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Cold start advance on Bosch VE pumps

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I have been trying to understand a little more about the cold start advance facility on the Bosch VE pumps which the owners manual of my 300TDI waxes lyrical about.

A cold start advance unit advances the injection timing to further assist starting. Idle quality is improved by the high idle setting. The cold start advance unit is connected to the engine cooling system via hoses. It contains a temperature sensitive element which is retracted when cold and pulls the advance lever, via cable, towards the rear of the pump against spring pressure. As coolant temperature rises, the cold start element expands releasing tension on the cable and allowing spring pressure to move the advance lever forwards.

Have located this as a useful reference


But there does not seem to be any info on this or indeed other popular Defender forums about how you can tell its working or if its not how to make it work - can anyone help me out...


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I don't believe the Bosch FIPs on the 2/300Tdi have any cold start facility as its not really needed on Direct Injection diesels.

The mechanism you described is used on the Peugeot 1.9 XUD diesel engine as fitted to Pug 205/306 and Citroen ZXs. These are indirect injection engines.

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I reckon there is a cold start mechanism on my D300 and it's that which has gone wrong (massive over fueling) at start up causing my SAS smoke cloud in the mornings.

You may have notice a previous thread where a number of suggestions were made as to the cause of my cloud but my local mechanic and I believe it is something to do with the cold start timing of injector pump. :huh:

Maybe earlier 300 tdi pumps had a mechanical advance and the later'ns went 'lectric

As per Western I too looked for an additional mechanical link but could only find an electrical connection. Can't comunicate with it diagnostically until I locate 'a man who can' in the next couple of days. ;)

I reckon there is a tie up too between the sensor on the top of the head (discussed recently in yet another thread), the EGR removal and the cold start timing of the pump but don't really know yet! :unsure:

Don't know whether this helps or hinders the thread but thought I'd get the info in. :)

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This is some of an essay I wrote on Diesel Fuel Injection Systems a couple of years ago. I don't however no what type a Defender has?

On a Bosch VE type pump, a manual cold start device advances the injection timing at idle and during low-speed running. A lever turns a cam that pushes the hydraulic piston to the left, advancing injection timing about five degrees. This injection advance provides more time for the fuel to burn, which improves performance and prevents smoking during cold starts and warm-up. However, above 2200 RPM the piston operates normally and does not contact the cam.

There are different types of automatic CSDs (cold start devices) available for the VE injection pump.

One popular type is the vacuum-operated CSD that uses a vacuum pump, water thermo valve, and a dual-stage diaphragm located on the injection pump. The thermo valve, applies vacuum to the diaphragm, depending on coolant temperature.

Another CSD, called the KSB, advances injection timing by controlling supply-pump pressure. A KSB control valve mounted on the side of the pump overrides the pressure regulator, increasing supply-pump pressure and advancing injection timing. For example, if the temperature is below the set value of the temperature switch, the switch closes and the KSB solenoid switches on. This increases pump pressure. Above a preset value, the temperature switch opens, the KSB solenoid opens, and the pressure regulator now controls supply-pump pressure.

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Page 41 (thumbnail 43) covers cold start enrichment devices.

This manual appears to cover most if not all the options that might be fitted to a basic VE pump. Not all of them will be fitted on every pump. Some of them are mutually exclusive, perhaps depending whether the pump being examined is wholly mechanical or part mechanical and part electrical.

You should, I hope, be able to recognise what is fitted on 'your' pump.

I found I had to read the earlier sections to understand the basics before I could move onto the 'electrical' section, because in those sections they assume the reader does understand the basics, so they don't give the 'hand-holding' the earlier sections do.

Good Luck, and if you've been on the sauce, leave the book studying until tomorrow.

Edited to add:

Sorry, I had forgotten that you had posted a link earlier in the thread. This appears to be that manual, although in my case it was already on my hard drive. I can't help with any more detailed knowledge of the 300TDi engine.


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