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Post Number:#1  PostPosted: Sat Jan 26, 2008 1:08 am 

Joined: Sat Jan 05, 2008 7:01 pm
Posts: 8
I thought I'd start a new thread on this since I took the other one way off topic.

With the help of other members (mainly plenzen & asavage) I think I've figured out the basic function of the "Cold Start Device" after spending hours of playing around on mine and figured out that it does not work.

Correct me if I'm wrong.

Advance stage - when engine cold
-advance lever pushed back against CSD plunger by spring tension
-at the same time the advancer lever pushes on the idle bellcrank above raising the rpm to above 1000 RPM (not sure the exact value)
-coolant only bypasses CSD in this stage

No advance - when engine hot
-wax pellet inside CSD melts and allows reciculating coolant to pressurize plunger
-plunger is pushed out and in turn pushes against advancer lever
-advance is now disabled
-idle bellcrank lever is also disabled

No advance - above 2000 RPM
-this is automatically done by the pump

picture courtesy of "after oil" and asavage.

The problem I have found with mine is that the CSD pressurizes as soon as the engine is turned on, which leads me to believe that there is something wrong with the wax pellet internally. I'm pulling mine apart soon to check it out

1987 Nissan D21 - SD25

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Post Number:#2  PostPosted: Sat Jan 26, 2008 1:33 pm 
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Joined: Sat Nov 26, 2005 7:28 am
Posts: 5271
Location: Duvall, Wash.
jozsef61 wrote:
I thought I'd start a new thread on this since I took the other one way off topic.

We have a thread on the VE-style CSD already (from which you borrowed the pic above), but if you insist . . .

I suppose that at this point in time I might be the most qualified here to respond to this. If not, and someone else has something to add, please jump in.

First, let me remind folks that though the VE-style IP is fathomable, it is not a simple mechanical device. It is Germanic in nearly the most extreme sense. If one is serious about learning the functions of the components of the VE-style IP, for a modest investment of US$27, one can purchase the Bosch "Distributor Type Diesel Fuel Injection Pumps" softcover technical "Yellow Book" from Amazon. It is slim, at 134 pages, but fairly dense. It is chock-full of illustrations that are better than average. It is also, unfortunately, a starkly translated manual and as such must be read with that in mind; it is very easy to misunderstand the intent of a statement, and this will lead you to incorrect conclusions that can be hard to bend back to reality later.

With the foregoing out of the way, I have only one correction/modification to what you've stated above:
. . . wax pellet inside CSD melts and allows reciculating coolant to pressurize plunger . . .

. . . The problem I have found with mine is that the CSD pressurizes as soon as the engine is turned on, which leads me to believe that there is something wrong with the wax pellet internally.

The thermal element may or may not be wax on the D21 version of the VE-style IP, and I have my doubts as to whether the wax melts. I envision (a fancy word for imagine) that internally, the CSD is no more complex a device than a conventional wax-pellet thermostat that controls the overall temperature of the cooling system. It moves a mechanical device that pushes a plunger, part of which protrudes outside the thermal element and can act upon the external linkage. The photo which member "after oil" provided and which I marked up shows this interaction.

If you are successful in disassembling the thermal element portion of the CSD, please take photos if possible and send them to me.

Regardless of the internal mechanics of the thermal element of the CSD, you have stated the functions of the CSD correctly as best I can tell.

Here, I reproduce three pages from the above-mentioned Yellow Book, with the text OCR'd for the local search function (click on any image for larger):
Image Image Image

Bosch Distributor Type Diesel Fuel Injection Pumps Yellow Book wrote:
Page 55

Control modules for distributor injection pumps Mechanical torque-control modules

Cold-start compensation
The cold-start compensation device improves the diesel engine's cold-start response by advancing the start of delivery. This feature is controlled by a driver-operated cable or by an automatic temperature-sensitive control device (Fig 13).

