Webasto airtop 5500 - fuel pump not clicking but 10.7v present.....?

[West Coast]

Webasto heating unit showing a problem. Not starting, error message shows F02 flame abort, and suggests a fuel problem. Clear fuel pipes feeding the unit are empty. On investigation, fuel pump not clicking on the start up cycle. I removed the fuel pump lectrucal connection, and during start up cycle measured 10.7v on DC meter setting on the fuel pump electrical supply cable. Is this telling me conclusively that the fuel pump is shot?

 

[ghostlymoron]

10.7v is very low. Does it work with the engine running (if you can start it)

 

[pcatterall]

10.7v is very low. Does it work with the engine running (if you can start it)

+1 on that it does sound low! Low operating voltage is one of the most common problems I come across with 'non starting' Ebers.
A simple test is to put battery voltage direct to the pump by fitting one lead to the battery and just taping the other lead to the other terminal there should be an audible click each time you tap the lead to the terminal.

 

[West Coast]

Thanks both,

Main supply voltage is fine, engine was running at the time and same problem existed on shore power.

 

[cpedw]

The fuel pump electric supply is a series of pulses so a digital meter can't give an accurate indication of the voltage.

If the pump's not clicking, it may be the pump itself that's bust. Test it as pcatterall described.

Derek

 

[West Coast]

The fuel pump electric supply is a series of pulses so a digital meter can't give an accurate indication of the voltage.

If the pump's not clicking, it may be the pump itself that's bust. Test it as pcatterall described.

Derek

Ok, that makes sense. I was not sure if the electrical supply to the pump was pulsed, or a dc supply with the pulsing being effected by the pump itself.

I will try the direct connection test - see what happens.

 

[savageseadog]

You won't read anything sensible with a meter. Make up some leads connected to 12V connect the negative and tap the positive on the other terminal. You should be able to hear and feel the pump actuate and if connected to a fuel supply it will pump spurts of fuel if you disconnect the outlet. Already covered above, didn't read all the thread.

 

[pcatterall]

I have had hundreds of pumps across my bench many horrible rusty old things, 99% have worked fine!

 

[QBhoy]

Very sensitive to battery condition and voltage these things. Also even to the angle of the fuel pump. 10.7v will not allow the unit to start its cycle.