Unburnt Fuel Smell

floydman · 05-13-08, 06:02 AM

I have a 77 FJ-40 I bought last fall and did a lot of cosmetic work to it over the winter. I just started driving it. It came with a webber carb. It runs really well and has lots of power. My problem is that when it is running it has a really bad unburnt fuel smell. The tail pipe is really black instead of gray. I ran a 428 stang with 8 barrels for years and the exhaust pipe was always gray. Should I leave well enough alone or is there an adjustment I can make to it to lean it out. Any help would be appreciated.

venpick · 05-17-08, 10:53 AM

The smell is only when its running, and its comming from the exhaust? I ask because its common for the gas tank under the passenger seat to rust out and start leaking. I think that unburnt? gas smell has to be a leak in the lines or tank somewhere. if it is running rich from lots of fuel into the motor the spark plugs will tell you by looking at the color A black dry fluffy residue on the plugs if its getting to much fuel. There should be a mixture adjustment for this. good luck here is a good link with plug pictures and colors to help diagnose engine probs. Reading Spark Plugs

Gumby · 05-18-08, 05:29 AM

It sounds if you are running way too rich. Check a plug to know for sure like venpick says.

That's assuming you've looked for fuel leaks in the lines and at the carb. Obviously, that would be pretty important. You should also check that your fuel system vents are hooked up. If someone changed the carb, they might have disabled the EVAP system.

Webers are known for being sensitive to fuel pressure. If you don't have a fuel pressure regulator on yours it might be over pressurizing the carb.

It's kind of a major step to fix a somewhat minor problem, but I would throw that Weber in the bushes and get a stock carb. my opinion only. Lots of guys run Webers successfully.

Otterav · 05-18-08, 10:31 AM

Quote:

Originally Posted by Gumby

It sounds if you are running way too rich. Check a plug to know for sure like venpick says.

That's assuming you've looked for fuel leaks in the lines and at the carb. Obviously, that would be pretty important. You should also check that your fuel system vents are hooked up. If someone changed the carb, they might have disabled the EVAP system.

Webers are known for being sensitive to fuel pressure. If you don't have a fuel pressure regulator on yours it might be over pressurizing the carb.

It's kind of a major step to fix a somewhat minor problem, but I would throw that Weber in the bushes and get a stock carb. my opinion only. Lots of guys run Webers successfully.

Hey,
Ditto, Weber carbs are very sensitive to inlet fuel pressure, a pressure regulator is absolutely necessary. My BMW 2002 was running so rich it would soot up the plugs at idle. Mileage was in the mid teens, I pulled the pressure regulator off my wrecked '02 and installed on my DD, car immediately ran smoother and mileage jumped to 24MPG. Weber float needels are easily overpowered at idle when fuel requirements are low. HP publishing has a book on tuning Webers, invaluable! BTW Webers are very misunderstood, their ease of tuning makes them very easy to mis-tune, conversely that very ease of tuning can make for an excellent performing engine.
Hola
eric
P/S Amazon.com: Weber Carburetors (HP Books 774): Verlon P. Braden: Books

randyr · 05-20-08, 09:21 PM

A burnt out exhaust valve on #2 cylider caused me the same problem...unburnt fuel smell, blackened exhaust. I had no idea until I performed a compression test and found 0 compression.

floydman · 05-31-08, 06:34 PM

Thanks guys, been away on vacation and just getting back to the cruiser. In the middle of a transfer case rebuild and will get back to the fuel smell later. The smell I was refering to is not inside the vehicle although I did remove the tank and replace all the lines. The smell was the fumes left over after I started it in the barn. Have to back it out quick or it becomes overpowering really quick. I do have the webber carb book that otterav mentions and it looks helpful. I will try a few tweaks to it. Thanks again.

