Running/starting problems

[jordan_meakin]

Yesterday, my Series III was running rough when I came to it - had been fine the day before.  It was smelling of fuel and very hesitant to move off but sort of improved in higher revs, black smoke indicating unburnt fuel.  Seemed like ignition problems to me so I started off by taking of the leads individually to check it was running on all cylinders.  Removing each lead in turn had an effect although not significant on the already rough running.  Therefore, I looked at the distributor cap and rotor arm - looked fine but I had spares so replaced with new.  Still running rough.  I don't use points on this, I have the contactless ignition. like these: https://rimmerbros.com/Item--i-GRID010339 , so am loosely assuming it's not those.  So attention turned to leads - all good other than corrosion on the coil end.  So I removed the coil and it was quite gunked up in the terminal.  So I cleaned up the lead contact and undid the screw of the female contact on the coil so that I could remove for cleaning, to see if there was any improvement.  After this, it wouldn't run at all and has refused to since.  I have (I think) checked the coil primary resistance but have to be honest, electrics and such are wizardry to me so if Goggle can't tell me how, I don't know.  I had my meter set as such:

On this setting, it gave a reading of 0.1 which if I am doing it correctly, leads me to believe the coil is dead. I had a spare (but condition unknown) coil that when wired up, also did nothing but gave the same reading on the meter also suggesting it's bad.  I have no reason to believe the second coil is good or that I have tested correctly.  I then started thinking I had wired the coil back up incorrectly but can't see how, just trying to rule things out.  So on the negative ( - ) side of the coil, I have the black lead of the ignition module from the distributor, the condenser and a small device on the carb.  On the positive terminal ( + ), I have the red lead of the distributor's ignition module and another wire that goes in to the cab, presumably the ignition switch.  I am confident I had it like this when running but just for clarity have included this information.  Am useless with wiring diagrams.

The simple thing is to buy a new coil, I know but, I would prefer to actually know that it's that causing the problem before wasting money.  So, does anyone have any advice or suggestions?  I am sure this is a simple problem to someone else but as I say electrics are beyond me.

Thanks in advance.

[rtbarton]

In ballpark figures, a coil takes 4 amps at 12 volts which gives a resistance of 3 ohms.  You need to set your meter on the 200 Ohm range to check this.

A quick check would be to connect a stop light bulb in series with the primary and a 12v battery, it should light up, but a bit dimmer than normal.

To check if the coil is giving a spark connect the HT lead to a spark plug, the base of the spark plug and battery -ve to -ve on the coil and hold a wire from battery +ve to +ve on the coil.  When you disconnect this wire you should see a spark.

I use one of the old fashioned timing lights (the ones you connect in series with a plug lead) to check the HT.

From your symptoms I would be looking at excessive fueling, eg level too high in the float chamber, choke cable stuck and so on.

[steve b]

That device on the carb is an anti-run on valve and should be wired to the ignition live wire not the distributor side - it should have constant live with ignition on (+ve terminal)

cheers

Steve b

[jordan_meakin]

1 hour ago, rtbarton said:

In ballpark figures, a coil takes 4 amps at 12 volts which gives a resistance of 3 ohms.  You need to set your meter on the 200 Ohm range to check this.

A quick check would be to connect a stop light bulb in series with the primary and a 12v battery, it should light up, but a bit dimmer than normal.

To check if the coil is giving a spark connect the HT lead to a spark plug, the base of the spark plug and battery -ve to -ve on the coil and hold a wire from battery +ve to +ve on the coil.  When you disconnect this wire you should see a spark.

I use one of the old fashioned timing lights (the ones you connect in series with a plug lead) to check the HT.

From your symptoms I would be looking at excessive fueling, eg level too high in the float chamber, choke cable stuck and so on.

Thanks - already confused with the electrical stuff but I'll try to decipher.  Choke cable is free and as it was running well, I can't imagine float bowl setting is madly out, certainly not to stop it running entirely.  Left it over night to rule out flooding, too.  So judging by your advice, my coil is getting around 1ohm...

54 minutes ago, steve b said:

That device on the carb is an anti-run on valve and should be wired to the ignition live wire not the distributor side - it should have constant live with ignition on (+ve terminal)

cheers

Steve b

Thanks for this - definitely had this connected to the negative before (not suggesting that's correct!) as it's on a joint connection with the other wire.  You can hear it click on and off as you connect/disconnect - is that working?

