1992 730 - Smell of petrol

"Nathan_Jo" wrote:
> Hi, total newbie here, not only to the site but to BMW's in
> general (I just googled "smell of petrol on starting" and this
> is where I ended up, to be honest). The thing is I am
> currently test-driving a J-reg 316i for a month - the seller's
> a neighbour of mine, asking £1500 - and have noticed just the
> same problem. Do you any of you have any advice to someone who
> has precious little idea what goes on under the bonnet (the
> shame of it!) as to whether this is pricey to have sorted at a
> garage? I defer to your greater wisdom...

I had a similar problem on a 91 318i, I had it back to the dealers on
2 seperate occasions and they couldn’t find anything. I changed the
hose’s mentioned earlier. In the end a friend of mine found out where
it was leaking from, the "o" ring seals on one of the injectors.
They are hidden away under the intake manifold on top of the engine.
The replacement parts were quite cheap ("o" ring seals) and the job
was done by my friend in about 1 hour. I have never smelt fuel since.

"dandaire" wrote:
> I had a similar problem on a 91 318i, I had it back to the
> dealers on 2 seperate occasions and they couldn't find
> anything. I changed the hose's mentioned earlier. In the end a
> friend of mine found out where it was leaking from, the "o"
> ring seals on one of the injectors. They are hidden away under
> the intake manifold on top of the engine. The replacement
> parts were quite cheap ("o" ring seals) and the job was done
> by my friend in about 1 hour. I have never smelt fuel since.

Thanks for the tip. Guess I’ll look at the fuel lines / regulator /
injectors, and if that doesn’t work I’ll buy another car. Another
3-series that is - hooked on them now...

In article >,
SteveG <\s.goodfellow\@blueyonder <dot> wrote:
> Funny you should mention the regulator I've been wondering about that. I
> was trying to decide why it would happen just the once and some sort of
> temporary blockage (e.g. the regulator stuck shut) seamed a possibility.
> Also I remember that the idle was a bit rough when I had the leak.

> There's an air hose connected to the top of the regulator which
> disappears down a hole in the inlet manifold casting. I haven't tracked
> it yet but I guess it connects to the manifold somewhere so that fuel is
> only circulated when the engine is running.

Although petrol is forced through the injectors at moderate pressure -
somewhere roughly about 40 psi, the vacuum state of the inlet manifold
influences this too by the 'suck' on the injectors. So the regulator is
controlled by engine vacuum, and counteracts this effect.
So when the engine vacuum is high, like at cruise, the regulator reduces
the fuel pressure. At full throttle, the vacuum is at its lowest point, so
the regulator is wide open, and the pressure is at maximum.

So the rest position of the regulator is fully open (no vacuum). Any
vacuum leak to it (or elsewhere) will tend to produce a rich mixture. A
regulator which was stuck open would likely make hot starting and idling
impossible or difficult. Fuel consumption would also suffer.

It's a crude but effective system.

--
*I am a nobody, and nobody is perfect; therefore I am perfect*

Dave Plowman London SW
To e-mail, change noise into sound.

When my fuel pressure regulator failed I disassembled it to see what had
caused the problem so I would like to offer this
clarification on the operation of the fuel pressure regulator.
The regulator is downstream of the fuel rail and injectors and the fuel
that is allowed to pass it is on it's way back to the tank. So if the
regulator valve were to fail open there would be no fuel pressure at all.
The rest position of the regulator is fully closed with the return path to
the tank closed off by a small metal disk being spring loaded onto the the
end of the pipe that is the exit path from the regulator. When fuel is
pumped into this chamber the fuel pressure acts on the diaphram that the
metal disc is attached to and lifts it off from the exit path allowing fuel
to flow through to return to the tank. The manifold vacuum is plumbed to
the other side of the pressure diaphram so that the resulting regulated fuel
pressure is relative to the manifold pressure instead of relative to
atmospheric pressure.
My regulator failed because the metal sealing disk became detached from the
diaphram so the return path was always blocked regardless of the pressure
generated by the pump. It was 20 years old with 300k miles on the car when
it failed so this problem should be fairly rare.


"Dave Plowman (News)" > wrote in message
...
> In article >,
> SteveG <\s.goodfellow\@blueyonder <dot> wrote:
>> Funny you should mention the regulator I've been wondering about that. I
>> was trying to decide why it would happen just the once and some sort of
>> temporary blockage (e.g. the regulator stuck shut) seamed a possibility.
>> Also I remember that the idle was a bit rough when I had the leak.
>
>> There's an air hose connected to the top of the regulator which
>> disappears down a hole in the inlet manifold casting. I haven't tracked
>> it yet but I guess it connects to the manifold somewhere so that fuel is
>> only circulated when the engine is running.
>
> Although petrol is forced through the injectors at moderate pressure -
> somewhere roughly about 40 psi, the vacuum state of the inlet manifold
> influences this too by the 'suck' on the injectors. So the regulator is
> controlled by engine vacuum, and counteracts this effect.
> So when the engine vacuum is high, like at cruise, the regulator reduces
> the fuel pressure. At full throttle, the vacuum is at its lowest point, so
> the regulator is wide open, and the pressure is at maximum.
>
> So the rest position of the regulator is fully open (no vacuum). Any
> vacuum leak to it (or elsewhere) will tend to produce a rich mixture. A
> regulator which was stuck open would likely make hot starting and idling
> impossible or difficult. Fuel consumption would also suffer.
>
> It's a crude but effective system.
>
> --
> *I am a nobody, and nobody is perfect; therefore I am perfect*
>
> Dave Plowman London SW
> To e-mail, change noise into sound.

