Engine/Transmission (1994 - 1998) More fuel problems

[MatthewPark]

To keep from hijacking a thread, I started this one.



My truck has started this moody thing where sometimes it has all the power it should, 40 pounds of boost and 1250 EGTs, and sometimes it has no power, 16 pounds of boost, and 700 EGTs. Today, for example, it was running just fine for my 10 mile drive to my shop. Drove 15 miles back past my house, still running fine. Drove to my house, still fine. Everything after that, no power, boost, or EGTs. Something happened while I stopped at my house that causes it to not get anywhere near the fuel it should. This has happened probably 5 or 6 times now, maybe an average of once a week for the past couple of months.



Now I did discover that I can get under the hood and shut the truck off manually by pulling down on the shutdown solenoid arm. It's VERY easy to pull down (with the engine running and the key in the run position). I don't imagine this should be the case. This could be the culprit. However, every time I reached in there (while the truck was in gutless mode), the lever was all the way up, I could not pull it up any further. That's not to say it doesn't drop down under throttle, it's just to say it's always all the way up when I first touch it.



I guess tomorrow I should take the solenoid off, and zip tie the lever up and take it for a spin. I did previously remove the plate during one of these episodes and it had no effect, so I don't think it has to do with governor arm adjustment or anything like that.

 

[Forrest]

I'll take a wag Matt ... sounds like a Valet switch that's on the fritz. Plus or minus a few pounds of boost, that's exactly what happens when I flip off the switch.



It's a vacuum solenoid that interrupts the line from the intake manifold to the AFC housing. Blocking/cutting off the air limits rack travel & you get the "symptoms" you're seeing. Wonder if that line is cracked or loose somehow.





do a search, but here's one:

http://www.dieseltruckresource.com/dev/showthread.php?s=&threadid=39686&highlight=valet+switch









Forrest

 

[MatthewPark]

I've checked that line, no leaks or problems with it anywhere.

 

[Joe G.]

Take the AFC off and cover the hole to keep oil from flying all over the place. Go for a test drive. It should smoke like a forest fire and have lots of power. If it does not then you have an AFC problem of some sort.