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MG Midget and Sprite Technical - Weber 45, flooding?

Spec:
Weber 45, Filer king pressure regulator, facet pump.

I'm suddenly getting starting problems. Hot start not cold, ie when I've left the car an hour or so.
Normally she starts like a dream: ignition on, 4 pumps with the pedal and fires first turn.
Now, she's turning over & over without starting. It seems to catch when I let go of the key (as I'm giving up)
Strong smell of petrol on these occasions.
Yes, I've tried just turning her over without touching the throttle...
I cleaned the plugs.
any ideas out there?
(engine bay photo attached)




Mallorcaben

Is your choke on or sticking? Make sure its definetly off by manually closing the lever on the carb next time.
b richards

Cold start technique on my Sprite with a Weber is 3 pumps or 5 pumps if it's very cold.

However, the hot start technique has always been to gently easy the throttle to flat on the floor, hold it there and crank till it starts.
Daniel Thirteen-Twelve

<<Now, she's turning over & over without starting. It seems to catch when I let go of the key (as I'm giving up)>>

That would make me suspect an ignition problem rather than fuel. Sounds like you're only getting a spark when you turn the ignition off.
David Billington

Could be Dave but equally the moment you release the key the battery voltage increases so will the spark voltage. Needs investigating.
Bob (Robert) Midget Turbo

Have you changed anything lately?
Brad (Sprite IV 1380)

Faulty Coil would be my first thought... What fuel pressure are you running the Weber at?

Mark.
Mark T. Boldry

The problem is that when a 45 dcoe floods neat fuel runs into the cylinders. Could be that when you release the ignition key the extra power manages to ignite the rich mixture. I think you need to check a couple of things that are simple. Check that the fuel inlet valve (needle valve) is closing correctly and also quickly check that the float pivot has not slipped out of one side of it's pivot point. I have seen that happen on at least 3 occassions albeit over a good number of years.
Bob (Robert) Midget Turbo

points closed up?

anywhere but Mallorca and I might suspect damp inside the dizzy cap too

and of course there is always the....

The spark isnt working hard enough!

If the jets havent unscrewed themselves or the filter hasnt dumped sh-t into the opened up jets and tubes the carb losing its settings is at best unlikely.

if a ballast resistor is fitted it might show similar symptoms if it went open circuit
Bill

Bill,

Points closed up is sort of what I was thinking having experienced it on one occasion where the heel of the points wore rapidly, and I suffered from a similar problem with month old points. Ran fine when cold but started to misfire when warmed up, Ben hasn't mentioned that symptom, but it's possible. The firing on ignition off made me think the coil was powered but not firing, hence possible no points gap when hot. It surprised me that the engine would run seemingly well with virtually zero points gap but it closed when warmed up to show problems.
David Billington

In t'AA we were always encouraged to "fit points, then set points, then before any other treatment lift the dipstick out of its 'ole and let the end drip onto the dizzy cam where the points will rub when the engine is operating"

It isnt JUST new make points that would wear down rapidly aganst some dizzy cams, some cams would make it happen just by sharing a dizzy with a new set...

The dripped oil was enough (usually) to do the job of lubing the cam lobes
Bill

I agree with Bill on that one, i've had new points wear out in 500miles due to insufficient lubrication.
Mallorca isn't that dry this time of year so could be condensation.
Best go visit Abaco for one of their special mixtures & have a think about it.
Brad (Sprite IV 1380)

* Choke working & returning fine.
* Not changed anything, but problem seemed to get worse.
* Luminition electronic ignition, no points.
* The starting as I let the key go only happened twice,
not sure if its relevant.
* Starter spins fine (modern non pre engage starter,
best £200 I ever spent!)
* Bill mentioned damp. Its not stopped raining here for
a month! Very, very damp. Liberal use of WD40.

She normally starts so well, but it just turns & turns. Not failed to catch yet, but I'm sure Im going to get stranded soon.
The only different thing Im doing at the moment is not using the car every day. I only work in the summers here in Mallorca, In the winter I hibernate! I use her every few days. But normally I can leave her standing for 2 weeks when I go to the uk & she stars fine.
Its baffling me.





