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Sat Oct 20, 2007 11:51 am

hi
im trying to get my heater runing well in my 181. but the fuel pump is playing up i think.
it makes a tapping noice that i think should not be so loud.
and the heater when starting up misses lots till the fan realy cuts in then it runs ok but not great. it does not sound smooth like i think it should.
is it just that i need to adjust the amount of fuel its pumping?
the heater is the standard eberspacher BN4.

thanks luke

Sat Oct 20, 2007 1:52 pm

the amount of fuel is regulated by the fan. The fuel solenoid opens once for every so many revolutions of the fan. That might be why it doesn't work well until the fan gets going good.

Sat Oct 20, 2007 2:11 pm

i thought you could adjust the amout of fuel the pump puts out by turning somthing on the pump.

Sat Oct 20, 2007 2:36 pm

I think VW used 2 different types of pumps. The one I have is basically a solenoid type valve that doesn't exactly pump the fuel but opens to allow fuel to pass. I don't think there is any type of adjustment on that one. There was a thread here a few days ago that posted a link to the heater repair manual that describes both types.

Sat Oct 20, 2007 3:55 pm

This page may help

http://veewiki.com/HeaterBN4

Manual here:
http://failsure.net/oacdp/ebersp.html

The solenoid pump is an actual pump, not a valve. Each tick is it pulling the plunger inward to squirt the gas. If you pull it from the car, feed it some gas and give it 12v, you'll get a squirt of gas shoot (yes SHOOT) out of it.

Sat Oct 20, 2007 11:29 pm

Ian Epperson wrote: This page may help

http://veewiki.com/HeaterBN4

Manual here:
http://failsure.net/oacdp/ebersp.html

The solenoid pump is an actual pump, not a valve. Each tick is it pulling the plunger inward to squirt the gas. If you pull it from the car, feed it some gas and give it 12v, you'll get a squirt of gas shoot (yes SHOOT) out of it.

That's true. Both styles have pumps that are just that, pumps; not gravity fed fuel lines. Early BN4's have a pressure regular that regulates the fuel going into the heater and the later pumps every 33 revolutions of the fan.

So you should hear a tick, tick, tick sound with a later style heater.

Sun Oct 21, 2007 2:42 am

i guess that iv got the later style as theres a tick and no regulater. iv got it to run better now but stops firing every now and then.... only for 3 sec or so and every thing else keeps runing. it runs like this all the time.
its as if theres not enough fuel geting through. i will check out the links your give my thanks luke.

Sun Oct 21, 2007 4:56 pm

jex_the_bug wrote: i guess that iv got the later style as theres a tick and no regulater. iv got it to run better now but stops firing every now and then.... only for 3 sec or so and every thing else keeps runing. it runs like this all the time.
its as if theres not enough fuel geting through. i will check out the links your give my thanks luke.
The left most knob, right next to the driver's door, controls the thermostat. If the furnace is kicking on and off strangely, it could be that the thermostat needs adjusting. Just for fun, here's the owner's manual page pertaining to the heater.

Sun Oct 21, 2007 7:55 pm

To a certain extent it is suppose to turn on and off. Once the heater reaches the desired air temperature it shuts off the fuel supply and just blows warm air. Once the air temperature has dropped below the desired temperature it kicks the fuel back on and heats the combustion chamber back up. Just like your furnace at home.

If it just kept feeding itself fuel it would get to hot and melt or some other catastrophic break down. Basically what you’re describing is a safety feature.