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MG Midget and Sprite Technical - not starting......again

So in my stupidity I took the frogeye out the other night for a run, and it broke down ! I think it got so hot that the fuel started evaporating and causing vapour lock, as it just started chugging then stopped altogether. its done this before and usually starts the next time I go to it, but not this time, the battery was weak and wouldn't turn over the starter, so I took that off and charged it overnight, put it back on this morning, so now I have spark and fuel, but no starting ! I think i may have flooded it trying to start it the other night, surely if I did, it should have evaporated out by now?

Any suggestions are welcome as I am moving in 4 days, and really want to avoid having it towed to the new place!
RUS(59SPRITE)

Rus -
When they flood, the only cylinder open to atmosphere is the one with the exhaust open, a long and tortuous path - which may also be full of fuel vapours.
Pull the plugs and see if they are wet.
If so, or even not, crank it over plugs out a few turns, to blow the fuel out and ventilate. Disconnect the coil first so random sparks don't ignite the escaping fuel vapour - don't ask! Clean and dry the plugs; the most effective way is to heat the firing end with a propane torch. Have a beer while the plugs cool and the cylinders dry out. Reassemble and light it up. If it doesn't start, did you plug the coil back in? - Don't ask!

This week's weather is prime time for this trouble, most especially if your gas is from a few weeks ago before the shift to summer blend.

FRM
FR Millmore

You said you got spark and fuel and no start and its badly over heated ...id recheck the firing order and do a compression test.

Prop
Prop and the Blackhole Midget

I took the plugs out to have a look, not pleasant in there!

thick black gunk all over the plugs, am guessing this is less than ideal.






RUS(59SPRITE)

....so I put some rag down the bores, what cam out smelt petrolly and oily, I have now left the plugs out to see if I can get it a bit dryer in the bores.




RUS(59SPRITE)

Russ-
Can't recall the history/condition of your car - refresh?

Plug looks typical of oil burning followed by flooding.
What is the plug heat range? (Looks like Champion, should have a "12" in the number as in UN12YC- they keep changing them!)How long in use?
Condition of oil? thin, or especially overfull, which may indicate fuel dilution due to carb problems or a lot of low speed cold running with the choke on.

Good news is I've seen plugs like that that can be torch cleaned as I said before that then work fine for years. It all depends on what caused the fouling to start. I've had cars where I had to clean the plugs every few months if I drove it in town, but not for years of hard highway driving. I've had cars with plugs like that (using a qt oil per hundred miles) cure themselves after 1-500 hundred mile of full throttle thrashing, and never have a problem again (and using no oil between changes).

Right now I have a lawnmower that is worn out to the point of fouling such that you cannot see the electrodes at all, uses 1 qt oil per tank of gas! I torch the plug one or sometimes twice per fill, when it gets hard to start or starts firing every other time.

FRM
FR Millmore

Fletcher,

The car was restored 7 years ago, only 4000 miles since, the engine is standard tune with twin su's 1 and 1/8ths.

The oil is a little black now, so it might be time for a change, its been a couple of years since this was last done.

The spark plugs are champion and are only a year or so old.
The car does get a lot of use in town, with barely any highway miles.

I cleaned off the plugs, and got as much of the gunk out of the bores, will go and put them back in and see what the result is.

RUS(59SPRITE)

Engine was rebuilt?

That kind of use is Extreme Severe Service, worse than desert racing. Oil & filter changes at 1000 miles max or every year.

Heat range is critical, what's the number?
How did you "clean off" the plugs?

If you brought me this car I would first change the oil & filter, then take it out for 25 or 50 miles of hard running and give it back to you, probably without doing anything else. And the usual comment after that from customers is "Fantastic tuneup, runs and idles great, but you didn't charge me for it!"

Get it running and drive it!

FRM
FR Millmore

Right, back upstairs again, the plugs are N9YC, and the engine was a fresh rebuild 4000 miles ago, I used a wire brush on the plugs, however I am now thinking its not fuel related, as I tried the spark plug on the block and didn't get any response at all, no spark of any kind, so could this point to the coil failing ?
RUS(59SPRITE)

Im a bit confused...

I thought you said you had spark...whats changed from then to now..???

Make sure the plugs are grounded agianst the block
Next see if the spark plug cables are giving a spark
Next see if the coil is giving spark to the dissy

Prop
Prop and the Blackhole Midget

Prop, turns out I was wrong! What do you mean 'grounded against the block' ?
RUS(59SPRITE)

N9YC are too cold, not helping the fouling at all, especially in that kind of service. UN12Y(C) was the spec for A series normal.

