51 cad., fuel in the oil

[69_granprix]

We thought we were ready to go to the upholstery shop!!!BUT, we discovered fuel in the oil. ALOT of fuel. We removed the fuel pump, both diaphrams seemed ok. Is there another way fuel can get into the oil besides a cracked diaphram? We're showing two inches above the full mark. We don't think the carburetor is leaking. It doesn't act like it's loading up. Frustrated...Joe /Ralph

[Guest De Soto Frank]

You probably have a bad fuel-pump... have had this happen to a few vehicles, old and "new", over the years...

Unless the carb float is stuck open, flooding horribly, dumping lots of gas into the intake, which then gets past the rings, there's no other way for fuel to enter the crankcase... (and if there's that much floodage, it's doubtful the engine would even run... )

Time to replace or rebuild the fuel pump and change the oil & filter.

Good luck!

[69_granprix]

Thanks Frank, that's what we thought .But, we wanted to run it by the experts first. Did you disassemble the pumps that were bad. Were the diaphrams cracked, if not, how was the fuel getting into the oil?

[Guest De Soto Frank]

Most of the ones that've have gone bad in my vehicles were the newer crimped-can style...

The older screwed-together pumps have been primarily on flat-head MoPar and Chevy "Stovebolt" sixes, and I've been able to get new pumps, so I have really bothered disassembling the old pumps to see what went wrong inside...

Generally speaking, the older diaphragms were were made from laminated fabric layers, impregnated with rubber or similar sealer... these deteriorate over the years and become cracked or porous (newer fuels with ethanol blended-in tend to cause rapid deterioation of older rubber in fuel systems too). They may retain enough integrity to still move some fuel, but when the float-needle in the carb closes, the fuel pump keeps operating, until the pressure on the carb side of the diaphragm equals the tension on the spring under the diaphragm; then the diaphragm and linkage just kind of "float" against that pressure until the fuel level in the carb drops, the needle opens, and the pressurized fuel flows into the carb, and the pump starts to "pump" again...

All of which means, there's usually about 3 lbs of fuel pressure working against that diaphragm while the engine is running, and for a while after the engine is shut-down, until the pressure bleeds down. It doesn't take much of a pin-hole or crack in the diaphragm to allow fuel to spritz into the crankcase... and it's going to stay there unless the engine gets hot enough to vaporize it out of the oil... which usually doesn't happen "just idling in the driveway".

The last vehicle I went through this with was a "new car", a '77 Ford LTD II, with a 351 Windsor. The car had been running fine, but "suddenly" started running really rich... black smoke out the tailpipe, bucking, stalling... when we lifted the hood, we smelled a strong odor of gasoline, but saw none leaking anywhere. We pulled the air cleaner, to see if the carb float was stuck and the carb flooding... it wasn't... but when the top was off the air cleaner, the engine smoothed-out and stopped belching black smoke...

Clogged air-filter? Nope... brand new, clean. Put it back together w/o the air-cleaner element...starts bogging, belching black smoke, etc.

After about 1/2 hour of "looking for the obvious", we pulled the dip stick, and noticed the oil level way over the full mark, and the oil had a very strong odor of raw gasoline. We determined that the fuel pump was going bad, and was leaking fuel into the crankcase. We further determined that the reason the car was running so rich and poorly, was that once the engine was up to operating temp, the gasoline was being vaporized out of the hot engine oil, drawn into the PCV system, and being sucked into the intake manifold, creating a very over-rich condition...

(The "we" in this story refers to my best friend, who owned the car and who is a fair mechanic in his own right, and myself)

It would've probably taken longer to detect the failing fuel pump in a vehicle with the old open crankcase breather ...

The Antique Auto Parts Cellar in Weymouth, MA has been providing rebuild kits for mechanical fuel pumps for years, and they are very helpful people... would suggest contacting them about a repair kit for your Caddy's pump...

Good luck...

[69_granprix]

Thanks again Frank for the kit tip. A new pump is about $125.00. Joe/Ralph

[Guest De Soto Frank]

Ouch!

Hope you can rebuild yours for a lot less !

[Guest mena]

Frank is probably right, but look down the carb to see if there is a puddle of raw gas in he intake.

Did you see any sign of gas in the parts of the fuel pump where there shouldn,t be any. I.E. vacuum lines, or mounting flange.

Good luck

Mena

[Ron Green]

Once you track down your fuel in the oil problem you may want to consider switching over to synthetic oil.

Many here will argue that synthetic is a waste of money however with these old vehicles that use carburetors there is always a small amount of fuel that seems to get in the oil, even when they are running perfect. Synthetic will keep its lubricating qualities even when saturated with fuel where conventional oil can only handle a small amount before it loses most of its lubricating qualities.