Fuel sending unit

GPD

Greg
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Would appreciate some thoughts. The new E3 Bavaria I purchased smelled of gas with a full tank and I was eventually able to track it to the trunk - having read the prior posts on this. It looks like the last owner replaced the fuel sending unit but that is still likely the source. Could they have somehow got the gasket wrong? Has anyone dealt with this?
 

Dick Steinkamp

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Could be the sending unit is not gasketed properly. Also...

Fuel line leaking at connections or old and cracked hose (BTW, ALL fuel hoses should be replaced if you don't know when they were last replaced)
Fuel tank leaking (see richiemcb above)
Fuel cap leaking
Fuel vent leaking somewhere in the vent system or actually missing hoses, surge tank, etc.
 

Thomas76

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Same issue I have, did not track it down yet myself. Couple things though.
1. Is your tank lid bent where the sending unit spins on? O ring new?
2. Some cars have a vent on the top of sending unit, some don't.
3. Tank fill tube look ok? How about the gas cap rubber?
 

GPD

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Setting up to change out all the hoses and gasket and see what happens.
 

bavbob

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As Dick says, the venting system may not be the entire problem but good chance it is adding to it. Blue plastic hose off filler neck runs to a plastic container on the rear pass fender above the wheel well, from there it makes its way to the charcoal canister below the battery tray and from there to the nipple on the bottom of the air filter housing. Line is usually cracked somewhere. My Euro E9 thankfully just vents to the outside world near the back bumper.
 
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Honolulu

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New to the list, apparently. I think we're here to help (I am anyway) but this has been discussed many times, and there are over a dozen possible leaks. Use the Search function and you should bring up quire a list of things to check, and how.

Changing out the gasket and hoses is not the first thing to do, unless they are shown to be defective. That's just throwing money at the problem and hoping you get it right. We call it flailing. Read up, check in what appears to be a logical sequence. You may/not find the leak, some of us don't.
 

bavbob

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Would appreciate some thoughts. The new E3 Bavaria I purchased smelled of gas with a full tank and I was eventually able to track it to the trunk - having read the prior posts on this. It looks like the last owner replaced the fuel sending unit but that is still likely the source. Could they have somehow got the gasket wrong? Has anyone dealt with this?
See end of first line.
 

GPD

Greg
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Flailing is a definition I am familiar with and suspect will revisit in due course. I am only pretending to understand at this point but am reading the old forums. It may take me more than one round to figure it out and there will be some flailing for sure, hopefully for your entertainment and not angst.
 

mulberryworks

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My Euro E9 thankfully just vents to the outside world near the back bumper.

Do you store your car in a garage? I would think that while having the tank vent outside the body would keep the trunk from smelling, it would just move the fumes to the volume of your garage. Sure, it would be diluted, but that would be a no go in my house.

The carbon canister in my US version 1970 2800cs, if it had one, is missing and the container above the gas tank is severely cracked. So I plan to install a all new gas fume recovery system with all new parts during the restoration to avoid any future issues with gas smell and thus the Mrs.

I did buy an import hydrocarbon sniffer to help with finding the source of a gas smell in another car, and while not cheap, it wasn't anywhere sensitive enough to find a small leak. It did sing when pointed at a large amount of fuel, but it was no help in pinpointing the source of the smell. I'd hope there are very good instruments out there that can do the trick, but probably priced beyond what most hobbyists would want to pay.
 
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Ohmess

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Do you store your car in a garage? I would think that while having the tank vent outside the body would keep the trunk from smelling, it would just move the fumes to the volume of your garage. Sure, it would be diluted, but that would be a no go in my house.

The carbon canister in my US version 1970 2800cs, if it had one, is missing and the container above the gas tank is severely cracked. So I plan to install a all new gas fume recovery system with all new parts during the restoration to avoid any future issues with gas smell and thus the Mrs.

I did buy an import hydrocarbon sniffer to help with finding the source of a gas smell in another car, and while not cheap, it wasn't anywhere sensitive enough to find a small leak. It did sing when pointed at a large amount of fuel, but it was no help in pinpointing the source of the smell. I'd hope there are very good instruments out there that can do the trick, but probably priced beyond what most hobbyists would want to pay.

