340 1.4 rough ans slow idling
 

Hi there, I'd be grateful for some advice.

My 340GL manual has run well for years.

A few days ago I filled up at the local Asda Petrol Station, after a short distance the car was tending to stall and tickover slower than usual and rough, something like 200 RPM.

The next morning I started the car and again had the same problem I disconnected the fuel feed to the carb and pumped out about 2 litres of fuel. Reconnected the feed and car ran OK. The next day I did a round trip of about 10 Miles and the car was fine. However, today the car is playing up with the same erratic and slow idle.

I did contact Asda about the possibility of contaminated fuel, they responded on the day that I filled up, several hundred cars filled from the same tank and no reported problems other than mine.

I have checked distributor, rotor arm, air filter and for air leaks around carb. The ignition leads are fairly new.

Of course, MOT is due soon, so I need to resolve this. Many thanks in advance.

Would i be right in saying it's also harder to start cold and tempremental until it's warmed up and even then not as it should be?

If so, it sounds as if you have a build-up of condensation in the tank, worth trying as a "first port of call". Wait until the fuel level is down to ~1/4 tank (about 3 gallons left) then add 2L of meths to the tank :

https://www.toolstation.com/methylated-spirit/p99550

Cheapest way of buying it at that volume as far as i know. This will emulsify with the water and allow it to be burned off normally. If it doesn't work, it's cheap enough to know you've tried a quick, cheap and easy fix that has got rid of the condensation. Note that the best ratio is 1:10 so more than 3-4 gallons of petrol will dilute it too much to have any real effect.

Hi, thanks for the useful reply.
I going near Toolstation today, I'll get some meths. Yes, more temperamental when cold, but still bad tickover when hot. Of course, Ive got over half a tank of petrol.

Apologies for the typo in the title. Must concentrate!

Testing the car yesterday, Ive got good brakes on the 340, was going to go through the second set of traffic lights, decided to stop. Range Rover to the left of me decided to go through, he got flashed.

My £6 dashcam filmed this.

https://youtu.be/SQHPWMLzR_w

Just got back from Toolsation to get methylated spirits, car still playing up, bit like kangaroo petrol. Relatively new thing, engine ran on a bit after turning ignition off. Does not usually do that.

You've still got over half a tank of petrol so you haven't put the meths in yet so if it is condensation it will be.

No, not put meths in yet. Will get the tank a bit emptier first. Will be doing a few miles tomorrow, then perhaps over the weekend will pump some more out of the tank. I have a little electric pump for this, about thee years ago I filled with diesel by mistake!

Good idea pumping it out! If you can, put it in a clear container to settle, you'll see the condensation/water at the bottom if you happen to pump any out from the bottom of the tank.

Three years ago when I pumped out the diesel. I just disconnected the feed pipe to the carb, and connected the electric fuel pump to that. I need to find some empty cans though!

Just noticed another error of mine, I'm registered here under two names, this one and 340man.

What about a 25L tub from somewhere? Many places that use clear plastic 25L tubs are happy to let one go free or for tuppence ha'penny and a brass farthing.

Pumping from the carb feed pipe would also mean you're pumping from the bottom of the tank so likely to get a lot of the condensation - could be why when you did similar and got the engine started you pulled through some petrol instead of condensation.

The large clear container would have to be petrol resistant of course. What I'll probably do is run the car a bit tomorrow, may put in a new set of plugs, over the weekend get a 5 gallon jerrycan from a friend and pump out a lot.

This is the pump I bought three years ago, works fine, just a bit noisy.

https://www.ebay.co.uk/itm/363392093855

That's true about the container but most PVC and similar containers will hold petrol for a sensible amount of time.

I'd hold on putting new plugs in until you solve the petrol problem or at least have got the meths in the tank and driven it a bit. Simple reason being, a new plug might be faulty - it's rare but not unknown - you may have cleared the fault but by fitting the new, faulty plug have unwittingly created another with similar symptoms.

Yes, one change at a time. I had read that a faulty/dirty plug could cause bad idle.

