Rather than disconnecting the wire going to the overboost valve, you
will want to just bypass it for the time being to see if that is the
problem. If its plugged up(which most of them are) unplugging the wire
wont help.
[EMAIL PROTECTED] wrote:
In a message dated 5/11/2006 9:55:52 P.M. US Mountain Standard Time,
[EMAIL PROTECTED] writes:
My 82 300SD (Garret turbo) suddenly lost turbo boost last weekend. The banjo
fitting id not plugged and the circuit to the ALDA is not leaking.
Measuring the manifold pressure, I get almost no boost until 3-4,000 rpm and
then I get about 6 psi max. I don't see any obvious leaks in the intake or
exhaust and I can hear the turbo turning.
Any guesses on probable cause? I'm wondering if the waste gate is somehow
suck open. I have noticed jerky boost at high power settings (boost cuts in
and out near max power) in the past so I'm wondering if the waste gate may
be sticking. And If it is a sticky waste gate ... what's the cure?
Scott,
#!. Look for loose nuts that hold the exhaust manifold to the head, much
pressure can be lost here.
#2 Disconnect the single wire going to the pressure sensor on the intake
manifold. It sounds like it may be defective and is cutting off your boost
signal way too soon. You can drive it like that for testing purposes.
#3. Run the boost sense line direct from the banjo to the ALDA, teeing into
it right at the ALDA to verify the boost signal is getting to the ALDA.
#4. Remove the U shaped pipe from the filter to the turbo so you can reach
in and give the nose of the turbo a spin with your fingers. It won't spin
much but should feel free, with no roughness. Wiggle the shaft side to side to
see if you can make the impeller touch the housing. Some play is
acceptable. Look for FOD, foreign object damage, on the parts of the impeller you can
see.
#5. If all looks good, adjust the screw on the top of the ALDA about 1 1/2
turns CCW to add more fuel, which will add more boost, which will add more
fuel, etc.
#6. Get back to the list with your findings.
Jim Friesen
Phoenix AZ
79 300SD, 262 K miles
98 ML 320, 142 K miles
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