Petrol smell on startup

[Charlieepie]

So another post from me about a funny smell. The last issue (smell of oil when parking up) was investigated by my local garage and they said my engine bay is absolutely spotless, so nothing is leaking oil at least.

Anyway… Last Sunday I started my car up after she’d been sitting unused for a couple of days before. Immediate waft of fuel into the cabin which cleared within a few secs.
Car sounds and feels absolutely fine so I put it down to maybe a spill from a recent refuel or residue from another nearby car. No dash lights and fuel economy is as expected.

Drove it down the motorway about 130 miles - with a stop on the way. No more fuel smell, nothing when I stopped (or when I started it back up), no visible drips etc.

Left it parked up until today as I’ve been away - completely forgot about it to be honest - started it up, again there was a smell of fuel into the cabin which cleared very quickly. Got out of the car with the engine on and the exhaust fumes were fairly strongly petrol-smelling. Drove it 15 miles ish - checked again when I parked up, no smell of petrol from the exhaust. Had a look under with the engine running and system pressurised and again no obvious leak. Started it up again about 20 mins later - maybe a very faint petrol smell, but I’m not convinced I didn’t imagine that…

It’s not smelling when it’s idling etc or anything and as it clears so quickly on startup and clearly smells in the exhaust fumes too I don’t think it’s a leak (which is why I’m still happy-ish to drive it - I’m 130 miles from my home address, going back on Sunday, so I don’t have a lot of choice!).

Any ideas what else I can check to narrow it down? At the moment I’m thinking either something exhaust related (but what?) or maybe the beginning of an injector failure - though wouldn’t I see a dash light here? Any pointers, anyone had similar?
I can take it into my local independent next week but they’re not a Jag specialist so I’m not sure what diagnostics they’d be able to do especially as it’s not throwing up any codes. A trip to a Jag dealer / specialist will require a bit more planning on my part!

 

[NaCl]

I've also noticed the strong petrol smell on startup but it only happens when I've started up the car after 5-7 days of not driving it, and is especially prevalent on colder days. The smell usually goes away after a couple of seconds and I don't experience it again on startups during the same trip or the day after.

Immediate waft of fuel into the cabin which cleared within a few secs.

Were the windows down when you caught the waft? I can only smell it when I have the windows down (or door open) on startup.

 

[Charlieepie]

I've also noticed the strong petrol smell on startup but it only happens when I've started up the car after 5-7 days of not driving it, and is especially prevalent on colder days. The smell usually goes away after a couple of seconds and I don't experience it again on startups during the same trip or the day after.

Immediate waft of fuel into the cabin which cleared within a few secs.

Were the windows down when you caught the waft? I can only smell it when I have the windows down (or door open) on startup.

No - windows were up, but my AC was on and the fan is fairly powerful. That's why I got out of the car to see whether I could pin point where it was coming from, in or outside - I got a face full of petrol fumes round the back of the car so definitely coming out of the exhaust!

What you've said sounds similar to mine but not sure on how long I need to leave my car before I get the smell again. I'm driving it first thing so I'll see then.

Unhelpfully google seems to suggest for *some* vehicles that a petrol smell after a few days parked isn't unusual but I'm not buying that with my F-type as it's never done it before in 18 months of ownership even in the dead of winter!

 

[scm]

I've never noticed a petrol smell on startup, even when the car has been sitting for 4 or 5 days. MIne's a V8, maybe there's a differencee with the V6 engines (but I can't imagine why)?

If you have a code reader you could check if any codes are set.

Hope you get to the bottom of it!

 

[cj10jeeper]

No smell whatsoever on my V6S. Starts in a garage, often cold after long stands and nothing. Same hot or after long drives.

Have you checked the filler cap? The rubber gaskets can craze and then leak as tank is pressurised. Hence it’s part of the mot check to ensure gasket and flange are in good condition and seal.

 

[Charlieepie]

Yeah I definitely don’t think it’s a normal thing especially as I’ve had 18 months of nothing before this.

Filler cap was the first thing I checked, I had recently filled up when I first smelled it but it seems ok to me and definitely on correctly.

I started it up about 30 mins ago and couldn’t smell much then, then I realised I had my AC on windows as they were iced up (in April!!!) so that may explain that. Will see how it is later.

 

[gasgas]

leaking petrol not good , i would get it checked out urgently.

 

[Charlieepie]

I’m fairly sure it’s not a leak - no sign of a leak and no smells when it’s warm at all. Pretty sure it’s an issue with the fuel system meaning excess fuel / fumes are ending up out the exhaust.

I will get it checked this week just wanting to see if there’s anything to check first - as my local independent can only do so much and getting it to a specialist is an ordeal.

 

[cj10jeeper]

Yeah I definitely don’t think it’s a normal thing especially as I’ve had 18 months of nothing before this.

Filler cap was the first thing I checked, I had recently filled up when I first smelled it but it seems ok to me and definitely on correctly.

I started it up about 30 mins ago and couldn’t smell much then, then I realised I had my AC on windows as they were iced up (in April!!!) so that may explain that. Will see how it is later.

Did you have a really close look for fine crazing in the rubber gasket? It's a common issue

 

[Charlieepie]

So I went and had another look at my filler cap - last time I was just looking for damage and missed this - the rubber bit on the car that the cap sits onto had on one side raised up so there was lip over the metal. So I’m not sure the cap was sealing right onto it even though I was getting the click… Photo attached!

I’ve just moved it back into position by pushing the rubber back down on the left. Started the car up and there was no fuel smell in the cabin. Nothing particularly offensive when I got out of the car either, just ‘normal’ exhaust fumes. It’s been in the sun all day though, so if it’s an issue only on truly cold startup I wouldn’t notice.

So this may have solved the issue. I hope so - will keep an eye over the next few days. I’m not really sure though why this would only cause a smell on startup - is it some kind of build up through the potentially leaky seal that then is released when the system is pressurised?

I hope that’s as simple as it is and not an ejector stuck open.

 

[cj10jeeper]

That won't be the issue unless flap of rubber was in some way preventing the cap seating correctly, but fingers crossed it helps.
Next time you start up have someone around the fuel cap area and exhaust to see if you can detect a vapour source.

It's worth clearing out that drain in the lower edge. Nothing to do with your vapour smells, but it is designed to get any rain or even fuel spills out without running down the paintwork.

 

[Charlieepie]

That’s what I thought. I’ll cross my fingers it was preventing the cap from seating and see what tomorrow brings. There’s definitely no damage or cracking I can see though so if not that I’d be surprised if the source is around the fuel cap.

Already cleared the drain bit out after taking the photo before I put the cap back in place so that’s sorted.

Edit - have also popped the bonnet to sniff around the engine bay. Absolutely no smell with the engine on or off so I don’t think it’s a physical leak anywhere near this area (which is good!)

 

[scm]

It's worth clearing out that drain in the lower edge. Nothing to do with your vapour smells, but it is designed to get any rain or even fuel spills out without running down the paintwork.

I asked my indie to clean that drain when the car went in for a service.MOT last week and he said it was blocked at both ends! Worth keeping an eye on.

 

[Charlieepie]

An update in case anyone else has this issue.

Pretty sure it was an issue with the fuel cap not seating correctly, whether it was to do with that rubber lip or not.

None of the starts the last few days have produced any unusual smell outside the car above and beyond what I’d expect a cold-starting car to smell of… I will keep an eye but certainly no cabin smells which is good news. The proper test will be when the car has been sat for a few days.