Years ago with my 1100cc Classic Mini, I ran it for decades on Champion plugs, just for a change went to a set of Bosch plugs, immediately a bit of insulator fell off the plug. Amazingly engine was still OK after this. I still have the 1962 Mini (bought it in 1968) and put in a Morris 1100 engine, modified with 12G295 head, duplex timing gears and a single 1 1/2" SU, 3.44 final drive.

The car would easily exceed 100 MPH, still have the Mini.

That was sheer bad luck with the insulator on the Bosch plug - chances are it had been dropped in the shop or somewhere between manufacture and purchase at least.
I had a set of Champion plugs once, lasted about 70 miles. Never again! Also known so many of them misfire from new in others cars that i wouldn't dream of fitting them to anything i owned except in an emergncy - which was why the set i had for 70 miles were fitted.

These days i only use and recommend NGK plugs, had a few "less than good" experiences with Bosch plugs and since i've discovered Honda PGM-Fi and its intricacies, have come to the conclusion that Bosch Jetronic and Motronic isn't as good as it's made out to be!

Sounds like some very useful mods on your Mini (a proper Mini, unlike the new one!), Minis aren't my thing (i find the driving position uncomfortbale) but if i had one i'd be tempted to do very similar but with the 1275cc lump rather than the 1098 and either a twin sequential choke Weber (32/34DMTL or similar) or a pair of 1 1/4 SUs, LCB manifold and a slightly sporty sounding stainless exhaust system.

Take out the electric idle solenoid from the carburettor , pull the jet off the end and look carefully for dirt , I assume it goes ok once you get going and the trouble is only when idling?
There should be an in-line filter in the hose between the pump and carburettor , it was a service item back then .. be very careful when tightening the solenoid , not very tight ...


With the ignition on take the wire off the above solenoid and touch it back on and off a few times , there should be a defined click each time it opens and closes .

Yes, standard Mini seats and driving position are uncomfortable. Actually my Mini has a 1275 unit in it now (from a Vanden Plas 1300, single 1 1/2" version). Not really any more performance than the 1100 (a particularly good build, which I still have.

I did have a Vanden Plas 1300 (twin carb version), beautiful car with all that wood and leather, would move quite fast too. Gave the car away, fool!

Thank you, I'll have to look at the manual to see which this is. I think there is only one electrical wire to the carb, and I thought that was an anti run on thing. The main trouble is idling, but the car is a bit hesitant to drive above idle.

Yes, there is an inline filter, I had though of replacing it. Looks clean, but has been there many years. I'll look for one on ebay.

Its official name is an anti-dieseling valve, also called anti-run-on solenoid, idle valve, idle solenoid and a few others. Usually if it's playing up it will stop it idling completely and also prevent starting, not let it start and idle roughly. Usually they're one of those things that either work or not, no half measures.

Usually if the valve plays up, driving above idle is ok but it won't idle and won't start without throttle.

Thank you, car starts from cold (with choke of course, and that gives fast idle). I do have somewhere one of these valves with the tip cut off. I believe that this was a mod done when the valve fails.

Today, checked the anti-dieselling valve and it clicks when disconnecting the lead when ignition is on. Also disconnected the lead to it when engine is idling, engine stalls, so valve appears to be good. Also removed it from car and applied poer, seems to work OK, gave it a clean away and put it back. Car still idles badly.

I was fairly sure it wouldn't be that valve which is why i didn't mention it beforehand.

Something that did cross my mind is it could be a partially blocked main or idle jet in the carb, often they can be cleared by getting up to ~40mph then changing down to 2nd and maintaining the speed, close the throttle for a few seconds then literally floor it as fast as possible then repeat.
The sudden shots of vacuum hitting the jets as the throttle is opened quickly can often clear a jet blockage but you need fairly high revs and hence vacuum to do it.

For now i'd pursue the condensation idea as that seems the most likely.

Although the valve seems to be operating OK now, I think I had problems with it many years ago.

