1981 2lt cu engine electtronic ignition - advice please

[Albatross]

Still havinging problems ! Might have carbs somewhere near after having exh sniffed at MOT station and tweaked by mechanics there. Very little popping at exhaust - CO2 to MOT, seemed to be driving well., Mechanical friends and myself all thought it sounded OK tick-over and running OK, did see just over 70mph.
Then for some reason just not sure about it ! Sounded to be running on all four cylinders, pulled plug lead out of dizzy and no diference in exh note ! Changed plug + lead - still no difference. Still sounds to be on all 4. Lead out and no exh note change ? Dizzy cap off - Oh - Rotor arm top burnt ! What causes this ?
Haynes book states - only use R1 iKohm arm. What does this arm look like ? Anyone got any pics ?
Yes I've bought someone else's probs and running out of ideas - too old me and the camper (30 + 60 yrs)
Help needed please, and if there is anyone local to Broughton Astley, Leics, who could help or have a look it would be greatly appreciated.

[Footprint]

Resistor rotor arms have a resin insulated section on their upper side, (there's a resistor in it), rather than a continuous strip of brass across the upper surface. Some blackening of the rotor arm and contacts in the distributor cap is normal, it's difficult to describe how much is too much - a picture is worth a thousand words

Do you mean it slows when you pull three of the plug leads in turn, but stays at the same speed when a certain lead is disconnected?
If yes, then the fault is unlikely to be the rotor arm as it's working OK for the three other cylinders. If it's only one cylinder that's not running it's probable that the fault lies in the distributor cap/HT lead/plug cap/plug of that cylinder.

Or am I misunderstanding what you're describing? I have previous in doing that .

I have become deeply familiar with CU carbs and ignition systems over the last few years - I wish I could assist but you're a distance from me.

[fullsunian]

Still havinging problems ! Might have carbs somewhere near after having exh sniffed at MOT station and tweaked by mechanics there. Very little popping at exhaust - CO2 to MOT, seemed to be driving well., Mechanical friends and myself all thought it sounded OK tick-over and running OK, did see just over 70mph.
Then for some reason just not sure about it ! Sounded to be running on all four cylinders, pulled plug lead out of dizzy and no diference in exh note ! Changed plug + lead - still no difference. Still sounds to be on all 4. Lead out and no exh note change ? Dizzy cap off - Oh - Rotor arm top burnt ! What causes this ?
Haynes book states - only use R1 iKohm arm. What does this arm look like ? Anyone got any pics ?
Yes I've bought someone else's probs and running out of ideas - too old me and the camper (30 + 60 yrs)
Help needed please, and if there is anyone local to Broughton Astley, Leics, who could help or have a look it would be greatly appreciated.

Is Grantham to far away...

[Albatross]

To: Footprint - Done all that , yes only one - No 3 cylinder which seems to be affected. When plug leads are pulled out of dizzy cap on 1, 2 & 4 those cylinders show effect. When lead pulled out of No 3 on dizzy cap - no effect. When putting No 3 lead back into dizzy cap spark can be seen but is yellowish. Still very concerned about the burnt out rotor ? What can cause this ? Could it be wrong coil or wrong rotor arm as fitted by previous owner ?
Don't know how to post a photo, but could send one via e-mail if you care to PM your details to me.

To: Fullsunian - Thanks but camper not safe to drive that distance at present.

[BOXY]

Try swapping spark-plugs between no.3 and one of the others and see if the non-fire moves with the plug. If it stays on no.3 swap a pair of HT leads (both ends) and see if the non-fire moves with the lead. Doing this will confirm if the plug or the HT lead is the problem. If the non-fire stays on no.3 then the fault is either the distributor cap or possibly a valve or piston problem.

I'm not sure what you mean about the rotor arm being "burnt". The tip of the rotor arm has a spark jump between it and the posts in the distributor cap when working normally so a build up of black carbon isn't a problem. The metal pad on the centre on the rotor arm should be in contact with the sprung carbon brush that is fitted inside the distributor cap so there shouldn't be any sparking or burning of the pad. If it is the centre of the rotor arm that's burnt check inside the cap in case the carbon brush has gone AWOL.

[Albatross]

The part of the rotor arm that is burnt is the resistor between the centre of the rotor to the outside brass conductor. Haynes workshop manual states never replace R1 K ohm rotor arm with any other. Also noticed in Haynes specs coil is of different resistance for electronic ignition. Not knowing what the R1 rotor looks like I don't know if previous owner has replaced the rotor and coil with wrong parts. After putting spare rotor rotor in (looks same type) started up, engine ticked over fairly well, pulled lead No 3 out of dizzy, and no difference in exhaust note as before. Again, do not know how to post photo, could only send one via e-mail.

