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Join Date: Jun 2015
Location: Chicago, IL
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Draining a fuel tank and lines of bad gas
Technical question, but non-Porsche so it's in OT.
I need to drain bad gas out of one of my other cars - it had been sitting in the garage since 2008 when I got it back on the road a month or two ago. I sort of knew that I should drain the gas out, but I procrastinated finishing the car and when I was down to the wire I didn't have time, so I put a couple of gallons of new gas in it and hoped for the best. Car runs like crap, so the gas has gotta come out. Maybe the injectors need to be cleaned, but obviously the first thing I'm going to do is replace the gas and the fuel filter and sew how it runs then. Fuel pump is in-tank. Access is through the top of the tank, under the back seat cushion. There is a gasket to the access port in the top of the tank that should be replaced that I don't have a replacement for yet, so I'd rather not open the tank up if I don't have to. Is it reasonable to drain the tank by powering the fuel pump through the harness and just running the fuel filter input line into a bucket? Is it going to take forever to do it this way? There's a first time for everything, and this is the first time for me for this.
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'80 SC Targa Avondale, Chicago, IL |
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05-20-2016, 10:04 AM
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How accessible is the fuel tank? I would drop the tank and clean it out completely. An alternate way is to remove the access cover for the fuel pump ( if it accessible ) while in the vehicle and try to get it clean that way. By pumping it out with the installed pump there will still be bad fuel leftover and as it went dry the fuel pump could be damaged.
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05-20-2016, 10:25 AM
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On further thought, if it has been sitting that long I would drop the tank and replace all the fuel lines while I had it out.
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A nose heavy airplane flies poorly, a tail heavy plane flies once. |
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05-20-2016, 10:26 AM
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Fuel tank is not hard to get to - standard position under the back seat, in front of the rear suspension. To get to the pump you remove the back seat cushion (just pulls right out), undo a cover panel in the body and then you have access to the cover panel on the top of the tank. Replacing the fuel lines is something I will do eventually in any case, as some of the fuel and brake lines have external corrosion and I want this car to be drive-across-the-country-at-a-moment's-notice safe again. I've owned this car for 23 years and 220k miles and it was my primary transportation until about 2004.
What I had in mind to do was leave the tank and lines in for now and just pump all the old bad gas out this weekend and put good gas in it and see if it runs well then, or if I need to pull the injectors. Then drop tank and clean it and replace fuel lines later this summer, when I drop in a spare motor and put the original one on a stand to do rod bearings and an engine-compartment cleanup job.
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'80 SC Targa Avondale, Chicago, IL |
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05-20-2016, 10:41 AM
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can you disconnect the fuel line and pump the tank dry with the fuel pump?
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poof! gone |
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05-20-2016, 10:44 AM
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Depends how bad it is. Too much goop in the tank and you'll be buying a new pump and blowing out the lines. I used that approach to empty the tank before it went into storage. If it runs now the odds are its not too bad but it could be, you wont know until you get your eyes on it. I would pop out the pump.
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05-20-2016, 11:12 AM
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In answer to your question, yes, you can drain it that way, but you might be surprised how much pressure it comes out under since it's a FI car from the sounds of it. I'd have a fire extinguisher handy when doing it this way if it were me.
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Scott '78 SC mit Sportomatic - Sold |
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05-20-2016, 11:14 AM
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Now in 993 land ...
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Buy a basic 12v fuel pump, connect a couple long hoses, add a switch, connect to 12V (be safe to avoid sparks) and pump that tank empty. Modern cars have recirculating fuel, so with fresh gas on an empty tank, it will recirc the remnants of the bad gas out of the lines.
If you don't want to go electric, you can get siphon pumps at any autopart / auto tool store. I used to resurrect old cars, it has always been sufficient for me to pump out the tank and refill with new. Sometimes a bit of MMO would help with deposits on carbureted vehicles ... on FI, a can of FI cleaner ... G |
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05-20-2016, 11:19 AM
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Car is EFI (1993) so point taken on fuel system pressure. Also good reminder about damaging the pump by running it dry but I figure a few seconds wouldn't hurt it.
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'80 SC Targa Avondale, Chicago, IL |
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05-20-2016, 12:12 PM
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I think it's probably easiest to siphon the fuel out and put in half a tank of good fuel for dilution. Add a bottle of Seafoam with that first half tank. Replace your fuel filter after an hour of run time or so. Not the best clean-out method, but usually "functional" if you're in a hurry and not predisposed to disassemble the fuel system.
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05-20-2016, 02:07 PM
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Location: Marietta GA
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What do you do with bulk stale gas when you get it out? I think I've got about 10 gallons to get rid of.
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05-20-2016, 06:11 PM
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Now in 993 land ...
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G |
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05-20-2016, 07:29 PM
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05-21-2016, 04:33 AM
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1979 Porsche 911SC
My former car
