Cleaning the OEM tank seemed to be the cheapest way to go, but our tank also had some dents in the bottom, and without cutting it open there was no way to tell if the line was clogged with goo or physically crimped.
If you remember from our recent Ocala test, our car’s perpetual rich-run condition seemed to be related to a clogged or restricted fuel return line. We were seeing 90 psi of fuel pressure at idle, as the fuel coming from the pump had nowhere to go once it was done feeding the fuel rail. It wasn’t the fault of the fuel pressure regulator (we replaced that), and the line was found to be clear as far back as the entry point to the fuel tank. That meant that the line was messed up somewhere inside the fuel tank. Unfortunately, that meant it was time to take the tank out.
Our two options were to remove our stock fuel tank and get it cleaned or to buy a new tank. Cleaning the OEM tank seemed to be the cheapest way to go, but our tank also had some dents in the bottom, and without cutting it open there was no way to tell if the line was clogged with goo or physically crimped. Cleaning might not have fixed anything. Most of the replacement tanks we found online were going for more than $300, with OEMs listed closer to $500.
That’s when eBay came to the rescue. It took a bit of digging, since searches like “BMW 325 fuel tank” didn’t work, but when we got specific and searched for “BMW 325is gas tank” a shop called The Radiator Connection popped up. They had both the early BM1A and later BM1B tanks listed, the former for $100 and the latter for $130 (plus about $40 shipping in each case). Naturally we were skeptical of the low price, but the seller had more than 17,000 transactions and a 100 percent positive rating, so we figured it was worth the gamble.
A miss-read on our part led us to first order a BM1A tank, which is for the earliest 325is models. We actually needed a BM1B, so we returned the earlier model tank after taking some pictures for posterity. In both cases we had tracking numbers for the packages within 30 minutes of placing the Buy It Now bid on eBay. We added our own positive ranking to the seller’s 100 percent streak.
The eBay tank was a dimensional match for the OEM one, although it lacked the small plug at the bottom of the passenger’s side that can be used to drain the tank. For what it’s worth, our OEM tank’s plug was completely frozen in place anyway. We drained most of the fuel by MacGyvering up an extra long hose off the fuel return nipple on the fuel pressure regulator running it into the fuel tank of one of our other cars. (If you do attempt this, refrain from smoking, please).
Replacing a gas tank is a messy chore, as it requires the removal of the exhaust as well as the driveshaft. Also, get used to smelling like gasoline, as it’s nigh impossible to completely prevent spills as you disconnect the many lines carrying fuel hither and thither. Label lines and hoses as you go, and take the opportunity to replace any worn looking hoses with new replacements. Just make sure that you use fuel injection hose for the pressurized lines; we bought two feet of the stuff (about $10 at Pep Boys) and that was plenty for the three or four hoses we replaced. Since the OEM hose clamps are of the cheap single-use variety, buy a bunch of stainless screw-type hose clamps as well and replace as you go.
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