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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > NA Engine (non-turbo) / Drivetrain / Exhaust Modifications > Need Help: Fuel Leak and Long Crank on Cold



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      03-07-2021, 04:29 PM   #1
yupetc
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Need Help: Fuel Leak and Long Crank on Cold

Folks,

I haven't had the time to dig into this, but I figured if I posted a quick note up here, I may save a lot of troubleshooting. Below are my symptoms:

1. Strong Fuel smell near the driver-side in the rear seat position. If I dug under the car I can really smell fuel right under the gas tank. I do see a slight soil/moisten trace at the lowest spot of the gas tank looking from under the car. So I'm quite sure there's a leak there, probably from a higher position.

2. When cold, cranking the car takes some time. Recent 2-3 months, I noticed it takes 5-9 seconds to crank the car up depending on how cold I left it cold. But If I go to the grocery, in and out within 10-15 minutes, cranking doesn't take more than 3-5 seconds, almost as well as if everything has been normal.

3. No engine code whatsoever. Not even a lean mixture code registered by the O2 sensor. I'm wanting to say when fuel leaks, I shouldn't get enough fuel to pressurize the fuel rail, but it drives fine and no codes. So I reckon the fuel system is most likely intact.

4. I did pull the entire injector rail off 2 months ago when I first noticing the fuel smell. I even rigged a whole firing jig and pressurized the injectors with intake throttle cleaner, that cleaned up the injectors well, and each injector fires properly with re-optimized spray pattern.

5. A bit about my car, I'm the second owner since 2012 at 50k miles. Did put a few power mod in, it's almost as good as a NA N52 can get in terms of mods and power. I'm a mechanic buff, able to do engine build and DIY many things on the car, therefore I've never skipped a beat with maintenance and repair. However, this is the first time I faced a fuel system problem.

I'm wondering if there's anyone with similar experience and if you can directly point what the issue might be. I'm sure there is a leak on the driver side gas tank, just not sure if there's a common issue I can directly and conveniently take on the lead with.

Thanks folks.

--
Pete
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      03-08-2021, 09:38 AM   #2
tom.gnade
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I had an issue with very smelly exhaust, loss in mileage, and very long cranks - it was much worse in the cold. It got progressively worse until the car just flat-out wouldn't start. I was getting worried that the starter was going to melt every time we tried to crank it. Anyhow, last night I replaced the crankshaft position sensor - and it does seem to have fixed some of those issues. I still have a boatload of other troubles with my car right now, so this is just one part of it, but it very well could be the problem. When I got to the sensor - which is a bit of a PITA - the electrical connector was covered in oil, as was the sensor surface. It also seemed to have some debris on the surface. Anyhow, the new sensor went in with a brand-new o-ring, and the car started right up - within 2 cranks, just like it should. The smelly exhaust is gone, some of the rough-running is gone, the idle is perfectly smooth, and the throttle response is significantly better.
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      03-08-2021, 12:25 PM   #3
yupetc
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Quote:
Originally Posted by tom.gnade View Post
I had an issue with very smelly exhaust, loss in mileage, and very long cranks - it was much worse in the cold. It got progressively worse until the car just flat-out wouldn't start. I was getting worried that the starter was going to melt every time we tried to crank it. Anyhow, last night I replaced the crankshaft position sensor - and it does seem to have fixed some of those issues. I still have a boatload of other troubles with my car right now, so this is just one part of it, but it very well could be the problem. When I got to the sensor - which is a bit of a PITA - the electrical connector was covered in oil, as was the sensor surface. It also seemed to have some debris on the surface. Anyhow, the new sensor went in with a brand-new o-ring, and the car started right up - within 2 cranks, just like it should. The smelly exhaust is gone, some of the rough-running is gone, the idle is perfectly smooth, and the throttle response is significantly better.
It's good to hear your experience with this issue and that you've found a fix for it. I have ISTA-D and did run a full diagnostic. It seems the all the pos sensors are just fine. I don't think it's the same case as yours. Also I'm a bit OCD about keeping the engine clean because if there are any leaks I know the ramifications it does to other parts once gunk started building up on them. I did look under the car today again after a short drive in the morning and I can see drips of gasoline coming from the tank. It's driver side under the rear seat location. Some research points to possibly having to replace the whole pressure sender and fuel filter assembly as there could be some hair-line cracks to the sender housing. This makes sense for me as I think what I'm experiencing is not enough fuel pressure in the fuel line until the car runs and sort of skips the leaks from the fuel line. By the way, gas mileage is very poor right now, averaging 9-13 mph at best. I've ordered a new part from ECS, will be installing it soon to see if this addresses the issue.
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2015 X535i - CP Piston, Manley Rod, ACL/King bearings, MILVs VRSF full charge Pipe, Wagner FMIC, Hybrid Turbo, MHD2+ VRSF DP, UR Front/Rear Sway Bars, Eibach springs, Bilstein B6
2015 MINI COOPER - Mahle Pistons, Max Rods, BMS intake, CTS charge pipe, Wagner Intercooler, ByteTronik Tune, VRSF DP
2017 540i - MHD2+, VRSF DP, TU Pump
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