Lightweight not starting, no spark at plugs and...

[Madcowz]

Hi,

I am trying to help a friend who's Lightweight won't start and would appreciate some grownup advice please.

I think there are two faults here:

1) Starter motor has trouble turning engine over, although it is easier with plugs removed.

2) No spark at plugs or from HT lead

The battery is fine, fully charged and no problems there so I think the starter motor either has a poor earth or is faulty. With the plugs in it only manages to turn the engine a tiny amount, not even one full turn. Taking the plugs out helps and it manages a few turns but is still weak and feeble.

Turning to the plugs. We have no spark at the plugs and nothing from the HT lead. I suspect the points are faulty as he rushed out and bought a new coil but this hasn't helped, and we are going to check this tonight.

What I don't know is where to look for them. I take it they are below the distributor rotor arm section? Or are they elsewhere? Does anyone have any pictures of how it all looks. Unfortunately I have no idea what the engine is apart from a 4 cylinder petrol and it looks tiny and green.

If I can find the points we can see if there is 12v going to them and try making the contacts. At least this will rule another section out of the puzzle.

Am I missing anything here? Is there an obvious item to check?

thanks for your help,

mad

[Bowie69]

Here's a lovely picture of the distributor:

http://www.britishcarpartsco.com/images/P8050010.JPG

You can clearly see the points and condenser -if you change the points, change the condenser at the same time.

Obvious things.... no not really... you need to look at each section in turn to make sure it is working. Do a search on here and I am sure you will find it pretty easily.

The starter... are you SURE the battery is OK? Have you tried jumping it from another car? If that doesn't work then it sounds like it is dead -they aren't TOO expensive to replace fortunately.

[david1701]

yeah bettery sounds like the prob - wat about the chassis earth? that would explain the lack of power to motor and coil

[Madcowz]

Ok,

thanks for your replies.

can I just confirm that we are doing this correctly.

12v+ feed goes to the +ve terminal on coil, -ve terminal goes to the breaker arm which when the cam closes it, closes the circuit to earth on the primary coil?

We went up tonight and found that there was nothing happening across the point so we cleaned it and now when it closes we see 11v across it. But there is no spark when the point closes. I take it that this is the condensor stopping the arc?

There is also still nothing coming off the HT lead.

[TheRecklessEngineer]

11v sounds a little on the low side...You should see full battery voltage across the points with them open and you should see no volts across them when they are closed (as they are a dead short).

You should get a spark when the points open rather than close. The condenser suppresses the spark across the points to stop them burning out - ignore it for the moment.

[Bowie69]

Yep, as long as you get a voltage, then no voltage when it is closed, it seems to be working OK.

11V is low.... you should be getting 12+ to it really -try jump starting it to check, as above

Sometimes when a starter is on it's way out, it will start to just run slowly -this is because the bearing has collapsed to the point where the rotor is starting to hit the stator winding -this will eventually short out and leave you with effectively only half a starter.... so not DEFINATELY the battery, but first, and easiest thing to. check.

[Madcowz]

Yep, as long as you get a voltage, then no voltage when it is closed, it seems to be working OK.

Excellent, that is the point definately working then. One more thing to tick off the list

11V is low.... you should be getting 12+ to it really -try jump starting it to check, as above

Ok, will take mine up at the w/end and try jump starting it. See if that helps.

Sometimes when a starter is on it's way out, it will start to just run slowly -this is because the bearing has collapsed to the point where the rotor is starting to hit the stator winding -this will eventually short out and leave you with effectively only half a starter.... so not DEFINATELY the battery, but first, and easiest thing to. check.

This is my thinking as well. I think there are two faults here. One the starter is on it's way out and two, the point was faulty.

I forgot to say that we tried jump starting it right at the begining so that we could (I thought) rule out the battery as being at fault. When we did this the starter was still slow and weak and there were no sparks at the plugs (but this could have been because of the dodgy point).

Will try again and report back.

Thanks for all your help so far. Appreciated.

mad

[Roverdrive]

Just double checking what you have said.

quote

"We went up tonight and found that there was nothing happening across the point so we cleaned it and now when it closes we see 11v across it. But there is no spark when the point closes"

unquote

You said when it was closed you were seeing 11v, you should be seeing 0v

What do you get if you measure between the +ve side of the points and earth?

Another thing to check is the resistance between the points base and a good earth. I have seen the small braided wire between the points base and the casing break down.

HTH