In article >,
Jack > wrote:
> When my fuel pressure regulator failed I disassembled it to see what had
> caused the problem so I would like to offer this clarification on the
> operation of the fuel pressure regulator. The regulator is downstream of
> the fuel rail and injectors and the fuel that is allowed to pass it is
> on it's way back to the tank. So if the regulator valve were to fail
> open there would be no fuel pressure at all.

Not so. You'd simply get the full pressure the pump can deliver.

> The rest position of the
> regulator is fully closed with the return path to the tank closed off
> by a small metal disk being spring loaded onto the the end of the pipe
> that is the exit path from the regulator.

Think you're wrong. They reduce the pressure in proportion to engine
vacuum to compensate for that vacuum sucking fuel out of the injector.

And engine vacuum is high at low throttle openings,so the pressure needs
to be reduced. At full throttle you want the designed maximum pressure.

> When fuel is pumped into this chamber the fuel pressure acts on the
> diaphram that the metal disc is attached to and lifts it off from the
> exit path allowing fuel to flow through to return to the tank. The
> manifold vacuum is plumbed to the other side of the pressure diaphram so
> that the resulting regulated fuel pressure is relative to the manifold
> pressure instead of relative to atmospheric pressure.

Which will tend to pull the diaphragm down and reduce the pressure?

> My regulator failed because the metal sealing disk became detached from
> the diaphram so the return path was always blocked regardless of the
> pressure generated by the pump. It was 20 years old with 300k miles on
> the car when it failed so this problem should be fairly rare.

Most are sealed units anyway, so you just fit a new one.

--


Dave Plowman London SW
To e-mail, change noise into sound.

Hi.

I am new to this newsgroup.

I've onwed (and still own, amazingly) my first BMW 318i E36 1993 model since
2001.

My car used to also emit the petrol smell. Initially, I was a little
worried, as it was quite strong when the car was initially started. Of
course, at the same time, my car had damaged rockers, camshaft, and tappets
due to infrequent oil changes.

I have recently had the rockers, camshaft, and tappets replaced by my
trustworthy mechanic, and now I do not smell any petrol.

I will confess that the annoying tapping noise that could have been
considered noise pollution was the primary reason for taking my car in for
the repair.

Kind Regards,

--
Jason Tepoorten
@HOME

8MP
Australia

"Nathan_Jo" > wrote in message
news:1_631500_0ee66bda6a49539e13d5d0f6896322c3@aut oforumz.com...
> "dandaire" wrote:
> > I had a similar problem on a 91 318i, I had it back to the
> > dealers on 2 seperate occasions and they couldn't find
> > anything. I changed the hose's mentioned earlier. In the end a
> > friend of mine found out where it was leaking from, the "o"
> > ring seals on one of the injectors. They are hidden away under
> > the intake manifold on top of the engine. The replacement
> > parts were quite cheap ("o" ring seals) and the job was done
> > by my friend in about 1 hour. I have never smelt fuel since.
>
> Thanks for the tip. Guess Ill look at the fuel lines / regulator /
> injectors, and if that doesnt work Ill buy another car. Another
> 3-series that is - hooked on them now...

"" wrote:
> Hi.
>
> I am new to this newsgroup.
>
> I've onwed (and still own, amazingly) my first BMW 318i E36
> 1993 model since
> 2001.
>
> My car used to also emit the petrol smell. Initially, I was a
> little
> worried, as it was quite strong when the car was initially
> started. Of
> course, at the same time, my car had damaged rockers,
> camshaft, and tappets
> due to infrequent oil changes.
>
> I have recently had the rockers, camshaft, and tappets
> replaced by my
> trustworthy mechanic, and now I do not smell any petrol.
>
> I will confess that the annoying tapping noise that could have
> been
> considered noise pollution was the primary reason for taking
> my car in for
> the repair.
>
> Kind Regards,
>
> --
> Jason Tepoorten
> @HOME
>
> 8MP
> Australia
>
> "Nathan_Jo" > wrote in message
> news:1_631500_0ee66bda6a49539e13d5d0f6896322c3@aut oforumz.com...
> > "dandaire" wrote:
> > > I had a similar problem on a 91 318i, I had it back to
> the
> > > dealers on 2 seperate occasions and they couldn't find
> > > anything. I changed the hose's mentioned earlier. In the
> end a
> > > friend of mine found out where it was leaking from, the
> "o"
> > > ring seals on one of the injectors. They are hidden away
> under
> > > the intake manifold on top of the engine. The replacement
> > > parts were quite cheap ("o" ring seals) and the job was
> done
> > > by my friend in about 1 hour. I have never smelt fuel
> since.
> >
> > Thanks for the tip. Guess Ill look at the fuel lines /
> regulator /
> > injectors, and if that doesnt work Ill buy another car.
> Another
> > 3-series that is - hooked on them now...

Thanks Jason – useful to know. In my case the tapping isn’t that loud
but the smell of petrol can make my eyes water at times! Pollution of
a different kind I guess... Out of interest how much did replacing
that lot cost you?

--
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