air filter position

[tonym911]

Sorry yes I'm mixing up the damper with the piston, I've got that (the piston!) out now and am cleaning the damper tube with white spirit as per Alex's advice prior to refilling with 3 in 1. Will revert with results shortly. Thanks to all so far, a fantastic resource this.

[tonym911]

Piston had a small (5mm) scuff on the bottom edge (the needle side) but goes up and down OK. Have reassembled it all with 3 in 1 in damper tube as advised. Will check fuel pump next as per Millerman's tip. I assume that's the large, quite shallow brass nut under the thicker end of the pump.

[autolycus]

All this discussion about grades of damper oil and incoming air temperature is great fun, but nothing to do with the OP's problem. Given the "naming of parts" problem with carburettor components, I think he'd better get someone a little more experienced to check the obvious ignition stuff.

In particular, since the coil and cap are new I'd either inspect the rotor arm very carefully for tracking, or if he's not sure what to look for, just replace it. The new one will probably be rubbish, and fail in a few weeks, but it should pin down the problem. I'd also make sure the coil is the correct one, bearing in mind that some electronic ignition systems require a particular type of coil, and some, e.g. Lumenition, tell you to use a low resistance coil with a ballast resistor even if your car has no ballast resistor bypass for starting.

I agree with Roy, though: go back to points and a plain 12v coil. The limitation of a simple system only becomes significant under conditions no ordinary Moggy should ever experience. OK, the points are one more thing to maintain, but you can see them working and check them with trivially simple equipment.

Kevin

[tonym911]

I'm genuinely sorry to be taking up everyone's time like this, and equally sorry for my enduring ignorance. Despite my blunderings I am enjoying myself. I did look at the rotor arm while I was poking around the distributor. It looks almost new. There was a kind of scorch mark on the very tip of it but my experienced garage-owning friend didn't think that would be an issue. I replaced the distributor cap with a new one. Ditto the coil. I have just gone through the dashpot damper procedure and I did get mixed up there thinking it was the damper that had to drop down, not the piston. That was stupid. I have just checked the fuel filter, and it is completely clean. The element is slightly twisted and I can feel it getting 'bound up' on the last couple of flats, otherwise it seems fine. I will ask the car's previous owner if it has Lumenition ignition. I suspect it does, in which case it sounds from what you're saying here that I have probably put the wrong coil on there. I'm afraid I don't know the specification of the new coil other than it's black, it's got 12V written on it and it is the only one sold by Bull Motif for the Minor (no mention of ballast resistance etc on their website). Again I am severely hamstrung by my ignorance and have to go on trust to some extent. Now that I've got that coil, which I assume is the correct one for non-electronic ignition, I may as well revert to points as my next (and hopefully last) move. PS What's an OP?

[tonym911]

In my defence re the piston confusion, the damper wotsit could legitimately be described as a piston, seeing as how it is a thicker thing on the end of a stick.

[LouiseM]

All this discussion about grades of damper oil and incoming air temperature is great fun

I think you need to get out more Kevin

[bmcecosse]

OP = Original Poster I presume! Don't worry about confusion over parts - we understand what 's going on. The oil etc check IS worth doing - in case the 'piston' etc had been binding. It doesn't seem to be - so that should be fine. Rotor arm is a possibility - certainly worth a swap. You really need to beg/borrow/steal another standard dizzy - and try that - does your garage mate not have one ? They were common to many cars in the BMC fleet. Maybe someone reading this and near to you - could pop over and have a look/lend you a dizzy ???

[linearaudio]

PS The chap I was with when I put the new coil on was curious about the fact that one of the two leads from the coil went to earth just below the fuse box (the other one obviously going to the distributor).

As you state one side of coil is going to earth, is this connected to the -ve side of the coil?
"Normal" orientation is the -ve side going to the distributor (assuming -ve earth on a 1970 model) But yours would presumably want to be reversed. Also, did the fault only occur since putting the new coil/ cap on?
Usually an electronic distributor would tend to work or not, rather than peter out and recover. Sounds much more coily to me!

[bmcecosse]

Aye -but new coil fitted already!

[bmcecosse]

Note - in this page http://auto.howstuffworks.com/engine4.htm they show a coil connected to earth - so clearly - with SOME electronic systems - this is how it is done !

[tonym911]

As bmcecosse says, these new part fitments - distributor cap, coil - and air filter, fuel filter check, carb piston/damper check were done to fix a problem that cropped up about three weeks ago. None of these fixes have worked.

[Peetee]

Had a look at the fuel pump?
The points gap on mine had eroded and opened up too far and gave similar symptoms to what you first described.

[bmcecosse]

Generally - they either pump, or they don't pump!

[RogerRust]

OK while you have the dashpot off. Polish the INSIDE with metal polish ans clean the piston as well. When you put it together again don't just tighten the screws check that it moves freely as you screw it down, its easy to get it slightly off and then it sticks. Then refill the dashpot oil I use proper dashpot oil now but never had a problem with 3 in1. When you put the damper thing in the top of the dashpot it should be hard to push in but easy to pull out, this is so that the piston rises slowly but drops quickly.

If the rough running is a recent problem now would be a good time for a check for air leaks , I spray some soapy water from a trigger sprayer all around the carb and manifold and listen to the engine note if it smooths up you have a leak somewhere.

Having said all that it could well be the petrol pump playing up. It's not a difficult job to strip and rebuild but you nead a manual and make sure you do it over a sheet of newspaper somewhere clean.

[tonym911]

Checked filter but not had a look at the points, I'll have a go at that this morning, thanks

[tonym911]

Had a look at the fuel pump?
The points gap on mine had eroded and opened up too far and gave similar symptoms to what you first described.

Was it running OK for the first few minutes then gradually running more and more poorly?

[tonym911]

My garage pal was showing me a solid-state fuel pump, a small square thing which he reckoned might be a step in the right direction. Do they exist for Minors?

[bmcecosse]

Yes - and they are horribly unreliable on Minors. They are not designed for 'sucking' fuel up from a low mounted tank to a high mounted pump. When the engine mis-behaves, is the fuel pump ticking away madly ? Have you tried taking the fuel filler cap off - just in case there is a vacuum developing in the tank ?

[tonym911]

Fuel cap removal was the first thing I did. I felt fairly confident of my ability to do that! It's a Wipac-style locking cap. No signs of pressure buildup. Was wondering whether tank might have rust in it but the spotless fuel pump filter would seem to discount that one. Fuel pump ticks 'normally' ie a reducing-frequency series of clicks when starting up, then I hardly ever hear it except in heavy traffic when it sometimes makes itself heard again, but I gather this is normal. I'll try and source a new rotor arm from the local motor factors today and see if that helps.

[tonym911]

To drain that out, do I remove the whole suction chamber and then just tip it upside down?

Thats the easiest way only 3 screws.

Oddly you're the second person to say three screws. There are only two on mine, at 180 deg to each other. That's not significant, is it? Just trying to think of everything at the moment!