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Troubleshooting Webasto

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webasto
2K views 9 replies 5 participants last post by  Greenbull 
#1 ·
I've reinstalled my webasto after doing a disco 200Tdi swap and it's giving me some headaches.

I know it circulates coolant.
I can hear it fire up and the fuel pump pulses after start up. The exhaust gets warm, but never really gets HOT. After running for approximately 70 minutes today in 45F weather, the on-contact temperature of the thermostat housing was 65F which matched the coolant hose to and from the webasto.

I noticed today when I approached the truck, that the coolant pump was on, but no fuel pump running. I turned it off at the controller, and turned it back on. The fuel pump started to pulse, but shut off after approximately 2 minutes.

When reinstalling it, I did not use the smaller diameter fuel line that came with the kit. I had to use rubber fuel line which had a larger diameter. When I looked at the fuel filter, there was a small air bubble at the top of the fuel filter (oriented on its side).

Do you think that the larger diameter fuel line is causing fuel feeding issues? I've found some more fuel line that came with the kit and I plan to replace the larger diameter fuel line with the line that came with the kit.
 
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#3 ·
I would start by reading the manual. The heater goes through a very specific start sequence. There is a high fan purge then a low fan ignition at a slow fuel rate. Once ignition is detected the fan and fuel rates increase.

From your description it is not completing the ignition. You do not mention hearing the combustion air fan. It is quite loud and if it is not running you will not get a flame.
 
#4 ·
Here are excerpts from the manual.

Switch On
The glow plug, the combustion air fan and the circulation pump are activated. After 30 seconds the fuel dosing pump starts operation and combustion air fan operation is suspended for 3 seconds. Subsequently the combustion air fan speed is increased in two ramps within 56 seconds to nearly full load operation. After a stabilisation phase (constant speed) of 15 seconds the combustion air fan speed is again increased in a ramp within 50 seconds to nearly full load. After reaching full load fuel delivery the glow plug is deactivated and the combustion air fan operation increased to full load. During the subsequent 45 seconds as well as in normal operation the glow plug functions as flame sensor to monitor the flame condition. After all these events the automatically controlled heating operation starts. In case of a no flame condition or a flameout, a restart is automatically initiated. If the no flame condition persists, fuel delivery is stopped and the heater enters an error lockout with a run-down of the combustion air fan. A flameout during normal combustion operation causes an automatic restart.

Heating Operation
When the temperature rises to reach 72 °C the heater switches to the energy saving part load operation. A rise in temperature up to 76.5 °C causes the heater to enter a control idle period. This also happens when exceeding a total heating operating time of 76 minutes. The circulation pump, the vehicle's own heating air fan, and the operation indicator light remain on during control idle. After cool-down of the coolant to 71 °C the heater resumes part load operation. Another rise in temperature to 76.5 °C causes the heater to enter again the control idle period. A drop in the coolant temperature during part load operation due to an increased demand in heat will cause the heater to switch to full load operation at 56 °C. Should the coolant temperature drop during the control idle period to but not below 71 °C within 900 seconds, a subsequent drop in the coolant temperature below 71 °C causes the heater to perform a regular starting sequence into full load operation.
 
#5 ·
As far as fuel line goes, smaller is better for purging air and preventing air locks. Always going uphill from the tank helps as well. Any large descending lines will not work. The pump must be horizontal or pointing up. There are limits to the pump height above the tank and fuel line length. If the line was full of air, you may need to cycle the heater a bunch of times to purge it of air.

There are a bunch of suggestions in the manual as well as drawings showing what is good and what is bad. Here are some excerpts.
Fuel tappings from the supply or return line may only use the special Webasto fuel tap.

As in most cases a permanently rising fuel line routing cannot be ensured, the inner diameter must not exceed a certain value. Starting from an inside diameter of 4 mm, air or gas bubbles accumulate resulting in malfunctions should the lines be descending or having sags. The diameters specified in Fig. 803 (the drawing indicated 2 mm ID) ensure no disturbing formation of bubbles. A descending line routing from the dosing pump to the heater should be avoided.
 
#6 ·
Butting in here with my own question. I'm trying to find a fuel pick up that I can route through my in tank sender and thinking I'll have to get something none Webasto. I'm seeing some aftermarket ones with an ID of 1.6mm would be too small? Not seeing anything in the manual taking about minimum size.


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#7 ·
I would think it would be okay. For the vertical pickup a bit big is okay. They just want to avoid the decending lines being too large. My pickup is a normal piece of 1/4" stainless tubing.
 
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