Coil Problem? HELP

fast911s · 11-01-2003, 12:33 PM

Transporter just dropped my car off...the minute he drove away, the car stopped idling. Turns over, fuel pump working...no spark arc when I pull a plug wire. Just had conversion from Marelli to Bosch, and car had been running fine (a used coil in coversion).

So its Saturday afternoon in Houston...and the only coil I can find is very similar...but. The number on the bottom of my coil is 0221 121 001 with a 122 under it. The coil a friend gave me (not sure of orign year but off a 911) has same number but with a 244 under it.

Am I going to mess something up big time if I try this coil? Also, how can I otherwise trouble shoot this problem. Would sure like to drive this weekend!!

fast911s · 11-01-2003, 02:41 PM

So now I swapped out the coils, and still no spark. Checked fuses in engine compartment with ohmmeter - all ok. Pulled the ground wire off the coil, and inserted a voltmeter between gound post and ground with ignition on...have juice there. Reset points about four times just to be sure.

Oracle · 11-01-2003, 03:08 PM

Hi,
That coil number is Ok, the one I got has a 908,a few months ago I did some research and I think those numbers are either a batch number or manufacturing place (Brasil, Slovakia, Germany, etc)

I wish I had a clue on what's wrong with you car. Good luck!

-J

john70t · 11-01-2003, 03:22 PM

Also make sure the CD Box is making a whine and the coil and CD grounds are on correctly.
I guess check for volts at fuse, then at CD...(?). Good luck and post any tips.

Allenk · 11-01-2003, 05:15 PM

How are your cap and rotor? I had a guy stuck down the road from me with this same problem and it turned out to be a bad rotor. Odd because there was continuity through it but not enough to fire the plugs. Take the lead from the coil and ground it out while someone cranks the engine to see it it is producing. same test as with a plug.

RoninLB · 11-01-2003, 06:06 PM

I never had to jump the dizzy to check a Permatune or Bosch box.
But I just installed a new MSD and confirmed my install by removing the dizzy external trigger wire and grounding it touch and no-touch a few times with the coil high tension wire about 1/4 from a ground.........Ron

Early_S_Man · 11-01-2003, 06:27 PM

Jim,

I seem to be missing part of the story ... why was the car on a transporter??? Was it running and functional before heading home to you?

The three-digit numbers below the Bosch part number on the coil base are a date code ... xyy ... where x is the last digit of the year and yy is the week of the year it was manufactured.

Quote:

Pulled the ground wire off the coil, and inserted a voltmeter between gound post and ground with ignition on...have juice there. Reset points about four times just to be sure.

What EXACTLY were you checking? Continuity to ground??? What did you find that you described as 'juice?' There ISN'T supposed to be a Voltage between chassis ground and the coil ... except when a 350 - 460 Volt pulse is generated by the CDI-unit after triggering by a ground pulse to the trigger input lead from the distributor ...

Please use conventional terminology is your descriptions!!!

fast911s · 11-01-2003, 08:05 PM

Oops...sorry for the misuse of terms - ignorance on my part.

Bought the car in California...had the car checked out (rebuilt carbs, bosch dizzy, clutch, etc.). Put about 200 miles on it before transport home to Texas. All was fine in California. It was unloaded from the transport in Texas; started fine to roll off the transport, and was sitting there idling while I paid the driver. Just as I gave him a tip, the car died and would not start. I thought it had loaded up, so I waited, and waited - no fire, not even a spurt.

Check fuel - seemed to be OK, (pump running) , so checked for spark (pulled coil wire - no spark). Replaced coil, reset points - no spark. Wondered if it was a fuse or switch problem, so pulled negative side of coil (post that is grounded to fan shroud) and ran voltmeter between post and shroud) - had voltage (reading escapes me now). No particular reason for checking there, just had enough brains to not jump across the coil terminals, but wanted to see if iginition switch was doing anything.

Thanks for your help

Don't know how to check CD's (or coil), and hate to keep buying replacement stuff until I stumble upon a fix.

RoninLB · 11-01-2003, 08:12 PM

Quote:

Originally posted by fast911s
Don't know how to check CD's (or coil), and hate to keep buying replacement stuff until I stumble upon a fix.

I never had to jump the dizzy to trigger a spark on a Permatune or Bosch so I'm not suggesting non hard info.......Ron

Early_S_Man · 11-02-2003, 08:54 AM

Jim,

The best way to test coil and CDI-unit is by putting the engine on an ignition scope such as an old Sun machine ... or conventional oscilloscope with a special-purpose 40 kV - rated high Voltage probe.

Bench testing can be done by powering the CDI-unit from a 13.8 Volt power supply of at least 3 Amp capacity. A substitute pulse source [to replace distributor & points] can be assembled from a 5 Volt or 12 Volt reed relay and powered by a suiable 5 or 12 Volt wall transformer with full-wave bridge added -- giving a 120 Hz pulse train.

If you know a Ham-radio or electronics enthusiast, he/she would be able to test the CDI-unit and coil together. Don't test the CDI and coil without a load on the coil! A suitable load for the coil consists of an old, tested-good, spark plug wire and a new or used spark plug with attached ground lead.

Grounding of the relay/fuse/regulator panel -- specifically the grounding of the CDI-unit -- is VERY CRITICAL!!! I usually run a heavy braided ground strap equivalent to an 8 ga wire from under one of the mounting bolts for the CDI to under one of the fender mounting bolts for the relay panel. Remove the CDI-unit and clean the grounding 1/4" Faston tabs -- remove from the magnesium case and clean both under the tab location on the case and the tab itself with vinegar and stainless steel toothbrush, followed by brushing and rinsing with water. When everything has dried, apply silicone grease coating to Faston tab and re-attach to CDI case. The four-wire female connections to the CDI-unt can be cleaned with vinegar and have the sides of the connectors that slide onto the male Faston tabs crimped slightly to make a better connection. Don't close the gaps on each side to zero, just slightly crimp! The three wires in the special three-wire connector can be slid out an inch or so by lubricating the wires at the back side with silicone spray, then pulling the wires all out, gently, with needle-nose pliers.

john70t · 11-02-2003, 09:25 AM

Jim, also if you have the time, go through the archives of Warren Hall's posts on everything electrical, mechanical and chemical. Very informative as to how to do things right.
I think there are a lot of people waiting in line for his next book