Just Got the OEM Tach to Work With the 4.0 MPFI
ThisGuyUKnow
Full Time Jeeper
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- Harleysville, PA
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- 1986 CJ7 Laredo 4.0,Nv3550,D300 Twin Stick,AMC20 3.31, 31 BFG
Honda vtx1800c
For anyone who has to MPFI and either had to go with an aftermarket tach or just have a non working tach:
Today I defied the man and I successfully got the OEM tachometer to work with the 4.0 coil. I need to do some fiddling with it to make sure I can get the tach in the dash and still have the same result and Ill post up the wiring. But for now it is pretty simple you cut Positive wire to the positive side of the coil and wire the the tach in between.
I need to make sure it will work if I run the wiring into the cab. Currently I have it right at the plug for the coil. The CKT is shared between the alternator and the injectors, so am not sure if I splice into the ckt at a different point whether or not the injectors would mess with the signal.
So here is a video of it working. I am hoping that it is reading high because it is a cold start, I talked to a buddy with the Hesco tach and he says his idles that high when cold, which makes sense.
Today I defied the man and I successfully got the OEM tachometer to work with the 4.0 coil. I need to do some fiddling with it to make sure I can get the tach in the dash and still have the same result and Ill post up the wiring. But for now it is pretty simple you cut Positive wire to the positive side of the coil and wire the the tach in between.
I need to make sure it will work if I run the wiring into the cab. Currently I have it right at the plug for the coil. The CKT is shared between the alternator and the injectors, so am not sure if I splice into the ckt at a different point whether or not the injectors would mess with the signal.
So here is a video of it working. I am hoping that it is reading high because it is a cold start, I talked to a buddy with the Hesco tach and he says his idles that high when cold, which makes sense.