running out of stuff to change.

OK, got carbs from the bloke on eBay. one appears almost brand-new (although it has been used and has been apart, judging by the evidence.

put it on Edward... makes almost no difference. Now got more or less perfect idle, but still won't run right above idle, and at high throttle openings misses often but erratically and makes much bang and pop in exhaust, which seem to imply fuel getting through.

Summary:

Fuel pump almost new, and delivers mucho petrol if the pipe is pulled off when it's running, not suspect.

Distributor (inc cap, condenser etc.) new.

Inlet manifold intact, no sign of big hole under the carb (was one thing that needed eliminating).

No obvious air leaks.

cranks normally and starts on idle with no trouble. Idles nice and smooth and can be slowed down below normal idle speed without stalling. ergo nothing major wrong with compression or suchlike

Crankcase ventilation thing removed and blanked off, to eliminate it.

Coil changed for known good one from another motor.

temporary supply with a bit of wire from battery to coil didn't affect it either.

Plugs changed for other ones (not new) but with no effect. Leads ditto, no effect on fault symptoms.

Replacement carb opened up, float level correct and all squeaky-clean inside

- specifically, no crud blocking the main jet. It'd have to be something quite noticeable to give the observed symptoms. Carb really does look almost new. Also, fault is the same (bar for better idle) as with the Weber carb on - and I think if I'd slowed the idle down on the weber it'd be OK - speeding the idle up makes it erratic.

Moving ignition timing 'til it's obviously retarded made no difference, so not ignition timing - it'd have to be miles out to give the observed symptoms, anyway, and it'd not idle properly. Vaccuum pipe appears to suck. missing vacuum advance doesn't, in any case, produce symptoms as severe as these, IME.

Engine earth must be OK, or it'd not crank properly.

Apart from trying new plugs and leads, what have I missed? I probably will try new plugs and leads, but I'm not confident.

Reply to
Austin Shackles
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"Austin Shackles" wrote in message news: snipped-for-privacy@4ax.com...

Reply to
Nige

FFS!

Weak valve springs?

Reply to
Nige

Austin Shackles waffled thusly

Fuel pick-up filter clogged in petrol tank? It's a fine wire mesh and easily gets clogged up if dust/dirt.whatever gets into the tank.

We had _exactly_ those symptoms with out S3 (not a V8, mind) ... Idled and ran superbly when not under load, but as soon as load applied, ie moving anywhere, it really struggled. Showed a healthy flow of fuel from fuel pump when testedm but simply couldn't cope under stress.

Easy fix, just take the pick-up out of the tank and clean in paraffin with a small nylon brush (swmbo's pot-washing brush was ideal) ;)

Reply to
Paul - xxx

I had this sort of caper with a triumph bonneville once after an engine rebuild. Turns out the plugs were tracking across the carbon from burnt oil rather than a good spark across the electrodes. Idled fine but spluttered like hell once I opened the throttle. I was demented and as a last resort replaced the plugs - a new set sorted it out instantly. Maybe you have a couple of plugs off? In desperation I'd also be thinking about bypassing big lumps of the fuel and ignition system by hot wiring the ignition and even maybe rigging up a temporary gravity fuel supply to the carb. (I may have missed similar suggestions in the many posts on this btw.) Good luck Graham

Reply to
Graham Bowers

I'd try another coil. Stranger thiongs have happened than a "known good coil" being anything but good.

Stranger things seem to happen to me all too often at present ;)

Reply to
Tim Jones

On or around Tue, 27 Mar 2007 17:58:12 +0100, "Paul - xxx" enlightened us thusly:

possible, but this won't run above idle even off-load, yet there's plentiful petrol out of the pipe. running at (say) 2000 revs off load takes only a bit more petrol.

forgot to say that this is a fault caused by some kind of failure - it happened fairly rapidly - was intermittent to start with but within about 20 miles had become more or less permanent.

Reply to
Austin Shackles

On or around Tue, 27 Mar 2007 18:33:45 +0100, Graham Bowers enlightened us thusly:

I've bypassed the supply to the ignition circuit with no effect. New plugs is the next thing, rather than just different plugs. Could be plugs breaking down, although it's a trifle odd that it idles so well. But something has to be causing it and there aren't that many things that have no effect on idling yet cause huge problems off-idle.

Reply to
Austin Shackles

Sounds like coil or plugs to me. but I'm not a mechanic

Reply to
Danny

Sounds similar to a problem I had with a series motor many years ago - turned out to be an intermittent breakdown on the LT side caused by improper earthing of the dizzy baseplate as it moved under operation of the vacuum capsule! It was confirmed by the addition of a second earth braid between baseplate and body - at that point it then ran as sweet as a well-oiled nut on a clean thread. Might be worth revving it to the point where it does it with a strobe gun connected up to see if it's losing HT sparks.....?? Badger.

