While doing some work on my 86 Jetta, my friends and I debated the
following questions.

1. What is 'hot' start and 'cold' start? Nowhere in the Bentley did
it describe. I think 'cold' start means the engine hasn't run in a
while, and my friends think it means 'the temperature outside is -5
deg C'

2. The definition of 'cold' then affects our understanding of the cold
start valve. Since the cold start valve is dependent on the
thermotime switch, I would imagine then that the cold start valve is
only operative below a certain temperature. Do you know what this
temperature is? Do I ever have to worry about that out here in sunny
California?

3. The control pressure regulator according to Bentley is supposed to
have a resistance across its two terminals of "about 22 ohms". I
measured mine to be at 18 ohms. Anybody have any idea if 18 ohms is
OK?? What do yours measure?

4. Here's the latest update on the problem. Car does not start at
all. All electrical tests pass OK. Gas flow and pressure at the fuel
distributor intake is good. No gas comes out of any of the injectors,
unless we raise the air flow sensor plate (at which point fuel can
'piss' out of the injector hose without the injector nozzle but not at
a pressure high enough to shoot out the injector in a conical mist).
The air flow sensor plate rest position is picture perfect, and
resistance of plunger in distributor seems fine. Air ducts and filter
are OK. So, pressure into distributor = OK, pressure out of injectors
= not OK. What does this indicate to you? For me, it indicates
either a clogged distributor or a faulty control pressure regulator
(faulty CPR = less pressure to 'upper' portion of metering port in
distributor = springed diaphragm not open further in metering port =
less pressure to injector?). Would the CPR fail gradually over time
or suddenly? What would the symptoms of gradual CPR failure be?
Would a bad CPR cause bucking at low RPMs?

5. How much wouldn't you pay for a CPR?

Vinny
1986 Jetta (CIS-Lambda)

Cold is defined by the value on the water temp sensor. It is a
thermoswitch. I think the value might be 120F or so. When cold the
Lambda circuit is not engaged. Injection system runs a bit richer for
easier iddling. Lambda clicks on in about 1 minute after car starts. A
few minutes if you live in the land of snow.

Open your Bentley manual. You cannot test flow and pressure without a
pressure guage. Well you can check flow but you need to check
pressure.

Meters are not always accurate so 18 ohms may be ok. Probably is.

A clogged cpr will lead to higher pressure which makes the car harder
to start because the mixture is leaner. Remove CPR and fush in and out
lines with carb cleaner. The screen sometimes gets clogged with rust
and crud.

Fresh fuel filter and pressure gauge are what you need next.

Last car I saw that had that problem solved it with a different fuel
distibutor. I was not the mechanic but he had similar symptoms.

Bucking can be low pressure and volume.

lay_out (AT) hotmail (DOT) com (I Throw Thumbers) wrote:


Jim B.