Snead Hearn · 05-31-08, 06:53 PM

Same (more or less) issue. What a pain! Good luck as you hunt down the problem.

http://forum.ih8mud.com/40-55-series...v8-stinks.html

05-13-08, 06:02 AM	#1
floydman IH8MUD Rookie Join Date: Mar 2008 Location: New Hampshire Posts: 14	Unburnt Fuel Smell I have a 77 FJ-40 I bought last fall and did a lot of cosmetic work to it over the winter. I just started driving it. It came with a webber carb. It runs really well and has lots of power. My problem is that when it is running it has a really bad unburnt fuel smell. The tail pipe is really black instead of gray. I ran a 428 stang with 8 barrels for years and the exhaust pipe was always gray. Should I leave well enough alone or is there an adjustment I can make to it to lean it out. Any help would be appreciated.

05-18-08, 05:29 AM	#3
Gumby Former Wheeler Join Date: Dec 2002 Location: Knee deep in hookers and gin TLCA# 5658 Posts: 5,681	It sounds if you are running way too rich. Check a plug to know for sure like venpick says. That's assuming you've looked for fuel leaks in the lines and at the carb. Obviously, that would be pretty important. You should also check that your fuel system vents are hooked up. If someone changed the carb, they might have disabled the EVAP system. Webers are known for being sensitive to fuel pressure. If you don't have a fuel pressure regulator on yours it might be over pressurizing the carb. It's kind of a major step to fix a somewhat minor problem, but I would throw that Weber in the bushes and get a stock carb. my opinion only. Lots of guys run Webers successfully. __________________ War Pig and Cerdito "Don't you know, Stan, it's *always* between a Giant Douche and a Turd Sandwich."

05-20-08, 09:21 PM	#5
randyr IH8MUD Rookie Join Date: Jan 2006 Location: Va Beach Posts: 23	A burnt out exhaust valve on #2 cylider caused me the same problem...unburnt fuel smell, blackened exhaust. I had no idea until I performed a compression test and found 0 compression. __________________ '78 FJ40 nice lookin 2F surrounded by lots o' rust

05-31-08, 06:53 PM	#7
Snead Hearn IH8MUD Rookie Join Date: Jul 2007 Location: Central Oregon TLCA# 16749 Posts: 60	Gratuitous attempt to attract help to my thread Same (more or less) issue. What a pain! Good luck as you hunt down the problem. http://forum.ih8mud.com/40-55-series...v8-stinks.html __________________ "Please God, help me to be the person my dog thinks I am" 1980 FJ-40 383 SBC W/OD, 33's W/OME, BFD

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05-17-08, 10:53 AM	#2
venpick IH8MUD Junior Join Date: Jun 2007 Location: SLC UT TLCA# gave up Posts: 135	The smell is only when its running, and its comming from the exhaust? I ask because its common for the gas tank under the passenger seat to rust out and start leaking. I think that unburnt? gas smell has to be a leak in the lines or tank somewhere. if it is running rich from lots of fuel into the motor the spark plugs will tell you by looking at the color A black dry fluffy residue on the plugs if its getting to much fuel. There should be a mixture adjustment for this. good luck here is a good link with plug pictures and colors to help diagnose engine probs. Reading Spark Plugs __________________ 77 fj 5.7 vortec, h55f, marks 3.05:1 geared transfer, 4.88:1 ring and pin., arbs,six shooter knucks with high steer, marfields, 3 link front, 4 link rear, custom dents.

05-31-08, 06:34 PM	#6
floydman IH8MUD Rookie Join Date: Mar 2008 Location: New Hampshire Posts: 14	Thanks guys, been away on vacation and just getting back to the cruiser. In the middle of a transfer case rebuild and will get back to the fuel smell later. The smell I was refering to is not inside the vehicle although I did remove the tank and replace all the lines. The smell was the fumes left over after I started it in the barn. Have to back it out quick or it becomes overpowering really quick. I do have the webber carb book that otterav mentions and it looks helpful. I will try a few tweaks to it. Thanks again.