[Saloon-lovers] Name That Switch (please?)

Hi folks,

Since my idle drops about 300 rpm as soon as I put the DG250
in gear, I was wondering if the little pressure switch that
sits on a manifold bracket between the carbs might not have
something to do with it.

Truth be told, I’d removed the switch along with the P/O’s
home-made butterfly choke (starting) system, thinking it was
part of it, but now that I’ve read a couple of threads
mentioning ‘‘kick-down’’ and ‘‘anti-creep’’ switches located in
that same area, I started having second thoughts.

I re-installed the switch as it was, but it doesn’t seem to
do anything towards keeping the idle from dropping radically
when shifting into drive or reverse.

On the other hand, the tranny kicks down just fine without it.

Can anybody tell me what this switch is actually intended to do?

Thanks,

Jacques–
Jacques B / 62 MK II 3.8 Auto
Saint Augustine, Florida, United States
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In reply to a message from Jacques B. sent Mon 17 Jan 2005:

Jacques,
Are you still running with the vacum line to the brake
servo blocked off? IIRC your transmission has a moderator
valve which also runs on vacum. You seem to have a great
deal of vacum related issues, could it be that they all
appeared since your brake servo went South and you blocked
off the vacum line?
Which shop manuals do you have?

Andrew–
The original message included these comments:

Since my idle drops about 300 rpm as soon as I put the DG250
in gear, I was wondering if the little pressure switch that
sits on a manifold bracket between the carbs might not have
something to do with it.


1968 3.8S
Zurich, Switzerland
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Hello Jacques:

my mk2 has (had) a small switch (one wire) between the carbs. I believed
it released the device in the brake line which would keep the brakes
engaged when at a stop light. I do not beleive it had anything to do with
transmission, other than only vehicles with automatics were equiped with
the brake holding thingy.

george leicht

At 07:19 PM 1/17/2005 +0100, you wrote:

Hi folks,

Since my idle drops about 300 rpm as soon as I put the DG250
in gear, I was wondering if the little pressure switch that
sits on a manifold bracket between the carbs might not have
something to do with it.

Truth be told, I’d removed the switch along with the P/O’s
home-made butterfly choke (starting) system, thinking it was
part of it, but now that I’ve read a couple of threads
mentioning ‘‘kick-down’’ and ‘‘anti-creep’’ switches located in
that same area, I started having second thoughts.

I re-installed the switch as it was, but it doesn’t seem to
do anything towards keeping the idle from dropping radically
when shifting into drive or reverse.

On the other hand, the tranny kicks down just fine without it.

Can anybody tell me what this switch is actually intended to do?

Thanks,

Jacques


Jacques B / 62 MK II 3.8 Auto
Saint Augustine, Florida, United States
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In reply to a message from Jacques B. sent Mon 17 Jan 2005:

HI JB, that RPM change seems about right for the no load to full
load transition on the engine. Do not Know about little switches–
FWIW—GNB–
The original message included these comments:

Since my idle drops about 300 rpm as soon as I put the DG250
in gear, I was wondering if the little pressure switch that


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Jacques,

That switch is for the “Hill Holder” Function (or anti-creep) on your
brakes. It should not have an impact on your engine speed. Typically engine
speed will drop when you put the transmission in gear due to the hydraulic
load being added. It is usually only a problem if it puts such a load that
it causes the engine to stumble.

Dave McKay

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In reply to a message from gpl@eos.net sent Mon 17 Jan 2005:

Yes the thingy beetwin the carbs is the the ground connection to
the anti creep, or hill holder solenoid. its only on automatics.
when you come to a stop you can take your foot off the brakes and
the car wont move, until you step on the gas pedal. there is a
solenoid in the rear brake line that acts as a one way valve and
wont let the brake fluid return to the reservoir, its electric but
when you step on the brake, it brakes the circuit of the solenoid,
and you can take off. So it has nothing to do with the tranny. The
kick down is done with a rod going to the carb linkage regards
Pajtas–
The original message included these comments:

Since my idle drops about 300 rpm as soon as I put the DG250
in gear, I was wondering if the little pressure switch that
sits on a manifold bracket between the carbs might not have
something to do with it.
Can anybody tell me what this switch is actually intended to do?
Thanks,
Jacques


jaguarjoe 54 XK 120 rdstr 1961 MKIX 94 XJ6
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In reply to a message from JagWaugh sent Mon 17 Jan 2005:

Andrew,

Good point, but I’ve eliminated (temporarily) the entire
servo vacuum line and sealed-off the connection on the
intake manifold. I’m sure I don’t have a leak there, and
therefore can’t see how that would affect the transmission
moderator valve (whatever and wherever that is).

