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Thu Jun 12, 2025 4:30 pm

74 thing, dual port 1600, electric fuel pump, electric ignition. The rest of the motor is stock.

Started my thing today and fuel began to run out from the bottom of the bell housing while running? There is no fuel leaks coming from above and running down the sides of the housing. All fuel lines are intact. It is literally pouring out of the very bottom where the engine and transaxle mate. There is no fuel in the oil. I'm totally stumped and confused. Yes it is a gas leak not oil.

I've disconnected the electric fuel pump and the fuel still pours out while running. No fuel leaks when ignition is on with electric fuel pump running and engine is not running.

Please see the YouTube video link below.

[youtube] https://youtu.be/Uh5U41IkDVA?si=z7HKKtx2Q4aHH17Z[/youtube]

Fri Jun 13, 2025 5:38 am

Weird. There’s only 1 fuel line running through that area. It likely has a couple connections where rubber lines meet a metal lines. Maybe triple check those areas?
The other option might be to run a small jug / bottle of fuel from the back of the car directly to the carb and pinch off the line from the tank somewhere to eliminate it. Then see if it’s still leaking.
Leaking fuel and oil can make some odd paths traveling down from higher areas, so it might not be leaking from directly above where you see it. Maybe get in there with a mirror if you haven’t already and inspect things closer?

Good luck. You’ll find it I’m sure.

Fri Jun 13, 2025 1:56 pm

So I decided to pull the motor as I've concluded that the rear main seal most likely blew. I've gone through this process many times before 30 years ago.

I went back and looked at the bucket a was catching the leak in originally; and saw most of the fuel had evaporated and some oil was left in the bottom. The cardboard was also oil soaked as the fuel had evaporated.

I pulled the oil drain and the oil was mostly gas. The dipstick read between the two lines which is where I kept it.

I'm really confused as how the block filled with so much fuel? The manual fuel pump had been previously replaced with an electric fuel pump like 10 years ago. The pict34 carb is about 3yr less than 1k miles.

The motor always fires right up and runs fine. I don't really have any problems with it. There's a dead spot in pedal when accelerating through 1st and 2nd untill it really warms up. Just never been able to work that out. Could that be related?

I don't know if it's even possible for that much fuel to be leaking through the float into the cylinders? Is it?

Fuel will not pass through the electric fuel pump when off. The pump was not left on.

I drive this around town pretty often it doesn't really sit a whole lot. I just don't go very far with it.

Any ideas?

Fri Jun 13, 2025 2:49 pm

Sounds like the valve in the float in the carb is not closing.

Also. what PSI is the pump putting out?

Max

Fri Jun 13, 2025 3:12 pm

I don't know what the PSI the fuel pump is or have a way to test it. I was thinking the same tho, the carb float stuck open or too much fuel pressure; but wouldn't that cause running issues? Flooding the cylinders out, hard starts.?? But I also don't have any other explanation for it.

Sat Jun 14, 2025 7:23 am

Sounds like the float in the carb is stuck, or can no longer keep up with the pressure from the electric fuel pump. Normally, this would cause an extraordinary rich black exhaust. But, you didn't mention that, and you also say the engine is running fine.

So, I suspect you have another issue in addition to the carb float, which is allowing the unburnt fuel into the crank case. Initially, I'd think sticking valves, perhaps caused by a broken spring, or a bad seal between the jugs and the crank case, or worn rings (in every cylinder, which is unlikely). You could do a compression test to find worn rings or sticking valves or a bad jug seal very quickly and isolate the issue to a particular cylinder.

Sat Jun 14, 2025 9:25 am

Yes a compression test is a good idea and on my list, I didn't think to do that prior to pulling the motor. The clutch, flywheel and rear seals are currently removed and new parts are ordered from JBugs.

I disassembled the carb and tested it with the fuel pump and it all seemed to function properly. But it could also be an intermittent problem.

I'll check the valves\springs and lash as well while it's out. When I get everything reassembled and running again I'll do a compression test and keep a closer watch on things. I'm not expecting the compression to be off as the thing runs great just a dead spot in the pedal in 1st and 2nd untill it gets really warmed up. Most noticable in the cooler months. I don't get the dead spot so much in the summer. It's probably the choke or how I have it tuned; but just was never was able to get rid of it, only change it. IDK? I'm just a hobbyist.

I've had this for 7 years now and never had to do much of anything other than the basics since my initial overhaul at time of purchase. When I bought it, the motor was a fresh rebuild that "was broke in" then sat for about 8 years and neglected. It was purchased from the original owners daughter. Her dad had passed and the thing sat untill my purchase.

Tue Jul 08, 2025 8:06 am

Well I've got my thing back together and running better than it ever has before.
I replaced the rear main seal, flywheel, clutch, pressure plate, throw out bearing, plugs wires, cap, rotor, adjusted valves, reset timing, tuned carb.
The rear main does have a tiny drip to it. IDK maybe I needed to grease the seal rather than oil it. I feel like it may have been slightly damaged upon start up due to lack of lubrication? A brand new seal with brand new flywheel should not be dripping. Yes I have and used the installation seal tool.

There has not been any gas in the oil yet.

Final diagnosis engine casing filled with gas which is unknown on how that happened and rear main seal wore out.

I'm guessing I have a very clean inside engine.