Fuel Pump Question

[ldrhawke]

I decided to start my 1980, original owner, 928 that has been setting up for 6 years.

I added fresh gas and installed a new battery...cranks fine. but won't start.

Removed the airfilter and poured in a few ounces of fuel.....cranked and started, but quickly died.

I assumed the fuel pump was frozen up. It's happended before. I pulled it off and made a direct 12V connection to test. Filled with WE40 at let sit for awhile. Hooked up 12 volts direct. It's bad...new one on order.

I further check to see if I had 12V at the fuel pump wiring connections with the key on..................No 12 volts.

I looked at the fuses under the dash...all seem good. I wasn't sure which fuse was the fuel pump to double check.

What is the next thing in the fuel pump electrical that could be bad, and where i it located?

Thanks

[Maleficio]

A relay is more likely stuck open.

[aluminum]

Save Yourself a lot of grief and pull and wash out the tank > The old fuel well be all jellied up on the bottom of the tank. ( most likely inside the fuel pump also ) You may have a Pump inside the Tank also . Hot mix Soak in TSP perhaps over night Flush until runs clean with pressure washer and rinse water. Drain and dry Tank. (self service car wash well work also )
Open Fuel Rail's One place at a time Like the end on the Pass side . Then when you get the pump going you can flush out the line's / Fuel Rails > Rubber hose to Plastic bottle well show you when the fuel is clean. Open the other end ( Fuel Line ) and also pump it out . You well see rust and dirt come out with dirty fuel.
Once your clean and get fuel pressure inspect for Leaks before trying to start motor .
Now your ready to start checking power to Injectors Pump ect .
Pull the coil wire from the Cap and hold close to ground and check for spark on Key cranking mode ( I expect you well see spark if it started then died )
Pump well come on when you tap the starter ! > Build Pressure then stop > so open a line and connect a hose to bottle to test the pump > Tap starter and expect fuel to pump out some .
************************************************
when you get all that going if it starts ( Cold start valve) and die's on the run mode ( Injector's ) of the key check the injector relay > ( Sends power to the injectors on the run cycle ) Car starts on cold start then switches over to the run cycle "Injectors ".
All working right you well most likely need to prime fuel it until the injector's clean out and get working . Some may be stuck . You can power them with 12 volts to see if they click without removing them > No Click ? tap them with wood lightly and keep trying they stick .
Check again for fuel leaks .
A fuse Chart well show you all the relays and fuses

[Landseer]

To bring one of these back to life after sitting that long, a sequential approach is the high percentage play.


Systematically clean the electrical connections, grounds, CE panel contacts, new fuses (proper VW type, not Buss), and replace fuel filter, pump and in-tank strainer.

Order new fuel pump relay.
If its a USA car with Ljetronic, then also order a new ignition relay.

Are you the original owner, then?


(There is enough voltage / amperage in these special electrical systems to stop your heart so don't touch the spark plug or coil leads manually while cranking one over.)

[stepson]

Idr,
The fuel pump circuit is set up to turn off the power to the fuel pump after 3 seconds if the engine is not running, a safety feature. The circuit makes it harder to test the fuel pump correctly. To bypass that, you can pull the relay and fit a jumper wire between terminals 30 and 87 where the relay had been. That will allow you to test the voltage at the fuel pump.

[Landseer]

You can also read voltage at the other two terminals during starting to determine if 12V power is being applied for the purpose of triggering the relay.