Spring Sprint sparks

It has been a long winter -this very morning it was cold and even my modern car (a full on spaceship compared to the Sprint) was somewhat inhospitable for the first 10 minutes of my drive to work as dewy windows, fogged mirrors and cold leather slowly came around.  About 6-8 weeks ago, when we had our first ‘hey it’s spring!’ weekend I decided it was time to dust the Sprint off, charge the battery, and start using it again.  Everything was going fine -it cranked over nice and fast, the carb was atomizing fuel, it had spark but it wouldn’t start.  I ended up bump starting it on my long steep driveway.  This was the first bump in a somewhat long, thoroughly bumpy road that only recently smoothed.

Starting at the happy ending… Me and the Mrs. in our Sprint on the track at Sears Point.  Thanks for the picture Greg!

The Sprint had been hard starting for a while -usually catching after the key had left the start position, and frequently wetting the plugs.  My first thoughts were that it was carb related because the Weber DCD I had been using lacked a functioning cold start device, but even warm it was a gamble parking because it frequently wouldn’t start and required bumping.  I borrowed a Solex from Laurence (thanks again Laurence) that was a known good, in adjustment, fully functioning carb pulled from a good running car when a pair of DCOE’s replaced it a few years back.  The addition of this carb seemed to improve things, but not as transformationally as I hoped.  Cold starts still required bumping and warm starts seemed to require luck.

My attention next turned to the coil.  When I rebuilt the engine I installed the original Lucas coil that came with the car.  I swapped it for a new generic ‘Made in China’ coil I had laying around and it seemed to help.  I say seemed, because it started right up when usually it would balk.  I drove the car home and then went to drive the car to my neighborhood grocery and I got about 100 meters from my driveway when the car quit.  Mike offered to lend me a spare coil he had for his SS (thanks again Mike) and once I installed this the car started right up.  I continued my trip to the grocery store.

When I left the grocery store the car started right up but as I pulled out of the parking lot it started running rough.  I barely made it home.  Some head scratching and careful observation revealed oil on the points of the Marelli Veloce distributor.  A quick cleaning improved things.  After this I decided to heed Duff’s advise (thanks again Duff) and checked the voltage at the coil.  Okay, finally some pictures!

Here is the coil voltage, no cranking.  Not too good, but capable of producing a weak spark.

So with the ignition on, but not cranking, I had just over 11 volts at the coil.  It must have been sparking with this or it wouldn’t have bump started or occasionally caught when the ignition left the start position.  Next I put the car in neutral and cranked it over.

 Cranking voltage at the coil of 7.38 volts will not result in a spark!

Aha, low voltage at the coil when cranking.  I drove home, put the car on a charger overnight and when I returned from work the next day I tried to start it -no start.  I decided to check the tightness of the battery leads and when I pulled on the negative lead it simply fell apart in my hand!

The low coil terminal voltage culprit.  The captive fastener heads had simply worked their way out of the lead. 

I went to Kragen and for $6.99 was able to buy a new negative lead in the right length.  Leaving the store I found $5 in the parking lot -sweet.  I installed the lead and vroom, it started right up.  I switched it off and then vroom, it started right up again.  I felt dumb that I hadn’t thought to check such a simple, easy to check thing as the battery leads, but glad none the less that my woes seemed to be over.  When the Mrs. got home I decided to take her for a triumphant drive in the Sprint.  The points oiled up again 100 meters from the house.  D’oh!  This was the evening of April 5th.  The next morning I made a decision after reading some testimonials -I bought an electronic ignition distributor and Bosch blue coil from Centerline.  They arrived Friday night (the day before the picture on the track above was taken). 

It took me about 45 minutes to swap them.  This is actually a long time to do this job.  I couldn’t get the distributor shaft seal into the front cover and ended up removing it and using the old hard o-ring from the Marelli unit.  Needless to say the car simply leapt to running life when the ignition switch hit the start position.  I adjusted the timing based on running sound and did some hot laps around my neighborhood.  I was so enthused by how good the Sprint was running I even drove us that night in the Sprint out to eat at Sidebar -a little restaurant on Grand across from Lake Merritt.  The next morning I set the timing with a light -it was 10 degrees too advanced – and headed up to the track.  Case closed?  The Snowball rally is less than 2 weeks away so I plan on driving the Sprint a lot before then, but so far so good!

Rebuilding the Marelli distributor that I no longer am using…

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4 thoughts on “Spring Sprint sparks

  1. Looks like you’ve chased the gremlins away and are ready to enjoy the Sprint once again. Are you back to the Weber DCD ? If so, any difference in performance ? I’m thinking of changing from Solex to a vintage Weber, 36, DCD but am uncertain as to the needle specs for a 1300 Sprint engine. My carb was, previously, used on a 1300 Mini Cooper.

  2. Hey Matt,
    Excellent photo sets of a spectacular gathering! See you driving your Sprint at the Lap of Marin today?
    Laurence

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