78 FI Bus #3 Running Lean (?)

[vwlover77]

'78 Bay, Stock FI....

I pulled my plugs just to get an idea how things are looking mixture-wise since Colin adjusted the AFM in June.

1, 2, and 4 looked good, maybe just a little on the rich side with light, fluffy gray/black everywhere except the area just around the spark gap.

#3, however, had a white ground electrode and looked a lot grayer/whiter than the others.

I'm positive the intake manifold gaskets at the heads are well sealed, the injectors have new o-ring seals, the hoses at the plenum are new, and they are clamped to their plenum connection. T

The injectors were cleaned and tested by Cruizin Performance in 2005 and were very equally matched and passed all tests. The weird thing is, if my memory is correct, anytime I've pulled the #3 injector out, it's always wet with fuel.

#3 is my highest compression cylinder (120lbs) compared to the others:
#1 100 lbs, #2 110 lbs, #4 115 lbs

Any idea what's going on?

[texabus]

malfunctioning injector?

[KYLE]

you might consider that you have high resistance on one of the wires in your harness causing a lower voltage to reach injector #3. It could also be extra resistance in the FI Resistor bank. One easy way to check this is to swap connectors on injector #3 and #4. All injectors fire at the same time anyway, so it should have no effect on the system as a whole. If this happens to be the case, then next time you check plugs you would see #4 looking lean.

[vwlover77]

Good idea! I'll give that a try.

Thanks!