Mallorcaben

Hi Ben

Starting when you release the key normally means:

1. Somehow the ignition has become (is becoming) disconnected when the key is turned to the start position (starter switch us deteriorating); stick a bulb on the coil +ve (other end of bulb to ground) and check it stays on when the starter is turned (it may dim a bit - that's usual)

2. The coil is not delivering a fat spark to the plugs when the starter is turning - of course there is some lessening of the spark when the starter loads the battery, but this is normally not significant; so:

- does your coil use a ballast resistor? It's in-circuit when ign is on, but shorted out when the starter is operating; maybe the 'shorting out' part is not working?

- the luminition 'light' is losing brightness (I'm not a fan of the complication of Luminition; the 'bulb' inside the dissy who's light is 'chopped up' for the sensor the other side of the disk can fail suddenly as well as deteriorate slowly); try replacing with points (mind you, this could mean a backplate change and you may not have the original back-plate; another reason not to use Luminition!)

- there are loose connections in the ignition system... check security of call the white and white-black connections / spades

- check also engine earthing straps, incl tightness of bolts etc (your long-stroke engine will cause many bolts/nuts to shake loose)

- dampness of HT system, as other replies.

Whatever you do, don't adjust carb/ignition etc; find the fault!

A
Anthony Cutler

Ben,
check the glass bowl of the filter king, the valve fell out of mine & caused flooding.
Brad (Sprite IV 1380)

Although this COULD be a carb fault I doubt it

You need to do the proper tests for ignition faults

first if you have a meter

resistance through coil at LT terminals up to (3 ohms or so)

check voltage at BAT side of coil then at SW side of coil (this is to the dizzy) volts in the volts out

without volts out the dizzy cannot fire the mixture

check voltage where the LT wire reaches the dizzy

If you have volts (numbers important but not as important as having SOME!)

check out the inside of the cap and the inside of the Lumenition unit, muck of any sort can diffuse the light the sensor uses to signal a firing moment

Google Lumenition they do have a downloadable test sequence you cn try for the system (at least they used to!)

do check the connections from loom to Lumenition and to the backplate earth wire

Simplest check of all:-

King lead from coil to dizzy, unplug from dizzy and push the end onto a used spark plug. Rest the plug on the metal of the engine

(somewhere earthed to the car, not for God's sake on the battery earth. The only time I saw an idiot try that I almost had a heart attack!)

get somebody to crank the engine on the key while you look at the end of the plug. You should see a spark between the outer and centre electrode

if you do, take out the plug put the king lead back into the dizzy cap and put the plug on any pluglead, repeat the test with the plug on the engine block.

If you have leads screwed inside the cap (old style leads and cap) use a spare old plug lead in the nose of the coil to perform the test

This test takes all of three minutes, costs nothing and confirms before beggaring about whether you have an ignition problem or not

If spark at first test but not at second part, maybe there is a rotor arm fault

If there is a spark at the second test, then there might be a fuel problem.

if there is, unbolt the carb and manifold and post it to me in time for Christmas and I will send you a very nice SU HIF44 and Titan manifold in fully working order and suffer beggaring about with yours while you dash serenely around the Balearics

Gosh, the things I do ...

:-)
Bill

looks like you have been reading the MGCC midget register website Bill.LOL only kidding

Here is another version of the kind of tests Bill is refering too

http://www.mgcars.org.uk/mgcc/midgetreg/workshop.shtml
and click on the link for ignition system
you could also look at how to use a multimeter
Bob (Robert) Midget Turbo

''In t'AA we were always encouraged to "fit points, then set points, then before any other treatment lift the dipstick out of its 'ole and let the end drip onto the dizzy cam where the points will rub when the engine is operating"''
You were lucky, all the AA told me was to stop drinking.

:-)
Brad
Brad (Sprite IV 1380)

This thread was discussed between 14/12/2008 and 16/12/2008

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