Cleaning with a wire brush can deposit metal on the insulator causing shorting, and WILL NOT clear the oil/carbon sufficiently. Hence the torch trick.
Check spark off the wires, as that eliminates the plug from the equation.

If no spark off wires, check off coil wire. If good then rotor/cap is bad.
If no spark off coil, check for spark at points while cranking. Spark there but not off coil = bad coil
If no spark at points cranking, points are set/assembled wrong, cond is bad, broken lead coil>dist or earth breaker plate to dist base, or there is no power to coil.
If opening points by hand when they are closed = off the cam gives a spark, then all that is right except point gap.

FRM
FR Millmore

Fletcher,

I cannot find any UN12YC spark plugs in Toronto, but can source some RN12YC....would these be ok as substitutes?

Russell
RUS(59SPRITE)

Russ-
Yes. UN12Y was the number for most of the time I was changing plugs by the bushel so that's what I recall. "R" is the resistor version, which you don't need but lots of modern (computer) cars do, but it won't hurt. (C) means copper core, a change from some years back.
Or use the NGK equivalent, which I don't remember the number of.
When NGK first came on the market, they gave us boxes of them to get us to switch from Champion, but my Jaguars wouldn't pull over 4500 loaded, so I sent them back. But all that has been solved now and many people say the NGK are best. I will use either by choice, or Denso, or standard Bosch, but NEVER Bosch platinum trash.
Whatever you use, check the listings/cross ref. as many are wrong. A series does not take the same plug as B series (MGB) which are *N9Y**.
(N)= long reach, (9)(12) = heat range Y = extended tip.
Other pre/suf fixes = confusion

FRM
FR Millmore

I got those, so that will help in the future, I also got a tester, and no spark is present from the coil, so am guessing its a new coil for me !

RUS(59SPRITE)

Hey russ

Try running a jumper wire from the pos side of the coil to the pos side of the battry...and see if you get a spark from the coil

If there is a spark... The problem Is some where from the key switch to the coil, if still no spark... Then the issue is most likely a bad coil

Prop
Prop and the Blackhole Midget

Ok, tonights update....

I replaced the coil, condensor and rotor arm, and still no spark of any kind,either at the plugs or the coil itself.
The battery is turning the starter quite readily with no signs of weakening, I can't think of anything else - anyone got any ideas?

RUS(59SPRITE)

Do the whole procedure as I detailed above.
Random replacement of parts without diagnosis is a good way to introduce multiple problems, a much harder thing to sort.

GRM
FR Millmore

Rus,

with a problem like this you’ve done right by keeping the battery fully charged as a low battery could disguise when you’ve solved the problem

being a bit hard to be kind - it’s as FRM has put go through procedure again and never assume that new parts can’t be faulty and that the parts on the car or previously on the car were the original or correct parts or that those parts are/were working properly

a lot of times a simple bulb with wires is a good tester rather complicating things with numbered readings but with both types of tester you must checker the tester is working before and after every test you do if case the tester goes faulty or stops working thus giving wrong or no results

it’s often good to rule out the forgotten ‘bleedin’ obvious’ like have you got a perhaps hidden immobiliser type of switch anywhere, you already checked fuel is getting through, so it’s electrical and the logical step by step diagnostic like FRM has put is required, check then move on to next step

once you’ve got it going again bear in mind that your car previously had on average done less than 50 miles of mainly town driving and an oil change >>a couple of years since<< is doing it or you no favours, use it more regularly and more miles of open road and the car will get better and you will enjoy it more

good luck
Nigel Atkins

Have you checked for a spark at the contact breakers ?
Ignition on, dizzy cap off, flick the breaker points and look for them sparking.

Have you set the breaker points gap? They gradually close down, you get rough running at first and then eventually the car dies with no spark of life. Check gap is at 15 thou. If you have already replaced them, did you get the insulating washes in the right places?

Check that the ( white / black ? ) wire from coil to dizzy isn't either broken or shorting anywhere.
Guy Weller

Ok, back online now we are at the new house...the distributor cap was worn, so was replaced, the points were also not sparking, again have been replaced (and set correctly),finally there was a small wire inside the distributor broken as well, this was also replaced, the car now starts but is lumpy as hell, it idles, but will not accelerate at all, so is undrivable at the moment.
RUS(59SPRITE)

you've double checked the HT leads for correct firing order and that all HT and LT wires and connections are all clean, secure and protected

dissy cap is fitted correctly and secure at both clips

rotor arm is fitted correctly and fully pushed down into position

and as Guy has put the insulation washers are in the correct order from fitting points
Nigel Atkins

Double check the points setting - may have moved.

R.
richard boobier

This thread was discussed between 23/06/2012 and 11/07/2012

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