Fuel tank venting & internal corrosion of fuel lines

[Jay M. Blaine]

I have a 1991 Lexus LS400 which has venting issues in regards to pressure built up in the fuel tank. It appears the fuel lines have corroded internally thus  affecting the venting of the fuel tank. Lines, evaporator canister have been replaced with used parts as these parts have been discontinued by Lexus. Has any other owners of the 1st Generation LS 400’s come across with this issue, if so what was your resolution. Additionally, is there any Company that has acquired Lexus OEM Old/New Stock which you can contact to acquire discontinued parts. Look forward to your responses. Thank you, Jay

[paulo57509]

These are the only search sites that I know of for unobtanium parts.  You need the Toyota/Lexus part numbers.  I've had luck with finding Acura parts, but long shots, at best.

https://www.rearcounter.com/

https://www.partsvoice.com/

You might try: https://www.amayama.com/en

[300EChuck]

Jay:  The LS 400 uses a green colored valve which sits vertically at the front of the engine, called the BVSV, or, Bi-metal vacuum switching valve.  It has 2 ports which always break off, since they handle gasoline vapor which weakens them internally.  When you super carefully pull off the vacuum lines, say to remove the intake manifold, bink, these ports break at the base of the valve.

This valve opens at 54 degrees, and pulls gasoline vapor from the carbon canister, through the valve, and into the intake manifold through that beautiful metal vacuum tree. 

This valve is unobtainium, and was only $350 new when available. Yikes.  It CAN be repaired with JB Weld plastic epoxy, reattaching the broken little green vacuum ports.  Initially with super glue, then with a nice dose of JB on the exterior of the ports at the base, making sure the ports aren't plugged with epoxy.  Or, use white vacuum tees available at NAPA, trimmed to fit.

I have NEVER seen any first gen LS400 where this valve is in one piece and functioning properly,  except mine of course. 😊

The carbon canister can itself be tested to make sure it isn't plugged or has a broken check valve (this from the official factory repair manual). 

The top of the canister has two outlets.  Blow low pressure compressed air through the larger outlet; air should flow out the other port at the top (the purge port) AND from the bottom port, without resistance.  Then, blow compressed air into the smaller port at the top (the purge port).  NO AIR SHOULD ESCAPE FROM THE OTHER PORTS, top or bottom.  This tests the check valve.  If it fails this second test, replace the canister.

The canister might fail the first test, but that's because the internal filter is plugged.  This can be cleaned by blowing 43psi of compressed air into the larger port at canister top, while holding the purge pipe closed with your finger.  Air should freely come out the bottom port.

No activated charcoal should come out.  And, you can't wash or clean the canister.

Simple system.  Hopes this helps.

Chuck