MG won't tick over without stalling.

[Shugster]

As the title says the motor runs and seems to accelerate OK but when I stop at the lights it just conks out unless I keep my foot on the accelerator or give it some choke even though the engine is hot.

It only just started when the missus drove to her folks about half an hour away, it was OK on the way there but was dodgy on the way back. I had a spare set of plugs and as they hadn't been changed in years I swaped them out. I checked inside the distributor and cleaned the contacts even though they looked OK, I checked the HT leads and they look clean too. I wanted to check the timing but my bloody gun stopped working just when I needed it DT_Xtremez_25:.

I don't think it is the timing anyway as it wouldn't drift off in an hour after years of being OK, so maybe the carb has dirt in it? There is a fuel filter fitted and as I said it seems to accelerate OK so I'm happy to listen to any good ideas from you old boys who remember carbs and chokes!

 

[needsabiggerfuse]

Try a half turn of '3' in a clockwise direction.

View attachment 12349

 

[Weebl]

Sounds like fuel starvation at low throttle openings.

Fuel filter is an easy check. If that is ok then....
Carbs.

You can try the easy fix and squirt some carb cleaner in. You may get lucky. Don't leave it sat in there though, if it gets to, and sits in, the diaphragm rubbers they might not like it.

Failing that, pull em apart, from the symptom it sounds like you have some crap in the float bowls and down the Pilot screw\idle jet\whatever it is called on your make, but if you have em apart you may as well clean them all.

Is there an idiots guide to removal and maintenance of your particular carbs on the 'net anywhere, would be good to find one so you know how many turns out the pilot screw needs, float height etc.

You may, in whatever guide you find, see that they recommend ultrasonic cleaning. You can do that, but personally I just wash them out under the tap (in bits) to get any visible crap out, I have even used a toothbrush with some fairy liquid to get them clean before, a squirt of Carb cleaner and a good drying out later and I have never, ever had a problem with this not being thorough enough.

If you can, squirt carb cleaner down any removed jets, and down any visible air or fuel drillings in the carb body.

After re-assembly and refitting, if you have more than one carb, you need to balance them. If you need to, add it to this thread and I will show you how to make a Manometer for a couple of quid.

Sorry, not an MG guru so cannot help in that way.

 

[Hot Shoes]

Its 20 years since the money pit but:-

look at the ultra thin air tube running from the carbs (I think) to somewhere??

If it is split or off, the car definately won't run on tickover.




The workshop manuals are in the loft so thats all I can remember, apart from the pointers in previous posts.

 

[busby1971]

Always start with the cheapest and easiest thing first, go for the idle check first, then do all that other stuff.

Sent from my MZ601 using Tapatalk 2

 

[Tin basher]

Take the MG and your credit card to a reputable garage listen intently to the sharp intakes of breath and non binding diagnostic statements from experienced staff of afore mentioned garage. Then return to said garage 48 hrs later and insert your card in machine and collect serviceable MG, simples.

 

[grumpyoldb]

You could try asking on here.

 

[Shugster]

Thanks for the replies. I don't want to turn up the idle setting as that is only masking the problem.
The car was sat in the garage for 6 years but has been used more often in the last 2.
It's a twin carb engine and it hasn't been touched in years, (I bought it as a JT in '96 and haven't touched it apart from Oil changes), so it's long overdue a wee bit of TLC!

I'll look at my manuals and forums and take it apart.

Washing things under the tap is a good idea, (I had a friend who used to put things in his dishwasher and he swore by it... as long as his missus didn't catch him)

 

[John Lloyd]

Try a 1/4 turn back on the jet adjuster screw. It may have crud in it which blocks your tick-over fuel supply when the needle is fully down. When you rev and the needle lifts every thing is fine. Don't forget to check your dashpot oil level is equal.

Ahh, 24 years since the joy of twin SU Dolomite fettling.

I saw one in a car dealers in Wigan last week £1800 for what appeared to be a tasty 1850HL, I was turning back to have a closer look, until I had a word with myself.

 

[pie sandwich]

My '01 Astra did the same thing, all that was needed was a good squirt of carb cleaner, and wipe around inside by the butterfly valve and it was fine after that.

 

[Shugster]

I think I'll go down the spray cleaner route first as spare time is in short supply at the moment.

Do you spray it in while the motor's running or let it soak in for a couple of minutes?

 

[MingMong]

Many moons ago, I had a VW Jetta with a similar problem. It turned out that the car had an idle solenoid that kicked in when the accelerator was released to keep enough fuel flowing to maintain idle revs.

The fuse to this was ruptured, so every time the car was supposed to idle, it stalled. Don't know if your MG would have similar, but could be something to look into.

 

[Shugster]

It was built in '71 mate, so it's just pure mechanics. No fancy stuff in those days!

 

[Barch]

Simple things first ...

Air Filter?

Fuel Filter?

Check the HT leads in the dark, if the insulation is breaking down you will see them arcing.

Inlet Manifold Vaccuum hose check not losing vaccuum.

Inlet Manifold Vaccuum hose check not blocked.

 

[Lamptramp]

Simple things first ...

Air Filter?

Fuel Filter?

Check the HT leads in the dark, if the insulation is breaking down you will see them arcing.

Inlet Manifold Vaccuum hose check not losing vaccuum.

Inlet Manifold Vaccuum hose check not blocked.

I would give the vacuum automatic advance and retard pipe to the distributer a good looking at as well.

If it is that old check for feathering on the points.

 

[Goatherdingsplitter]

The carbs should have oil-filled dash pots to damp the movement of the needle. If they have dried out in storage, you will get erratic running. I little engine oil, might just restore your tickover!

 

[gemarriott]

Its 20 years since the money pit but:-

look at the ultra thin air tube running from the carbs (I think) to somewhere??

If it is split or off, the car definately won't run on tickover.




The workshop manuals are in the loft so thats all I can remember, apart from the pointers in previous posts.

Vaccuum advance rings a dim and distant bell

 

[Stevienics]

...or set the tickover to 1200rpm. Sounds a bit weird at the lights but it doen't stall.

 

[Shugster]

I went to take the carbs off today and found that the K&N air filter was loose on the rear carb allowing more air in as the long bolts were loose and one had somehow found its way in to the air inlet! I lifted the pistons and both seem smooth in both directions. I've cleaned the air filters and am letting them dry out now. Once it's all back together I'll see if I have to go for the full strip or not.

 

[Shugster]

I refitted the airfilters after Oiling them first, (Yes, I said Oil... that was a new one on me too), and the car runs fine and ticks over nicely at about 800 RPM.

However, there is still an open question that is hard to answer. The chap who restored the car before I bought it told me that he put a different camshaft in to it to increase performance, there seem to be quite a few variations in camshafts so I'm not sure whether to just stick to the original specs on dwell angle and valve clearances or not.

To get an idea of the cam I would have to clock the rockers to find the high and low points, that is possible as the calibration gear I have from work is calibrated to 0.1um but it would be right pain in the derriere to do.

Does anyone know anything about the subject who can give some rule of thumb advice?