I also thought of a blocked jet, already tried your suggestion.

Never taken a jet out of a Webber before. Hope I don't have to.

As you say, I'll pursue the condensation thing. Not had my travel out in the car today.

Are you sure yours is a Weber? Fairly sure they were all Solex and/or Pierburg-Solex on the 340, especially with the anti-diesel valve.

If it is a Weber, it's fairly simple to remove the idle jets (they screw into the side of the carb at the top of the venturi usually) but the main and air correction jets will need the top half of the carb body lifted off and a new gasket (preferably) fitted.

The main jets are normally accessed from within the float chamber and are at ~45deg angle from vertical at the bottom of the float chamber adjacent to the venturi they serve. The air correction jets sit in a drilling that connects via the emulsion tubes with the main jets which also draws the fuel up and into the "spray bar" (can't remember the correct name for these, Auxiliary Venturi i think but could be wrong) that sits in the actual venturi.

All fairly simple and easy as long as you're methodical on a Weber. Solex are a French manufacturer so expect some Gallic influence but usually a similar construction, might find the jets aren't removable and are cast in the housing though.

Hopefully it's my first suspect of condensation, especially as you've already tried the jet clearing trick.

https://www.carb.parts/pdf/Exploded_...4_DMTL_USD.pdf

That link is useful as it shows the exploded view giving a good idea where everything is.

Thanks for the above. Well, the carb is a Weber, says so on it! Otherwise I would not know!

Started engine again, same rough idle.

Thoughts I'd take out the anti-dieselling valve, tested it again, works. It has an O ring seal on the threaded bit, it looked a bit compressed, so put another on as well, took the advice and did not tighten valve up much. Started engine, went up to about 2000 RPM (I had days ago adjusted it up to stop car stalling). Unadjusted idle screw, probably to where it had been prior to this problem, engine idled nicely at about 900 RPM. Continued running engine for about 20 min, all seems OK. I can't really understand this!

I will probably take the car for a good run tomorrow and report back.

Some boring pics of 340 carb below.

https://live.staticflickr.com/65535/...8bf7bc91_b.jpgDSCF0220 by A60man, on Flickr

https://live.staticflickr.com/65535/...a76a3e04_b.jpgDSCF0221 by A60man, on Flickr

https://live.staticflickr.com/65535/...ff07ef63_b.jpgDSCF0222 by A60man, on Flickr

https://live.staticflickr.com/65535/...ea809546_b.jpgDSCF0218 by A60man, on Flickr

https://live.staticflickr.com/65535/...5655d730_b.jpgDSCF0219 by A60man, on Flickr

That definitely looks like a Weber conversion, i'm wondering if what had happened was the "O" ring on the anti-run on valve had perished and was admitting air - essentially a small air leak, just enough to make it run excessively lean.

When you removed the solenoid for the anti-dieseling/run-on valve, does the plunger in it have a conical tip?

If so, is it gummed up around the edge where it seals the airways inside the carb off?

No, the original O ring on the valve was not perished, just a bit compressed, put another on top. Yes, tip of plunger was conical, no gumming up.

I will probably drive the car a few miles tomorrow.

For now, thanks to all.

The carb is a Weber DIR as fitted to the later B14's

The most common cause of rough idle is air leaks with that most often being carb base warpage. Testing for air leaks is the very first step.

Your problem could relate to the fuel and could be worth running off and filling with some branded fuel to prove one way or the other

I did a sort of air leak test early on, just sprayed WD40 around carb / manifold joint. Did not find anything that way.

Did you pull the idle jet off the end of the solenoid and check it for dirt as I explained yesterday ? It sounds as if you might have disturbed the dirt when you removed the valve ..

Now to clear up some misunderstandings ..

ALL B14's from 1976 to 1991 had the DIR Weber carburettor which is a very good quality carburettor which does not suffer from wear , there were several variations over the years ...

The B14 DIR never had problems with a warped base , that could happen on the low quality solex used on the 1.7 engine , mainly by being overtightened my ham fisted people ..... I must have flatted off the base of several hundred of these carburettors when the cars were current !

