Heya folks.

Finally having dealt with (other than a new oil return seal) the dead turbo (Put in a slightly bigger td04hl-15g) on my 740, I'm back at the problem I was having before it died.

When running above idle speeds, the injectors will stop pulsing for anywhere from an instant for up to 10 seconds. I determined this by backprobing an LED into the injector wiring and seeing the LED stop flashing every time the engine cut out. Sparks continued uninterrupted.
Signal to the fuel ECU from the ICU looks consistent.

Fuel ECU is throwing codes about the AMM, TPS, and lean/rich conditions. The AMM and TPS feed from a common circuit powered by the main fuel relay - I've resoldered 2 relays and tried both of them, but it persists with both.

I pulled the fuse panel apart and found #1 fuse a bit melted. Took off the top cover and wire-brushed all of the connectors and reassembled - no change.

I'm about to go borrow a -560 (problematic w/fuel circuit failure) ECU and see if it works.


I was just doing some more research, and came across a mention of a traction control system called Luxor that shuts off injectors when wheel spin is detected, and also that the injectors shut off when the throttle switch says the throttle is closed "when coasting". I wonder if the throttle switch or its wiring is shorting out.

I'm interested in exactly how the wiring runs and how the injectors are grounded by the ECU. I think it's pin 18 responsible for grounding them, the RSR feeds them power, the main fuel relay feeds the RSR, and the ECU grounds/energizes the main fuel relay to turn it on.

Is there a logic tree somewhere of how the injectors pulse? Can someone help me build one?

Cheers!