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MG Midget and Sprite Technical - No spark. Don't know why?

I recently had the engine out of my 1500. Put it back in yesterday but was annoyed to find it wouldn't start. I appear to have no spark on any of the plugs, this was not a problem before I stripped it apart a couple of weeks ago.

Anyone got any ideas what might be the problem, I'm stumped.
matthew stubbings

Matthew. You did not connect up the ignition system properly. Get a copy of the wiring diagram for your year vehicle and check out the tech article on ignition system trouble shooting on the MG section of my website, www/custompistols.com/.

If you have no spark at the coil lead, you have a low tension ignition circuit problem (or a bad coil). If you have spark at the coil lead, but not at the spark plugs, you have a problem with the rotor or distributor cap.

But, the tech article will walk you through trouble shooting both systems.

Les
Les Bengtson

basicly what les is asking is if you pull the coil wire off the dist. cap...the middle one. can you get a spark off the end of the coil wire?

if NO spark, the problem is deeper like a bad coil,or problems in the igniton wire or the wire coming from the dissy, ect.

If you do get a spark, then the problem is in the dist. area...bad cap, rotor bug, an issue with the carbon stick&spring that rides agianst the rotor bug.

Prop
Prop

Matt

Can you tell us more on what you did to the engine when it was out? Eg. did you change the points? Does the rotor arm turn when you crank the starter?

A
Anthony Cutler

did you reconnect the main earth strap??
Mick - trying to sort the wiring

Hi Mick

No main earth-strap = no crank on starter. I assume starter is behaving... but...

A
Anthony Cutler

Hi all, thanks for the responses.

Some answers. When I took the engine out I left the distributor in place, didn't touch it. Removed dizzy cap and ht leads from plugs and from coil.

I have not amended the timing of the crank, cam or distributor at all, not touched any of it.

Wiring diagrams are a bit of an issue, the car appears to have something of a checkered history as there are bits of different coloured wire, scotch locks, connector blocks etc all over the place. None of the wires connecting to the coil resemble the colour references I have in my haynes book.

Will the coil lead spark against the engine block if coil is working? If so I will give that a try, to at least try to narrow the field of potential problems

Thanks again
matthew stubbings

Matthew

Try the coil lead against the block as you suggest; it's one of the basic tests.

Then with ign ON, measure the volts on the coil terminals.

One terminal, normally supplied from the ignition +ve (white on a 1275 with no ballast resistor) and marked +ve or similar should have ~12V on it (or ~6v? with ballast resistor). The other will be at 12/6v when points open and 0V when points closed (this changes obviously when engine is rotated).

If there's no + volts on either terminal, then you may have problem with loom. As a temporary measure, you could connect battery +ve terminal to +ve terminal on coil. If you get spark from coil lead against block, you need to investigate loom.

(Don't forget to disconnect your new battery lead, otherwise you'll risk burning our coil.)

A
Anthony Cutler

Matt as Anthony suggested also this procedure should help you from our website.

http://www.mgcars.org.uk/mgcc/midgetreg/ignition%20system.shtml
Robert (Bob) Midget Turbo

That didn't work too well? try this link and then click onto "Ignition".

http://www.mgcars.org.uk/mgcc/midgetreg/workshop.shtml
Robert (Bob) Midget Turbo

then agian have the uncle or idoit brother and law hold the coil lead while you turn the engine...just make sure they got a beer in the otherhand, that way no suspesion of whats to come as well as no fighting back, becaue it might spill the beer in the process.

Prop
Prop

Finally got this problem sorted last night, thanks everyone for your answers. It turned out to be a short on the wire from the coil to the distributer.

I now have another problem and think I may start a new thread..........
matthew stubbings

This thread was discussed between 29/06/2009 and 30/06/2009

MG Midget and Sprite Technical index

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