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MG Midget and Sprite Technical - Engine won't fire

Hi all,

Recently reintroduced the engine to my 1977 1500 after nailing a type 9 gearbox onto it. Everything back in, everything reconnected but the engine won't fire. Turns over fine, and when the carbs are charged with some fuel it will fire and splutter to a stop. fuel pump works, ignition works (I think otherwise it wouldn't start at all right?) and fuel is fresh. Guessing it must be the carbs but they seem fine. What am I missing? (apart from a working car!)

Thanks in advance for any help.
James Ballard

It fires when you pop fuel into the carb and then dies... suggests that the ignition LT isn't connected unless you're cranking?

A
Anthony Cutler

There is definitely power going to the leads, word to the wise, do not ask a disinterested girl friend to assist you in the garage especially if her hand is on the ignition when you pull a lead to check connection. Nice little electric shock tells me there is power going to the plugs!
James Ballard

Not quite sure of the logic there Ant? but I thought it sounded like fuel not getting to the carbs?

When James primes the carbs with fuel it runs/fires then the fuel runs out and he would then have to prime them again, is that the case James?

Try dripping fuel into the carb throats as you turn the engine over. It shou;d run.
Robert (Bob) Midget Turbo

take the fuel line off at the carbs end, place into a container and crank engine - to check pump is functioning properly.
David Smith

Done that David. It does pump but I'm not entirely sure it's a regular flow. Seems to spurt. Thinking it could be gunk in the line? New filter?

Bob, tried pouring in fuel as it turns (also spraying a can of 'Start You Bastard' into the carbs) but same problem. As soon as it picks up the starter motor disengages and it dies.


Also, noticed the cables to the battery getting very hot as I turn it over, related or normal?
James Ballard

James,
check the ballast wire feed to the coil.
The correct way is to ensure the engine is stopped with the points closed. Use a volt meter on the +ve side of the coil. You should get a reading around 6v with the key in the "run" position and 12v in the start position.
The quick way is to run a new wire direct from the battery BUT ONLY FOR A TRIAL PERIOD or you will burn out the coil.

MGmike
M McAndrew

Thanks mike, was beginning to think the ignition system was the culprit. I'm a bit lacking in the electrics department but will investigate tonight and report back.
James Ballard

Ok. Just about ready to lock the garage, seal it up and inform everyone that there is NO garage.

Tested the coil. Fine. Tested the ht circuit, all sparking, in sequence and at correct voltage.

Fuel pump is pumping.

Engine is not running!

Got it to run after priming the carbs with petrol and judicious fettleing of the throttle but then it ground to a halt and locked up. Tried the starter motor a couple of times and it freed up.

What is going on?

Could there be a block in the carb itself preventing fuel getting through?
James Ballard

James,
look on the bright side, you did get it running for a while so it can't be that bad...... famous last words...

At least that should just about eliminate a number of possible causes...

Need to you to explain "after priming the carb ... and judicious fettleing" in a little more detail. How and what exactly did you do?
And I am a little concerned about the "locked up" are you saying the engine seized up for a short while or just that the starter motor didn't engage?

MGmike



M McAndrew

Hi Mike,

Primed the carbs by spraying petrol into it and fettled the throtle by adjusting it constantly.

The locking up is a concern. I've just fitted a five speed gearbox and reading some other threads shows that some type 9's have a longer input shaft that can cause problems. But it does turn most of the time so surely not the culprit?

James Ballard

Sure this locking up isn't a starter problem, or just a low battery if you haven't run it properly for a while?

As to starting, then dieing, what air filters do you have on it? Are they fitted correctly so as not to block the air balance holes. Is your firing sequence correct?

Last thought - are you sure it isn't flooding? With the mechanical pump as soon as the engine is running and the pump operating at speed, it will flood the carbs, splutter and stall if the a float or needle is not closing off and limiting the fuel supply. This is different from an electric pump which operates independently of the engine and will flood it before the engine starts, whilst a mechanical pump floods after the engine starts..
Guy

Floats appear to be rising and falling properly.

Battery is fully charged and has a jump starter battery pack on it.

Could be the starter but hear it disengaging as it starts up.

Possibly flooding but the adjustments on the carbs are unchanged since it was running correctly.

Could it be a blockage in the carbs? When I took the fuel line off the swirl pot it seemed to be under pressure as I had a gush of fuel from the pump end. Also here a squirting noise when the engine stalls as if fuel is squirting into the chambers.
James Ballard

I wasn't meaning flooding due to wrong carb adjustment. I meant flooding if there is dirt or poor seating of the needle valves allowing the fuel to continue to flow into the float chambers. This causes the fuel level to be too high in relation to the jet in the carb mouth and flooding which will then cause it to splutter and stall.

Take the tops off the float chambers, remove the needles from the fuel valves and make sure that the valve seating is clear. Visually check the conical surface of the needle - they should be smooth with no wear ridges.
Guy

Thanks Guy,

Checked the needles last night and the chambers were clean (if a little petrolly) and the needles were clean and smooth. I am beginning to think that the fuel delivery has to be the problem. Should the fuel line be under pressure? (re my previous post) or is this normal?
James Ballard

If the carb float chambers are full the needle valves are then held shut by the floats, and resist pressure from the pump. This will mean that the fuel lines between the pump and the inlet to the float chamber is under a bit of pressure when the pump is operating. When you stop the engine the pressure will gradually dissipate but this will take a few minutes.

