15 replies to this topic

[ac427]

The battery voltage is 12.7v and the engine spins over fast but will not start.

There is fuel at the carburettor. Which is a lovely new AC Dodd HIF44 that i have just fitted to replace the knackered original. Which suffered fuel corrosion.

The engine hasn't been run for years.

 

The coil measures 3 ohms and the distributor is a 45D4 with standard points.

I replaced the spade connectors on the coil supply too.

If I measure across the coil I get zero volts. However, if I remove a spade connector and then measure across the coil supply leads i get approx 10 volts.

 

 

Could the condenser pull the voltage down?

 

 

The ignition leads for cylinder 1 and 2 measure around 20k ohms with the rest coming in at about 9k ohms. Is that a little high for a set of standard Mini Spares leads that are several years old?

 

I think ignition leads are supposed to be around 2k ohms?

Edited by ac427, 14 September 2024 - 04:59 PM.

[Steam]

Back to basics will help. Pull the lead from the centre post of the dissy and hold close to block , 1/2 inch and crank. You should get a fat blue white spark. If yes continue tracking to the plugs, if no chase fault in dist or coil.

[timmy850]

Does the coil have a ballast feed (pink wire)?

What voltage are you getting at the coil + feed on your multimeter if you measure from that lead to an earth point like the block?

If you have a ballast feed of approx 10v then it would run better with a 1.5 ohm coil, but it should start with the 3.0

 

20K resistance is very high and won't be helping your cause.

What plugs do you have? Are they new? Have you set the gap correctly? Are there any deposits on the electrodes?

 

By themselves the coil and high resistance leads shouldn't stop it starting, but a combination of parts that reduce spark at the plugs definitely won't be helping

[ac427]

Steam, on 08 Sept 2024 - 06:55 AM, said:

Back to basics will help. Pull the lead from the centre post of the dissy and hold close to block , 1/2 inch and crank. You should get a fat blue white spark. If yes continue tracking to the plugs, if no chase fault in dist or coil.

Will do.
 

timmy850, on 08 Sept 2024 - 07:35 AM, said:

Does the coil have a ballast feed (pink wire)?
What voltage are you getting at the coil + feed on your multimeter if you measure from that lead to an earth point like the block?
If you have a ballast feed of approx 10v then it would run better with a 1.5 ohm coil, but it should start with the 3.0

20K resistance is very high and won't be helping your cause.
What plugs do you have? Are they new? Have you set the gap correctly? Are there any deposits on the electrodes?

By themselves the coil and high resistance leads shouldn't stop it starting, but a combination of parts that reduce spark at the plugs definitely won't be helping

Thank you both. Sorry for the late response. i was trying to get the car going for an AC Dodd tuning day.

I was measuring across the coil instead of to Earth.

 

I cannot see a ballast resistor and the coil leads are white and white/black.

I'll do some more measuring and report back.

Not that it is the issue but what would you expect the secondary resistance to be on a 3 ohm coil to be?

Edited by ac427, 09 September 2024 - 10:06 PM.

[68+86auto]

Start with testing that the battery is good. Measure the voltage at the starter when cranking for 15 seconds. If it's below 10v then you have a bad battery or poor connection.

 

Once you've confirmed that the battery is good you can start to check the ignition system. First start with the primary ("12v") side, the secondary (HT) will generally always allow the engine to run as long as the rotor isn't shorted to ground. Put a test light across the coil primary terminals and crank try to start the engine. the light should flash. If it is constantly lit then you have a short on the negative side wiring. It could be the condenser but more likely a wiring or points assembly issue. If the light does not come on at all then you either have no connection to ground thru the points or you have no 12v to the coil. connect the test light between the coil positive and the engine earth (with the key on). If it lights up then you are getting 12v. Your problem is then on the points side. Check the wiring and clean the points. Once you get it so that the light flashes when connected across the coil, you can proceed to test the secondary side. Note that this test doesn't confirm that the points are set correctly. You'd need a dwell meter for that and if you had one you probably wouldn't be asking the question.

