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WEBASTO Dosing Pump operation.


Brian422

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Webasto Thermotop C intermittent operation with occasional white smoke from the exhaust.

 

Have followed Thermotop C Troubleshooting Tree to Page 3 where last block advises to disconnect fuel line from fuel pipe inlet where it suggests fuel pump should expel fuel approximately 12 inches. However, dosing pump on my system does not deliver more than a drop each time pump clicks.

 

I’m confused as I’ve watched a you Tube video reviewing a Chinese pump which say the pump only delivers a very small amount.

 

I’d be grateful for any help and guidance as to what to expect.

 

Regards and Thanks

Brian.

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I looked at my pump recently. It's been tested as good since. I reckon it spurts out nearer half that distance, and I'd guess about a ml each pulse. It's supposed to deliver 20 ml / minute, but not sure at what click rate - probably normal running speed, so maybe 20 to 30 pulses a minute?

 

(Mine was giving out white smoke and failing to run after the start-up sequence hence my following the fault tree and getting to possible pump issues and checking it; I decoked the burner and it was good for a while, then failed again. The repairers said the burner was knackered, replaced it and it was fine after that. I took the boiler and pump out and took them up to Evesham Marine who did a good job. Might be worth a chat with Paul Hands there 01386 768500, he'll tell you if there's anyone more local but it's not a long drive from Saul).

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Hi Onewheeler.

Thank  you for your response.

 

If I interpret your reply correctly. A small amount of fuel was expelled with force.

 

I neglected to mention that the fuel only dribbled out of connection to heater fuel input.

 

Further suspicion suggesting a Dosing Pump failure was when I reassembled fuel line after checking for blockages.

Before refitting fuel lines I manually filled both fuel line from tank to pump and from pump to fuel supply heater input. The heater then ran normally for a short time but long enough to heat the large metal case area, which I think is the heat exchanger/ combustion chamber, to 90 Degrees Centigrade before suddenly stopping.

The theory being my manual priming of lines provided enough fuel for short run.

Another thing that might have contributed to Dosing Pump failure is that the Coventry based boat builder did not fit a filter between tank and Dosing Pump - not a good idea given the crud found in diesel.

 

One more thing before closing if you'd be good enough.

Did you fit a replacement Webasto or aftermarket Dosing Pump?

 

Regards and Thanks

Brian.

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2 hours ago, Brian422 said:

Hi Onewheeler.

Thank  you for your response.

 

If I interpret your reply correctly. A small amount of fuel was expelled with force.

 

I neglected to mention that the fuel only dribbled out of connection to heater fuel input.

 

Further suspicion suggesting a Dosing Pump failure was when I reassembled fuel line after checking for blockages.

Before refitting fuel lines I manually filled both fuel line from tank to pump and from pump to fuel supply heater input. The heater then ran normally for a short time but long enough to heat the large metal case area, which I think is the heat exchanger/ combustion chamber, to 90 Degrees Centigrade before suddenly stopping.

The theory being my manual priming of lines provided enough fuel for short run.

Another thing that might have contributed to Dosing Pump failure is that the Coventry based boat builder did not fit a filter between tank and Dosing Pump - not a good idea given the crud found in diesel.

 

One more thing before closing if you'd be good enough.

Did you fit a replacement Webasto or aftermarket Dosing Pump?

 

Regards and Thanks

Brian.

You mentioned 90C, are you sure the heater is not cutting out due to over-temperature? Which is what I'd expect if the coolant reached 90C. Is the coolant circulating with no air-locks in the heater?

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I had exactly these symptoms, primed pipe as you did, dribbling pump, white smoke, didn't get through start up etc, exactly - I was short of diesel. I'm sure you wouldn't be so daft, but if it shares tank with the engine, the outlet (within the tank) is likely to be a lot higher up than the engine one (to retain fuel for the engine) even if it exits the tank low down. Mine has to be at least half full for the Webasto to work. I would stick a few gallons of fuel in the tank if in doubt.

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9 minutes ago, Brian422 said:

Hi Slow and Steady.

 

Thanks for the thought and we've all done things considered as daft but in this case my heater has a separate fuel tank; still possible but not this time ;-).

 

Regards

Brian.

 

Mine too, but cunningly they are joined together out of sight so you fill the heater one to the brim and half an hour later it's levelled off with the drive tank. ;)

 

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Hi Nicknorman.

 

Unsure of lots of things at this time.

 

Not sure how significant 90C is as combustion chamber extends into heat exchanger space and therefore unsure as to whether measuring water temperature or result of combustion.