Another thing may be worth checking - that the short fuel line between the bottom of the float chamber and the jet itself are also clear of any debris. Grit in there will play havoc with the mixture - either starving it if fuel or conversely, preventing the jet needle from dropping fully down and causing flooding.
Guy

Thanks Guy,

I've never taken off those hoses, is it easy? How do i then clean them? Blow down it? Soak it in petrol?
James Ballard

Slacken and remove the small brass nut on the bottom of the float chamber. Have something handy to catch the bit of petrol that drains from the carb. Pull the pipe out. Take care not to loose the small plastic collar and washer. At the other end remove the very small Phillips screw that connects the choke lever to the just. It screws into the plastic so don't overtighten when replacing.

Remove the jet tube and blow through it / rinse in petrol or whatever you need to do to make sure it is not obstructed (watch out again that you don't loose those small collars. Reassemble. Don't overtighten the small brass nut, it just needs to nip up. To tight it will damage the seals and will for ever more leak petrol!

You may be able to short circuit the job by just removing the choke lever screw and pulling the bras jet tube off, leaving the small hose undisturbed. Let a bit of petrol run through it from the float chamber to wash it clear.

Your problem, of course, may be nothing to do with this! ;-)
Guy

Thanks a million Guy, much appreciation going your way!

Will give it a try tonight.

Have emailed Rob multisheds to try and enlist his assistance but it's a busy time of year for him, I might be able to lure him over with the promise of beer or the like ;)
James Ballard

Yup. Just got the Email, JB.

I'm on nights (Friday 4pm until Saturday 6am and then Saturday 7pm until 8am Sunday) so will not be conscious during normal office hours until the start of next week.

I'll put money on either the solenoid being knackered and not firing down the main 12 volt feed, the main feed to the coil being broken or the ignition module not being compatible with your revcounter/switch configuration.

Can you see if there is a small serial number on the solenoid somewhere on the steel casing? How is the electronic ignition wired in?
rob thomas

Ignition timing off?
I've had it where an engine was a pig to start and 'locked up' sometimes on cranking.
Timing was far enough out that the pistons were getting blown back down too soon and trying to make the engine run in reverse...till it got spun up.
Didn't like throttle at all either.
Advancing the timing by about 1/8 a turn on the dizzy had it going well enough to time it up properly (dynamic).
Taught me a lesson about being lazy and not static timing the engine 1st.
RoadWarrior

hi Rob,

all i can see on the solenoid is 4.S.T. REG D DES

The electronic ignition is wired to the ignition switch and dizzy with a box of tricks in between. As I've said before, the plugs spark, the voltage is high enough.

Tried setting the static timing but now that I have a five speed box on it the gear ratios are too high to push the car in gear to get the timing marks in place. cant get it to turn by hand either.

Tried turning the dizzy 5 degrees advance and now I'm getting nothing, put it back to where it was and cant even get the semi splutter i had before :(

I'm off to put a bigger battery on it (thinking a 015 unless anyone can suggest a bigger one that will still work) and trying again. My battery (038) seems to be on its last legs now.


I'm stumped!
James Ballard

New starter solenoid ordered. Worth £10 just to rule it out. any other suggestions gratefully received though!
James Ballard

Just be careful with the new solenoid - I ordered one because the original would (very rarely) sometimes not switch - taking a couple of turns to finally start the starter. It had only done it about twice in a month or so, but like you I thought shame to dilly dally for a tenner. New one arrived and it didn't switch at all. Checked wiring and connections etc nothing to be done. Had to get them to change for a new new one, which (touch would) has been fine.
OrangeSpyderMan

"touch would"

lol - sorry, tired, and missed the 5 minutes correction period :(
OrangeSpyderMan

James,
why are you changing the starter solenoid? Is the engine not turning over now?
You will need to get the static timing set somehow. I'm surprised you can't get the engine to turn in any gear! No matter what gearbox is fitted you should be able to move the engine in one of them. If all else fails get a 46mm socket on the crank bolt (you'll need to take the rad off, remove the engine mountings and lift the engine on a jack to get it in!)
Please give some details on the make of electronic ignition you have fitted?
It sounds like you need to go back to first base and set the engine, carbs and ignition up again.

Daft question, you did put the earth strap back on between the block and body when you put the engine back in?

I don't mean to upset you but it sounds like you need to draft in some experienced help. Is there no one local that can help?

MGmike
M McAndrew

Hi mike,

Rob is my local expert and his suggestion that the solenoid may kapputen.

Hoping to abduct him and lock him in my garage until a working car rolls out!

The lack of movement in gear does worry me though, just hoping it is the gear ratio and not something more dreadful .

Have ordered the correct size spanner for the crank bolt (don't quite have one big enough at the mo) and will then be able to sort the timing.
James Ballard

James,
In your very first post I understood you to say that the car turned OK on the starter motor, fired, ran for a moment but then spluttered to a halt. I also thought you said that it stopped running after the starter motor had disengaged and was no longer "helping" the engine to turn. Later you seemed to be having difficulty in getting the starter to spin the engine properly.

From this I would have thought that the ignition side and solenoid is all OK otherwise it wouldn't have spun,fired and run. The starter problem is a secondary fault as the battery was beginning to run down (or maybe poor cable connections).

With a better or re-charged battery are you now back to the first scenario of firing but not then continuing to run on its own? This sounds to me like a fuelling problem - possibly over-rich mixture. But have you checked that the firing order on the HT leads is correct?
Guy

Not only the firing order, --- but someone also mentioned about the ballast resistor and LT circuit.

So, it runs whilst the starter circuit is engaged, and dies when the starter circuit is not engaged.

I don't have a ballast, but from my memory of a car that did, I seem to recall that you run 12 volts to start, then 6 volts to run.

If the 6 volt circuit is dead, then the coil will not charge and the engine will stop.

Do you have a ballast in circuit? if not, then of course ignore my post as another red herring.
Lawrence Slater

This thread was discussed between 11/07/2011 and 24/07/2011

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