Troubleshooting Fuel Odor

[s4cruiser]

I need some help with direction/next steps.

I've had this car for less than two weeks and have been trying to track down a mystery fuel smell. I did not notice any smell when being around this car prior to purchasing it and for the first couple of days owning it. Once I filled up the tank (was <1/2 full for the first two days) I started noticing the smell.

The smell progressiving got worse over the course of 4 days of daily driving (10-15 miles per day). Smell was not as noticeable in the mornings and was most noticeable after the car had sat for 2 hours or so after driving.

Took the car to the shop last Thursday (with fire extinguisher in passenger seat) for them to sort out. They serviced the fuel fittings at the fuel pump as they were weeping slightly. Went to pick up the car and both myself and shop owner noticed fuel smell and could see wetness under the pan (was looking from underneath near the rear passenger tire).

Replaced fuel cap with new OEM part. Drove the car last night to the store with no fuel smell; however, when I took out the dog before bed I noticed a fuel odor.

Car runs great, idles smooth, starts on the 2nd or 3rd crank and not clicking from the fuel relay. Fuel smell is strongest near the passenger side rear of the car.

Looking for guidance on what to check for next.

Thanks!!

 

[clarkz71]

9 times out of ten, it's the filter feed line.

Part# 124 470 80 75

 

[gsxr]

If the smell is only OUTSIDE the car, you'll need to carefully inspect all the hoses underneath. They should all be bone dry, any sign of wetness is bad. The hose exiting the fuel filter (that Clark describes above) is the most common leaker. On the passenger side you have the return line and vapor vent valve/hose.

If the smell is on the INSIDE of the car... you may be experiencing a failing fuel tank, which is not fun to diagnose or repair.

 

[s4cruiser]

Great info here. Looks like I've got three items that I can replace.

Filter feed line, return line, and vapor vent valve/line.

The smell appears to be OUTSIDE only...UNLESS I am in slow traffic with windows down.

 

[gerryvz]

Yes, for ALL of our cars it's getting (if not past) time that all fuel lines should be replaced. I did this several years ago on my 560SEC at the rear of the car at the fuel pumps, and during my Top-End Rebuild four years ago, where I replaced the lines underhood going rearward to the tank (feed and return lines).

When I did the E320 Wagon top-end rebuild a year ago, I also found that the fuel lines underhood were cracked, and I replaced both of them out of hand.

Unfortunately age and some engine heat gets to these fuel lines (just like with brake lines) and it becomes an IMPERATIVE that they be replaced proactively. You don't want to be the recipient of a fuel line failure - that could be catastrophic.

Again, it's part of the GVZ $5K maintenance holdback for these cars. I don't care if your car has 10K miles on it ... the fuel lines are stlll 20+ years old now, and the rubber is degraded and in need of replacement. Hmmm....seems a topic for another HOW-TO....

 

[samiam44]

can be simpler as just a crush washer not sealing on a fuel filter or fuel pump.


But Clark's suggestion is good and a common problem. Track it down ASAP!!- leaking fuel is a recipe for a fire!


M

 

[s4cruiser]

On the passenger side you have the return line and vapor vent valve/hose.

What are the part numbers for these two items? I searched via EPC, but there are a TON of fuel system components.

 

[s4cruiser]

What are the part numbers for these two items? I searched via EPC, but there are a TON of fuel system components.

I think I figured it out...

Return hose: 124 470 69 75
Vapor vent hose: 124 471 32 23

Also - I "assume" that if the EPC names a part as "hose" then it's a rubber part and if it's named "line" then it is a hard fuel line that normally doesn't need servicing? I figure I should service what I can all at once versus piecemealing it.

 

[samiam44]

There is the charcoal canister and it's lines in there. I know the MOT valve is below the EZL on the fenderwell.


Micahel

 

[s4cruiser]

9 times out of ten, it's the filter feed line.

Part# 124 470 80 75

Winner, winner chicken dinner!

Line was dry rotted and did not weep when car was running; however, after driving and letting the car sit for a couple hours it did start leaking (my guess is pressure build up??).


Also replacing filter and the other rubber line (#124-470-69-75). In addition, replacing lower oil pan gasket (#119-014-08-22)and transmission to oil cooler hose (#220-997-16-52).

I was a stubbornly fighting the GVZ deffered maintenance edict...but in just 2 weeks I am become a wholehearted adherent.

In just 2 weeks of ownership I took a well maintained car and have somehow managed to find 2.5k worth of parts that I considered it needed.


FOr some reason I just can't leave 'well enough' alone as things need to be as they should.

 

[clarkz71]

Winner, winner chicken dinner!

Line was dry rotted and did not weep when car was running; however,
after driving and letting the car sit for a couple hours it did start leaking
(my guess is pressure build up??).

If I had a dollar for every time I've seen that.

It is pressure build up from engine heat in the fuel rail.

 

[gerryvz]

Indeed, another successful diagnosis and advisement from Lord Vader.

The $5K deferred maintenance figure is a round, and yet conservative number.

I'll say it yet again.....ALL fuel lines in the vehicle should be replaced, because they are now more than 20 years old.

Same thing goes for brake lines, if they've never been done. It's really important stuff.

 

[s4cruiser]

I'll say it yet again.....ALL fuel lines in the vehicle should be replaced, because they are now more than 20 years old.

Same thing goes for brake lines, if they've never been done. It's really important stuff.

Agreed - this is advice that could end up saving both your and someone else's life (not to mention the car).

 

[gerryvz]

I have seen more than one young timer Benz catch fire/burn up due to failed fuel line.

Go to my M104/W124 Top End Rebuild HOW-TO thread and take a look at the condition of the underhood fuel lines in my photos. That was a 1995 E320 wagon......


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