Fuel Pump Question for 78 Westy

[[email protected]]

The only thing that has noticeably changed since she last ran is now the fuel pump runs all the time. If I turn the key to the On/Run position and hop out of the bus and listen to the pump it continues to run and run...This is without the bus running. Before my problems, I remember the fuel pump running for about 2 seconds and then stopping. What causes the fuel pump to continue running? Is it a bad fuel pressure regulator? What could it be?

Thanks.
Brian

[ratwell]

Brian, you are going to have to check the wiring to find this out. The wiring diagram is here:

http://www.vintagebus.com/wiring/bus-77-78.jpg
http://www.vintagebus.com/wiring/bus-77-78-key-bottom.jpg
http://www.vintagebus.com/wiring/bus-77-78-key-right.jpg

Use a volt-ohm meter (VOM) and we'll help you figure out what's wrong but at this point we have no idea what the previous owner (PO) did to your bus. In the diagram get familiar with the starter, double relay, AFM and of course fuel pump.

The fuel pressure regulator opens up when the fuel pressure reaches 35 psi. The extra fuel is sent back to the tank to circulate it. If the pump is running all the time, the fuel is simply circulating so as long as there is enough in the tank the pump will be ok (it will overheat if it goes dry).

The main problem with the current setup is that in the event of an accident the pump will continue to run as long as the key is in the on position. If the fuel lines ruptured this could lead to a fire.

[Karl]

You may have a bent arm in the AFM and it is telling the double relay that the engine is idling. Try unplugging the AFM [the unit between the air cleaner and the big S hose] and see if the pump stops. You can access the plug connector by removing the engine access cover. It will be on the right side.

[[email protected]]

Thanks, [email protected] my easter egg troubleshooting, I disconnected the AFM connector and took the resistance readings--one of them failed. With it disconnected I started the bus and it idled fine. With it connected it runs like crap. Needless to say, I just ordered a AFM.

Thanks, again!
Brian