 

Testing the secondary: Remove a spark plug and rest it on the engine with the lead connected. Try and start the engine, you should see a spark. If you do then the problem is mechanical or timing, not electrical. If you don't see a spark, connect the coil HT lead to the coil and set the other end near the engine block or head but not touching it. Try and start it again, you should see a spark between the lead and the engine. If yes then the problem is in the rotor, cap, leads or plugs. If there is no spark then the issue is in the coil or the primary circuit (already tested).

 

None of this testing determines if the parts are good but the engine should run.

[ac427]

Start with testing that the battery is good. Measure the voltage at the starter when cranking for 15 seconds. If it's below 10v then you have a bad battery or poor connection.

 

Once you've confirmed that the battery is good you can start to check the ignition system. First start with the primary ("12v") side, the secondary (HT) will generally always allow the engine to run as long as the rotor isn't shorted to ground. Put a test light across the coil primary terminals and crank try to start the engine. the light should flash. If it is constantly lit then you have a short on the negative side wiring. It could be the condenser but more likely a wiring or points assembly issue. If the light does not come on at all then you either have no connection to ground thru the points or you have no 12v to the coil. connect the test light between the coil positive and the engine earth (with the key on). If it lights up then you are getting 12v. Your problem is then on the points side. Check the wiring and clean the points. Once you get it so that the light flashes when connected across the coil, you can proceed to test the secondary side. Note that this test doesn't confirm that the points are set correctly. You'd need a dwell meter for that and if you had one you probably wouldn't be asking the question.

 

Testing the secondary: Remove a spark plug and rest it on the engine with the lead connected. Try and start the engine, you should see a spark. If you do then the problem is mechanical or timing, not electrical. If you don't see a spark, connect the coil HT lead to the coil and set the other end near the engine block or head but not touching it. Try and start it again, you should see a spark between the lead and the engine. If yes then the problem is in the rotor, cap, leads or plugs. If there is no spark then the issue is in the coil or the primary circuit (already tested).

 

None of this testing determines if the parts are good but the engine should run.

 

Thank you. The battery is good. i was measuring across the coil instead of with respect to Earth.

 

From Earth to Coil + is the full 12 volts.

 

I'll run through the other checks you listed above. Ta.

Edited by ac427, 14 September 2024 - 04:07 PM.

[ac427]

Does 22 thou sounds like a reasonable points gap or does it depend on more factors?

 

It's a 59D4 with a 3 ohm coil.

[timmy850]

The dwell angle should be measured with a dwell meter (or timing light or multimeter if they have that function) as the dwell angle is more important than the points gap

[68+86auto]

Does 22 thou sounds like a reasonable points gap or does it depend on more factors?

 

It's a 59D4 with a 3 ohm coil.

 

That's too large of a gap but the dwell is all that really matters and is far more accurate (I don't even measure the gap). If that is the gap required to set the correct dwell then there is excessive wear somewhere.

 

To be clear, that's the gap of the points inside the distributor, NOT the spark plugs. The spark plugs should be around 25 thou but it won't matter for getting it running unless you have an issue elsewhere.

[gazza82]

Always used 15 thou at contact breakers.

[Maccmike8]

I had something similar recently and was a bad earth connection.

[ac427]

I had something similar recently and was a bad earth connection.

Do you engine to body earth?

[Maccmike8]

 

I had something similar recently and was a bad earth connection.

Do you engine to body earth?

 

 

Yes it was this that was causing my problem.

[ac427]

 

 

I had something similar recently and was a bad earth connection.

Do you engine to body earth?

 

 

Yes it was this that was causing my problem.

 

Thanks, can you sill have that even though the engine spins over?

[68+86auto]

 

 

 

I had something similar recently and was a bad earth connection.

Do you engine to body earth?

 

 

Yes it was this that was causing my problem.

 

Thanks, can you sill have that even though the engine spins over?

 

 

The tests that I specified will confirm if your earth is good.