2.0 CDT - fuel pump failure and FBH - Page 3

Roverron · 12th November 2006, 13:22

Quote:

Originally Posted by JohnFol

Agreed, however I do get a pulsing voltage it just happens to be 10V and not 12V needed to drive the pump.
I'm trying to solve the problem by using the 10v to switch a relay. Tried Halfords (Winnersh - name and shame) and got asked "wot's a relay?" followed by "wot carzit 4?"

Just popping over to Maplins to see if they can suggest a solution.

Scotty, any progress on checking the voltage you get?

A relay is not a good idea - the contacts won't handle continuous on/off switching.
Its better to use a mosfet, protected by a flywheel diode.
Maplin sell them.
HUF75337P3 part no UE47B.

You also need a 3.9v diode from gate to ground and a 4k7 resistor in series with the 10v pulse lead from the fbh.
I'd recommend a 3amp diode across the mosfet as well.

Ron

simpsora · 12th November 2006, 13:37

Hi
You probably have RAVE,but just in case you haven't then the following Quote may assist "After 20sec.the ECU starts to operate the 'dosing' pump at 0.7 Hz. The fuel entering the combustion chamber is ignited by the glowpin." If an analogue DC voltmeter is used on pulsing DC it may only register 10v or so. Needle may not be seen to pulse up and down .
Hope this info may be of some use.

Thanks , Simpsora

JohnFol · 12th November 2006, 13:45

In fact, just got back from Maplins.

One comment that was made is the "driver" may be a problem. To explain, When I get the 10V and connect it under bonet to a relay, the voltage drops to zero and there is no click. The suspision is there is not enough current to drive the relay, or equally the solenoid.

Got a few more tests to try . .

Scotty, the pin I was testing is no.6 (just to the right of pin 3 that gets grounded).

It would be really usefull to know if anyone else gets 10V with a working pump . ..

Roverron · 12th November 2006, 13:53

Quote:

Originally Posted by JohnFol

In fact, just got back from Maplins.

One comment that was made is the "driver" may be a problem. To explain, When I get the 10V and connect it under bonet to a relay, the voltage drops to zero and there is no click. The suspision is there is not enough current to drive the relay, or equally the solenoid.

Got a few more tests to try . .

Scotty, the pin I was testing is no.6 (just to the right of pin 3 that gets grounded).

It would be really usefull to know if anyone else gets 10V with a working pump . ..

There would enough to drive the mosfet, they need a a few microamps!

simpsora · 12th November 2006, 14:01

Hi
if the ability to provide the required current to drive the pump is suspect (even if volts are there) then then this would throw suspicion on an internal circuit (ie the .7 Hz pulse circuit)of going wrong, ie high resistance,which may be pre-curser of failure.

Roverron · 12th November 2006, 14:15

Quote:

Originally Posted by simpsora

Hi
if the ability to provide the required current to drive the pump is suspect (even if volts are there) then then this would throw suspicion on an internal circuit (ie the .7 Hz pulse circuit)of going wrong, ie high resistance,which may be pre-curser of failure.

This is true, but rather than replacing the internals of the fbh, or even the whole fbh, if there is enough current available to drive a mosfet, then this would be much cheaper.

Ron

simpsora · 12th November 2006, 15:18

Hi Roverron
what you are suggesting would work (as MOS FEt's have extremely high input impedence) However , this would be 'working around' problem rather than pinpointing the real cause, which may be as simple as 10 pence resistor going increasingly high resistance till it fails altogether .When this happens there would be no output to drive MOS FET solution.
That's why a copy of webasto circuit diagram/ component layout would be very usefull.

Thanks, Simpsora.

JohnFol · 12th November 2006, 16:17

If I can delay or avoid the cost of replacing the internals of the FBH for a few pence then why not?

In fact Maplins suggested a Medium Power lenear transistor (TIP120)

Just need to remember my base collector emmoter stuff now to be able to use it!

Roverron · 12th November 2006, 19:00

Quote:

Originally Posted by JohnFol

If I can delay or avoid the cost of replacing the internals of the FBH for a few pence then why not?

In fact Maplins suggested a Medium Power lenear transistor (TIP120)

Just need to remember my base collector emmoter stuff now to be able to use it!