I’ve got the Haynes and the Heritage CD manuals, which have
so far proven to be identical in their lack of info on the
automatic tranny.–
The original message included these comments:

Are you still running with the vacum line to the brake

servo blocked off? IIRC your transmission has a moderator
valve which also runs on vacum. You seem to have a great
deal of vacum related issues, could it be that they all
appeared since your brake servo went South and you blocked
off the vacum line?
Which shop manuals do you have?


Jacques B / 62 MK II 3.8 Auto
Saint Augustine, Florida, United States
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In reply to a message from GNB sent Mon 17 Jan 2005:

GNB,

But if that’s so, it would mean that if I set the curb idle
at the recommended 500 rpm, I’d end up with a 200 rpm idle
in gear… doesn’t that seem a tad slow? I’ve got to peddle
my Schwinn faster than that just to keep from falling over :slight_smile:

The ‘other’ Garry solved the switch problem, but I’ll have
to drive the car to see if it creeps or not.–
The original message included these comments:

HI JB, that RPM change seems about right for the no load to full
load transition on the engine. Do not Know about little switches–


Jacques B / 62 MK II 3.8 Auto
Saint Augustine, Florida, United States
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In reply to a message from gpl@eos.net sent Mon 17 Jan 2005:

Sorry George,

I just called you Garry in my reply to GNB. Thanks for the
info. I’ll see if it actually works as soon as I get her
back on the road. Actually, I was kind of hoping that the
anti-creep device consisted of some sort of valve on the
converter circuit which would have lightened the load at idle.–
The original message included these comments:

my mk2 has (had) a small switch (one wire) between the carbs. I believed
it released the device in the brake line which would keep the brakes
engaged when at a stop light. I do not beleive it had anything to do with
transmission, other than only vehicles with automatics were equiped with
the brake holding thingy.
george leicht


Jacques B / 62 MK II 3.8 Auto
Saint Augustine, Florida, United States
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In reply to a message from David G. McKay sent Mon 17 Jan 2005:

Thanks Dave,

My drops so low that it doesn’t cause the engine to stumble,
it down right causes it to stall!

I guess I’d best start looking for the culprit in the
transmission itself.–
The original message included these comments:

That switch is for the ‘‘Hill Holder’’ Function (or anti-creep) on your
brakes. It should not have an impact on your engine speed. Typically engine
speed will drop when you put the transmission in gear due to the hydraulic
load being added. It is usually only a problem if it puts such a load that
it causes the engine to stumble.


Jacques B / 62 MK II 3.8 Auto
Saint Augustine, Florida, United States
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Autos should idle about 700 - 800 in park, dropping to 500 in drive.

There is a separate manual for the DG gearbox. It is readily available,
it covers the XK cars also.

Some DG gearboxes are 2nd gear start, but those inthe Mk2 / S-Type were
all 1st gear start.

As others said, the switch is for the anti-creep. It should be adjusted as
soon as the throttle is moved, the switch is interupted. Most do not now
work, the actual pressure switch is located on the brakeline to the rear
brakes. If badly adjusted your rear brakes can bind.

Alastair Lauener
64 S-Type
@Alastair_LauenerOn Mon, 17 Jan 2005, Jacques B. wrote:

In reply to a message from GNB sent Mon 17 Jan 2005:

GNB,

But if that’s so, it would mean that if I set the curb idle
at the recommended 500 rpm, I’d end up with a 200 rpm idle
in gear… doesn’t that seem a tad slow? I’ve got to peddle
my Schwinn faster than that just to keep from falling over :slight_smile:

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Hello Jacques,

My idle drops from roughly 600 to 400 rpm when I switch from Park to
Drive, which I consider to be normal.
In one of my service manuals it provides the following information for a
car which shudders and stalls when the selector is moved into Drive:

  1. Incorrect adjustment of accelerator to governor linkage cable.

  2. Improper governor valve operation

  3. Damaged main shaft oil seal ring or front planetary set ring gear oil
    rings.

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In reply to a message from Jacques B. sent Mon 17 Jan 2005:

Oh, how astonishing ! I often think that workshop manuals are the
antithesis of Asimov’s ‘Laws of Robotics’. For ‘a robot cannot harm
a human being or, through inaction, allow a human being to come to
harm’, read ‘a shop manual will not assist a human being’ etc, etc.

