No Start unless Accellerator Pressed
I have been experiencing a minor problem for the past month:
The car used to start up crisply on the first crank, but now takes 2 or 3 cranks. However, if I press on the accelerator pedal slightly, it will consistantly start on the first crank.
A previous post to the List said that failure to start on the first crank could indicate a defective fuel pump check valve.
I hooked a fuel pressure gauge to the test port on the injector rail and saw the following readings:
idle: 3.3 bar
engine off: 3.6 bar
after 20 minutes: 3.2 bar
after 100 minutes: 1.5 bar
next morning: 0.0 bar
The service manual says that 3.3 bar at idle is within spec for my MY. It also says that pressure after engine has been shut off for 20 minutes should be above 3.0 bar. And it is.
So, my question to you knowledgable folk is:
What do these reading indicate?
a) there is nothing wrong with the fuel pressure
b) leaky check valve
c) leaky fuel injector
d) some combination of b and c
'87 928S4 5-sp, Venetian Blue
I've got the same exact problem, I think. It takes about three seconds of cranking to fire off, which I've been living with, since it always does start. I do have another symptom however, which may or may not be related. I have an intermittent loss of power, at any throttle setting, or RPM. It feels like one cylinder breaking down. So I'm wondering if I could have a leaky injector. Which brings me to the big question, is there any *simple* trick to trouble shooting this?
I had similar problems before I had the injectors refurbished. Sent them to Marren Motorsport, and a week later all was fine. The engine catches within a second of turning the key, and no longer has any hesitations.
Merry motoring, Ed Ruiz
Here is a simple test to check to see if the fuel pump check valve is most likely the problem.
Let your 928 sit overnight or at least 8 hours or so. Instead of trying to start the car as you normally would, turn the key so you engage the starter for just a second and turn the key back off (do not let the car even try to start), do this 3 or 4 times in a row. Then try to start it like you normally would, if it starts OK at this point then it is most likely the fuel pump check valve.
Basically what you are doing with this procedure is "cycling" the fuel pump (the pump runs for a few seconds every time you engage the starter) to build up fuel pressure in the system.
Note: If you listen carefully every time you do the starter engagement as described above you should hear the fuel pump run for a second.
Due to the changes in the climate you may want to take a look at the connectors on you temp sensor II and also test it for proper operation.
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