Diagram attached.

Ron

simpsora · 12th November 2006, 19:33

Hi There,
Yes, roverron's circuit suggestion should work ok for you Johnfol, go for it and let us know how you get on. However ,for those of us who have no remaining vestige of pump pulse (including mine )then restoring correct operation
of circuit within webasto remains the best way forward (possibly) .

Anybody ever successfully got a defunct webasto working again? (not including complete replacements or retro fits etc)

Also, as webasto's (fitted as standard) must all be coming on for 5+yrs . old approx. then it may be an age related fault!

Thank's,Simpsora

12th November 2006, 15:18	#27
simpsora Regular poster 2001 2.00 CDT 116 bhp Join Date: Nov 2006 Location: aberdeenshire Posts: 97 Thanks: 1 Thanked 1 Time in 1 Post	FBH burner Hi Roverron what you are suggesting would work (as MOS FEt's have extremely high input impedence) However , this would be 'working around' problem rather than pinpointing the real cause, which may be as simple as 10 pence resistor going increasingly high resistance till it fails altogether .When this happens there would be no output to drive MOS FET solution. That's why a copy of webasto circuit diagram/ component layout would be very usefull. Thanks, Simpsora.

12th November 2006, 19:33	#30
simpsora Regular poster 2001 2.00 CDT 116 bhp Join Date: Nov 2006 Location: aberdeenshire Posts: 97 Thanks: 1 Thanked 1 Time in 1 Post	FBH burner Hi There, Yes, roverron's circuit suggestion should work ok for you Johnfol, go for it and let us know how you get on. However ,for those of us who have no remaining vestige of pump pulse (including mine )then restoring correct operation of circuit within webasto remains the best way forward (possibly) . Anybody ever successfully got a defunct webasto working again? (not including complete replacements or retro fits etc) Also, as webasto's (fitted as standard) must all be coming on for 5+yrs . old approx. then it may be an age related fault! Thank's,Simpsora

12th November 2006, 13:37	#22
simpsora Regular poster 2001 2.00 CDT 116 bhp Join Date: Nov 2006 Location: aberdeenshire Posts: 97 Thanks: 1 Thanked 1 Time in 1 Post	Hi You probably have RAVE,but just in case you haven't then the following Quote may assist "After 20sec.the ECU starts to operate the 'dosing' pump at 0.7 Hz. The fuel entering the combustion chamber is ignited by the glowpin." If an analogue DC voltmeter is used on pulsing DC it may only register 10v or so. Needle may not be seen to pulse up and down . Hope this info may be of some use. Thanks , Simpsora

12th November 2006, 13:45	#23
JohnFol Gets stuck in 75 Conn SE - XVWY* Join Date: Nov 2006 Location: Reading Posts: 564 Thanks: 0 Thanked 2 Times in 2 Posts	In fact, just got back from Maplins. One comment that was made is the "driver" may be a problem. To explain, When I get the 10V and connect it under bonet to a relay, the voltage drops to zero and there is no click. The suspision is there is not enough current to drive the relay, or equally the solenoid. Got a few more tests to try . . Scotty, the pin I was testing is no.6 (just to the right of pin 3 that gets grounded). It would be really usefull to know if anyone else gets 10V with a working pump . ..

12th November 2006, 14:01	#25
simpsora Regular poster 2001 2.00 CDT 116 bhp Join Date: Nov 2006 Location: aberdeenshire Posts: 97 Thanks: 1 Thanked 1 Time in 1 Post	Hi if the ability to provide the required current to drive the pump is suspect (even if volts are there) then then this would throw suspicion on an internal circuit (ie the .7 Hz pulse circuit)of going wrong, ie high resistance,which may be pre-curser of failure.

12th November 2006, 16:17	#28
JohnFol Gets stuck in 75 Conn SE - XVWY* Join Date: Nov 2006 Location: Reading Posts: 564 Thanks: 0 Thanked 2 Times in 2 Posts	If I can delay or avoid the cost of replacing the internals of the FBH for a few pence then why not? In fact Maplins suggested a Medium Power lenear transistor (TIP120) Just need to remember my base collector emmoter stuff now to be able to use it!