I have a 1971 Triumph TR6. After sitting through the winter the car ran very rough and eventually wouldn’t start. My mechanic found almost a gallon of gas in the engine. The initial repair was replacing the Fuel pump with an electronic. This removed any direct connection of the fuel line to the engine block. Carburetors were also rebuilt as part of a full tuneup. After driving for 20 to 30 miles and having a car sit for a week the gas was back in the engine. My mechanic is stumped. He thinks I must have a mad ex-wife who is purposely pouring gas into my engine. But I have never been married and do not have any such angry person in my life. Does anyone have any suggestions on how gas can make it into the engine on a TR6 with a modern fuel pump and rebuilt carburetors?
Murph
The third sentence of your post is garbled. Please clarify so we can understand what happened.
I have a 1974 TR6 and the stock fuel pump is driven off of the camshaft, it’s purely mechanical, the diaphragm on the fuel pump can leak though I’m not sure why you would replace the oil pump though. The carbs on these cars are very temperamental, and that would be first place I would look, even if they were recently rebuilt.
I’m guessing the FUEL pump was replaced with an electronic one. With that much gas getting into the engine and oil, the carbs are highly suspect even tho they were rebuilt. That should be the only connection left.
I hope the correct electrical fuel pump was used, with a pressure regulator as needed.
If you’re using ethanol gas, it can cause the pot metal that the carburators are made of to become pourous. The gas then leaks from the body of the carburators into the engine, past the rings into the oil.
Tester
I the engine was run for an hour +/- with the crankcase oil diluted with a gallon of gasoline the engine is likely toast. Was the oil pressure low the last time it was driven? Was there excessive smoke out the tailpipe?
These carbs have external float chambers …Many of them had cork floats sealed with shellac, which alcohol will dissolve…A leaking float chamber will allow gasoline into the engine if it is being supplied with gasoline under pressure. Assuming the new electric pump is wired into the ignition switch so it shuts off when the engine is turned off, the only way for gas to get into the engine is if the fuel tank is pressurized to some degree…Many older cars had gas caps that maintained a slight positive pressure in the fuel system…
Does this car have a mechanical choke and are you leaving it pulled out?
It has a pair of Stromberg carbs, which may have integral float chambers…I’m not sure how the chokes work…
http://www.hemmings.com/hmn/stories/2006/08/01/hmn_feature11.html
The Zenith Stromberg carburetors have the float bowl attached directly the carburetor body, Caddyman. And although the starting enrichment is termed a “choke” it actually moves the fuel metering seat downward to increase the fuel flow for cold starting and has nothing in common with the choke that is familiar on most carburetors. Constant velocity carburetors from Skinner Union and Zenith Stromberg have been a PITA for me for years. I could eventually get them working acceptably well but it was a time consuming and aggravating process.
If by some chance this does turn out to be carburetor related it could be due to a severe ignition miss on even one cylinder.
Just mention this because I’ve seen some old VWs with gasoline diluted engine oil and in many of those cases it was caused by a faulty plug wire resistor and had nothing to do with the actual fuel system.
Thanks for the comments - I would add to this, the car has run very smooth initially, seeming to rule out an misfiring in any of the cylinders/plugs. The actually still starts up and runs well, but I am avoiding firing the engine at this time. I am curious on the comment that the engine would be toast, versus attempting to flush it out. What permanent effect would gas mixed in do that could not be easily cleaned or repaired? I guess I would be back to looking at the carbs, but need to try a different mechanic.
Murph
To answer other questions on this one: the is not smoke in the tailpipe, choke is not engaged, oil pressure was low but was back to normal after the initial repair and remained that way. I am not sure of the Ethanol gas issue, but I assume this is highly possible as I was not aware of this issue to track the gas I purchased. The cork floats in the carbs were replaced with modern upgrade.
I had a 1970 Chevelle that had a failed fuel pump diaphragm and the crankcase filled up with gas. This was in the summer and the gas tank was not properly vented apparently, allowing pressure to build up and keep filling the engine, even while it was not running. I hadn’t driven the car in a week or two and fortunately I pulled the dipstick to check the oil before I started the engine.
Now that you have removed the fuel pump from the equation, I suspect your carburetor’s float system isn’t shutting off the fuel flow completely. If the car runs right now, it may just be a tiny trickle. (or the fuel bowl may be porous like someone else said, or there may be a crack somewhere) I’ve seen carburetors with stuck floats and normally the gas spills out onto the engine instead of into, but your carburetor may be designed such that it’s spilling into the engine instead. Your fuel tank is probably becoming pressurized like mine did, and the fuel is draining into the engine through the carb. Which is in a way worse than if it was the fuel pump, as it is probably washing out all the lubrication in one or more cylinders on its way down.
However it is leaking, I’d suspect the carburetor now.