[fullsunian]

If cylinder 3 is not doing alot as you say...When you had the MOT gas tester up it, what were the HC'S like? They should of bin high if it was missfiring at the time. Have you had the cylinders compression tested, if you have and everything is ok. . Have you got a spark at the spark plug on cylinder 3? Find a spark plug connect to number 3 lead and earth..is it sparking? If you done all that and you still not found the problem then it time to look at the carbs. I had one similiar last week BUT that was down on one side..ie two cylinders not one. Turned out to be a blocked needle valve in a carb..
Or if your really stuck.....
Ring me 07740344341
IAN

[Footprint]

The proof of the pudding is in the eating etc etc, by which I mean the next test I would try would be to get another clean and suitably gapped plug, put it into the problem cylinder's cap and make sure it's securely grounded, a bit of heavy wire under a convenient screw head and wrapped around the body of the plug will make certain, just don't hold it by the plug cap in you hand - that can really hurt. Then get someone to turn the motor over for a couple of seconds while you watch for a spark.
If you're not confident that the spark you're observing is one of sufficient quality, try it with another cylinder, if the one is clearly poor the comparison should make it obvious.
Failing that, it would appear that there's a mechanical fault - it's unlikley to be carburation as each carb feeds two cylinders and you have a fault only in one. The next thing I'd check is tappets, either one is grossly out of adjustment, or collapsed and empty of oil, usually that makes a rather rattly noise and thus difficult to miss, but a couple of years ago one of mine just did nothing as it was a dud that was completely silent in it's failure, and allowed no mixture in

The other possibility is less happy of course, but considering that it's cylinder number three - the one that gets the least cooling and the one that fails the most commonly it must be considered as a possibility.

[sarran1955]

Hello,

I think a compression check would be in order.

Gauge not expensive.

You should be showing say 120 psi = 8 bar pressure.... most important that it should be the same on all 4 cylinders.

If one is low,perhaps no 3 squirt a bit of engine oil in, ( I use the syringe from a ink cartridge refill kit), if the reading significantly improves, then its the piston rings, if it doesnt change, then its a valve issue.

Does the engine start well from really cold? Low compression on one cylinder is not always apparent, as when the engine is at running temp it will behave ok, just not contribute much.

Any idea on the engine mileage?

If you're intending to keep it a while, an engine out and top end overhaul is not expensive to do.

Cordialement,

[Albatross]

Thanks for info from all.
Took off No 3 lead and fitted another plug,spark OK. Started engine -had to use peddle slightly for very short time/ not sure if chokes full on. Little ticking from 3/4 side but went off very quick (under a min). Fairly steady tick over from then on, did have a couple of little pops on exhaust. Nobody who has heard engine running has said its running on 3 cys including mechanics ?
When MOT mechanics first tested emission said it was very rich after carb rebuild before they adjusted it to spec whilst I was there. I didn't get read out !
Will have to try to get comp test. Reading Footprint's info - surprised at silent failure of hydraulic tappet, was it just working on internal spring/ not oil pressure ? Might have to give up - getting too old - me not VW !

[fullsunian]

Thanks for info from all.
Took off No 3 lead and fitted another plug,spark OK. Started engine -had to use peddle slightly for very short time/ not sure if chokes full on. Little ticking from 3/4 side but went off very quick (under a min). Fairly steady tick over from then on, did have a couple of little pops on exhaust. Nobody who has heard engine running has said its running on 3 cys including mechanics ?
When MOT mechanics first tested emission said it was very rich after carb rebuild before they adjusted it to spec whilst I was there. I didn't get read out !
Will have to try to get comp test. Reading Footprint's info - surprised at silent failure of hydraulic tappet, was it just working on internal spring/ not oil pressure ? Might have to give up - getting too old - me not VW !

So is the plug thats fitted to cylinder 3 got sparks? Did you test that or just fit another plug to the lead?

[Albatross]

Yes, three different plugs in and swappd No 4 plug and checked, OK - firing - still no improvement.

[Footprint]

So the plug in the suspect cylinder's lead is firing OK, yes? If so then it's looking more like it's mechanical then. Do you have a compression tester or access to one? If yes, then do a compression test. If no, then before spending any money on one or someone who has, (a subject close to my heart - I consider the amount of money spent as a precise measurement of my failure ), get the rocker cover off and have a look at the tappet adjustment, and for freaky silent hydraulic tappet failure. If that's the case, with the engine rotated to the point at which adjustment would be made, (TDC on the compression stroke), it will be possible to depress the rocker against the pushrod with firm finger pressure, you'll be compressing the spring inside the tappet rather than it being hydraulically locked with oil, it will take a good shove - but if it's not completely full of oil it will move.
I haven't heard of this odd sort of failure on anyone else's hydraulic tappet - but I've seen it with my own eyes, on my very own van, so I know it can happen. In the case of my van it was diagnosed for certain by rotating the engine and checking for the valves lifting - one inlet wasn't moving at all.
If there's nothing odd happening there then a compression test must be the next step.

[Albatross]

Laying under camper, thinking! Take rocker cover off. Put in gear and rock about with wheel nut wrench and watch tappets. Got rotor arm/dizzy in No, 3 position and if problem with hydraulics might be able to move rocker arm ?
Mrs Albatross came out with cuppa and said you have a reply from Footprint, had arread and pritned off. Thought we must be telepathic! Here I am doing just that. Tried pressing rocket down on push rod (hard pressure - right thumb on left thumn) No movement! Mrs Albatross pushing forward and me on wheel spanner whilst watching rocker/valve movement - OK. Undone and reset rocker arm as to book. Bit late in day now so will start up in morning - lets hope. Local garge can do comp test. Will let you know what happens.

[Footprint]

Will let you know what happens.

Please do - I is intrigued now .