Mechanical cold-start accelerator (KSB) on roller ring

The KSB is mounted on the pump's housing. In this assembly, a shaft (Fig 12, Pos 12) connects the stop lever (Fig 13,
Pos 3) with an inner lever featuring an eccentrically mounted ball head (3). This lever engages with the roller ring. The stop lever's initial position is defined by the full-load stop and the leg spring (13). The control cable attached to the upper end of the stop lever serves as the link to the adjustment mechanism which is either manual or automatic.
The automatic adjuster is installed in a bracket on the distributor injection pump (Fig 13), while the manual adjustment cable terminates in the passenger compartment.

There also exists a version in which the adjuster intervenes through the timing plunger.

Operating concept
The only difference between the manual and automatic versions of the cold-start accelerator is the external control mechanisms. The key process is always the same. When the control cable is not tensioned, the leg spring presses the stop lever against its full-load stop. Both ball head and roller ring (6) remain in their initial positions. Tension on the control cable causes the stop lever, shaft and inside lever to turn with the ball head.

This rotation changes the position of the roller ring to advance the start of delivery. The ball head engages a vertical groove in the roller ring. This prevents the timing plunger from advancing the start of delivery further before a specified engine speed is reached [1].

When the driver activates the cold-start acceleration device (KSB timing device), a position shift of approximately 2.5° camshaft (b) [2] remains, regardless of the adjustment called for by the timing device (Fig 14a).

Fig 12
1 Lever
2 Adjustment window
3 Ball head
4 Vertical groove
5 Pump housing
6 Roller ring
7 Rollers in roller ring
8 Timing plunger
9 Pin
10 Sliding block
11 Timing spring
12 Shaft
13 Leg spring

Fig 13 Mechanical cold-start accelerator, adjuster with automatic control (cold position)
1 Retainer
2 Bowden cable
3 Stop lever
4 Leg spring
5 Control lever KSB
6 Adjuster dependent on coolant and ambient temperatures

Page 56
Control modules for distributor injection pumps Mechanical torque-control modules

In cold-start systems with automatic control, the actual increment depends on engine temperature and/or ambient temperature.

Automatic adjustment relies on a control mechanism in which a temperature-sensitive expansion element translates variations in engine temperature into linear motion.

This arrangement's special asset is that it provides the optimum start of delivery and start of injection for each individual temperature.

Various lever layouts and actuation mechanisms are available according to the mounting side and rotational direction encountered in individual installation environments.

Temperature-controller idle-speed increase (TLA)
The temperature-controlled idle-speed increase, which is combined with the automatic KSB, is also operated by the control mechanism (Fig 15). The ball pin in the extended KSB control lever presses against the rotational-speed control lever to lift it from the idle-speed stop screw when the engine is cold. This raises the idle speed to promote smoother engine operation. The KSB control lever rests against its full-load stop when the engine is warm. This allows the rotational-speed control lever to return to its own full-load stop, at which point the temperature-controlled idle-speed increase system is no longer active.

Hydraulic cold-start accelerator [3]
There are inherent limits on the use of strategies that shift the timing plunger to advance start of injection. Hydraulic start of lnjection advance applies speed-controlled pressure in the pump's inside chamber to
the timing plunger. The system employs a bypass valve in the pressure-control valve to modify the inner chamber's automatic pressure control, automatically increasing internal pressure to obtain additional advance extending beyond the standard advance curve.

The hydraulic cold-start accelerator comprises a modified pressure-control valve (Fig. 17, Pos. 1), a KSB ball valve (7), an electrically heated expansion element (6) and a KSB control valve (9).

Fig 14 Effects of mechanical cold-start accelerator KSB
a Injection adjusted by timing device
b Minimum adjustment (approximately 2.5° camshaft) [2]

Fig. 15 Mechanical cold-start accelerator (automatic) with temperature-controlled idle-speed increase
1 Rotational-speed control lever
2 Ball pin
3 Control lever KSB
4 Full-load stop

Page 57
Control modules for distributor injection pumps Mechanical torque-control modules

Operating concept
The fuel supplied by the supply pump (5) flows through the distributor injection pump's inner chamber and to the end of the timing plunger (11), which compresses the return spring (12) and shifts position in response to the inner chamber pressure to vary the start of injection. The pressure-control valve controls the pressure in the inner chamber, raising pressure for greater delivery quantity as engine speed increases (Fig. 16).

