Oil in Carburetor Bowl - blow by?

SpyderJoe · Post by **SpyderJoe** » Fri Oct 05, 2007 3:58 pm

Hi all
My 79 Spider was running a little rough when I took it out for a drive without letting it warm up. I have been here before. The car hesitates when I begin to accelerate. I have a 34 ADF Carb on an 1800 intake. It may be time to rebuild the carb, (5 years since the last rebuild).

Anyway, while I had the air filter off of it I noticed oil puddled in the corners of the carb bowl, (I have a Ramflow domed Air filter on it). I then took the air filter element and gave it a squeeze and oil was dripping from it. What is causing this? I have the large hose from the Oil Vapor separator connected to the tube in the carb bowl.

I was told by a very reputable source that it could be engine blow by and it may need a valve job or a ring job which would require an engine rebuild.

Has anyone seen this before? I gotta think that the oil saturated filter element isn't helping the engine breathe and could be causign the hesitation.

Any advice is appreciated.

So Cal Mark · Post by **So Cal Mark** » Fri Oct 05, 2007 8:38 pm

blow by can cause that, but if your oil level is overfull at all, liquid oil will be forced up into the air cleaner above 4000rpm

SpyderJoe · Post by **SpyderJoe** » Fri Oct 05, 2007 8:58 pm

Mark,
It isnt the oil level. If anything, the oil level runs low because I have had a small oil leak and continually checked the oil level. It has never been over the full line and I try to keep it in the middle between min and max.

Danno · Post by **Danno** » Fri Oct 05, 2007 9:09 pm

Not looking good, because it really could bad with the blow-by like your source suggested. It could be bad valve seals, worn valve guides, bad piston rings, or (probably an easier fix) would be a plugged up oil seperator or whatever it's technical term is. Someone here warned me to clean it up before I swapped on my new intake manifold and carb. I did, and mine wasn't too bad, but i've heard of several people (on mira, etc) have theirs all clogged up and a cleaning fixed it right up.

cross your fingers for an easy fix.

So Cal Mark · Post by **So Cal Mark** » Fri Oct 05, 2007 9:42 pm

if the oil separator was plugged, how could oil come back up thru it to the air cleaner? Unlike most engines, Fiat used the breather hose and oil separator as a two-way path; fresh air comes into the crankcase as well as vented pressure coming out. Most engines have two separate paths; one for fresh air to be drawn in and another to vent pressure.
Next step is to do a leakdown test and see how much pressure loss occurs in each cylinder

SpyderJoe · Post by **SpyderJoe** » Fri Oct 05, 2007 9:44 pm

Danno,
Thanks for the advice. I never thought of it being a clogged up Oil Vapor Separator. I plan on removing the carb for a rebuild. It is not a big deal for me to pull off the oil separator and try and unclog it. To remove it, do I just need to remove the one bolt in the center of it?

Thanks.

So Cal Mark · Post by **So Cal Mark** » Fri Oct 05, 2007 9:46 pm

before you waste your time removing the separator, start the engine with the hose disconnected and see if you can feel air flow coming out

manoa matt · Post by **manoa matt** » Fri Oct 05, 2007 9:47 pm

If you try to accelerate hard when the carb is not warmed up it will backfire/sputter thru the carb. If you accelerate gradually it won't do that.

Fortunatly for me I live at the top of a large hill, by the time I coast to the stop sign at the bottom the car is warm. Comming off that stop sign is important because of oncomming traffic. If the car is not warm enough then it won't have full power and it will sputter in the intersection (dangerous).

I've noticed that when it sputters or backfires there is some residue at the underside of the air filter cover plate, but not as much as you describe.

In your post you state: "I have the large hose from the Oil Vapor separator connected to the tube in the carb bowl."

I hope you don't have the PCV valve hose connected to the float bowl vapor outlet.

If you have a stock air filter housing then there is a double fitting on the bottom. The large diameter fitting is for the oil/vapor seperator. The small fitting should be connected to the PCV valve located on the lower front drivers side of the carb.

Most aftermarket air filter housings don't have the proper provisions for these connections. You should be able to find a fitting for the pvc valve and attach that to your aftermarket air filter housing. For the Oil/vapor seperator hose you can buy a crackcase ventelation filter at Autozone for about 5-7 bucks.

Both the oil/vapor seperator and the PCV (positive crankcase ventilation) valve should be cleaned periordically. The PCV valve is made of plastic and can melt and deform. If it does, then the valve will either be stuck open, closed or partially open/partially closed.

Matt

Danno · Post by **Danno** » Fri Oct 05, 2007 9:51 pm

So Cal Mark wrote:if the oil separator was plugged, how could oil come back up thru it to the air cleaner?

Mark, you know my auto technical knowledge is pretty limited! but I gathered from those other guys that the seperator, when clogged, didn't stop the flow through the breather hose, but it DID stop the separator from separating and they had oil coming out their breather hose. And that's ALL I know about that, lol. I like your idea of making sure air is still coming through that hose first.

So Cal Mark · Post by **So Cal Mark** » Fri Oct 05, 2007 9:57 pm

the separator is a series of chambers to keep raw oil from coming up the hose, I've never seen one clogged. But if it did clog, it would be much harder for oil to come through than for air. It would take quite a bit of sludge to clog that thing. If you engine had that much sludge in it, you're going to need a rebuild anyway

racydave · Post by **racydave** » Fri Oct 05, 2007 11:25 pm

I had exactly the same problem and fixed it. All I did was to replace the short hose because it was cracked. Its best to order one cause its hard to find any other hose thatll fit! I didnt clean the seperator and found it all a B to deal with, especially since I had my intake off previously, and thats the best time to do it!!!