I have been trying to hunt down the little box that holds the relay and timer for the injector blower that comes on after driving on a hot day. I have read that it is supposed to be either by the fuse box, or near the fan shroud and battery. But I just cant seem to find it anywhere. It also doesnt help that I have no idea what it actually looks like. I followed the wire for it a little bit, but I would rather not cut open my entire engine harness. Another small thing is that the haynes manual labels the positive wire for the fan as being pink with a black stripe, while mine is solid orange.

 

I won't be able to help but I'd like to learn something.

What is an injector fan?

 

'87-'89 trucks with the 4.9l came with a little fan that turns on for a few minutes after you shut the truck off that blows onto the fuel injectors.

 

The blower is supposed to turn on to cool the injectors after you shut down the engine for easier hot starts.Not sure how effective it was because the blower was omitted after a few years. The relay is behind the fan shroud near the battery.Its about the size of a deck of cards.

 

Ahh cool. First I've hear of that. Cool, (if it worked).

 

So I was able to find the fan's power wire in the main harness one the drivers side of the radiator, which points to it being on the interior of the truck. And then I found this diagram in one of my service manuals, which shows it on the interior where it looks like it is behind the dash in the radio/ash tray area. So Ill go looking there tomorrow.

 

You might want to consider disconnecting it because I have my doubts if it is really needed since the 1990 and later 300's seem to get along fine without it.

 

So I ended up finding the relay. It was behind the radio and near a few other relay boxes. When I opened it, one of the capacitors had fallen off and was loose in there. So I soldered that back on and put everything back together.
As for the usefulness of the fan. I have heard a few things about an updated design to the fuel pressure regulator being why the fan wasn't needed starting in 1990. Along with claims that the new fuel pump system used in 1990 also made it unneeded. But regardless of whether or not that's true. The fan doesn't cause any problems for the truck, so I don't see a reason to remove it.

 

Thanks for letting us know where that rascal was hiding behind the radio.

 

When it causes a problem, it'll be too late to remove it. The only problem I've heard of it causing is the truck catching fire.

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