean earth from the battery to the engine - and still getting intermitant missing with a dimming of the strobe light.
I have put a meter across the coil and getting about 6v ac when idling - drops to about 4v ac when the engine falters.
Any ideas?
I have put a meter across the coil and getting about 6v ac when idling - drops to about 4v ac when the engine falters.
Any ideas?
Had problems once that look a bit like yours, but not completely. Other ECU solved it. Had the old one resoldered, and it is back in now with the other being my spare. Probably you tried swapping ECUs to rule it out.....
Other 'option' perhaps:
Isn't their a sort of sensor on the engine that is used for timing purposes/engine running signal for the ECU, etc.? Like in the flywheel or crankshaft balancer, or a part that is used by the sensor. Could perhasp be the source to all your problems.
Hope you find the problem and cure it.
Rob
Other 'option' perhaps:
Isn't their a sort of sensor on the engine that is used for timing purposes/engine running signal for the ECU, etc.? Like in the flywheel or crankshaft balancer, or a part that is used by the sensor. Could perhasp be the source to all your problems.
Hope you find the problem and cure it.
Rob
danny hoffman said:
I thought the ECU had no impact on the ignition system?
I know the ECU needs a pulse from the distributor to run the fuel injection though.
I know the ECU needs a pulse from the distributor to run the fuel injection though.
You are right that the ECU has nothing to do with the ignition control. But it picks up a signal from it (from the amplifier if I am not wrong). It was just that the symptoms looked like mine. Thinking about it now: if the ECU picks up a signal from the ignition, it could perhaps 'pull' more power than supposed, due to an ECU board issue and cause ignition grief in an indirect way. Or the lead from the amp to the ECU is shortcutting somewhere. Wedg1e probably can explain more about it.
Sorry if it isn't a help, only trying.
Rob
danny hoffman said:
Still not sorted, changed the distributor, amp, coil, leads, cap, rotor, checked all connections (all crimps have been soldered, ran a clean earth from the battery to the engine - and still getting intermitant missing with a dimming of the strobe light.
I have put a meter across the coil and getting about 6v ac when idling - drops to about 4v ac when the engine falters.
Any ideas?
I have put a meter across the coil and getting about 6v ac when idling - drops to about 4v ac when the engine falters.
Any ideas?
Is the high side of the coil dipping i.e. brown-out on the switched ignition circuit? Or the low side not being pulled down as far / as long (faulty ignition module, wrong dwell, whatever)?
danny hoffman said:
Just run a lead directly from the battery + to the coil and still get the same problem. I have a steady 13V volts at the coil and at the ignition amp.
Dodgy distributor or amp? Seems like an incredible co-incedence to have exactly the same fault?
Dodgy distributor or amp? Seems like an incredible co-incedence to have exactly the same fault?
It seems the ignition amp isn't sinking enough current to pull the coil -ve down, or it isn't sinking the current for long enough.
If you have access to a dwell meter you could find out whether you have a dwell problem.
It could be the ignition amp isn't earthed well enough. It could be the ignition amp as partially failed and isn't sinking enough current from the coil, or isn't able to hold it down for long enough.
It could be the coil resistance is too low and the coil is making the ignition amp pull more current than it is designed to. This could be from a faulty coil or the wrong spec coil. I'd expect either the coil or the amp to get very hot and eventually burn out if this happened but you might get a weak spark along the way.
It could be the pickup inside the dizzy is failing or misaligned and not triggering the ignition amp properly. The misalignment could be the side effect of some other problem such as a badly worn bearing in the dizzy.
Ran a wire tonight directly from the negative in the battery to one of the mounting screws on the ignition amp and still have the same problem. Got a steady 13.x volts on positive terminal of the ignition amp and coil. Got the same 6.x volts ac on the other terminal of both. When I snap the throttle open the strobe light goes really dim and the engine nearly dies
Gassing Station | Wedges | Top of Page | What's New | My Stuff