Fuel Smell at Cold Starts

[McLoven1t562]

Hey everyone, I tried searching the 3rd Gen section but wasn't finding my problem.

Lately I've been getting a strong fuel smell that comes into the cabin only on cold starts regardless of outside temp. Strong enough to where I need to open a window. Then of course once the temp goes up (about 5+ minutes) the smell is gone.

I did just replace the EVAP Canister with a brand new OEM from Toyota because I had this issue for a few weeks and once I replaced the canister it stopped happening for about a month, but now it's back to smelling and I can't see any visible leaks.

Hoping you kind folks could help prioritize what I need to be looking out for.

Thanks in advance

 

[19963.4lsr5]

Until the CAT warms up you will smell it. Colder temps make it worse.

Cold starts cause it it go into fuel enrichment mode. (Old school Choke). It will start out at a cold loop rich as all get out, and when it senses a valid Primary O2 sensor signal it will go closed loop and slowly ramp up the Air Fuel mixture from 8:1 to 14.7:1. By the time the engine hits 180f it should be at 14.7:1 AF and it will update its fuel trim map for the current operating parameters.


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[McLoven1t562]

Until the CAT warms up you will smell it. Colder temps make it worse.

Cold starts cause it it go into fuel enrichment mode. (Old school Choke). It will start out at a cold loop rich as all get out, and when it senses a valid Primary O2 sensor signal it will go closed loop and slowly ramp up the Air Fuel mixture from 8:1 to 14.7:1. By the time the engine hits 180f it should be at 14.7:1 AF and it will update its fuel trim map for the current operating parameters.


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So you trying to say this is normal? Because that definitely makes zero sense to me. I had a 97 4Runner for a few years and I never once smelled fuel, then same with this 96. First like year n a half never smelled fuel, and now it happens for a couple weeks, then magically goes away for months.

 

[RandyBobandy]

When was the last time your primary o2 sensor was replaced? I’d start there if it hasn’t been done recently even if there’s no code

 

[19963.4lsr5]

So you trying to say this is normal? Because that definitely makes zero sense to me. I had a 97 4Runner for a few years and I never once smelled fuel, then same with this 96. First like year n a half never smelled fuel, and now it happens for a couple weeks, then magically goes away for months.

when the EVAP system has a leak I it will code for a slow leak or rapid leak. In some cases you will smell gas as the tank vents.

Are all your readiness monitors set? EVAP, CAT, and O2?

Valid point about your pre-cat O2 sensor.


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[GRIPGRAIN]

I had a fuel smell that i recently resolved by replacing all the hoses coming in and out of the evap system and throttle body. They were seriously dry rotted from the previous owner negligently using E85 and had cracked in unobvious areas. The PO had replaced a fuel line under the intake manifold due to it leaking. If the smell comes back, the next line item will be Injector seals. If you have replaced all the vacuum and evap hoses, you could add a uv dye to the fuel and check around with a light after a few drive cycles. Consider full coverage insurance until resolved, best of luck!

 

[GRIPGRAIN]

when the EVAP system has a leak I it will code for a slow leak or rapid leak. In some cases you will smell gas as the tank vents.

Are all your readiness monitors set? EVAP, CAT, and O2?

Valid point about your pre-cat O2 sensor.


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I had LARGE evap leaks with no codes present.

 

[McLoven1t562]

When was the last time your primary o2 sensor was replaced? I’d start there if it hasn’t been done recently even if there’s no code

Only owned it for less then 2 years so definitely that old lol. I went ahead and just bought two new Denso ones that I'll replace this weekend....if anything, can't hurt to swap them out regardless.

I'll likely take another commenters advice too and start swapping out old hoses around the engine bay. I replaced a couple so far just because the previous ones were rock hard, so I'll likely check the condition of more and keep replacing them. Small price to swap hoses and if anything, good preventive maintenance thing to knock out

 

[LittleCaesar]

How is the gas mileage? If the injectors are original, one or more may be leaking when cold.

 

[Devbot]

They were seriously dry rotted from the previous owner negligently using E85 and had cracked in unobvious areas.

Some people, you seriously wonder how they ever drive :ranger:

 

[19963.4lsr5]

How is the gas mileage? If the injectors are original, one or more may be leaking when cold.

He should be able to pressurize the fuel system with a jumper wire to look for leaks with the engine off.


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[desertegal7]

i would also suspects leaking injector(s)

 

[McLoven1t562]

How is the gas mileage? If the injectors are original, one or more may be leaking when cold.

Roughly like 14-15 mpg? I get around 200 miles on a tank of gas and takes 13 or 14 gallons at the station. Apparently I have a "low fuel" light but it's super unreliable lol, I'd love to swap the fuel pump assembly at some point but I just don't have the space or tools to do it. In an apartment so I have no jack and no stands, nor a legal spot to drop it

He should be able to pressurize the fuel system with a jumper wire to look for leaks with the engine off.

really? I'll have to browse youtube to check out how I do that one.

 

[19963.4lsr5]

If you’re injectors are leaking through the pintle you won’t see it without a borescope or pulling the injector out of the o-rings and looking for them dripping.


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[BretMann]

If your injectors are getting clogged there could be some backpressure buildup. RCFuelInjection.com does a good job testing and cleaning them out.

 

[gamefreakgc]

I can say that fuel smell in the cabin is not normal. Fuel smell with the windows down, going in reverse and huffing your own exhaust, yeah I could see that. Not with the windows closed though.

A good tune-up can go a long way as well. In a related issue, I was getting fuel smell in my Altima when it idled and got so bad it made my eyes water. Replaced the air filter, cleaned the MAF sensor and tightened down some questionable hoses and the smell and fuel in the interior is gone. I think there was a vacuum leak or faulty MAF signal that was pouring on the fuel at idle to compensate. Might be worth doing the same, especially cleaning the MAF sensor as that is a known issue.

 

[McLoven1t562]

I can say that fuel smell in the cabin is not normal. Fuel smell with the windows down, going in reverse and huffing your own exhaust, yeah I could see that. Not with the windows closed though.

A good tune-up can go a long way as well. In a related issue, I was getting fuel smell in my Altima when it idled and got so bad it made my eyes water. Replaced the air filter, cleaned the MAF sensor and tightened down some questionable hoses and the smell and fuel in the interior is gone. I think there was a vacuum leak or faulty MAF signal that was pouring on the fuel at idle to compensate. Might be worth doing the same, especially cleaning the MAF sensor as that is a known issue.

lol right? I definitely know it's not normal - so I just replaced my O2 Sensors since I have no idea how old they were, the sensors were pretty dark so looks like it was time anyways. Swapped the fuel filter because I had a new one just sitting around, going to clean the MAF Sensor this weekend and then see what hoses I can get and swap those out as well. I've swapped a few hoses that connect to my new oem evap canister but the NAPA didn't have all the sizes I needed at the time.

I'm just going through maintenance stuff overall, whether it's fuel or not. Luckily with my 3 inch lift I don't need jacks for most undercarriage things either lol

 

[hawkcharmer]

I had LARGE evap leaks with no codes present.

How did you resolve the EVAP leaks? I have no codes, but getting fumes as well

 

[CougarHound]

Sounds normal to me. OBD checks for leaks and throw codes if there is anything wrong with the emissions system. Maybe clean the mass air flow sensor or oxygen sensors? Prob running too rich for some reason.

Also maybe you bought a crappy charcoal canister? Or the charcoal canister is getting over saturated somehow? Do you top off your fuel?

 

[GRIPGRAIN]

How did you resolve the EVAP leaks? I have no codes, but getting fumes as well

replaced the cracked hoses