vaillant turbomax 242 pump faulty?

Hi,
I am a new member but I have checked past Vaillant postings.
I have a turbomax VUW 242/1E that fails to light the burners. I have followed the instructions on p44 of the servicing manual for fault finding. It was working fine but stopped one night recently. I have set the shower and central heating demand to 9. When I switch on the power indicator lights up followed by the demand indicator. The fan indicator and ignition indicator then come on for about 3-4 seconds before it shuts down leaving only the demand indicator on, and the power indicator flashing.
Fault finding sheet A: the power indicator glows - go to C
C: central heating control switch is correctly set; burner does not light: go to D
D: Does pump run? apparently NOT but the ignition indicator does not flash after 30s (the system has shut down by then); burner does not light: radiator control IS set to 9; switching on and off has no effect; 230V appears at the pump connector when the system is switched on ... Does the pump run? No - this sets me on a loop.
I assume the problem is the pump. Is that right?
"Check the pump' - how do I do that? I have tried unscrewing the central screw and the water does not seem pressurised.
Should I go and buy a new pump?
Many thanks
DesmondA

you will only get a dribble from the pump when you remove the screw.
Go through the starting procedure with the screw removed and check if the central spindle of the pump rotates. If it does then it suggests the pumps ok but it might have a sludged up impeller.
Chances are u need a new pump.

OK thanks. I checked the spindle movement in situ and it didn't move. I have removed the pump, but there is no sign of sludge. I put 230V across it - and it seems to spin fine.

just behind the pump top left is a pressure differential switch black a small 4mm pipe attached and a red microswitch on the top there is a white lever on the top when the boiler opperates the pump starts and this white lever lifts breaking the microswitch it then goes into the ignition sequence if the microswitch does not lift check that the small pipe the conection to the diverter valve and the small holes inside the pressure diif switch are all clear if they are then replace the diif switch, you could check everything else by a TEMPORARY link of the microswitch conections this would allow the boiler to fire do not leave the link in.hope that helps

I have the same boiler and I understand the pump isn't working as it should. It isn't pumping to the downstairs radiators.
A heating engineer has let me down and, after watching some videos, decided it looked easy enough to do it myself. However, after looking at the pump itself, it looks far more complex than the ones I saw in the videos.
In the videos, the pump looks in the open and accessible. They had isolating valves either side so obvious input/output supplies. In my boiler it all looks congested and I can't even see where the water goes in nor comes out, let alone where the isolating valves are.
Question is, is this something I should take on and if I can, is there anyone who can give me a heads up on how to do it?

Pete.

If your boiler boiler fires up the its pump is fine! Pump performance is checked by the black differential valve and microswitch mentioned a year ago.

Your problem seems to be a circulation problem in your system.

Just as well as boilers are not as simple as you seem to expect.

Look at the FAQs on this site for circulation issues.

Tony

Tony, thanks for the reply but I didn't mean to suggest any arrogance towards a lack of skill set needed for your profession. On the contrary, I wouldn't be searching the net for help if that were the case.
I had a heating engineer tell me I needed a power flush to solve the problem or I could try cleaning the rads myself. After taking hours and making a total mess cleaning one radiator (shouldn't do it after a long days work and feeling tired) and not having time to do more that night, I refilled the system but nothing had changed. Rightly or wrong, I expected the rad I cleaned (first in line I think) would have got hotter, if sludge were the problem. I decided to go for the power flush anyway, phoned the engineer, told him what I had done and the result and asked him to come to do the flush. He then said it is more likely the pump is faulty and needed replacing. However, if it still didn't do the job, he would power flush it, free of charge. That seemed a good deal to me and being the layman I am, was confident he had the problem nailed down.
However, he has let me down, hasn't come to do the job (yesterday) and won't answer my calls. I have been without heating for 2 weeks now, have been let down by 3 heating engineers, am feeling a bit desperate so I had a look to see if were possible for me to do it. The examples online look very straightforward, a pump with a pipe and isolater on the left and the same on the right, isolate the water, unbolt the pump then do the opposite with a new pump. My pump looks far from being that straightforward. I wasn't expecting it to be easy, I was hoping but it might not be that anyway.
I should add, my pump has clearly been leaking for some time, as it is wet underneath and is gunged up (limescale?) around the top of it. I will try what you suggest (differential valve and microswitch) but I know I am out of my depth and even simple suggestions are a bit confusing. I am just a bit desperate and very cold.
Thanks again.

Pete.

You dont seem to have followed what I said! I never suggested any problem with the diff switch and certainly did not ask you to do anything to it.

I think that your boiler is fine! Or at least the pump is fine.

Its difficult for me to follow how you have been "let down" by three engineers when you have only mentioned just one with no indication of what he has been paid ( or not ).

Your problem will be a very simple one which any competent heating engineer would be able to deal with.

Tony

Well, let down in the sense that 3 have arranged to come round to fix it or diagnose then fix but it is still broke and I have had no heating because no one has actually turned up to do what they say they can do. Maybe heating engineers have a different set of morals but I call that 'being let down.'
Of the 3, 1 didn't show up at all (a sudden illness but it was a friend of a friend and I know he made a miraculous recovery the very next day), 1 did show up claiming all sorts of experience but seemed unsure of what he was doing, said it could be one of several things, that he would consult a Vaillant supplier or something and would get back to me but I never heard from him again and the third one is the one I explained about in the post. He did do some work (cleaned the heat exchanger as the boiler kept switching off when the hot water was used) and he did a good job as the water is steaming hot now. However, he didn't have the time to sort the radiator problem because a power flush (his original diagnosis) would take 5 hours.
Maybe, as you elude to, I've had the misfortune to pick 3 incompetent engineers. Tony, if you are near East London, maybe you could come round and sort it? Or any other competent engineer reading this, that is in the area.

Pete