Need help with ignition

[HB Chris]

I finally got the engine back together after redoing the head and tried to start it. It wouldn't run more than 3 or 4 seconds so I checked the voltage on the + terminal of the coil and only saw 1.5 volts. When I checked the voltage before the coil resistor I had 12v, ergo resistor must be bad. I bypassed the resistor and ran the wire direct to the coil. Bingo, it would run! The resistor reduces the voltage while the car is running down to 9V or so to protect the points. There is a second wire to the coil from the starter solenoid that bypasses the resistor and provides a full 12v during starting only, that is why it would start but die quickly. Engine was smooth so I had the timing pretty close from setting it just visually.

I bought a new Bosch coil as insurance and swapped in the resistor from the `69 2002 which has the same specs (1.2 ohms). Again, I would get only 1.5v. Could it be that the 2002 is wired improperly and it also wasn't working (the 02 also has a relay near the coil, coupes don't)? Don't know, but both resistors got very hot and you could see them glow, I never noticed that before. So I just jumped the wire to the coil again and this time the starter would spin with the key in "run" position but not engage the flywheel, it just spun very fast. Very weird, perhaps because the battery was so low? But it spun when key was in "run" and not in the start position. Can't figure this one out. Starter is brand new lightweight M3 style Bosch 440X. It cranked great earlier when I couldn't get the car to keep running. I am waiting for a new resistor and a charged battery before trying again later this week. Anyone ever experience this before? Thanks.

 

[jmackro]

Chris:

It has to do with the wire between the starter and the coil "+" terminal. I would interrupt that connection, and see how it behaves.

- There is a path to ground through that wire - that's why the resistor is drawing so many amps.

- When you put the key in the "run" position, enough current flows through the resistor and back to the starter to energize the motor. I am guessing that the new lightweight M3 style starter has different internal wiring than your old starter - that the wire you have connected to the coil "+" goes to the motor.

You going to be at Cars & Coffee tomorrow? Or did you have to cannibalize your '02 for ignition parts?

 

[HB Chris]

Jay,

I will be there if you bring your coupe so I can look at your wiring. PC also thinks I have something going to ground.

 

[HB Chris]

Got it running

Jay,

I ran a wire from the battery to the resisitor to see if it was the green + wire that had an issue, nope. I then removed the thin black/red wire from the starter solenoid that bypasses the resistor and goes straight to the coil. Bingo! Resistor was not over heating and car started and ran great. Since it only provides un-resisted power during starting I assume I can just leave it unconnected. The solenoid is marked with terminal 50 which comes from the ignition switch and this is a thicker black wire. What bothers me is why I can't hook up the black/red. The wiring diagrams say this goes to terminal 16 (15?) on the solnoid but it isn't marked as such. In the attached pics I had it on the upper terminal that is connected to the braided power wire to the starter. The bottom spade terminals are both terminal 50. I didn't try to hook it up here since it started fine. The starter is a Bosch SR440X and the terminals aren't positioned like the old SR71X/41X.

Does anyone else have this starter, with the ballast resistor? You can only see it by holding a small digital camera between the intake manifolds which is what I did. Photo is rotated slightly, straight up appears at 2:00 and black/red is on right, black/50 lower left. Replies are welcomed.

I also had 14.5v before the resistor and 12.5 on the output side, is this too high?