'89 750il has strong smell of gas on startup

[ourv12]

My 89 750il has a strong smell of gas when i first start it when engine is cold. There are no fuel leaks anywhere. I checked from the tank, fuel filters and hoses all the way to the engine and all injectors and there are no leaks. What is causing the strong smell and where is it coming from? The 2 temp sensors in the intake manifolds were both replaced recently so they are fairly new. The 02 sensors were replaced several years ago and have less than 30k on them.

[shogun]

from exhaust or engine bay smelling?
If it leaks somewhere from hoses, usual spots are the short hoses before/after the 2 fuel filters, and in engine bay, and left front wheel housing, and there it is difficult to find. There was also a recall on the older 750 to replace fuel hoses and clamps, see here this TI where you can see the lines http://www.e38.org/e32/ open the file in the section engine>>> Fuel line replacement (750iL, BMW SI 130509 PDF)
in engine bay left side where these hoses come up from the wheel house near the heater valve and are connected to the fuel rail pipes. Then the hoses from fuel pressure regulator return line often leak, they go from FPR on front of the engine to a y-piece and then between bank 1 and 2 towards firewall and then to right side. See here some pics from Paulmer https://www.bimmerforums.com/forum/s...ight=fuel+line
To test fuel lines for leaks I founds easiest is to pressurize them, engine off, open fuse box, take a short wire and connect to B+ pole and then briefly touch fuse 23 and then fuse 24 for the other bank, then the 2 fuel pumps work briefly and build up pressure and you can even hear the fuel running thru the fuel pressure regulators.
here you see the fuel lines in engine bay and the fuel tank breather lines http://bmwfans.info/parts-catalog/E3...ration_system/

[ourv12]

Thanks Shogun, I will check it out today. Where can I purchase the best fuel line if I need to replace some ? I believe its 8mm ID hose correct? I want to use the best hose so i dont have this issue again. Thanks

[Cactuar]

Original fuel hose is 8x13mm.
When I redid all the fuel hoses on my 735iL I used BMW part 16121180409, it comes by the meter.
The genuine BMW hose fits perfectly on the fuel lines and FPR, I would use nothing else.
It is expensive but well worth it for safety and peace of mind.

Also I recommend to change all the hose clamps with part 07129952104.

I made a video about the hoses on my 735iL if you are interested.

[whiteghost1]

I had a similar issue and for me it was 1 of the short fuel hoses that join the FPR’s->fuel rail. It was weeping fuel at startup and gave a strong gas odour. But after a few mins of driving + thermal expansion, the weeping seemed to self seal almost every time. Check the 2x hoses & clamps to see if that’s the culprit.

[ourv12]

Well I checked all fuel lines in engine bay and they were already all updated to the newer screw type BMW clamps. So with engine running there were no fuel leaks to be found. All clamp are tight with no leaks anywhere. I then checked the top of gas tank in the trunk and where the fuel lines connect to the 2 fuel pumps and the one return line. All were already updated with BMW screw clamps. So while engine was running I tried to move and squeeze each fuel line and noticed the return line would leak slightly if I pushed on it. the other 2 fuel pump lines were tight with no leaks. I hope that the one return line was the cause of the gas smell. I tightened that return line clamp about 1 1/2 turns till it was good and tight. Strange though that it didnt leak on its own just looking at it. .....but only when I pushed on the hose then it leaked a bit.







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