Re: Round two (v2.1)... (archive)

Since I got the car back, I have removed the spark plug wires and tested the resistance of each one. Each measured about 6.5 kohms (some were 6.3 or 6.1 and others were 6.7 or 6.8), except for the number 2 wire on the driver's side. I cannot get a reading for that wire, the meter shows nothing. This is hard for me to believe and I have tried it several times, but still nothing on the meter.
When you say nothing, does that mean no resistance as in 0 ohm or do you mean nothing as in open circuit (extremely high resistance)?
a) if 0 ohm, it would appear as though the resistor on the plug end is bad - never had one apart so I don't know how the resistor would short out or whether or not it is DIY repairable. I do believe however the resistor is a replaceable item and a hell of a lot cheaper than a wire set.
b) if open circuit, it could mean a break in the wire between the ends or that it has disconnected from one or both of the ends. Again, I haven't taken these particular wires apart but if it is the end connections, there is a slim chance that you might be able to resurrect the connection. In the end though I would look at replacing at least this one wire if not the whole set with the expectation that, unless there has been some physical damage to this one wire, more failures are on the way. OUCH!!

The distributor caps also give some wierd readings, so I'm looking at replacing those and the rotors.
You can do a visual check to see how 'chewed' up the contacts are - clean them, and look very closely at the cap for signs of hairline cracks. You can also take the plastic cover off and, with it running in the dark, take a water spray bottle to it - watch for sparks jumping and listen for engine misses. Once you have the cap off, you can measure resistance from the center electrode to the individual contacts (should be 0 ohm) and the rotor center to contact resistance should be 1,100 ohm.

I also tested the ignition coils with the following results:
Left side - driver's side
primary - .7 ohms
secondary - 9.83 kohms
Right side
primary - .7 ohms
secondary - no reading
The bentley manual says
primary - .37 ohms
secondary 9.0 ohms

Do you think that the primary is bad (.7 vs .37)? Looks as if the secondary on the right side is bad. What kind of effect would that have?
The readings on mine were similar to what you obtained:
Primary (both): 0.6 ohm
Secondary (cyl. 1-6 left): 8.6 kohm
Secondary (cyl. 7-12 right): fluctuated from 57-1150 kohm during the few times I could get any reading at all. I find it very curious that both of us had problems with the same coil - coincidence!!
There are no problem with the primary readings on either coil but the RH coil should be replaced. It is not likely the sole cause but definitely one of the contributors as would be the wire, rotor, etc..

Another question, the Bentley manual mentions the part number for the ignition coil as 20510171101. The coil on the right side has this number, but the coil on the left side ends with 02. Should the numbers match?
No, they won't match because each coil is a mirror image of the other and therefore require their own part number. The BMW part number for mine (cyl. 7-12), which I think is the same one you are describing, was 12-13-1-742-926. The Bentley number might be the OEM's(?).

Keep digging, you'll beat it!
'88 750iL

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Re: Round two (v2.1)... Keith 14:00 7/05/2001 (0)

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