OK - I am sure you have all heard this story before but I am looking for advice on what to try next on my FBH.....

I have a Webasto FBH fitted to a 56 plate TDV8 which has only recently stopped working - it worked on timed start perfectly well last autumn but has since stopped. When the weather is cold, it will attempt to start every time but after several timed runs, it always shuts down at 4m 05s to 4m 07s. According to one of FrenchMike's posts on the 75 & ZT forum (excellent source), this points to a glow plug problem.

Yesterday, I stripped the unit and cleaned it and there was a lot of carbon build up but on re-assembly, and testing on the car, I get the same symptoms.

While apart, I've tested the resistance of the (cold) glow plug using a potential divider as 0.365ohms which seems to be at the to end of the range quoted for the correct resistance. When heated to something less than red hot in a flame, this rises to about 1.2ohms. All this suggests to me the glow plug is OK based on what I have read.

I've removed the gunk from all the resistors on the PCB and these seem to measure correctly.

I tried disconnecting the fuel supply during the early part of the firing sequence in there was never any fuel delivery but when I tested the fuel supply by pulsing the supply to the pump with a false feed, there was a healthy fuel delivery.

Any suggestions of what to try next? Send the PCB to FrenchMike or try a new glow plug first? Or any other good suggestions?

can you hear a ticking coming from the pump when it is trying to run? you should be able to hear it as soon as it starts to fire up, regular tick at just under 1 sec intervals.

If you aren't getting it and the heater fans and the blower in the webasto itself are trying to run then it sounds like the the pump isn't getting a signal, which could point to the PCB.

but there really isn't much to them, it sounds like what mine was like in the old 3.6, it would run for a few mins with the blowers going then shut down without ever lighting. LR replaced under warranty with an entire new unit.

Are you getting any heat from the exhaust of the heater? this would indicate that it has ignited. If you have ticking and heat then may be that the diverter valves for the water side of the system have seized and aren't letting the pump run properly, which may cause it to overheat and shut down, also a seized pump would cause it to overheat also, if you have it in bits have you checked the impeller and housing to see that it moves freely. There is nothing that can't be fixed with a hammer😜😜
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where abouts in brum are you
i can lend you a working pcb out of a rover to test the heater off the car, that will prove if its its the heater or pcb.
if its heater repair it your self,could be blocked fuel delivery tube into burner chamber(gives same fault code as glowplug)
pcb send it off to french mike
PM me
nige

Thanks to those that replied - much appreciated.
I got lucky with a quick reply from FrenchMike on the 75 & ZT forum as well which helped me get the heater working again.

After stripping the unit a second time and trying to test it on the bench I got no where but after reading elsewhere that the unit really needs to be on the car to even start I decided to go out in the rain today and have another go. I read elsewhere that the unit would not even start the sequence unless the kbus was connected as after a telestart command, the unit seems to look for a reply from the HVAC controller before it starts any other part of he sequence.

After refitting it to the car with no pipes connected and the unit hanging on cable ties in the wheel arch to avoid stretching the cables, I bridged the wires on the telestart controller (I don't have a remote!) in the boot. The unit ran through a start cycle and after about 30 seconds the dosing pump started and fuel deliveryeventually started from the pipe.

Reconnected the fuel line and a few seconds later firing started. I had to interrupt the firing by disconnecting at the telestart as there was no coolant to circulate! After fully refitting, I have been able to run two more firing sequences successfully before the unit reached full temp.

So my best guess is that what has happened is:
Unit worked in the Autumn.
It has got so coked up that fuel was not getting onto the glow plug and so was failing to start.
When I stripped it, coke fell out of the exhaust and the combustion chamber was full!
When I first tried it back on the car, I only tried one firing sequence and I suspect it never got as far as purging the fuel line properly - Doh

So, touch wood, tomorrow morning, it will be back to normal and I can look forward to a warm car! Next job - try and source a telestart remote!

Ok in case others use this thread in the future, problem was nearly solved but not quite. As I said above, a couple of test firings after it all went back together we're fine. What I didn't realise is that at the end of the second firing, it actually went off because of an overheat and was then locked out. So I actually had nothing again the next morning and even a manual start would do nothing.

Last night my present from Santa (IID-BT) was first used in anger to clear all fault codes, including in IC reset and we are back in business. Tried a manual start last night and a timed start and full warm up cycle this morning - all seems good at last.

So thank to all on here for your help once again - keep the faith!  Taking a rest from Land Rovers for a bit.......