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Crankcase full of gas

Hi guys, new member. I have 1986 f250 4x4. Just installed 1969 460 with 73 heads. New Edelbrock carb. Truck runs well and have put a couple of hundred miles on it. I had it sit for 12 days. (checked oil after 10 days and all good)When I went to start it it acted like battery was dead. When I went under the hood noticed a puddle of what looked and smelled like gassy oil. Checked oil and it was up to top of dipstick. Puddled gas on valleys of intake. Drained oil to find abbout a gallon of fuel in the crankcase. Pulled plugs, disabled coil and hand cranked to empty cylinilders of gas. No wonder it wouldn't crank. Hydraulic lock. Checked carbfloats and they shut off when lifted manually. So where did fuel come from? I have had 2 ideas presented to me. With tanks 1/2 full vapors have built up and pushed fuel up through carb and forced past needle and seat. (Edelbrock states 6 1/2 pounds max fuel pressure). Truck has no emmissions gear (vapor canister line plugged) Other thought is that involuntary power to fuel pump (22 year old ignition switch). I have put in fuel regulator. Any ideas? Sorry about long post. Need to find root cause. Replace ignition switch. Put switch on fuel pump relay to disable when truck sits? Thanks.
 

d-kuzmen

Master Ford Tech
2,109
79
Connecticut
I'd have to guess the fuel pump was running, probably too much psi for the float to stop, filling the engine with fuel.
 
Yikes. I hope regulator will control the fuel but what to do about pump running after sitting for 12 days? Battery cutoff switch? Thanks.
 

Lane

Part Time Good Guy
Like the guys above, I have to wonder about the pumps. My 1986 F250 has an electric fuel pump at each tank. As it happens, I have a little switch to bypass the oil pressure switch (installed during some fuel delivery troubleshooting), but the normal and unmodified truck should not allow the fuel pump(s) to run continuously, even if the key is left on.

Is there any chance an inadvertant wiring change was made during or before the engine transplant? As I've learned when flipping my little bypass switch, it's possible to leave the door open and hear the fuel pump run when you turn on the key (assuming no radio, heater fan, seatbelt buzzer, etc.). Was that battery dead? If it ran a fuel pump for days, I'd think so. With a good battery, can you hear the pump running when the ignition is on but engine not running? You should not hear it.

I'm curious, partly because I've had some maddening fuel delivery problems on my own 1986 F250 with 460. My buddy finally sorted it out, found a rusted and bad relay, and we learned my truck does not match the factory manual for 1986. It must be a late '86, because the fuel system is an electrical match for the 1987 scheme.

I used to have this "crankcase full of gasoline" problem with cheap 5kw Generac generators with Briggs & Stratton engines, after my renters would shut them down for months and leave the tank shutoff valve open. It's a real PITA in a truck.

Good Luck
 
This was 2nd occurance of this condition so I have been checking oil and looking for a puddle but all good until morning after 12 days. Battery not dead. Now that I have flushed out bottom end and refired it is running good. Have tried to turn on key and cannot hear pump running. Was it the fuel pump relay that was rusted? And if so, Where the heck is it? There is a single relay on forward side of firewall or is it under dash? Thanks for your help I would really like to put this one to bed.
 

Lane

Part Time Good Guy
The rusted relay was on the firewall. But your problem isn't NOT getting fuel like mine was.

I will ask my buddy who worked in the truck. In the absence of a running fuel pump, my limit is spilling the contents of the bowl onto the top of the engine from a leaky carburetor. I can't see any way to fill the crankcase with gasoline unless the fuel pump is running.

My truck has Ford's "hot fuel" system, but that's just a return line to the tank and a valve that lifts at a preset pressure to allow the return flow. It's supposed to prevent vapor lock, but it only makes sense to me if it's with an engine mounted fuel pump that sucks fuel from the tank.

The engine is higher than the fuel tank, so gravity won't get you, the way it did with those little Generac units I mentioned.

This bears further investigation, for sure.
 

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