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Some Help Identifying These Hoses

LScout800

LScout800

LS Powered Tractor
Joined
Jun 10, 2020
Member Number
1937
Messages
420
Loc
CA
Was coming down from Fresno and the heater vents started spewing smoke, pulled off the side of the road before the fire spread anywhere else, it went out right away.
Truck is a 1991 F250 with a 5.8 and a 5 speed.
20230624_133947.jpg

20230624_133939.jpg

Need some help identifying these hoses, and what exactly caused them to catch fire. There is a whole vacumn line mess on top of the engine and I was having trouble figuring out what did what. Truck needs a smog by the end of the month.
 
I used to know but I forgot because emissions systems on 90s trucks are irrelevant by over a decade here. :flipoff2:


Kinda looks like the air diverter valve.

Not sure why that shit would ever get hot enough to catch fire since it's got a smog pump feeding it air
 
I am no expert here, but after looking at many images I believe it to be an Exhaust Air Supply Valve:

7D1059.jpg


I've also seen it listed as an Air Bypass diverter Valve, but the pictures all show the same part. And it's part of the air pump system as 72Pstroke stated.

Hope this helps and good luck... :beer:
 
Will Scarlet said:
I am no expert here, but after looking at many images I believe it to be an Exhaust Air Supply Valve:

7D1059.jpg


I've also seen it listed as an Air Bypass diverter Valve, but the pictures all show the same part. And it's part of the air pump system as 72Pstroke stated.

Hope this helps and good luck... :beer:
Click to expand...
Looks like what it is. Will run to the parts store later today to check. Was having a lot of trouble figuring out what it was thanks.
arse_sidewards said:
I used to know but I forgot because emissions systems on 90s trucks are irrelevant by over a decade here. :flipoff2:


Kinda looks like the air diverter valve.

Not sure why that shit would ever get hot enough to catch fire since it's got a smog pump feeding it air
Click to expand...
My theory is that the engine has blows a lot of oil back through the intake (about 400k miles on the engine) and all the lines had a lot of oil vapor in them. The fire started after I dropped a gear to pass a semi so the RPMs were pretty high, it was also a hot day and the truck was hauling a trailer.
 
I might have some/ all of that stuff from a 91 e350 5.8 c6 truck

Got an inventory of what you need?
 
Make sure smog pump is still functioning and didnt self destruct and send shit all thru the system.

I had a 4.9 with ton of blowby and i rigged up the smog pump to pull crankcase vacuum and send into exhaust. It ended up fucking the pump and destroyed the vanes inside.
 
The only reason for a diverter valve to burn up like that is if one the check valves fail. The check valve is to prevent the exhaust gasses from entering the fresh air side of the system. You probably have more than one check valve, follow the hoses from the carnage to the right one.
 

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Levigarrett76 said:
Make sure smog pump is still functioning and didnt self destruct and send shit all thru the system.

I had a 4.9 with ton of blowby and i rigged up the smog pump to pull crankcase vacuum and send into exhaust. It ended up fucking the pump and destroyed the vanes inside.
Click to expand...
I did the exact same once too. Was hard to start so I didn't run it long enough to find out what it did to the smog pump.

You'd think oily air would be better for it than dry air since the steel vanes just ride on the aluminum housing but I guess not. :laughing:
 
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