Fuel Venting

[JohnC]

Hi all...So I've been reading on the issues of how slow it is sometimes to get fuel in. So a while back I replaced the fuel filler hose (someone squashed it pretty good between the frame and body), then replaced and took some kinks I saw in the vent lines, but really didn't get any change on how slow it was to add fuel. So, I lifted the car again and found a very severe kink in the vent hose right above the muffler where it enters the rear quarter panel on its way through the trunk. Now, I didn't want to remove the muffler and exhaust since someone did a bad job welding it on and since I'm going to replace the entire exhaust over the winter, I didn't want to cut it out just to put the junk back on. So, I cut the vent hose about 15" past the tee where the 2 vent hoses come off the tank. Now I can fill the tank up easily. Then I realized the gas is pouring out of that vent hose I cut, so as a temporary meausre, I put a bolt with a hose clamp on the cut hose and same issue, slow fuel up. My question is...Should I be getting fuel in the vent lines? How is it venting if it's blocked with fuel? Yesterday, I went to fill up, the car was near empty, when I removed the bolt on the vent hose and got blasted with a shot of an air blockage followed by fuel on the driveway
Thanks everyone

[Barry Wolk]

Kinks are not the only problem with vent lines. Toyota found that tiny spiders take refuge in vent lines and their webs can block the vent so badly that the fuel pump starves the pump, acting like vapor lock. Can you slip on a vent line that you can aimed for the end to be several inches above the top of the tank. That may get you safely to your exhaust change.

[JohnC]

I'm actually thinking of a way to re-route the vent hoses once I pull the muffler off. It's such a convoluted way it is run will all the turns and bends. The vapor lock seems to be an issue too as when I pull the bolt out of the cut hose I do get a blast of air. Are you thinking that extending the vent hose above the tank with no bolt will keep the fuel from spilling over? Should fuel be in the vent hose at all? Damn the spiders too

Thanks

[Barry Wolk]

Don't ever plug a vent line on purpose. When the fuel system becomes a closed system the efficient engine-driven fuel pump acts as a vacuum pump and creates a negative air pressure in the tank and could collapse it. However, you car would likely starve for fuel before that. I believe the cap is unvented. Some people insist on topping the tank off. Simple slosh on acceleration will drive gas out of the filler cover, hence the tank vent. Technically, the only way for gas to get into the vent is to overfill the tank. Do you know for a fact that the gas is coming from the vent and not the sending unit? If the screws were replaced it's likely they are too long, heaping the seal from compressing. Peel back the floor carpet in the trunk to find the sending unit access plate. It's pretty apparent when they've been leaking.

[txmasten]

Interesting thread that leads me to a related question. When I bought my car the fuel tank and sending unit were disassembled and out of the car. Does anyone know what fasteners should be used on the sending unit to attach to the fuel tank? I don't seem to have any of that hardware and am to the point of reassembly.

Car 3028 will hopefully be running for the first time in over 20 years in the next several days / weeks.

[Barry Wolk]

I believe they are 10-32, but they are a specific length so that hey are just long enough to catch with a new gasket, but not so long as to bottom out on the bulkhead fitting. It takes very little force to compact the gasket. Leave some room for future tightening. Double-check the size I quoted as original screws may be smaller. if you are rethreading always use a fine thread tap as the threads are stronger.