I pulled my throttle body off today to clean the IAC passage, and noticed fuel in the upper plenum. There was enough in there that basically the entire inside was wet with it. The car hasn't been run in a week, so I don't know how much was there to begin with. I was thinking maybe the fuel pressure regulator was leaking fuel into the intake, but it doesn't seem to be leaking. I know the cold start injector sprays fuel in the plenum, but I wouldn't think there would be this much.

 

Is it fuel or oil film from the pcv valve?

 

I'm pretty sure it's fuel, it has a strong gas smell. There was quite a bit of gunk in the plenum too, so it's a little hard to tell for sure.

 

Did it look something like this ?


What causing this thing?? I cleaned my out last year when I changed the injectors... that black "gunk" smelled alittle like fuel... hard to tell for sure..

 

Yeah, that's pretty much how it looked. I've got the runners and plenum off, and I've got it all cleaned out for now, but I'm curious what's causing it too.

 

It does not take much blowby to really gunk stuff up. The oil/gas fumes mix with the egr soot and it tends to make this black gunk.

I bought a 1985 6.3 diesel in 1988, 32,000 miles on it. The pcv was upstream from the egr. Had to pull the intake and clean out, 1/2 plugged up intake runners, they had this black oily carbon in them. Like real heavy grease.

This would be my quess, any other words of wisdom?

 

This is not normal at all!! I had this problem with mine last summer in August when I drove to the T/A Nationals and noticed I started having a hard start problem with the car and running rough at start-up. It would chug black smoke at start and then clear out. I got home back to Indiana and checked into it the next day. I found a lot of fuel in the plenum and couldn't figure it out. It then ocurred to me that the only thing even remotely fuel related that would lead to the plenum was the regulator. It is vacuum ported throught the plenum. When the car is off, it still holds pressure in the system and if the regulator diaphram is bad it will allow fuel to be pushed out through the hose into the plenum. I pulled it all apart after this assumption and found the diaphram to be torn in two spots. I replaced it with a new one and the problem was fixed and also my hard start problem went away also. I hope this is helpful because I know that sometimes on these babies it is a pain in the a$$ to diagnose these problems. Good luck!!!!

 

I'm afraid I don't have a solution for you but I can tell you that's not normal. I pulled my plenum off for the first time after 91000 miles and there was no fuel in it.

 

theres a hose that comes off the passenger side valve cover that runs to the throttle body check it to see if oil is entering through the throttle body and getting into the plenum,later jimmy

 

...another posible source could be the charcoal cansistor in case for some reason it got some fuel in it.

 

In an engine with pcv running through that portion of the intake, iwould say its ok. As long as no driveability problems are occuring with it. I take apart engines way worse, that run fine.

 

Today when Ive removed the plenum for installing the new FPR (Holley)
it looked like this in the plenum...

It smelled fuel... what can cause this, got a new PCV valve on the driver side...

 

the pcv valve will pull alittle oil like stuff in the plenum, like you have posted. My TPI and HSR both have alittle oil mixed in the plenum. it does have a hint of fuel smell since its crank ventilation gasses that mix with the oil to give it that fuel smell

but yes, a broken fuel pressure regulator can leak fuel into the plenum thru the vacuum line

AND the egr system takes exhaust gasses and throws it back into the manifold to get reburned so it can make it smell alittle like fuel as well

 

Some guys put filters/canisters in the PCV line to catch all the junk that is passing by.

Rebuild engine (blowby), remove EGR (black soot), remove vapor canister (gas smell), filter/remove PCV (blowby and oil) and the intake will be cleaner. Or you can wash it out with cleaners every once and a while.

Maybe just clean it up and park it, just dust it off like the museums.

Not sure what the issue is?