Problem - gas where gas shouldn't be - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Cornmeal · 08-29-2004, 04:36 PM

Hi all! This is my first post to the message board, and I have a problem with gasoline getting to places it shouldn't be.

Background: Bought a 67 GMC 'fixer upper'. Previous owner said he had just rebuilt the engine, but it ran kind of rough and looked kind of greasy, so I didn't really believe him - I planned to replace the engine anyway. Ran it for a few short trips, and it smelt pretty rich. Drained the oil pan, and there was a lot of gasoline mixed in with the oil. I figured it was a ruptured fuel pump, but didn't think much of it. As planned, I replaced the engine with a new Goodwrench 350... new fuel pump... new Edelbrock Performer 1405. Ran great for a few short trips. Then not so great. I checked the spark plugs, and they were fouled. Put new spark plugs in, leaned the mixture slightly, and seemed to run great again on a short (5 mile) trip. Then I parked the truck in driveway for a couple of weeks (slight incline, nose down).

The problem:
Went to start the truck this morning, and it wouldn't turn. Couldn't figure out why until I took a couple of spark plugs out and a cup or two of gas came out of the spark plug holes! I drained the oil pan and it was filled with gas too?!

My first thought was that maybe the carb had a stuck float, or that maybe the mech fuel pump was at too high of a pressure, but the carb is new and I find it odd that it showed similar symptoms with a different carb, pump, and engine.
I did notice that the gas cap is not original, and wondered if maybe it was not releasing pressure as the temperatures go up and down. Could that cause enough pressure to force gas past the carb? Any other ideas?

Thanks for any input.

jay6891 · 08-29-2004, 04:45 PM

First of all welcome to the board from Arkansas, where are you hailing from. My first thought was that you had a bad fuel pump but you changed it, right? Could have gotten trash on top to the needle and holding the float open. I would put a vented cap on it and try that. I wouldn't think that the tank would build up enough pressure to go past the needle and float but I have opened a gas can sitting in the sun and got a face full. What kind of carb you got on there?

my new 72 · 08-29-2004, 05:23 PM

Vent the Fuel tank, and the problem will be fixed. You have to remember that the only variable that has NOT changed in this whole process is the tank cap. I would replace it with an original vented cap and be done with it.

Cornmeal · 08-29-2004, 09:25 PM

Thanks.
I'm in (balmy) North Dakota.
Yes, I replaced the fuel pump and the carb is a new Edelbrock.
I've put in fresh oil now, and I'm going to try replacing the gas cap - and then hope that it doesn't turn back into gas/oil... As 'my new 72' says, it is the only thing I can think of that I haven't replaced.

08-29-2004, 04:36 PM	#1
Cornmeal Registered User Join Date: Sep 2003 Location: Fargo, ND Posts: 2	Problem - gas where gas shouldn't be Hi all! This is my first post to the message board, and I have a problem with gasoline getting to places it shouldn't be. Background: Bought a 67 GMC 'fixer upper'. Previous owner said he had just rebuilt the engine, but it ran kind of rough and looked kind of greasy, so I didn't really believe him - I planned to replace the engine anyway. Ran it for a few short trips, and it smelt pretty rich. Drained the oil pan, and there was a lot of gasoline mixed in with the oil. I figured it was a ruptured fuel pump, but didn't think much of it. As planned, I replaced the engine with a new Goodwrench 350... new fuel pump... new Edelbrock Performer 1405. Ran great for a few short trips. Then not so great. I checked the spark plugs, and they were fouled. Put new spark plugs in, leaned the mixture slightly, and seemed to run great again on a short (5 mile) trip. Then I parked the truck in driveway for a couple of weeks (slight incline, nose down). The problem: Went to start the truck this morning, and it wouldn't turn. Couldn't figure out why until I took a couple of spark plugs out and a cup or two of gas came out of the spark plug holes! I drained the oil pan and it was filled with gas too?! My first thought was that maybe the carb had a stuck float, or that maybe the mech fuel pump was at too high of a pressure, but the carb is new and I find it odd that it showed similar symptoms with a different carb, pump, and engine. I did notice that the gas cap is not original, and wondered if maybe it was not releasing pressure as the temperatures go up and down. Could that cause enough pressure to force gas past the carb? Any other ideas? Thanks for any input.

08-29-2004, 04:45 PM	#2
jay6891 Car Knocker Join Date: May 2001 Location: jefferson,arkansas Posts: 664	First of all welcome to the board from Arkansas, where are you hailing from. My first thought was that you had a bad fuel pump but you changed it, right? Could have gotten trash on top to the needle and holding the float open. I would put a vented cap on it and try that. I wouldn't think that the tank would build up enough pressure to go past the needle and float but I have opened a gas can sitting in the sun and got a face full. What kind of carb you got on there? __________________ 68 c-10,91 sportside bed,350 .030 over,4 bolt,10-1 comp,2.05 intake/1.94 exhaust,1.6 Harland Sharp roller rockers,edelbrock rpm cam and intake w/750 carb, 700r4, 3.73 gears,Jacabbs Electronic Igntion w/Accel HEI distributer and super coil. ZR-1 roll pan, filled tailights. Blazer tank. Hidden hitch. 2 1/2" Flowmaster 40's. Parts bought but not installed>> ford 9" posi with disc. CCP front and rear lowering kit 4/5. Cab corners,foor boards,rockers, cab braces, Phatom grill, Painless wiring kit.

08-29-2004, 05:23 PM	#3
my new 72 faster, faster, faster Join Date: Dec 2001 Location: Houston ,Texas ,USA Posts: 1,354	Vent the Fuel tank, and the problem will be fixed. You have to remember that the only variable that has NOT changed in this whole process is the tank cap. I would replace it with an original vented cap and be done with it. __________________ I'm going to Law School, wanna debate? It's good practice.

08-29-2004, 09:25 PM	#4
Cornmeal Registered User Join Date: Sep 2003 Location: Fargo, ND Posts: 2	Thanks. I'm in (balmy) North Dakota. Yes, I replaced the fuel pump and the carb is a new Edelbrock. I've put in fresh oil now, and I'm going to try replacing the gas cap - and then hope that it doesn't turn back into gas/oil... As 'my new 72' says, it is the only thing I can think of that I haven't replaced.



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