Ignition woe's

[Natesbillygoat]

Hi all! I've got an 85 720 4x4 Dx "Billy Goat."  I'm having trouble with the exhaust coil not shutting down. I only know this because of a tachometer thread on here that dove into this issue. I initially thought it was carbon build up. P.S. My tach isn't working either. So my question is which vacuum switch is the one for the exhaust coil. I think its the one nearest the coils,but I'm unsure. Does anyone have a pic or good explanation of where it is? Thanks in advance! Also I'm looking for a stock 4x4 steel wheel. If anyone has or knows of one.

[datzenmike]

The tach must be connected to the intake coil or it will shut off when the exhaust side is deactivated.  Nissan says the reason for deactivating the exhaust side during heavy load driving like passing or climbing steep hills is "to reduce engine noise". I think this is Nissan Speak for "what you hear is the two flame fronts colliding and the driver may be alarmed by the diesel like sounds." Nissan doesn't say there is any damage done by this, just the noise. Anyway they added a vacuum switch on the right inner fender right next to the vacuum switch for the fuel cutoff for the emissions system.  I don't know which is which as they are identical looking. The vacuum operated switch provides a ground for the special distributor and the module inside just stops the exhaust coil. If that weren't enough, the module also advances the timing to make up for the longer burn time with single plug operation so that no power is lost. Seems like a lot of trouble just to reduce some engine noise.

 

The old distributor had 3 wires wrapped up in a harness. The newer distributor has an added 4th (white) wire with a plastic plug, below

 

If your distributor was swapped and a 3 wire one put in you'll never get the exhaust side plugs to shut off as they are supposed to. Earlier Z series engines didn't have this and they were fine without it.

[Charlie69]

6 hours ago, Natesbillygoat said:

Hi all! I've got an 85 720 4x4 Dx "Billy Goat."  I'm having trouble with the exhaust coil not shutting down. I only know this because of a tachometer thread on here that dove into this issue. I initially thought it was carbon build up. P.S. My tach isn't working either. So my question is which vacuum switch is the one for the exhaust coil. I think its the one nearest the coils,but I'm unsure. Does anyone have a pic or good explanation of where it is? Thanks in advance! Also I'm looking for a stock 4x4 steel wheel. If anyone has or knows of one.

Flagstaff Pick & Pull has 3 720 and I believe 2 if not all 3 are 4 x 4s.

[Natesbillygoat]

Thanks for the info guy's!