The throttle port in the pressure-control valve's plunger (Fig 17 Pos 3) supplies the added pressure that allows the KSB to provide the forward offset in start of injection advance (Fig 16, blue curve). This conveys an equal pressure to the spring side of the pressure-control valve. The KSB ball valve, with its higher pressure setting, regulates activation and deactivation (with the thermal element) while also serving as a safety release. An adjusting screw on the integrated KSB control valve is available for adjusting KSB operation to a specific engine speed. Pressure from the supply pump presses the KSB control-valve plunger (10) against a spring. A damping throttle inhibits pulsation against the control plunger. The KSB pressure curve is controlled by the timing edge on the control plunger and the opening
on the valve holder. The spring rate on the control valve and the control port configuration can be modified to match KSB functionality to the individual application. The ambient temperature will act on the expansion element to open the cold-start accelerator ball valve before starting the hot engine.

Fig 16 Hydraulic cold-start accelerator (operation)
1 Start of delivery advanced

Fig 17 Hydraulic cold-start accelerator

1 Pressure-control valve
2 Valve plunger
3 Throttled bore
4 Inner chamber pressure
5 Vane-type supply pump
6 Electrically heated expansion element
7 Ball valve KSB
8 Fuel drains without pressure
9 Adjustable KSB control valve
10 Control plunger
11 Timing device
12 Return spring

Note 1: This is written in a misleading manner.
"This prevents the timing plunger from advancing the start of delivery further before a specified engine speed is reached". In fact, I believe that what they are trying to say is that the timing plunger operates normally, but because the ball head has moved the roller ring further around than the timer plunger can push (at low RPM); the timing plunger has no effect until the RPM reaches a level such that the timing plunger would advance the roller ring beyond what the ball head has already. The effect is that the timing is advanced (by the action of the ball head) to a fixed level, regardless of RPM up to the ball head's upper limit -- as illustrated by the Fig. 14 graph, page 56:

Note 2: This number translates to 5° crankshaft.

Note 3: Disregard discussion of the hydraulic CSD/KSB, as it does not apply to either the SD engines (or LD engines that we see in the USA).

Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

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Post Number:#3  PostPosted: Sun Jan 27, 2008 5:29 pm 
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Joined: Tue Dec 13, 2005 12:06 pm
Posts: 1494
Location: Southern California, USA
asavage wrote:
First, let me remind folks that though the VE-style IP is fathomable, it is not a simple mechanical device. It is Germanic in nearly the most extreme sense.

Back in the early '80s", while I was working in a BMW dealership, I recieved this. It's SO TRUE.


Compare a VE to the inline injection pumps. I rest my case.

Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"

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Post Number:#4  PostPosted: Sun Jan 27, 2008 7:36 pm 

Joined: Fri Aug 31, 2007 6:49 am
Posts: 753
Location: Cochrane Alberta Canada
Just throwing out an idea here, but. Does your thermostat on your SD25 work? I mean work correctly? I only ask that because I believe there are Fail Safe versions of the thermostat out there. If the one you have is failed (open) then I think perhaps the coolant is allowed to flow freely and unrestricted at start up and perhaps fooling the CSD into thinking that the engine is already warm.
Just a thought, and changing or checking a thermostat I would think would be easier that attempting to remove the CSD from the IP. (If it can even be removed without dire consequences internally)

Just a thought.


Retired Pauly
Problem with being retired is that you never get a day off.
1987 D21-J SD25 KC

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Post Number:#5  PostPosted: Thu May 18, 2017 10:18 pm 

Joined: Sat Mar 19, 2016 1:57 am
Posts: 44
Location: Hillman West Australia
Plenzen, hello, I just found your message wishing me a happy "74th Birthday", Thankyou very much, your Message very welcome indeed!

John Richards
"highway man"
Western Australia!

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