more electrical questions!

Mick Rae

Mick Rae

Active Member
In a previous thread, I reported I had cured my engine stumbling by popping in new plugs - I was wrong. Once I went a decent run with everything up to temp etc, it came back with a vengeance. Now, the only thing in the ignition (other than the coil) that I had not renewed was the points and condenser - essentially as I was wary of new ones, but also as the points looked absolutely fine. I changed the condensor in a layby - made no difference (was trying to just rule out one thing at a time). So then I popped in new points - this really did sort the issue. Indeed, with a 50 mile round trip yesterday, and a further 30 miles today, I can safely say the car is running perfectly. BUT.
I was a bad boy - when I was changing points etc at roadside, I did not disconnect the battery. So maybe I screwed up, touched something etc, I dunno - however, although running super sweet, the ammeter now behaves differently. Previously, it just stayed at zero, flicked to negative when putting the lights on, but always at zero. Now, at idle it reads zero, but once cruising along at 3500 rpm, its in the positive side, say approximately 15 (quarter of way to the plus 60. I have never had an ammeter before, but would suspect thats overcharging? Which would be the regulator in the alternator right? I put a hand on the battery, its not warm or anything. So, have I fried something - wish I knew how. Or maybe its just law of sod - either way, could you let me know if indeed this is abberant behaviour in terms of charging, and whats the solution - can a regulator be changed - its a 1975 2200sc.
One last bit of information which may or may not be connected. I wanted to check my coil feed to see if I had a ballasted system feeding it. I connected meter to plus terminal of coil, where two connections feed (which is correct, one from starter, other from ballasted coil feed). With ignition on, it reads 6V. So ballasted. But, if i disconnect the feed leads and check them at their terminals off the coil, its reading 11V. I'm a bit confused by that. I'm sorry for being such a div when it comes to this stuff, I hope you dont mind me asking - I know that the answer is probably that I am not smart enough with this stuff, but I am keen to learn, hence my avoidance of taking to the garage!
 
Hi Mick,

Is your alternator an 18ACR? If so, then yes the regulator can easily be changed. As to why your ammeter is now showing a charge when you drive, the most likely culprit would indeed be the regulator. The only time your ammeter should show a postive charge is when the battery is being charged. If it had been discharged for whatever reason, then that would be perfectly normal, but to just suddenly show a charge without an underlying logicial reason is a fault. Overcharging will reduce the life of your battery, so change the regulator as soon as you can. It is an easy job on the 18ACR, indeed the part that takes the longest is removing and refitting the alternator from the engine, certainly that's the case with the V8 ;).

Ron.
 
Hi Ron,
many thanks for the reply. Currently (pun intended) no idea what alternator I have, will remove it first opportunity and go from there. Do you reckon its possible I fried the regulator with my ignition fiddling - it happened once I had changed the points. I'm concerned that I screwed up, and don't want to again - well, of course I will, just not the same screw up hopefully!
Well, might as well start removing the alternator, I have a spare hour or two, then see whats what.
thank you
Mick
 
Mick Rae said:
Hi Ron,
many thanks for the reply. Currently (pun intended) no idea what alternator I have, will remove it first opportunity and go from there. Do you reckon its possible I fried the regulator with my ignition fiddling - it happened once I had changed the points. I'm concerned that I screwed up, and don't want to again - well, of course I will, just not the same screw up hopefully!
Well, might as well start removing the alternator, I have a spare hour or two, then see whats what.
thank you
Mick
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I think it’s unlikely your replacing the points would cause the issue. But I’ve had unrelated things happen at the same time before and it’s caused me no end of trouble.
Most memorable was after a full engine rebuild when. I started the engine for the first time and it ran beautifully, turned it off, went to turn it over again for it to be dead. Battery had gone from full charge to completely dead in 30 seconds! Took me ages to find what had happened, I was imagining mashed valves, dead starter motors, the works!
 
Ah well, that's nice to hear. I think that perhaps the electrical side of the car is in need of help, hence yeah,maybe I need to stop assuming it's always something I screwed up! It's nearly 47 years old, and I reckon that's pretty good going, so happy to spend the winter going over all the weak links so next year can be spent on a few touring adventures. I have plans........
 
Mick Rae said:
Ah well, that's nice to hear. I think that perhaps the electrical side of the car is in need of help, hence yeah,maybe I need to stop assuming it's always something I screwed up! It's nearly 47 years old, and I reckon that's pretty good going, so happy to spend the winter going over all the weak links so next year can be spent on a few touring adventures. I have plans........
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Yep, I found that a lot when I first got my car running. Best favour I did myself was to go through all the connectors and clean them with a small wire brush and some scotchbrite. Followed with a little dielectric grease to ensure they stayed clean. Any dodgy looking insulation or connectors was replaced as a matter of course. Made a huge improvement on reliability for the electrical system in general. Head lamps were brighter, indicators flashed faster etc.
 
