My newly purchased '77 300D seems to be harder to start when it's warm
than when it's cold. The glow plug light will go off after about two
seconds but I have to crank at least 8 seconds before it catches when
it's warm. It starts much faster when it cold. Sometimes there is a
puff of smoke when it first starts but it doesn't smoke after that.
Valves are adjusted, fuel filters replaced. It was suggested to me
that I run a can of injector cleaner through it and consider replacing
the injectors. Any other ideas?
First of all, yeah, the glow plugs do need to heat up
to (oddly enough) a glowing temperature even if it's
just a few seconds after the engine has been cut off.
They are the ignition source. At idle, let's say 1000
rpm (because the math is easier), each glowplug is
heated about 500 times per minute by combustion. As
soon as you shut the engine down, they go from glowing
hot to engine block temperature very quickly.
What I don't know, is when in the starting sequence the
glow plugs are no longer powered. Anyone? I _think_ the
glowplug light turns off when the system thinks the plugs
are hot enough, but they get power longer - till the starter
Try this simple experiment - turn on the ignition to run
position - then as soon as the glow plug light turns off,
quickly turn off the ignition, then back on again and try
to start the engine when the light goes off the second time.
If that helps, the glowplug temperature circuitry may be
gimpy. Or the temp sensor.
The fact that your car starts well when cold bodes well
for you. Sounds like the engine, pump and injectors are
working, and you just have a sensor or control issue.
try the easy way
turn on the dome light in the car.
turn the key to the glow position and see if the dome light dims a bit.
if it does WAIT till the GLOW LIGHT turns off.
it SHOULD brighten up after aprox 30 secs.
then try to start.
it may start better it may not.
you may need GLOW PLUGS or a relay box.
do the plugs first.
4 out of 5 of them are not to bad o get out. if it is a 5 banger.
some one here knows the size bit to stick in the plug hole to knock the
one thing i forgot to do my self.
the case, minus a few cans!
Since the engine fires quickly when it's cold speaks well for its
compression and glow plugs. Given the description I'd suggest the
shutdown device (bellows) isn't quickly releasing the fuel rack from its
OFF position as the key is turned from OFF to ON and then to START.
The shut down device is a small bellows that eventually wears out
usually allowing the engine to
trail off rather than a quick stop and then a slower start as the
bellows is oil logged. I believe the key clue is whether the engine
stops quickly or if it trails off to a stop.
The device is in the aft end of the injection pump; it has a vacuum line
attached to it. As a test, when the engine is hot, shut it down and
remove the vacuum line, then start the engine to determine if it starts
as quickly as it should. (You will then have to shut down the engine
using the STOP lever.)
The delay in starting and stopping will increase if the shut down device
is bad. Eventually the engine won't stop when the key is turned to OFF -
then you'll know it's time to fix it.
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