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MG Midget and Sprite Technical - GARGH!! She just...won't...START!

ok...help me PLEASE! midget 1500

When I tried starting last time, with the Zenith carb, she ran. With the Twin SUs nothing, but I'm getting gas! Plugs get wet and you can smell it!

1. Cabs are sending gas.
2. Got good spark.
3. I've gone back to basics and set static timing according to 3 different books all saying the same thing. (set to TDC. made sure #1 was on power stroke etc)

No matter what I do I just can't get the car to start. You can hear compression, but she just ain't firing. Tried reversing just in case I was 180 out and got tons of backfire through the carbs.

The only weird thing is: when I pull the distributor out and note to position of the "drive cog?" it's not at 8 and 2, more like 10 and 4. And...when I turn the engine by hand with the distributor cap off I see a spark.

Anyone? please tell me I've missed something obvious. After 17 years, she's THIS CLOSE to being on the road again...

Chris
1975 Midget 1500
Chris Elkerton

Yep.
Since the drive dog is not at stock position, you have the plug wires 90 deg out. Set it on timing mark, check which cylinder is on compression = both valves have clearance. The distributor terminal the rotor points at is the one which goes to that cylinder, Follow around by firing order in the direction of distributor rotation.

FRM
FR Millmore

ok. I just went back and checked, ignoring timing marks and everything. With Valve cover off, I checked to make sure #1 piston was at full compression at the top of the power stroke. #4 cylinder is rocking between #8 and #7 valves (exhaust to intake). At this point, assuming #1 cylinder is at the top of the stroke, the drive cog sits at about 9:30 and 3:30 and the timing mark is at 8 BTDC.

So if I line up my timing mark to TDC, the drive cog still isn't in the right position, according to the Haynes diagram, and the Official handbook.

I've tried setting the plugs at #1 based on the visual test and where the rotor is facing and going 1-3-4-2 in a counter clockwise direction. Nothing. Then I set it up based on the timing marks. Nothing.

I've tried every possible configuration and I get no HINT of firing up. Still nice bright spark at all 4 spark plugs when I pull a plug and hold it to the engine block!

What am I missing...besides my sanity?

Chris Elkerton

If it backfired at 180 out, everything is right save the basic timing.
My old Spitfire Haynes shows the drive slot at 9:30-3:30, big side down. TDC #1.
IGN ON, Plugs out but hooked to wires and laying on block
Turn the engine until there is a spark on some plug.
Whatever cap contact the rotor is pointed at is the cylinder that should be at TDC with both valves free.
Keep turning until you have figured out at least 3 of 4 wires!

Did you have the cam/chain off?

FRM
FR Millmore

you say it ran with the Zeniths. . . weird. . .i would have guessed at the drive being 180 out, but this seems to have been covered by FR. . .sounds like a re trace of your steps will be the answer, it must be basic. . .but keep at it. . .dont go mad !
p bentley

Some cars are reluctant to fire up after a rebuild unless the engine is spinning really fast - to the point that they really need a tow to get them going. Thereafter they will start normally on the starter. I think this may have something to do with proper atomisation of the fuel - just plain petrol on the plugs doesn't do it. It needs to be petrol vapour and for this the speed of air across the top of the fuel jet needs to be fast enough to draw the fuel up and atomise it. The engine needs to rotate fast enough for long enough to create the necessary manifold vacuum.

Do you have an opportunity to get a tow-start?
Guy Weller

FR...good test. I'll try it tonight. If this doesn't work then I have to go back to the twins and see what the problem is since they're the "big" change since she ran last.

When I've been spraying gas, I've been using a spray bottle that atomises the gas (fine mist spray) into the carbs with the pistons held up assuming this would get it going.

Keep y'all posted and thanks for the replies...

Chris
Chris Elkerton

Are you 100% certian the plug wires are on the correct plugs...there was a time i thought I was 100% also...didnt start for 3 months i was so certian... DOH !!!

Why is everyo.e one setting up there dissy as static...all that does is get it started nothing else...ive been seeing a big rash of this latly

Prop
Prop and the Blackhole Midget

Dissy 1 to plug 1
D 2 to p3
D3 to p4
D4 to p2

1342 on the dissy is not the same as 1342 on the block

Prop
Prop and the Blackhole Midget

To Prop's point about "thinking" I know what I'm doing, I though it best to show what I'm doing. Since I learn best with visuals, here's how she's set-up. Am I doing anything wrong?




Chris Elkerton

rotation and order is correct

I don't know about the position of 1 as regards the dissy position for a 1500 and/or your diagram
Nigel Atkins

If you've had it running previously with the Zenith, why are you now focusing on re-setting the timing? If the carbs are the only change, then surely it is a carb or fuelling problem. What else has changed?