The 1.7 engine had the rubber pip on the end of the idle valve that could stick when old and the car not used for a period of time hence the tale of the tip being cut off in an emergency to get you home . The idle jet itself was screwed into the side of the carburettor and if blocked was replaced as you could not get inside behind the jet to clear it ...

The idle valve is also an economy device , it shuts off the fuel when your foot is off the throttle over 1200 rpm .... this function was fitted around 1986 ...

There was a sort of brass bush on the solenoid valve, I did remove it, it was clean, but washed it in WD40 anyway.

My car is a 1.4 GL 1989, and I have a vague recollection that the previous owner may have fitted a replacement carb. I have had the car over 10 years and generally, it has run very well.

I did not know about the economy feature of the valve.

your brass bush was indeed the Idle fuel jet , you need a magnifying glass to see if there is anything in it , and try to look right through the centre at daylight ..

Thank you, I nearly lost it when it fell off!!

Back in the days when I used to worry about having my 340 nicked I wired a hidden switch to this solenoid. The car would start, run for a few hundred yards then stall, and stall again. Caught me out a few times too.

Do an LPG conversion. All the stuff about blocked jets stops being an issue. Lovely engine bay pics, all those lovely parts to salivate over...

It sounds to me like an air leak at idle. Usual symptoms are fine running at speed when the quantity of extra air won’t make a difference but at idle it significantly weakens the mix. A place worth checking is the brake servo. It draws its vacuum from the manifold and any leaks in the diaphragm will dilute the mixture. A simple test is to block off the pipe and see if matters improve.

After I've finished a cuppa I going out in Volvosaurus, 5 miles there, some work for a couple of hours, then 5 miles back. I report back later today. Not paid work I'm afraid!

My nephew is currently installing a Tesla motor in an original mini. Complete rust proof of body shell and the rest and a massive bank of batteries in the rear seat. Very original.

Just to clarify, are you using the words "Tesla motor" as a generic term for an electric motor or is it a genuine Tesla motor?

If it's the latter that thing will be seriously mad, the Tesla itself is mad enough in terms of performance but in a Mini that only weighs a fraction of a Tesla that will be scarily quick!

I did quite a few LPG conversions on 300's in the 80's Very successful , I still have the parts in the attic with the torpedo tank , as they were removed when it became uneconomic in the 90's , it would be transformed these days with electronic control and a low pressure turbocharger ...

This is very interesting, would like to know how this progresses. Some time ago I did a post here suggesting electric for the 340. I think it would make a great conversion. I have a Riley Elf Mini too, more space in the boot for batteries!

The 300 series would lend itself nicely to an electric conversion because of the rear transaxle. Either the space the transaxle takes up could be used to house the motor directly driving the rear wheels (perhaps through an integral gearbox) and the space and weight taken by the engine could be taken by batteries instead or alternatively the motor in the engine bay (with some batteries to balance the weight) with the majority of the batteries in the rear in the space the transaxle used with a different replacement rear axle.

On another forum, someone started a thread about converting classics and asking for suggestions of suitable classics for EV conversion. My suggestion was the NSU Ro80. Assuming an intact example could be found that hadn't been converted to Mazda RX-7 power and that the original ****el engine was dead, fitting a motor in place would be a good conversion as the rotary engines had a noise not unlike an electric motor working hard.

The possibilities are endless but i have a feeling that EVs will only be a "BandAid" on the environmental problems and a better, cleaner fuel will be found enabling the continued use of IC engines with little or no modification and much cleaner emissions.
If there was an easy way to create Browns Gas aka HHO aka Heavy Hydrogen aka HOH and other simlar names, that would be near perfect but at present it takes more energy to split the water atoms into hydrogen and oxygen than would be derived from burning it.

Meanwhile LPG is as near as we can get to that kind of cleanliness and only 50-60p/L. As you have a carb engine, it is much easier to fit than an injection engine and would be a good move IMHO.