I believe the carbon canister/gas fume recovery system was more of a US EPA thing as opposed to a consumer "smell" issue. If it were a consumer issue, European versions of our cars would not vent to the outside world. Moreover, there has to be pressure equilization somewhere, otherwise the drop in fuel level as the engine runs would create a vacuum at the top of the tank, potentially preventing fuel flow.

Also, when dealing with cars with carburetors, all carbs rely to some extent on the difference between atmospheric pressure and the vacuum created by the operation of the engine to atomize fuel. Unmodified versions of our cars will have the orifices where outside air can enter the carburetors contained within the air cleaner, which bottles up fumes. Aftermarket carb setups with aftermarket air cleaners may or may not do this.
 

Stevehose

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Mine vents out the trunk and it has no odor at all in the garage, probably because the fumes are not contained in a smaller vessel to then be concentrated enough to smell, or something like that

Do you store your car in a garage? I would think that while having the tank vent outside the body would keep the trunk from smelling, it would just move the fumes to the volume of your garage. Sure, it would be diluted, but that would be a no go in my house.

The carbon canister in my US version 1970 2800cs, if it had one, is missing and the container above the gas tank is severely cracked. So I plan to install a all new gas fume recovery system with all new parts during the restoration to avoid any future issues with gas smell and thus the Mrs.

I did buy an import hydrocarbon sniffer to help with finding the source of a gas smell in another car, and while not cheap, it wasn't anywhere sensitive enough to find a small leak. It did sing when pointed at a large amount of fuel, but it was no help in pinpointing the source of the smell. I'd hope there are very good instruments out there that can do the trick, but probably priced beyond what most hobbyists would want to pay.
 

bavbob

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I have never smelled gas in my garage but if I did, well there is the mower, weed wacker, blower, gas can etc. Yes the setup was a US emissions thing.

I do have a sniffer, works by detecting changes in O2/N2 tension so in a sense, detects anything. I'll give it a whirl when the car is up and running.
 

GPD

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Still piecing this together. The smell definitely was most intense in the garage. When the tank was full I smelled gas driving. As the gas burned, it became more of a garage smell.
 

HB Chris

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Gas smell from engine can be both hood seals by firewall, drain tubes/snorkels and plugs by hood latches in front of fresh air plenum. From trunk it can be trunk seal, fuel hoses, sending unit o-ring, trunk evap lines and reservoir, lack of hose to charcoal can from trunk and then on to air cleaner. Leaking tank seams/edges, fuel hose to sending unit.
 

mulberryworks

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Speaking of gas leaks under the hood, here's a video I shot when getting my car started up after sitting for about a year. It's pretty much in the same condition as when I bought it. I've replaced the points with a Pertronix but the timing is erratic because the distributor needs to be rebuilt, thus the occasional backfire from the carbs. The carbs were removed and cleaned, but the gasket for the front carb was too small and was catching the float and keeping it from shutting off the needle valve which caused a huge amount of gas to pour from the air cleaner to the ground. That was resolved and now in the video I'm trying to start the car up to move it.

The ground wire on the head is dirty and with extended cranking to get the fuel up to the carbs, the contact gets hot enough to put out some smoke, as noted in the video. Then as fuel enters the pump, the pump starts leaking onto the engine, running down the carb control rod and dripping onto the intake manifold. If the ground connection was hot enough, there easily could have been a fire. Not to mention the power wire to the Pertronix which is too short came off the coil connector, which also could have created an ignition spark. Whew.

Old lines, old pump, it all needs to be replaced. I have a rebuilt distributor waiting to go in during the restoration, when that finally happens.

 

GPD

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New to the list, apparently. I think we're here to help (I am anyway) but this has been discussed many times, and there are over a dozen possible leaks. Use the Search function and you should bring up quire a list of things to check, and how.

Changing out the gasket and hoses is not the first thing to do, unless they are shown to be defective. That's just throwing money at the problem and hoping you get it right. We call it flailing. Read up, check in what appears to be a logical sequence. You may/not find the leak, some of us don't.

Changed the fuel sending unit gasket, the plastic cracked white cap, replaced the gasket on the fuel tank cap and the old braided fuel hoses. Smell is gone. greg
 

halboyles

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the plastic cracked white cap
Very common fuel leak on many bimmers. Can be fixed with a simple plastic sleeve. If anyone needs this sleeve, just PM me and I'll send you one free of charge. I've been doing this on 02FAQ for years. This pic shows the sleeve on an '02 but it is the same for the e3s and e9s.
 

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