On the first start of the day, turn key and .5 secs later it starts. On the second start (after 10-20 minutes) it will take 2-3 seconds to start. Is this normal? I've not had the fuel filter nor the fuel pump replaced.
The cold start gets help from a cold start valve to enrich the fuel,
the later warm start does not. The fuel pressure regulator (blank round
thing at the fuel rail at the back of the air filter box), is supposed to retain
fuel pressure in the rail between warm-starts. I would check that first, by
connecting a fuel pressure gauge at the test outlet on the rail. Remember
to release the pressure by drawing vacuum at the regulator (to simulate engine load),
so that the fuel flows back to the tank, like it normally does when running, before
when connecting the gauge (or when replacing the regulator).
The cold start gets help from a cold start valve to enrich the fuel,
the later warm start does not.
br,
syljua
No cold start valve with electronic injectors. The computer enrichens the mixture for a cold start simply by increasing the open time for the injectors during cold starts. At least, that's my understanding. I really only know the M120, and there is no additional injector on this engine.
Could it be the fuel filter or fuel pump? The car runs great. I had a Porsche that was hard to start after a hot start and the fuel pump was the culprit.
Could it be the fuel filter or fuel pump? The car runs great. I had a Porsche that was hard to start after a hot start and the fuel pump was the culprit.
I would not suspect the filter at all. I'll assume you're talking about an older 911 (or maybe any older Porsche since they used similar fuel injection systems at similar times across the models). There is a check valve that is integral with the fuel pump. The check valve maintains fuel pressure when the car is turned off to help hot starting. In some years, you cannot replace the check valve separately, which is why an entire fuel pump replacement would have solved the hot start problem. I don't know enough at this moment to say that the fuel pressure regulator is also the "check valve" that maintains pressure in your S500 fuel system when the car is turned off, or not. I'd have to do some more reading about it.
No cold start valve with electronic injectors. The computer enrichens the mixture for a cold start simply by increasing the open time for the injectors during cold starts.
My mistake... But the reasoning of fuel pressure, should still be valid?
There is a check valve that is integral with the fuel pump. The check valve maintains fuel pressure when the car is turned off to help hot starting. I don't know enough at this moment to say that the fuel pressure regulator is also the "check valve" that maintains pressure in your S500 fuel system when the car is turned off, or not. I'd have to do some more reading about it.
Yes, you're right Brett, to maintain pressure, there must be a closing at both ends, end of fuel rail and
pump. I read about it in StarTuned (like always...;-) ) and this sums that part up;
Quote:
Originally Posted by , well more correctly written by StarTuned
3. The fuel pressure regulator. If it spills fuel
back through the return line before there’s enough
pressure, a bad regulator can prevent starting or
cause reduced power at every throttle setting. Like a
defective check valve in a pump, a defective pressure
regulator can dump system pressure right after the
engine shuts down, requiring a long crank to restart.
In that last article, it's even a description of leaking FPR, that will cause
fuel to enter the manifold, and cause rich running;
Quote:
The fuel pressure regulator is a pretty sim-
ple device, but that's no reason to overlook it.
Whenever you see high emissions, some
experts say to pull the vacuum hose off the
fuel pressure regulator and look for gasoline.
Diaphragms have been known to rupture --
"I've had them come in with gas running out
of the tailpipe!" one shop owner tells us.
Although we've never seen it, we've heard
that a diaphragm can rupture badly enough to
fill cylinders with gasoline and cause
hydraulic lock.
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