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[16v] Thermo-time Switch



Hi,

I've been having a cold running problem since I bought my car, an '87 16v.
The car will take two to four attempts to start, and finally stop
stumbling after much urging from the gas pedal, but as soon as I let off
the gas, the idle dips down to 300-400 rpm and the engine sometimes dies.
After I let it warm up for 30 seconds, I can drive if I rev it to 3000 rpm
and baby the clutch. For the next 2 minutes of driving, it will die as
soon as I let it idle pulling up to a stop sign or otherwise. Throttle
response is very slow and the engine doesn't have much power.

I've attempted to diagnose this problem before, but this time I was
looking at the cold start valve. I removed it from the intake manifold
port and noticed that it had a bit of corrosion under the carbon buildup
on the injector tip. I followed bentley's instructions aiming it into a
transparent container and cranking the engine. Nothing came out. Finally I
connected it directly to the battery and after about a second it began
spraying fuel. After that initial delay, there was no other delay when I
disconnected it and reconnected it again. The fuel spray was atomized and
cone-shaped, everything looked good. I bolted it back up.

So I began troubleshooting the wiring. Here is a simplified version of
what Bentley has for my wiring. The G/W is green wire with white line,
R/BK is red wire with a black line, etc.

                                      +---internal ground
                                      |
+---------+        +--------------------+
| starter |--R/BK--| thermo-time switch |----G/W----+
+---------+        +--------------------+           |
     |                   +---------------------+    |
     +--------BK---------| cold start injector |----+
                         +---------------------+

Both the signals from the starter seem to supply +12v when the starter is
cranking only. I used a test light at the wiring harnesses for the cold
start valve and thermo time switch and these circuits are both operating
correctly. I used a continuity meter on the green/white wire between the
thermo-time switch and the cold start injector and it tested out okay.
This only leaves two possibilities: a bad ground at the thermo-time switch
or a bad thermo-time switch. A bad ground is unlikely since the
thermo-time switch itself is threaded into the block. So I probably have a
bad thermo-time switch.

The thermo-time switch, as far as I can understand it, is a thermally
controlled switch that opens above a certain temperature. It is surrounded
with an electric heated element and it is also threaded into a hole in a
coolant passage. Above a certain coolant temperature, the switch is always
open. Below that temperature it is closed. When the starter is actuated it
stays closed until the heat from the electric element warms the switch and
opens the circuit to prevent flooding.

So, who has replaced one of these before? According to Bentley I'll have
to drain my coolant by removing the lower radiator hose. This is fine
since I don't think it has been changed for at least 2 years. Where can I
get the good phosphate-free coolant?

I think the hardest part will be getting a wrench on that sucker. It is in
a nice convienient spot right below a coolant hose.

Speaking of which, I need to replace the coolant hose that runs from the
block to the coolant bottle. I think this is the one right above the
thermo-time switch. What is the official name and part number for this
hose and where can I get one for a reasonable price?

Any pointers would be appreciated.

Thanks!

-Toby

--
'87 16v silver

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