No Start Spark Problem ?? Mystery to Solve

[Paul Bennett]

Background - The museum's (with 220 cars) owner supposedly used this 50 Merc as a daily driver for about 5 years. Then he didn't. When I got the car 15-20 years later, I surmise they probably had starting problems as when I got it, the air cleaner was disconnected from the carb (shoulders shrug when asked) BUT I now I buy a new dist cap only to learn the one on the car plus the rotor and points were already new. Cap and rotor had no sign of ever getting spark. Me thinks the museum's mechanic was troubleshooting an ignition problem, changed some parts and gave up after disconnected the air cleaner to spray starting fluid into the carb.

Today - When I lining up the timing mark I find the spark plug wires were 2 holes off but correct otherwise. Correcting that made no difference to getting spark to the plugs.

I have an old 60s timing light which I power from a 12v source and it doesn't constantly fire when connected to #1 plug. I also have a home made spark gap (needles with a 0.1" gap) which sparks freely on coil output but nothing to the plugs out of the rotor.

Crap spark wire is not solid wire. I can buy solid ignition wire at $.88/ft and will make a new set if I can get decent tips and caps. I will not order a premade set at $80 just to have solid wire. Not the problem but an issue anyway.

So, I suspect the coil is bad. Are they known for a weak spark? I see NAPA has 6v coils at $17 and $24 ... does $7 buy better quality? I'm tempted to get 2 $17 coils ... one for the toolbox in the trunk.
Thoughts?

[Big-Foot]

Disconnect the condensor at the points to see if you now have spark while cranking.
If you decide to try and start it this way - You cannot run the engine long without the condensor as the points will soon pit up and destroy themselves.
Or you can just replace the condensor as a maintenance item.

[51 MERC-CT]

Originally Posted by Paul Bennett

Crap spark wire is not solid wire. I can buy solid ignition wire at $.88/ft and will make a new set if I can get decent tips and caps. I will not order a premade set at $80 just to have solid wire. Not the problem but an issue anyway.

There are solid core spiro-wound 7mm universal wire sets available in the $35-$50 range with all the tips and caps included. Like what I use on mine. See here---

https://www.summitracing.com/parts/sum-g829b/overview/

[Tony, NY]

Sounds to me like it's cap to rotor problem.

[flatheadmurre]

If i read you right you got spark from the coil ?
Take just about any leftover sparkwire you got and just stick it in between coil and distributor to check if it´s wire that has degraded.
Next is check if rotor got contact with cap.
Short between rotor and distributor shaft.
If you got spark at coil and the above is ok you should get spark out of the cap.

[Greg58]

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Are you sure you are on the compression stroke? Remove #1 plug, hold your finger in the spark plug hole and have a helper turn the engine, when you feel the compression you are near tdc. Now line up the timing marks and wire it from there.

[Greg58]

One thing that gets over looked is the wire from the points to the coil, I would change it along with a known good coil. You might want to try another condenser also, I have had a bad one out of the box.

[Paul Bennett]

Lots of things to try to regain proper spark now that my carb is off for a rebuild. Thanks for the many suggestions. I will post the final solution once I have one.

Why remove the carb when working on spark you ask. I know the accelerator pump is inop but and I can troubleshoot the spark w/o gas. But when the carb returns I hope to sit in drivers seat to experience the engine starting on gas, not just a few cranks on starting fluid as it is now without gas flow.

Plus I want to remove the trunk to replace the rubber molding. This car will be new when I'm done. If I'm done - my 2017 work-list shown below. Enjoying the journey but driving would be nice since I just did DMV and ins for $500. Got a little ahead of myself there.

2017
4 Brake shoes + 1 drum + 1 cylinder
2 Coil springs + 4 shocks & bumpers
Clean grease & crap from underneath
Total rewire firewall forward
Underdash - dash lights - add el gas pump sw & relay
Tail light refurb new rubber
Optima 6v battery box fab
OD Kickdown switch replace
Headlight hi-low switch replace
Crankcase clean and replace
Starter refub and replace
Parking light refurb & replace boots
Replace fluids - antifreeze, crankcase, trans, OD and diff oil.
Drop clean replace gas tank
New rubber gas hoses, vacuum hoses, brake hoses
Carb rebuild - WIP
Distributor coil plugs wires replace - WIP
Trunk lid waterproof rubber - WIP
Drop rear axle 2" - WIP
Seat belts next year

[Greg58]

Paul your list looks like mine and probably most of the members list of things we have done. I replaced my trunk seal without removing the lid, I started at the bottom center an ended there. I used 3m weather adhesive.