They always omit the crucial bit that you want, don’t they ?–
The original message included these comments:

I’ve got the Haynes and the Heritage CD manuals, which have
so far proven to be identical in their lack of info on the
automatic tranny.


Anthony Richards
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In reply to a message from Alastair Lauener sent Mon 17 Jan 2005:

Thanks Alastair…

…I’ve been trying to get the unloaded idle down to 500 rpm
for the past TWO MONTHS, WONDERING WHY SHE WOULDN’T HOLD IT!!!

(Sorry for shouting, but I needed that).

She was running fine at a 750 rpm idle. Then, I read the
manual and tried everything under the sun (including a new
distributor) to get her down to 500, but with no success.

I was begining to wonder if I shouldn’t start shopping
around for a new hobby.

It’s funny the manuals don’t mention that, or at least refer
auto transmission owners to the DG manual or supplement you
mentioned.

In any case, I’m going to take two shots of scotch, and fix
it in the morning.

Thanks again to all who answered.

Jacques–
The original message included these comments:

Autos should idle about 700 - 800 in park, dropping to 500 in drive.
There is a separate manual for the DG gearbox. It is readily available,
it covers the XK cars also.
Some DG gearboxes are 2nd gear start, but those inthe Mk2 / S-Type were
all 1st gear start.

But if that’s so, it would mean that if I set the curb idle
at the recommended 500 rpm, I’d end up with a 200 rpm idle
in gear… doesn’t that seem a tad slow? I’ve got to peddle
my Schwinn faster than that just to keep from falling over :slight_smile:


Jacques B / 62 MK II 3.8 Auto
Saint Augustine, Florida, United States
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In reply to a message from JagWaugh sent Mon 17 Jan 2005:

Sorry but there is no ‘‘Modulator’’ valve on a Detroit Gear model
250. The most likely cause (all else equal) is the accel. pedal to
governor lever improperly adjusted. Failing that the governor is
suspect and possibly sticking on the shaft. You might try changing
the oil and add an additive. I do not believe in snake oils but I
have become a user of LUBEGARD (sp).–
George Camp
Columbia SC, United States
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In reply to a message from George Camp sent Tue 18 Jan 2005:

No sorry needed, I stand corrected.–
The original message included these comments:

Sorry but there is no ‘‘Modulator’’ valve on a Detroit Gear model


1968 3.8S
Zurich, Switzerland
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In reply to a message from JagWaugh sent Tue 18 Jan 2005:

Hi but if your rpm drops more than 2 to 3 hundred rpms when you put
it in drive, like I heard 500, than your torque converter is
seizing, have it checked by some one who knows, and the solutin is
to change the torque convertor. Is your fluid nice and pink? maybe
you should drain it, and on those models you can also drain the
torque converter. there is a plug on it. good luck Pajtas–
jaguarjoe 54 XK 120 rdstr 1961 MKIX 94 XJ6
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Not sure if this was picked up on, but the DG250 box has no vacuum
connections to it.

Alastair Lauener
3.4 S-Type
@Alastair_Lauener

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In reply to a message from Jacques B. sent Mon 17 Jan 2005:

 JB, That is correct , However, the Idle speed should be set so 

that under load the idle speed is about 500 RPM or a value close to
that which produces minimum creep.–FWIW—GNB–
The original message included these comments:

GNB,
But if that’s so, it would mean that if I set the curb idle
at the recommended 500 rpm, I’d end up with a 200 rpm idle
in gear… doesn’t that seem a tad slow? I’ve got to peddle


DAIMLER : V8 SALOONS SAFELY FAST AND BUILT TO LAST
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In reply to a message from Jacques B. sent Mon 17 Jan 2005:

Ah thats OK! Like I tell my mate I don’t care what you call me
just so you call in time for dinner.—GNB–
The original message included these comments:

Sorry George,
I just called you Garry in my reply to GNB. Thanks for the


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