Rust in Gas Tank...

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blasphemy101
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Rust in Gas Tank...

Postby blasphemy101 » Thu Jul 05, 2012 10:04 pm

So I've been having a fuel starvation problem at high RPM, with the engine cutting out around 3500 RPM, depending on the gear (1st = redline, 2nd = 4-4.5k, 3rd = 3.5k RPM). Originally, I attributed this to my noisy external fuel pump. I replaced both the transfer pump and external pump, seemingly solving the starvation issue. However, my external pump is already noisy again!

I pulled the send line on the transfer pump and it's flowing fine. I ran some of the gas out through the return line, so it was running through both pumps, and the new external pump sounded fine. I removed about 8 gallons from the tank, and the gas that was left in the tank was pretty murky with rust. Feeling in the tank with a wood paint stick confirmed a layer of rust in the bottom of the tank.

I've tried removing the drain plug, but the first turn of the wrench (with a properly sized allen head) completely stripped it.

Is removing the tank, flushing the debris out with a garden hose and running a few tanks of Iso-HEET treated gas an acceptable solution? After doing this, I would replace both the pumps under their 12 month warranties, just to be on the safe side.

I'd rather not replace the tank or any more fuel pumps!!!
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Re: Rust in Gas Tank...

Postby Yoshi » Fri Jul 06, 2012 12:48 am

what you suggest is about what I would do. I would also blow air and some cleaner through the hard lines and replace all rubber lines. Fuel filter while you're at it but I assume you were thinking the same.
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Re: Rust in Gas Tank...

Postby AustinR » Fri Jul 06, 2012 2:51 am

Agreed. And make sure the return fuel passage on the inside of the tank is clear while you're at it.
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Re: Rust in Gas Tank...

Postby Yoshi » Fri Jul 06, 2012 12:45 pm

basically, make sure your whole asshole is clean as a whistle before putting more stuff through it.
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Re: Rust in Gas Tank...

Postby blasphemy101 » Fri Jul 06, 2012 1:43 pm

Sounds like a plan. I imagine many of the rubber lines are easy to replace once the tank is down...

All of this is keeping me from getting my whodwho MegaSquirt running! I have it installed, and I'd really like to get it going!!!
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Re: Rust in Gas Tank...

Postby Yoshi » Fri Jul 06, 2012 1:52 pm

wait wait. do you have the MS installed now or is this with the factory ecu?
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Re: Rust in Gas Tank...

Postby blasphemy101 » Fri Jul 06, 2012 2:52 pm

I have an MS setup installed in the sense that I ran the vacuum line and it's waiting to be plugged in, but the car's running on the factory ECU.

New question - would it hurt the external pump to drain the gas tank through the transfer pump by using a jumper on the fuel pump relay? This would mean no fuel going through the external pump and letting it just spin...
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Re: Rust in Gas Tank...

Postby Nsquared97 » Fri Jul 06, 2012 4:09 pm

I'm pretty sure it would. From what I know pumps like that don't like to run without anything going through them.
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Re: Rust in Gas Tank...

Postby Yoshi » Fri Jul 06, 2012 4:19 pm

never run pumps dry. you could instantly kill them.
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Re: Rust in Gas Tank...

Postby blasphemy101 » Fri Jul 06, 2012 4:44 pm

Gotcha, thanks!
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Re: Rust in Gas Tank...

Postby blasphemy101 » Mon Jul 09, 2012 2:29 pm

Well, I've gotten all the gas out of the tank. The exhaust (what a bitch) and heat shields are off, and I've unbolted the driveshaft from the diff (slightly less of a bitch). It should be out tonight, then just the tank is left :). Things are going really quickly now that the exhaust is off.
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Re: Rust in Gas Tank...

Postby 7pilot » Fri Jul 13, 2012 10:00 pm

Any progress?
My M3 sat for a couple of years as I accumulated $ and parts to rebuild the engine.
After it was back together, both pumps died. I drained the the nearly full tank of rusty coloured fuel. I filtered the fuel and got a few grams of fine sediment.
I replaced the lift pump with OEM but bought cheaper Airtex for the main. The Airtex was also killed by sediment in the lines. I drained the tank again but the fuel was clear. Put another Airtex in and it is not doing well. I have fuel delivery problems punching out of left hand corners.

I think I'll replace the tank this fall. I hate ethanol with a passion.

m
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Re: Rust in Gas Tank...

Postby blasphemy101 » Mon Jul 16, 2012 7:59 pm

It sounds like you could be having some separate issues.

1) Rust in the tank - I'll cover this below

2) Transferring fuel between sides of the tank - if the tank in the M3 is anything like mine, there will be a hard line on the bottom of the tank that connects both sides of the tank. I believe this is there to help keep the gas level even across the tank. This may be clogged. I looked at replacing mine, but I was unable to locate a replacement.

3) Rust in your lines - these should be flushed with fluid (water/gas) and then blown clear of debris with an air compressor. You might want to replace all the rubber hoses aswell. If problems with your lines persist, look at replacing them (PITA).

Here's what I did about rust in the tank:

1) flushed with water to remove all flaked rust and sediment - my car sat for 6 years; there was a lot of this. I kept filling it and dumping it until I couldn't get more to come out.

2) rinse the inside with alcohol to help the water evaporate the next morning I poured 2 jugs of white vinegar in the tank, but I probably should have used more. Every 8-12 hrs (or when possible) I shifted the tanks position or stood it up on one end, so the vinegar was laying in different parts of the tank. The acidic properties of the vinegar should eat at the rust, and it will eventually become cloudy/orange/red from dissolving rust. I continued this for about a week.

3) I poured out the vinegar, added baking soda to the tank, and filled it with water, to counteract the vinegar. I emptied it and repeated this a couple times. When I was done. Most of the tank was bare metal inside.
READ: I've read suggestions to use more vinegar initially and adding the baking soda straight to the vinegar, letting the agitated mixture brake more rust loose, instead of flushing it with more water. I think this would work even better, but I didn't have enough vinegar to make it worthwhile.

4) I rinsed the tank with more alcohol to promote water evaporation.

5) Reinstalled tank and filled with good gasoline ASAP.

This was a major pain, but I was willing to try it before shelling out the $$$ for a new tank.
MANY tanks have at least some rust in them, so not removing 100% of the rust does not concern me. I am very confident this will be MUCH better than it was before. There was about 1/4" of sediment directly under my transfer pump, severely restricting flow.
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Re: Rust in Gas Tank...

Postby M20_fever » Mon Jul 16, 2012 8:34 pm

Muriatic acid will do in one day what vinegar did in a week. Is your car and early or late model? I have an early model tank id sell for cheap, though shipping might be a bit.
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Re: Rust in Gas Tank...

Postby blasphemy101 » Mon Jul 16, 2012 8:43 pm

M20_fever wrote:Muriatic acid will do in one day what vinegar did in a week.


This sounds like a good alternative! I chose vinegar for the cheap, easy acquisition ($4 for the amount of vinegar I used). It's also much more mild, though I'm not sure the acid would be too much of a problem. Either way, it's worth a shot before getting a new tank :)

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