[steve b]

Yes if it's clicking then should be ok . The coil should have around 3 ohms of resistance and RTB's suggestion of connecting a bulb first to earth to observe it's brightness then through the coil ( like this -   12v to bulb to coil +ve then coil -ve to earth ) and then you should see a dimmer glow . Bear in mind your meter has a battery  and if it is nearly flat readings may not be accurate

cheers

Steve b

[rtbarton]

Should have mentioned, but as a matter of habit always short your test leads before making resistance measurements to check the meter.

This is a throwback from the good old days of analogue meters where you had an adjusting pot to zero the meter to compensate for battery use.

[jordan_meakin]

So I have checked for spark on the plugs and seems to be nothing... Surely it's the coil?

[one0nine]

I'd also be looking at fuelling too, easy to get obsessed with something, overlooking the actual issue.

I had the Aldon hall-effect trigger assembly, which I assume is similar to the one you've fitted. Testing that will be difficult, but check that the sensor/magnet assembly is accurately positioned. You could always swap that out with a set of points to check, with the advantage that you can then open and close the points to check the coil, etc.

Given that a lump of tank rust, or ethanol-induced corrosion may be compromising the float/seat action, I'd be looking at the carb. closely.

 

[Bowie69]

You could also have two problems, fuelling and spark (or you have broken the spark side by fiddling -we have all done it), but black smoke is excessive fuel, normally you don't get black smoke with misfires caused by ignition, it is more often white, i.e. vapourised fuel than black, which is a rich burnt mixture.

Testing the coil standalone as rbarton suggests is your next step...

 

 

[jordan_meakin]

So, now testing the coil on the correct multimeter setting gives 4.1 ohms.  Bought a new one before I realised and that read 3.8 ohms so I don't think the old coil is the issue.  However, still no spark so I'm going to swap out the contactless ignition with the old points in case it's that that has died.  To fully rule the coil out, can I put a spark plug directly in the HT lead coming from that, bypassing the distributor?

Thanks for the thoughts on fueling.  I'm tentatively thinking that the smoke was due to incomplete combustion if it was that the spark was weak/dieing but of course can't rule it out.  As I've said, was running great and went very suddenly which in the past, I've associated with ignition problems...

[rtbarton]

"To fully rule the coil out, can I put a spark plug directly in the HT lead coming from that, bypassing the distributor?"

 

I suggested that earlier

Edited August 20, 2018 by rtbarton

[FridgeFreezer]

14 minutes ago, rtbarton said:

"To fully rule the coil out, can I put a spark plug directly in the HT lead coming from that, bypassing the distributor?"

Surely just pull the dizzy end of the king lead off and see if that sparks to the nearest ground?

I've seen dirty/damp coils arc from the top to the LT connections from under the boot.

[rtbarton]

10 minutes ago, FridgeFreezer said:

Surely just pull the dizzy end of the king lead off and see if that sparks to the nearest ground?

I've seen dirty/damp coils arc from the top to the LT connections from under the boot.

True enough, but taking the coil out of the system eliminates other faulty items, especially as he has electronic ignition.

[jordan_meakin]

10 hours ago, rtbarton said:

"To fully rule the coil out, can I put a spark plug directly in the HT lead coming from that, bypassing the distributor?"

 

I suggested that earlier

Sorry, missed that - will try today.

[jordan_meakin]

So, contactless points swapped for traditional points and fired straight up.  Seems to be solved!  Thanks for all your responses.

[rtbarton]

Thanks for letting is know

[lo-fi]

Out of interest, what brand were the contactless points?

[jordan_meakin]

16 hours ago, lo-fi said:

Out of interest, what brand were the contactless points?

S*hitpart - hasn't been on a year and done less than 2000 miles

[lo-fi]

Ah. Enough said. I can recommend the Powerspark modules, I've used on a few engines for some time now. They're not even particularly expensive. 

[jordan_meakin]

3 minutes ago, lo-fi said:

Ah. Enough said. I can recommend the Powerspark modules, I've used on a few engines for some time now. They're not even particularly expensive. 

Yes, quite!  To be honest, I bought a load of other parts at a local supplier and enquired about them and he threw it in FOC to try.  I can't say it effected running but saves setting points gap but realistically,  that's no bother anyway!  At least with traditional points they give you some warning of when they're getting knackered - these just gave up and could  have left me stranded.  Is there any significant benefits to the type you have used?

[lo-fi]

I like them because they're moisture proof, never need setting, manage dwell precisely and produce a very strong spark with the bosch coil I'm running. Also never get furred up and need changing or faffing with. Assuming they're decent modules to start with, of course. 

[FridgeFreezer]

To second LoFi's recommendation, I ran an Aldon Ignitor on a couple of V8's (before going Megasquirt) with a stupid sports coil (1.5 Ohm) and it worked lovely.

[Bowie69]

Third on that, excellent parts.