Strong gas smell when starting
 

Tried searching, but does anyone know if it’s normal for our Z’s to have a strong gas smell when starting after the car has been sitting for a couple of hours?

Absolutely not!

Any mods?
HFC and test pipes can make a difference. Cats burn off any raw fuel that gets thru to the exhaust. Once they heat up, that is. Take them out of the system with test pipes, or reduce their effectiveness with High Flow versions, and a gas smell can be more apparent.

Kirk B.

weird...you need to make sure that the fuel hose didnt come of the pump housing, by removing the small resting panel behind pass seat, after that remove the cushion, there you will find the access to the gas tanks fuel pump, check the fuel hose connection, make sure its all the way in and if there are fuel traces around, if its all the way in and no fuel traces, you need to follow the smell or fuel line to find the leak.

MAKE SURE THAT YOU DO THIS IN A WELL VENTILATED AREA!!!!

Engine Breather pipe/joints...check for cracks or broken joints.

No mods, been smelling it for a while now. First thing i checked was fuel pump since it was changed out a few months back and all is well there. Thought maybe leaky fuel injectors, but wouldnt that cause the car to be hard to start? Doesnt have an issue starting, just really strong fuel odor for about the first minute after starting the car.

One thing popped in my head when I read about fuel pump install;
Another member used screws that were too long & caused a problem.

Yeah, happen to someone else. Removed the bolts and put some RTV on the bolt threads.

With the aid of a helper or two, you should be able to locate where the smell is coming from. If smell is coming from exhaust, probably an injector.

If the location can't be determined using noses, you can rent an explosimeter.

Used to use them at work. :eek: They have to be set-up for the type of gas you are checking for. And for % of LEL. ;)

Very true, but ... OP is not wanting to know an accurate level; he/she just wants to know where the gas smell is coming from. Any explosimeter should work well enough, for OP's purposes, straight out of the box with no adjustments/calibrating.

Thanks for the responses guys, i will double check the fuel pump hoses but i know for 100% sure that the screws that were used to install the fuel pump are the originals. The fuel smell itself didnt start till a few months after the new fuel pump was installed. Not 100% sure without a second person helping, but the smell does seem to be coming out of the tailpipes. Guess it’s a good thing i picked up a fairly new set of injectors off of a fellow member here a while back lol

Maybe the gas cap is going bad, heat expands the gas vapors while sitting ,and could be the culprit.

Wasn't there some nissan tech article on the breather hose getting plugged? I think you can take your nissan in and have them check it for free.

There is but it only covers the car up to 150,000 miles if i remember right and im sitting at almost 160,000

Checked that the last time i put gas in, seals nice and tight still and no gas smell coming from it before i open the cap

Question: would a consistently rich reading from the long term fuel trims mean anything?

Bump

Does your Z fire right up (like when new) ?
I read back through the thread & seen 160k on it...with the poor quality gas these day's-you could have an injector or 2 dripping after engine is switched off.
I'd try some old school stuff; after driving & letting cool down somewhat-remove spark-plugs & read them,,,also look down in cylinders with a scope.
Your A/F sensors may be getting tired also.
How's fuel milage,power,oil consumption ?
Get a good tech to ride along w/a graphing scan tool & record it.....something is bound to pop up.
Any extra information is helpful.

Just an update, fired her up this morning from a cold start. Got out and smelled the exhaust from the tailpipes and sure enough i can smell a nice strong fuel odor coming from the tailpipes.

Forgot to mention AF sensors are new and fuel economy seems to be about normal going by what everyone on the forums gets. As far as the startup, i cant remember how fast a good running Z starts up, but it does seem to crank over a couple of times before starting up.

Having no mods; surprised it hasn’t thrown a cel,,,may want to peak at evap canister (R/R behind tire) it could have ruptured or maybe ran over something & damaged it,hose or fittings.

Went out and checked the evap canister, all hoses and connections look visually in good shape with no indications of any fuel leaks. Just the smell of gas coming out of the tailpipes for the first minute after startup.

An educated eye could catch this on a graphing scan tool; I’m learning this newer stuff/ as I come from heavy trucks,Diesel & Old school carburetors etc...it’s really easy for someone who really knows their test equipment & how to use it....not necessarily someone who works at a dealership either.
I’m gonna text & email a couple folks for you & see if I can further steer you in the proper direction.