Reply to
Badger

I wouldn't assume that, although it seems unlikely

Have you had the rocker covers off and inspected the rocker gear? It looks like a valve/spring/camshaft problem is about the only thing you havn't investigated yet. Is it possible the valves are worn as well? Wet compression let-by test should reveal valve problems.

Alex

Reply to
Alex

I second that idea

Could perhaps valve timing have slipped ? I look at one of my mothers cars many years ago it ran similar to the way you describe...would idle fine just didnt want to know after that....was a new old second hand car....did timing belt on it and that cured it(i know v8 doesnt have belt....but could chain have slipped or something) I'd tried everything on that little car......compression tested within spec...timed to perfection everything.....ran like a dream after changing belt (cant remember how far out it was.....but seem to remember it wasnt much)

It would certainly account for it suddenly happening....although i could be completely wrong!

Johnty

Mary the 1969 series IIa 88 Dave the 200 Tdi disco K-pax the 300 Tdi disco unknown the soon to be Td5 disco

So many discos......So little time

Reply to
Johnty

I'm wagering shagged valve springs at £5

Reply to
Nige

On or around Tue, 27 Mar 2007 18:19:29 GMT, snipped-for-privacy@btopenworld.com (Tim Jones) enlightened us thusly:

It's already had 3 on it. The one it had to start with, another which AFAIK is good and the one off the spare tranny that was running fine last week. None of 'em make any difference, and the chances of 3 of 'em being dud in exactly the same way is significantly less then 2. I have in fact got a fancy one on the 110, but I'd prefer to leave that there. The one on it now is the ford one from the minibus, which had no problems.

I reckon next thing to eliminate is plugs, by putting some new ones in - the ones that came out of it are old and doubtless past their sell-by date.

one other thing to check is the points gap in the new dizzy. It didn't look far out, but worth a check.

Reply to
Austin Shackles

On or around Tue, 27 Mar 2007 19:53:19 +0100, "Badger" enlightened us thusly:

I'll probably do that next time I feel cheerful enough. The odd thing is that it's not a total loss of sparks - I'm pretty sure now the fuel is OK - there's enough fuel getting into the exhaust to make some really impressive bangs when the fire does happen - if it was fuel starvation in some form, I'd not expect shotgun-emulation, and some of the bangs are almost that loud.

Since the dizzy is new, it shouldn't be suffering from that; also the braid on the old one doesn't look loose.

still, by the time I get it sorted it should have most of a new engine!

Reply to
Austin Shackles

On or around Tue, 27 Mar 2007 21:30:47 +0100, "Johnty" enlightened us thusly:

This one's a 2¼, and doesn't have a belt either. Might be worth a looksee though - not sure how much hassle it is to look at the timing. since the dizzy runs off the camshaft, it can only be that the cam and spark timing are both off WRT the crank, though.

there's really not much else left, though.

Reply to
Austin Shackles

"Austin Shackles" wrote in message news: snipped-for-privacy@4ax.com...

I've just come up with a stunning idea Austin ( dating back to me and a psycho Hillman Hunter problem in 1977) have you got a sparktune plug. I had a similar issue with the HH it would tickover beautifully run like a dream then die cough and recover after a short while - finally diagnosed to fuel starvation under load cause was a pinhole in the diaphragm of a mechanical fuel pump . The plug should tell you what condition the engine is running at when the trouble starts and give you a place to start from.

Derek

Reply to
Derek

"Austin Shackles" wrote "Paul - xxx" enlightened us thusly:

Austin, I wonder if it's the condenser or even coil, many years ago I had a car that had similar problems and it was the sparks breaking down under load, or more properly, under the requirement for more sparks.

Reply to
Bob Hobden

Chains slip too, if the tensioner is knackered.......

I had to rebuild a GM 3.0 straight six because the chain tensioner had worn and the chain had slipped one tooth. It was running fine at idle and pulled like a landrover at the bottom end, but you couldn't get any power out of it at all above 3000rpm.

I was baffled too, untill I decided to strip the front of the engine down because the chain seemed a little slappy when running, thats when I found the timing was out.

Alex

Reply to
Alex

you can test the operation of a mechanical fuel pump using a vacuum pump/gauge too (so the instructions in my new one say!) I think you just connect it to the from line. pump it up a bit and see if the gauge drops. if so the diaphram is holed and it is running back.. think thats the principle anyhow!

Reply to
Tom Woods

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