Operation of the 6.9 and 7.3 International-Navistar IDI fuel system

The fuel injection system on the classic 6.9 and 7.3 liter International-Navistar engine used in diesel fords from the 70s to the early nineties is relatively simple, but some confusion still remains about how it functions. The major components of the system are the lift pump, filter head and filter, fuel injection pump, fuel injectors, return system, selector valve, and the fuel tanks.

Fun with Fuel Delivery

In the continued saga of my 1993 Impreza LS, the fuel pump crapped out for real this morning (cycling the key on and off repeatedly did nothing) so I ended up having to swap it. I haven't fastened down the carpet since the last time I looked at it, so it was a fifteen minute job or so. The replacement is from a 1995 (IIRC) Legacy, but pretty much all Subarus use the little JECS canister pump also used by Nissans and such and only earlier, FWD Subarus have less displacement (and thus presumably less fuel delivery) than my '93 LS. This swap is even easier than on (for example) the 240SX because Subaru uses a slick connector for the fuel pump and sender. This connector, which is male on the outside, also has two male connectors on the inside, into which the sender and pump plug separately.


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