That air compressor mounting gasket doesn't leak very often, I suspect your oil leak is the HEUI pump mounting o-ring above the air compressor=typical oil leak on those engines(3126). The oil is probably seeping down the front cover onto the air compressor, so it just looks like an air compressor oil leak.


I have a 2002 Frtlnr FL70 and I changed my HEUI pump mounting o-rings and at the same time, I replaced the RPM/Timing sensors and their mounting o-rings to the newest, most updated(more reliable) sensors. NOTE: That is the easiest way to change those sensors (with HEUI pump off, on an engine with an air compressor) so do it at that moment.

2nd note: I had logged fault code for my rpm/timing sensors, too; BUT I could tell they were going bad, because it took longer to start(2-3 seconds), verses it starts immediately, now!

3rd note: rpm/timing sensors come in pairs, installed in a bracket (as a unit) DO NOT REMOVE FROM BRACKET, they come shipped in their proper positions.(also, make a note of each wire connector, to each sensor, they are different=must be hooked up correctly)



Also, the oil supply line/hose to the air compressor tends to seep oil, too ( I replaced mine also)