I have a 1976 TR6 with an electric fuel pump and twin Strombergs. When I fill the gas tank and park the car, there is a strong smell of gasoline. Upon checking the oil I discovered gallons of gas had migrtaed from the tank to the case. Apart from driving home a few miles from the gas station, the engine was not run at all.
Any ideas?

[Dave@Moon]

Do you mean the crankcase? "Gallons of oil" would certainly have flooded the crankcase and flushed the oil out of the engine several times. However there is a way that some gas can get in there, and it has more to do with the gas than the car.

If you mean that there is a strong odor of gas in the oil, the almost certain cause is heat from the engine vaporizing (boiling) the gas in the bowl (a.k.a. "chamber") in the carb. Todays gas boils at a much cooler temperature than it used too (not a problem with fuel injection). I have a Buick that is terrible for this, and I had to use a switched fuel pump and reroute the gas line to fix it.

With a CD Stromberg there would have to be enough pressure to raise the needle valve, or the valve could just be sticking open. In either case the gas would be forced out the metering valve, run down through the manifold and cylinders, and leak past the rings into the crankcase.

Several suppliers make heat shields for the TR6 to mitigate against this, including The Roadster Factory.

[Bill_Sohl]

Fuel in the crankcase is "probably" the result
of a bad fuel pump. The fuel pump on the TR-6 is
found on the driver side (in the USA) of the engine block
towards the rear of the block. The fuel pump has
a cam follower which drives the pump. The fuel pump
has an internal diagphram which, if it breaks,
can leak gasoline into the engine crankcase via
the cam follower opening.

If that is the case, you will also probably
see fuel leaking directly from the fuel
pump itself.

Also, depending on how much fuel is in the
fuel tank, if the pump diaghram is leaking,
gasoline can still possibly leak into the
crankcase while the engine is not even running.
That's not a good thing.

Be careful.

Cheers ,
Bill Sohl

[Dave@Moon]

Bill,

The original poster said that he'd installed an electric fuel pump, which is why I didn't mention it. It occurs to me that I just assumed he bypassed the factory pump and is using a correct fuel pressure electric pump.

Perhaps the electric pump is set to too high a pressure, or is wired to an unswitched circuit. In either case if the original fuel pump is still installed and the diaphragm is bad or even mildly marginal he could be having a serious problem! Depending on the degree here (pressure + time) a brand new pump could be made to leak.

[TRG69]

This is a new one on me. How common is a diaphragm failure leaking gas into the crankcase? It never occurred to me, however, upon investigation, it sure looks like it can happen! All the elements are there. Do I add sniffing the dipstick to the routine of weekly maintenance before taking my '69 out for it's weekend drive?

[Dave@Moon]

Quote:

Do I add sniffing the dipstick to the routine of weekly maintenance before taking my '69 out for it's weekend drive?

I do! You'd certainly want to if you find yourself with a rising oil level as I did in my Buick, but since oil retention isn't exactly a British speciality (and rising levels can therefore be offset) I'd watch for any kind of oil contamination routinely.

[Bill_Sohl]

Quote:

Quote:

Do I add sniffing the dipstick to the routine of weekly maintenance before taking my '69 out for it's weekend drive?

I do! You'd certainly want to if you find yourself with a rising oil level as I did in my Buick, but since oil retention isn't exactly a British speciality (and rising levels can therefore be offset) I'd watch for any kind of oil contamination routinely.

I'll ignor the reference to British specialties . Keep in mind also that oil and gasoline mix together rather well and initially becoming aware of any gasoline leaking into the crankcase may well only be indicated by a rising dipstickk indication.

[TRG69]

Great! My wife already thinks I'm a lunatic. I start the car like a baseball pitcher throws the ball. Touch the chin, touch the visor, slap the mitt twice, scratch the nose, adjust the pants, throw the ball. Every time! Sniffing the dipstick could put this over the top! No one responded to "How common is this?". The fuel in the crankcase from the fuel pump is new to me.

[Dave@Moon]

Quote:

"How common is this?".

With the increasing volatility of what we buy as "gas" (which may have a double meaning soon!) it's getting more common every year. There are components in gasoline today that boil at 90 degrees F, and it will often boil dry at less than 170!

In the case of my Buick the carb became a very serious fire hazard when I shut the car off. A relocated fuel line and a low pressure electric fuel pump (switchable and bypassing the factory pump) fixed it.

Also a bad pump diaphragm can cause this without any contributing factor (like the electric pump). I had a vaccum booster on a fuel pump fail which pressurized the crankcase on an old Ford 6 with air (sufficient to blow the oil out the road draft tube {pre-PCV valve car}). Doing so with gasoline would just be a matter of the other diaphragm popping.