I have an obd scanner that captures live data and can save it to excel if that would help, just let me know what pid’s you need captured.

How rich are we talking? If it’s constant and high and truly an issue you should have a check engine light by now. You say it’s only from cold start so I would think you may have a slightly leaking injector (if it’s a hard start as well?). This can be checked by doing a residual fuel pressure check and once confirmed you can remove the plugs and check the tops of the pistons for any that are very clean. Other though that comes to mind although I can’t say how it gets effected on Nissan with the vvel but you may clean the throttle bottles and check the air filters. On cold start the ecu opens the throttle more, adds fuel and also retards timing. This is to try and heat the cats quicker so your basically having the air and fuel burn in the exhaust. If you have a restriction on the air inlet (filters/ throttle body) no you have reduced your air to fuel ratio on cold start (you’ll also have a longer warm up time). Again not entirely sure how effected it is with vvel but can be an issue on GM.

Ps scan data won’t show you much if it’s a cold start issue because the AF sensor won’t be accurately reading at that point.

Long term fuel trims are constantly over -10%, they dont get up to the constant -25% that’s needed to trip the computer, but the long terms are definitely showing a rich condition is going on. Throttle bodies and air filters are definitely clean though as air filters are new and throttle bodies were cleaned less than 5,000 miles ago. Another thing to note is that when cruising with emgine rpm at about 2500 the long term fuel trim finally starts to level back out towards the nominal 0%, but as soon as the car is stopped and idling that number goes back up over -10%

Does your baro reading at KOEO match your altitude?

Yes, have tested that and baro reading matches what the weather station says is the current outside baro reading

If you do an ecm reset after warm how quickly and how high (or low I guess) do the short term fuel trim jump? Meaning does it jump to something like -15 and keep pegging there as long term drops.

It’s been a while since i did that so i woukdnt be sure about the exact behavior it exhibited. What i can tell you about the last time i did that is that i do remember it struggling and having a rough idle after i performed an ecu reset and performed an idle air relearn, it did finally smooth out after a few minutes though.

This is what the injectors looked like when i went to visually inspect them....https://uploads.tapatalk-cdn.com/201...20ec2f5db.heic


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I did the best I could getting a chart of what the fuel trims are doing with what tools I have, keep in mind the blue and gray lines are short term fuel trims for banks 1 and 2 and the orange and red are the long terms, this was taken today with ambient outside temps at 92 degrees while driving normally

http://www.the370z.com/members/z_eal...fuel-trims.jpg

Little hard to read, is this idling or driving? I was more just after seeing the short term % pegged - after a reset to idicate if you have an injector leaking or something else causing a large unaccounted increase in fuel. Unsure on the z but I've rarely actually had leaky injectors (maybe I'm just lucky). Your comment of it having a hard/stumbling start after reset would indicate an issue (especially if it says a hot start after reset). May be time to check fuel pressure (typical they fail low but I have on vary rare occasion had overly high pressures). Can check residual pressure at same time.

The peaks on the blue and gray stft are when it’s pegged at +25%, what might be interesting to you is that before i started recording the ltft was at -8% at a hot start with stft pegged at +25% for a good 10 seconds and then the engine stumbled and the fuel trims reversed with ltft shooting up to +10% and stft dropping to -15%. The graph i posted was recorded after this while i was driving in the city so it was a mix of acceleration and idling

So what's stft and ltft after full warm and leveled out, idle and like a steady cruise, no radical acceleration etc.

At idle after warming up ltft sits at -10.2% with stft fluctuating between +3% and +20%, usually i see the +20% and above after the engine is heatsoaked and idling. During cruising with rpm at a steady 2500 ltft usually sits at -3 to -5% with stft between 0 to +3%


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Ok so your cruising numbers look good. Idle I would like a lower number but not terrible for ltft but the huge fluctuations in short term don’t look so good (although not a vq expert but that doesn’t seem great to me). How many miles on this engine? No roughness or intermittent misfires at lower RPM/idle?

Just climbing up on 158,000 miles, the only roughness i encounter is when the stft pegs itself at +25% and then the engine stumbles and almost stalls and then that’s when the fuel trim numbers flip and the idle smooths out again, curiously the engine seems to act like it’s choking after this when i go to accelerate and does not really pick up power till after 5,000rpm.


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How's it drive with both mafs disconnected?