 

However,something else I neglected to mention was a knocking heard and pulses felt in Webasto Heater water pipes.

 

Also I've only noticed white smoke once. 

 

Thinking of removing water pipes from Webasto and dangling them in a bucket of water and then running heater.

This I think would eliminate any possibility knocking being result of air trapped in central heating and check coolant pump was operating.

 

Regards

Brian.

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Has it worked previously?

I know mine has isolation valves so it can be removed to service and as I also have the rads connected to the back boiler I keep them turned off to make it circulate through the rad nearest the Webasto rather than through the Webasto. Pretty sure it would not like it if I attempted to start it with those valves closed.  I know that it starts the circulation pump before firing up but not sure if it would realise the pump was pumping against a shut off valve. If not it would get very hot very quickly.

Edited by Slow and Steady
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Hi Slow and Steady.

 

System has worked but as I'm not a live aboard or go boating in cold weather, have not used heater often, which I now understand is not recommended.

 

Fortunately no such complication as I have only one conventional bathroom radiator ; the remaining radiators in lounge and bedroom are low level (skirting board height).

 

Suspect I might have two problems; Dosing Pump and Air Locks.

 

Regards

Brian

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On 18/01/2022 at 14:17, Brian422 said:

Hi Onewheeler.

Thank  you for your response.

 

If I interpret your reply correctly. A small amount of fuel was expelled with force.

 

I neglected to mention that the fuel only dribbled out of connection to heater fuel input.

 

One more thing before closing if you'd be good enough.

Did you fit a replacement Webasto or aftermarket Dosing Pump?

 

Regards and Thanks

Brian.

Well, the fuel spurted out 15 - 20 cm or so - less than the 30 cm suggested by Webasto but certainly more than a dribble. Thinking it was the pump, I fitted a replacement from Ebay but no difference. Evesham Marine tested both and said the original was still good, and the replacement out of spec. I think the latter includes a bit of sales pitch as the spec says 20 ml / minute and the replacement was giving 19 ml. The original was 20 and a bit ml / min.

 

If you want to give my replacement a go you're welcome to try it - I'm only 10 km from Saul (we used to moor there and I know the original owner of your boat unless it's the same name on a different boat!). PM me if interested. The replacement pump has rather short stubs of pipe (a long story but it's feasible to get a hose and clamp on). You won't get a compression fitting on.

 

Martin/

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Hi Martin.

 

Thank you for the offer of using your replacement pump but I intend to have pump tested in situ before making any changes.

 

P.S. I think your getting my boat confused with another of the same name. I am the original owner of my boat.

Before naming my boat I thought it was quite unique but since have found it's more popular than I thought. Even moored next to another with the same name in Birmingham😂.

 

Regards

Brian.

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  • 3 weeks later...

Tested pump again and found that a jet of fuel was expelled for approx 4cm so for some reason that problem appears to have resolved itself.

I've purchased Webasto inline filter and IS0 7840 Fuel Tube to make connection but would like some thought regarding fuel pipe coiling before and after the Dosing Pump - photo attached.

I can only think it's to absorb any vibration generated by pump.

 

Regards and Thanks

Brian

 

 

 

Dosing Pump Feed.jpg

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Assuming the photois correctly oriented, with UP at the top, that coil is a device for trapping air.  The spiral should be arranged round a vertical axis with the pump at the top, so that any air flows up the coil into the pump and away.

 

Keep the spiral as large a diameter as is practicable, with at least two full turns, better four. No benefit from more than that though.  If it is absorbing vibration a periodic anneal is a Good Thing.

N

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Hi BEngo.

The photo is correctly orientated and shows Heater Fuel Tank feed to Dosing Pump input.

Arranging the spiral as you suggest, in a downward spiral, with coils horizontal would allow fuel to flow easier using gravity and stop air being trapped in the coils.

 

However the Dosing Pump position is at the coil end and fixed.

 

Will also orientate Dosing Pump to Webasto as suggested.262959305_DosingPumpOutput.jpg.9e70cad7c19468c44ec368c4e86a2a9f.jpg

 

Regards and Thanks

Brian.

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  • 3 weeks later...

Hi all.

Have connected fuel tank to dosing pump and dosing pump to Webasto with straight lengths of copper pipe; removed coiling. 

During reworking found that tank union olive was loose on pipe even when nut tight; pipe would move in and out of connector allowing air/diesel leakage.

Webasto is now working 🙂

 

However there's no filter fitted and without the space necessary to fit Fuel Filter / Water Separator, I would be grateful for any suggestions for a suitable metal in line filter that complies with B.S.S. standards. 

 

Regards and Thanks 

Brian. 

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