In swapping the carbs, are you sure you don't have any manifold air leaks? I would still suggest a tow-start if you can arrange it. The SU carb needs a decent amount of suction to get started, and this means reasonable engine rotation speed, at least on the first occasion after first installation.
Guy Weller

You aren't holding the pistons up every time are you? This will cause a massively lean mixture even spraying a load in from the can.

You really want it set closer 10 degrees BTDC, although TDC should get it running.

We assume valve train is time correctly and compression is good. You seem to know how to find TDC on the cylinder that is on its firing stroke and then note where the arm is roughly pointing and put the leads around that.

Have you tried getting someone to crank the engine over, full choke, while you rotate the dizzy from where you think it should be to over retarded and back over advanced (say -90 degrees up to +90 degrees) from where you set it statically?

I had a B series that I swear I timed correctly (the drive dog was in some weird position...) and I was 90 degrees wrong and found it out only from the rotation test. I was tired...
RoadWarrior

Guy
Yeah...going to go back to the carbs since they are the one piece of the puzzle that has changed. Although I will set try all tests on spark etc first.

So carbs off this w/e. Check everything over there and see what happens. Will keep you all posted.

Chris
Chris Elkerton

It could be the plugs are getting wet from pooring fuel in manually...im wondering if the floats are getting fuel
Im guessing you also converted the fuel pump to a low pressure
pump electric....1 to 3 psi

Another thought...you havent mistaken the gasket backwords and blocked The round hole vents for the carb pistons...do the carb pistons move freely....do you have the A/F nuts turned down about 12 flats

Just a few thoughts
Prop and the Blackhole Midget

But i got to agree... If the spark wires are hooked up correctly and you got blue spark... Then the electric is and good compression is okay, if the valves are okay...its got to be carbs
Prop and the Blackhole Midget

Im sorry i forgot to mention ... The vent hole is on the carb body where the air filter housing attaches about the size of a #2 pencil...just above the air filter housing bolt holes...actually there are 2. Vent holes

Prop
Prop and the Blackhole Midget

A Spitfire just landed in my driveway. I built the engine about 15 years ago, and it sadly only has about 700 miles on it!

Plug wires clock as follows:
1 = 8 o'clock
3 = 5
4 = 2
2 = 11

This is as all Spitfire/Herald/Midget engines I've ever seen, which is a lot (x,000). Plug wires do not cross, and are the shortest wires on any known engine, as a group. #2 especially is about 3" between boots.

Check your valve opening/clearance again and get on the right cylinders.

FRM
FR Millmore

Fletcher, are you sure? 1500 should be 1342 going counter-clockwise

Sorry, misread! You said clock, not clockwise. I see you are referring to hour hand positions, 8, 5, 2 11. Which is counter-clockwise!
Guy Weller

Wow... Fleatchers comment dosnt match chrises diagram at all

Chrisis ... #1 is oppisite... Its clearly at 3 oclock and shod be at 8 ect ect
Prop and the Blackhole Midget

1 is 3 oclock
3 is 9 o'clock
4 is 6 o'clock
2 is 12 o'clock

This is chis firing order as he has it posted in his chart
Odd... And off somewhere... $$$


Prop
Prop and the Blackhole Midget

Hmm, What time do you think it is now Prop?
Guy Weller

No wonder Prop's car is never done!

For kicks and since I had to go through the camera/computer thing:

FRM


FR Millmore

Prop,
I'm not sure that Chris's diagram exactly matches his actual dissy position but if it does . . .

FRM,
that a very clear photo of the set up is it ok for me to added it to my firing order thread please

I'm always surprised by photos of long lead sets on the Triumph engines where they are much longer than required and double back on themselves and cross each other with the excess
Nigel Atkins

Nigel-
But of course!

The old OE wires were pretty stiff, and got stiffer with age. This came in handy, as you could take the cap and wires off, and they just fell onto the plugs in the right order when you put it back.

Also, one came in idling poorly and making strange noises. I looked at it and the cap was jumping around like it wasn't fastened. It was, but only to the top of the distributor which had been machined in half by the disintegrated mech advance - a result of not lubricating the works! But the wires held it in position enough that it came in under its' own power.

