"Yellow Dot" definition

[Nevadan]

What's the definition of "yellow dot" as used in referencing the rebuilt pumps.

My guess means it was rebuilt at Bosch, but I don't want to keep guessing.

I would be willing to put together a dictionary of terminology for the Mark II 1.6's, but I'm not fluent in the language just yet.

[coke]

The Yellow Dot pump actually had a yellow dot on it, signifying it was a yellow dot pump.

[Nevadan]

Right, but what does the yellow dot signify? Some internal difference in the pump? Designation that a Bosch tech serviced it? Something else? I'm curious since I have one pump with yellow paint on various adjustable components and one without. Or is my pump with yellow paint on the removable/adjustable parts just a rebuilders way to identify something?

[Quantum-man]

Right, but what does the yellow dot signify? Some internal difference in the pump? Designation that a Bosch tech serviced it? Something else? I'm curious since I have one pump with yellow paint on various adjustable components and one without. Or is my pump with yellow paint on the removable/adjustable parts just a rebuilders way to identify something?

I believe the paint has to be on the timing advance cover on the side. Do you have the pumps identifying numbers/letters?

[82vdub]

I believe the yellow dot pumps were pumps with their part number ending in 107A. They must have come with a yellow dot on them from the factory. There's got to be dozens (if not more) of different variations of these pumps, all with a different part number. If a pump has been rebuilt and sandblasted as part of the rebuild process, likely any evidence of a yellow dot from when it was made is likely gone.

[Quantum-man]

The yellow dot pump seems to have a faster increase of internal pressure to rpm than most other pumps if not all. As I don't believe they were ever issued in the UK, I've never seen one. It is felt that it is 'Sportier

There is a graph I made somewhere of 1.6TD internal pump pressures, and their corresponding dynamic advancethe Yellow dot is also there but what is missing is the dynamic advance for the yellow dot. All it needs is two readings with a diesel timing light to solve the mystery, as the advance spring is allegedly weaker than normal too, adding to the advance, yet paradoxically it needed greater static advance than standard, say 1.14 v 0.88.

A few folks have both pump and strobe, but are keeping the figures quiet

[Nevadan]

The yellow dot pump seems to have a faster increase of internal pressure to rpm than most other pumps if not all. As I don't believe they were ever issued in the UK, I've never seen one. It is felt that it is 'Sportier

There is a graph I made somewhere of 1.6TD internal pump pressures, and their corresponding dynamic advancethe Yellow dot is also there but what is missing is the dynamic advance for the yellow dot. All it needs is two readings with a diesel timing light to solve the mystery, as the advance spring is allegedly weaker than normal too, adding to the advance, yet paradoxically it needed greater static advance than standard, say 1.14 v 0.88.

A few folks have both pump and strobe, but are keeping the figures quiet

Perfect answer. I have a pump on my spare engine that has yellow paint on it. I'm going to take some pictures and post here, together with the part number, so people can tell me if it's a true "yellow dot" or just a regular pump with yellow paint on it.

[coke]

Yellow paint on the screws is common. Yellow dot pumps had a yellow dot on the timing advance piston cover. They put paint on the screws to make sure someone doesn't break them open and then screw stuff up and claim warranty.

[Nevadan]

Pump number is 068-130-110H. There's definitely a yellow dot on the timing advance piston cover screw. Does that count as "on the timing advance cover"?

This is the pump on the engine that will replace the engine currently in my Jetta that has the low oil pressure.

[Quantum-man]

There's no easy way to break it to you. The yellow paint is just a keep out sign

The 'R' number confirms this. The pump is a '0460494162 - VE4/9F2250R186
Thus it is a 'normal' pump as used by VW on mk2 stuff. The 2250 tells us that it is rated at 4500rpm crank. Yellow dots are rated at 2500 or 5000 crank. That is not to say that your pump wont operate higher.

Here's a graph of rpm v internal pump pressure. Complete in itself but I've not added the dynamic advance, as I wanted two data points from a yellow dot.

If advance spring was identical to the basic pump, then advance rate is clearly nearly 40% more aggressive at higher rpm's. Spring not the same though, and whispers tell me that it is softer, which seems excessive.

Failing dynamic advance figures, someone could take the two springs and compress them on top of bathroom scales with bottles of water and compare 'inch-rates'

[82vdub]

Weren't most, if not all, 107A yellow dot pumps found on 1.5 diesels?

[coke]

Yes yellow dots were exclusive to the 1.5. I had a 107A but couldn't find the yellow dot on it, ran it on a 1.6. It was interesting.

[Nevadan]

That clears it up for me.
Thanks for the explanations.

I'm just planning on what engine and components to replace the low oil pressure engine currently in my car.

[CarlosA]

I had a 107A that had been rebuilt, and any paint that was on it was lost. I confirmed that it was _probably_ a yellow dot because it liked to be timed in the 1.10-1.15 mm range, vs .92 on my 108K pump. Most manuals have standard timing specs then a unique spec for the yellow dot pump. I don`t think there is any real advantage, and it was eventually replaced/updated anyway.

The lime green spring is softer, and some people swap them into later pumps for some reason i`m not aware of. Something to do with getting more fuel with less effort, it has to do with the timing advance rotating as you pick up speed/throttle/flow.

Also, my 1983~ 108K pump has the same yellow paint on the bolts for tampering.

[Fatmobile]

Right, yellow dots were 1.5 pumps; 107As.
but not all 107As were yellow dot.
Since the paint was on the timing piston cover, I've always concidered it a timing thing.