Just to close this off. Alternator was decidedly second hand looking, replaced. All connectors on ignition system removed, and polished up. Charging now normal, and car running absolutely perfectly. On to the next job, cooling system.
Thank you all for your comments and help, and all the best for the festive season.
Mick
 
Mick Rae said:
Just to close this off. Alternator was decidedly second hand looking, replaced. All connectors on ignition system removed, and polished up. Charging now normal, and car running absolutely perfectly. On to the next job, cooling system.
Thank you all for your comments and help, and all the best for the festive season.
Mick
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Great to hear an excellent outcome Mick :)
Likewise, Merry Christmas to you and your family.

Ron.
 
Dammit. My intermittent misfire returns. I guess I never cured it after all, the joy of an intermittent issue!
Car drives perfect for miles, then loses all power for a split second, then ok, then happens again, to the point I just stutter quite violently along to nearest layby. Idles great in layby. I'm beat. Plugs, leads, condenser, points, distributer braided lead, coil, all replaced, one at a time to try to find the issue (and starting with cheapest bits!). Multiple points and condensers tried just in case). Every connection cleaned to perfection. Replacement alternator. Frustrating as everytime I think I have cured it, I just get to the point of enjoying the car, when oh no, it starts happening again. It's time I gave in and got it to a garage. Luckily there is one nearby that although a modern car place, always has a classic in, and are really decent folks, with electrical issues a speciality. I will report back what dumb thing I missed, in case anyone else also overlooks the obvious as I suspect I have.
 
I had a similar problem with my 2000TC a few years ago. In my case it was ethanol in US fuel causing the diaphragm in the fuel pump to curl and lose suction. Would only happen when engine had been running for a while and at higher loads/speeds. Kept getting worse until it finally died pulling onto the highway. That’s when I finally found it. Up until then I was convinced it was an ignition related issue.
 
Another possibility is an internal break in the low-tension wire from coil negative to distributor points, making intermittent contact. I've had this on two P6s and a Saab 96, with symptoms much as you describe. Might be worth running a separate wire from coil to distributor and see if it fixes the problem. If it doesn't, at least it was worth a try.
 
johnsimister said:
Another possibility is an internal break in the low-tension wire from coil negative to distributor points, making intermittent contact. I've had this on two P6s and a Saab 96, with symptoms much as you describe. Might be worth running a separate wire from coil to distributor and see if it fixes the problem. If it doesn't, at least it was worth a try.
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Especially as that’s where Rover chose to hide the ballast resister on such equipped cars.
 
Cap, rotor, points, condenser, leads, plugs, coil all been changed one at a time for new ( and just in case, sometimes more than one eg condenser). Also the braided leads in distributer. I am going to try a fresh wire from points negative as suggested above though. Will get to bottom of this eventually.
 
Possibly fuel vapour lock as these symptoms do describe it, sudden stuttering loss of power, just a thought.
But all of the above as mentioned.

Graeme
 
Hi Graeme, what causes vapour lock, sorry, not familiar with this.
Had no chance to play further with car today, as apparently there are more important things needing done. Was news to me;)
 
With a front mounted sucking fuel pump, if the fuel gets hot the low pressure of the suck can turn the fuel to vapour, and the pump ceases to function - they cant suck a gas. Low pressure lowers the boiling temperature. Immediate solution is to let things cool down. Long term you need to ensure there are no restrictions in the pipes to the pump , and protect them from engine heat as much as possible. On my 3500 I have covered the pipe over the bellhousing and along the block with a heat resistant tube (Firesleeve). When you get symproms of your problem check the pump sediment bowl for fuel - if its empty, that might be your problem. Could be dirt in a pump valve?
 
Two other electrical possibilities - one is the coil is on the way out with an internal intermittent fault when hot... Second if the car has the battery in the boot there is a plug in the floor round about where the clutch pedal is that takes the cable from inside the car to inside the engine bay. The connections down there can get grotty and loose. the first signs of trouble are after the car has been running a bit when the fitting gets hot. The fitting has other connections to it supplying power to various other bits which play up as a result.

I'd check your coil first. not just for operation but according to its specs.
 
Mick Rae said:
Hi Graeme, what causes vapour lock, sorry, not familiar with this.
Had no chance to play further with car today, as apparently there are more important things needing done. Was news to me;)
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The Vapour lock thing is a really common problem on P6B's, there are many reasons and many cures one of the problems can be the tower on top of the inlet manifold where the small tube water fittings corrode up an become blocked or restricted.
 
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