What is this part?

[ROCK HARVEY]

I was getting ready to do some testing to see why my cold idle isn’t working, and I saw this small box-looking thing just behind the thermostat housing. It has 4 wires going into it, is it a relay? I’d like to know what it is because it looks semi-melted and I’d like to replace it.

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[chillman88]

Thats a relay for the water in fuel sensor

 

[ROCK HARVEY]

Awesome, thanks. I was looking for it on the cold advance/high idle circuit diagram and couldn’t figure out what it was.

 

[david85]

Interesting. I don't remember seeing that in my truck. Is it something they did for 1987 and up only?

 

[chillman88]

Interesting. I don't remember seeing that in my truck. Is it something they did for 1987 and up only?

No clue. I only know about it because I dug it out of the harness on my 91 and looked it up on Google

 

[chillman88]

I think technically it's an amplifier and relay. I remember seeing something about it boosting the signal from the actual water in fuel sensor but I don't really know any specifics.

 

[IDIBRONCO]

Is it something they did for 1987 and up only?

It's probably for 1988 and up. The 6.9s all had the water separator underneath the brake booster. The 7.3s had it underneath the fuel filter.

 

[Nero]

I can testify the harnesses from an 88, 89, and 1990 that I have all have it. Never knew what it was for, but never cared enough to look into it.

 

[ROCK HARVEY]

Based on what I’ve read, it reads the weak signal from the sensor on the filter and sends 12v to the light in the dash like chillman said. Given that they’re $60-$100 to replace, I think I’ll live without my WIF light until I can salvage one off a junk truck.

 

[david85]

Ok, I get it now. I retrofitted something similar in my truck when converting to a 7.3 style separator.