The Triumph Dolomite Club - Discussion Forum

Trying to fire up a 1500 with a Sprint engine, no spark. I am running the dizzy with a britpart kit, ambassador cap and a new 12 volt ignition coil. I dumped the ballast coil, because I didn't like the complication.

The coil is directly wired to the ignition power feed on the positive side and two positive/neg terminals of the britpart module. No idea about the timing, at the moment I just want a spark.

There appears to be power to the coil. The obvious thing is there is no separate earth to the cylinder head. I have just added earths as I went along, one to the block. Does the head need its own earth?

Beyond that, I am a bit stuck, any ideas?

There should be a chunky earth cable from the o/s engine mount to the bodywork and battery negative.
If the engine is turning over O.K. I'd next look for the voltage from the coil negative to earth going form near 0V to near +12V when the engine is turning over ( Low wattage bulb or voltmeter ).
If that is O.K. I'd then check for a spark at the coil H.T. output. But take care as there are nasty high voltages here.
I seem to remember reading on here that the Ambassador cap is rather different to the Sprint one and needs timing in a different place. I hear others have done this mod; someone should be around shortly.

Did you introduce the sprint engine to the 1500 body? I used to know some sprint engines who weren't happy at all with their new body. Maybe they just can't get along with each other or the engine is playing hard to get.

Jeroen

cleverusername wrote: ↑Sat Nov 11, 2017 12:58 pm................

The coil is directly wired to the ignition power feed on the positive side and two positive/neg terminals of the britpart module.
........................

I don't understand?

GTS290N wrote: ↑Sat Nov 11, 2017 5:27 pm

cleverusername wrote: ↑Sat Nov 11, 2017 12:58 pm................

The coil is directly wired to the ignition power feed on the positive side and two positive/neg terminals of the britpart module.
........................

I don't understand?

The Brit part module replaces the points. It has two power feeds that go to the coil, I used the same setup on the 1500.

I am using a 12v coil, so I have bypassed the original feed to the coil and powered it from the ignition side of the fuse box.

One on the coil pos and one on coil neg. Not two power feeds.

Jeroen

soe8m wrote: ↑Sat Nov 11, 2017 6:40 pm One on the coil pos and one on coil neg. Not two power feeds.

Jeroen

Yes I know, poor use of English on my part.

So let me describe how I think the circuit works. The coil is power up when the ignition is on. When the magnet triggers the module, it turns on the earth to the coil, which is earthed through the dizzy.

This shorts the coil, causing a rapid collapse of the magnetic field in the coil. Inducing a large voltage which creates a spark via the HT leads and the plugs.

Is that about right?

I think I may have spotted the problem, there is no backplate earth wire in my dizzy. I seem to have got away with this on the 1500 setup, but I assume that I need to put in an earth wire?

Yes it may be worth clamping a lead to the dizzy body as a temp earth to check. Another check, with ign on, remove NEGATIVE wire from the coil that comes from dizzy and connect it on and off quickly. Aim coil ht lead from the cap to an earth point and see if the spark occurs. If it does then problem is distributor side. If its dizzy side replace with points and try it. £40 electronic kits are a 50/50 chance of working.

Tony

tony g wrote: ↑Sun Nov 12, 2017 5:59 pm Yes it may be worth clamping a lead to the dizzy body as a temp earth to check. Another check, with ign on, remove NEGATIVE wire from the coil that comes from dizzy and connect it on and off quickly. Aim coil ht lead from the cap to an earth point and see if the spark occurs. If it does then problem is distributor side. If its dizzy side replace with points and try it. £40 electronic kits are a 50/50 chance of working.

Tony

I might borrow the working module out of the 1500 engine and use that to test it.

I hate electrics, trying to find the fault is simply a pain. In theory it should be working, I have power, the dizzy rotates and everything is connected. It is just nothing is happening.

Oh for a compression ignition engine.

Is your 12v coil a normal or ballasted one. When it's a ballasted one without resistor it fries your module in a few seconds after ignition is switched on.

Jeroen.

soe8m wrote: ↑Sun Nov 12, 2017 9:42 pm Is your 12v coil a normal or ballasted one. When it's a ballasted one without resistor it fries your module in a few seconds after ignition is switched on.

Jeroen.

I now have a plan for the weekend. First test voltage to the positive terminal of the module.

Then in theory, if I measure the negative terminal, from the ignition module, while the engine is cranking. It should fluctuate between 12 and o, as the module breaks the circuit. If it doesn't, bad module.