It just dies.....then starts
03-12-2009, 03:52 PM
#61
Race Car
Join Date: Sep 2005
Location: England UK
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Nathan,
The CDI box, magnetic pickup resistance, and coil primary resistance are all within Permatune's specs. Car was competely dead on Sunday. On Monday I took the CDI box out, cleaned up its grounds and replaced. Car fired up immediately, thought I was in good shape, and then it died after a couple minutes. Happened two or three more times. Last night the car showed no problems.
Because the tach needle drops hard and stays there when shutoff happens and because of its sharp on-off nature, my technician and I are leaning toward a shaky CDI unit. Even with terminal resistances ok, if the CDI's inverter stops working, thyristor doesn't fire, or one of a hundred other internal electronic issues, the unit won't output pulses to the coil.
On Sunday when the car wouldn't start, there was a raw gas smell and at one-point quasi-hydrolock hard cranking. This seems to indicate fuel delivery.
The CDI box, magnetic pickup resistance, and coil primary resistance are all within Permatune's specs. Car was competely dead on Sunday. On Monday I took the CDI box out, cleaned up its grounds and replaced. Car fired up immediately, thought I was in good shape, and then it died after a couple minutes. Happened two or three more times. Last night the car showed no problems.
Because the tach needle drops hard and stays there when shutoff happens and because of its sharp on-off nature, my technician and I are leaning toward a shaky CDI unit. Even with terminal resistances ok, if the CDI's inverter stops working, thyristor doesn't fire, or one of a hundred other internal electronic issues, the unit won't output pulses to the coil.
On Sunday when the car wouldn't start, there was a raw gas smell and at one-point quasi-hydrolock hard cranking. This seems to indicate fuel delivery.
Usually ignition fails when it gets hot so I would bite the bullet and get a new CDI.
I would get an MSD6AL.
03-13-2009, 10:09 PM
#62
Instructor
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Nathan,
My tech and I also reached the same conclusion, but I took what'll undoubtedly be an unpopular path and got a Permatune...I wanted a plug and play fix that was minimally invasive. The unit arrived yesterday along with a new Bosch coil. I got the CDI in last night and drove the car for nearly 45 minutes with no problems. Coil is next.
P/N is 911SC902 and is apparently a redesign of the older unit: http://perma-tune.com/911SC902.html The shipping label was from Plasmatronics in New York.
As a performance metric of spark quality, I'll monitor how the CDI and coil affect gas mileage, hopefully favorably.
My tech and I also reached the same conclusion, but I took what'll undoubtedly be an unpopular path and got a Permatune...I wanted a plug and play fix that was minimally invasive. The unit arrived yesterday along with a new Bosch coil. I got the CDI in last night and drove the car for nearly 45 minutes with no problems. Coil is next.
P/N is 911SC902 and is apparently a redesign of the older unit: http://perma-tune.com/911SC902.html The shipping label was from Plasmatronics in New York.
As a performance metric of spark quality, I'll monitor how the CDI and coil affect gas mileage, hopefully favorably.