FRM
FR Millmore

Chris,
This isn't the old problem of old petrol is it ?
If it is a while since it ran before, it may be worth just trying some fresh petrol.
Guy Weller

cheers FRM,

>>a result of not lubricating the works!<<

yes I bang on about this as it's oftened overlooked even if the cam is greased - the Driver's Handbook reminds this is part of the service

some owners seem very quick to put on electronic igniters, which I think are good idea, but negelect the other part of the dissy and forget how neglected and worn it could be
Nigel Atkins

Well everyone: I pulled the twins off and put them away and(after thorough cleaning) put the ZS and manifold back on. Checked timing. Squirted gas, prayed a bit and after a LOT of attempts she came alive!

Saw a bunch of leaks from hoses etc, so dealt with those and fired her back up.

Only problem now is, she sounds like a 1970s VW Bug (which always makes me think one piston isn't firing) and she overheated within 5-10 minutes. I have a new electric temp gauge. Tested it and the thermostat a while ago (both worked great)but after running her, coolant came pouring out of the expansion tank (as it should)and the temp gauge had shot to the H.

So...off to sort THAT out along with everything else!
Chris Elkerton

What time is it.... Its a 1/2 past hinny time somewhere....hahaha

Wow... Sorry to hear that...coolent flowing out the over flow catch
Tank...GEZ... I hope its just a head gasket ..did it blow from running to hot or was it detenation from timimg to advanced

I guess the ZS carb could have been running to lean

So did you convert back to the mechanical fuel pump or did you have a regulater to adjust the flow to the carbs

It certianly sounds like you got your fun cut out for you

Here is hoping its just a blown head gasket and not a cracked cly head

Prop
Prop and the Blackhole Midget

Yeah...I put a new head gasket on after I ran her a few years ago...but I guess I didn't torque it down enough. So went back today and re-torqued all the nuts (following the order in the manual) and lo and behold...what a difference! She still runs "hot"(see pic), but isn't overheating. The system seems to be doing it's job (tested the thermostat again today and she opened nicely at 180F).

But based on running / smells she's running rich and out of time. Once I get wheels back on, I'll roll her out and flush the system again. And test the carb. And borrow a timing light. And test the compression...

But for today...I'm a happy guy cuz she sounded great! :)


Chris Elkerton

Also...I had to shoot a vid of her running just so people knew why I was doing the "Happy Dance"!

http://www.youtube.com/watch?v=T2S7bCEybMc&feature=youtu.be
Chris Elkerton

Considering we are all over the place on this engine with no real focas or game plan... And several curve balls thrown into the mix

Whats really needed is a good basic plan to take a system by system approach and just go thur the engine... It seems like we have covered several systems in a random fashion and not alot accomphised except for some confusion... So im not sure how to proceed


But to provide some new insight for new information...you probably dont have a blown head gasket or cracked head.... As you said you put in a new head gasket the last time and fled with coolant and im guessing never started it some time back

Whats probably happening is air pockets in the cooling system these little engines are notorious for air pockets when adding new coolent to an empty system

What you need to do is pull the rad cap and run tthe car about 1/2 hour... Then put the rad cap on and let it cool about an hour and restart and watch the gauge if it over heats agian, repeat the process

Next watch the hoses for the next 300 miles for leakage... They may need retightening

Keep us posted...and lets see if we can be more methodical

Prop
Prop and the Blackhole Midget

Yep to all points.

But I think my order is this: get the carb sorted as there are a lot of things that seem to be missing or modified. (parts of the emission system etc), idle, mixture.

Once I know she's not running too lean or too rich and is ok, then the timing to ensure it's firing as it should.

Once those are sorted, then it seems to make sense to check the cooling system if she still runs hot.

Agree / Disagree?

Chris
Chris Elkerton

Id probably set the timing 1st as thats a 5 minute job and dosnt matter to much as to which carb... The setting can be fine tuned later on... At this point just close...im not sure what the timing is on a 1500...im guessing 8-12 at 1000 rpm

Next id sort out the cooling, esp considering your hitting that type of temp in 10 minutes

Then id go back to the carbs and sort it out... As the carbs might take awhile to set and if the cooling isnt sorted...then you would be just chasing the dogs tail

In the mean time id take the SU carbs to a local brit classic car club and have them give it a look over... Or a good classic brit car repair shop....NOT a modern shop... The tech is to old for a modern shop to understand


Prop
Prop and the Blackhole Midget

Good plan. Thanks for all your input!
Chris Elkerton

Timing first ALWAYS EVERY TIME!!
And is that not where we started?
It is the one thing that will screw up, obscure, confuse, invalidate EVERY other tuning adjustment.
It is the one thing that will keep the car from running or destroy it or cure/cause many other ills.

FRM
FR Millmore

This thread was discussed between 14/06/2012 and 18/06/2012

MG Midget and Sprite Technical index

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