Weak spark

Shawnmcg777

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Hey all,

I have a 73 85hp Chrysler which I converted the Magnapower ignition to an automotive coil. So basically ran the blue wire to the positive side of the coil, ran the white tach wire to the negative side of the coil and then then negative side of the coil to the points on the distributor and added a condenser on the points as well. The issue I'm having is a weak spark on all 3 cylinders. When I connect the spark tester to the coil I'm getting a 15000v spark. But the spark at the plugs is very weak. The points in the cap and the rotor are sanded lightly... Any ideas? I'm guessing the points are ok since it's firing ok at the coil?
 

Shawnmcg777

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Oh and new spark plug wires also. Using NGK (52419) RC-FDX001 Spark Plug Wire Set
 

jerryjerry05

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You try running it with the weak spark? It might be all you need??

3days ago I was getting a 9.9 Nissan running and had a spark tester hooked up and had no spark.
When i first tried to start it coughed and sputtered like it had spark.
So hooked it all back up and the "no spark" started the motor on the first pull!!!
 

Shawnmcg777

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Hi jerryjerry05, I did try it but it would start. I tested the coil resistance and I'm getting 3.3 on the primary coil which I think is good but no reading on the secondary coil. So from what I'm reading I must have an open circuit. It's a new coil but maybe I got unlucky. Ordered a new one and will see if that solves the problem. Should be getting it today, will let you know how it goes!
 

Nordin

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Which kind of plugs do you use?
Converting from Magna Power system to regular auto style you have to change from surface gap style plugs to plugs with a bent electrode.
Is the timing right?
28-30 dgr BTDC at WOT is the setting.
 

Shawnmcg777

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Hello Nordin,

I changed the surface gap plugs to NGK br7hs-10. When I test the spark with the adjustable tester, the gap has to be really small for it to spark. The weird thing is sometimes I get a good strong spark.

I set the timing with the multimeter and confirmed it with the spark at 32 degrees btdc for wot and at 2 degrees btdc at idle by adjusting the idle screw.

The motor was running at 2000rpm or higher but would stall lower than that. I soaked the carbs and now all the idle jets flow well. After the cleaning I realized I had no more spark... so I went to the cdi and swapped it for the auto coil.

The spark I'm getting is very weak, maybe 2000v. Do you guys know what the voltage required for ignition is? I will also try spraying quick start in the carbs to see if it goes... Maybe it is a carb issue but I really don't think so.

Thanks guys
 

Nordin

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What capacitor (condenser) do you use?
The capacitor should fit the coil spec.
Think a 0,20-0,25 mikro Farad would be fine.
Have you set the points to 0,014 in (0,35 mm)?
Do you have solid copper core HT wires?
BR7HS-10 has a built in radio suppression resistor and the electrode gap is 0,040 in (1,0 mm).
Try BS7HS plugs and you must have solid copper core HT wires.
 
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Shawnmcg777

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I am using the acdelco d204 professional ignition capacitor. I want sure how to match it with the coil though. The points are set to 0.014.

What do you mean by solid copper core HT. Are you referring to the spark plug wires?
 

Shawnmcg777

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So my HT wires seem to be composite core. Thanks Nordin I'll get some solid copper core and test it out. Do you think my condenser is ok? I can't find any info on micro farad for it.
 

Nordin

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If the condenser is for regular auto style ignition coils I think it is okey.
Yes your high tension (HT) wires are composite/grafit wires.
How do you connect these to the distributor cap?
OEM wires (solid copper core) are split up (mushroomed) in the dist. cap to get good connection to the cylinder terminal.
I think your issue is in the dist. cap, the grafite wires are not made for this kind of connection.
 

Shawnmcg777

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Ahh makes sense! It did seem odd when I replaced them. But it did create a spark with the previous Magnapower CDI pack. Maybe because they put out a lot more power.

So to connect my HT wires to the distributor cap I have to do the following. The bottom of the cap unscrews with two screws and comes off. I feed the cut end of the HT wires through the bottom half of the distributor cap and onto copper spikes (that are on the top half of the distributor cap) that fit inside the HT wire. Then I put the bottom half back on and screw it back on and the pressure keeps the HT wires in tight.

The previous wires which were on had a bunch of individual wires which the previous owner frayed and attempted to contact the copper spikes with. But this seemed odd to me and that owner never had it running either.

So solid core copper would be the way to go?
 

Shawnmcg777

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R1813 New Universal Spark Plug Wire Set (4 Cyl.) Solid Copper Wire Core https://a.co/d/0aO7vAR

If you can confirm these will work better I'll try these. They seem to have the same silver wire strands that were on the motor before I replaced them. Maybe the wires were original.
 

Nordin

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I think that wire set would be good.
The distributor is made for solid copper core wires.
The application to the distributor would not work with composite/grafit wires.
 

Shawnmcg777

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Awesome! I'll order those and set them up this weekend. I'll let you know the outcome.

Really appreciate your help! My son wants the boat working asap :)
 

Shawnmcg777

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Hi Nordin,

So I set up the new wires and I have a great spark! Thank you

Now the timing at WOT is still 32 degrees but at idle I'm not getting anywhere with 2 degrees btdc. I've adjusted the idle screw and now the motor almost starts in neutral but I'm at 11 degrees btdc. Also, my idle adjustment screw is almost all the way in (see picture). I feel like if I advance it a bit more it'll start right away but I'm wondering how far I can go before the motor fires backwards... If that's even possible.

Is it normal to have idle so advanced? I can't imagine it's normal to have the screw in almost the whole way. Any ideas?

Thanks again for your help!
 

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Shawnmcg777

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Also, to be clear I'm adjusting the roller linkage also so the flies are closed at idle
 

Nordin

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Great, do not take any notice to the spark advance at idle.
These engines are set at WOT and the spark advance at idle will be what it will be.
I suggest you to set the spark advance to 30 or 28 dgr at WOT, then you tune the idle by the idle screw at the tower shaft and fine tune the carbs by the air/fuel mix screw.
Maybe you have to adjust the throttle by the remote control wire connector.
You have to set the throttle pick up point, the carb rod roller has an eccentric screw.
The roller should touch the cam mark at a mid point of the roller.
Adjust by loosen the nut and adjust by the screw.
There are a sticker at the top of this forum by Frank A how to adjust the throttle pick up point and the carbs.
 
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Shawnmcg777

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The eccentric screw is up against the cam and it is perfectly horizontal. There is a slight pressure but flies are completely shut. I will go through the remote control adjustments but I think it's good. As per the manual it says WOT timing should be at 36-4 (32) but if I set it to 28-30 degrees like you say, I it will bring it lower for idle too. I know you are saying not to worry about idle but It's so close to idling on neutral now. It goes a couple rounds then conks. My carb screws are out 1 turn.
 
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