Gas in Oil and Hot Start Failure

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Charles Brausch
356 Fan
Posts: 2
Joined: Sat Jun 14, 2008 8:50 am
Location: Northern Ohio

Gas in Oil and Hot Start Failure

#1 Post by Charles Brausch »

1960 356B T5 Roadster with about 35,000 original miles & original owner. Standard 1600 engine with Zenith carbs.
Sat in garage for a few decades until restoration in 2001.
Starts ok when engine is cold (requires many throttle pumps). Accelerates fine all the time.

Gas in oil happened for the first time in late 2014 while sitting in garage. Around this time the fuel shutoff in cabin leaked and was replaced. Oil was changed but gas eventually found its way into the oil again. It was mistakenly thought fuel shutoff failure caused gas in oil.
Car became impossible to start after the engine was at proper temp and shut off for only 20 -30 minutes. Starter would just crank. If engine cooled for any longer, it would usually start correctly.

Next the fuel pump was replaced. The diaphragm was beginning to separate. Oil was changed again.
Car still failed to "hot start" and once again we found gas in oil (way over full mark on dipstick).

I have observed zero fuel squirting down throat of left carb and only a tiny trickle down throat of right carb while pumping throttle linkage. This can be observed when engine off or on.
I have also observed randomly high idle after engine up to temp. Generally around 1200 rpm while at a traffic light or stop sign.

At no time was the car driven with gas in the oil!
I'm leaning toward a full rebuild of both carbs unless someone has any other ideas that can be tested/tried/eliminated.

Thank you,
Charles
1960 Roadster - Condor Yellow

Dick Weiss
356 Fan
Posts: 4181
Joined: Sun Apr 20, 2008 12:54 am

Re: Gas in Oil and Hot Start Failure

#2 Post by Dick Weiss »

Charles,

Yes, you should have the carbs rebuilt as the check valve(s) may not be working.
Also, the tank's petcock needs a check for correct assembly--it should shut off the fuel;
especially just before the engine is shut down--approx. 1/4 mile or so.
This will prevent the rising heat from expanding the fuel to overflow into the engine.

BTW, was the fuel pump reassembled correctly? The diaphram must be flat to the body
suface by pre-loading the pushrod before adding the top 1/2 and snugging up the
6-screws.

Dick

Steven Clarke
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Posts: 195
Joined: Fri Nov 26, 2010 11:10 am
Location: North Carolina

Re: Gas in Oil and Hot Start Failure

#3 Post by Steven Clarke »

Charles:
Just a guess, but I am going with a sunk float in one of the carbs.
Steve
 

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Doug McDonnell
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Joined: Sat Apr 05, 2008 8:21 am
Location: Augusta,Michigan

Re: Gas in Oil and Hot Start Failure

#4 Post by Doug McDonnell »

+1 on Dick Weiss suggestion.It sounds like you have float valve and accelerator pump issues. Have your carbs rebuilt by someone who has rebuilt a lot of carbs and knows 356s ( like Dick who lives and works in Cincinnati,Ohio).
1965 356C 2000 BMW 740i Sport 1967 Honda CL77 There is never enough time to do it right, but always enough time to do it over.

Charles Brausch
356 Fan
Posts: 2
Joined: Sat Jun 14, 2008 8:50 am
Location: Northern Ohio

Re: Gas in Oil and Hot Start Failure

#5 Post by Charles Brausch »

Gentlemen,

The fuel shutoff valve in the cabin seems to prevent gas from going into the oil while sitting for long period. I will try turning off the valve while engine it running to make sure it does in fact completely cut the fuel supply.

I cant confirm the fuel pump was assembled correctly but the man that did the repairs has been professionally working on euro cars for many many years. The next time I speak with him Ill ask about the assembly procedure.

The car gets mothballed every fall up here in the northern tundra so I'll have plenty of time to get the carbs rebuilt.

The help is much appreciated.
Thank you,
Charles
1960 Roadster - Condor Yellow

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