Fuel pump wiring 2.0

[Glistre]

I’m putting my 914 2.0 which has been converted to carbs back to original D-jet: how can I make sure that the fuel pump is wired correctly and nothing modified? I read that the fuel pump should buzz for 1.5 secs when you turn the key? I am using a two-port fuel pump not the original three port.

Also, I know that the AAR is supposed to have power from the fuel pump?

[Dave at Pelican Parts]

General advice to answer your questions:

Follow the wiring diagrams. They're available in your Haynes manual, among other places.

The fuel pump wiring is in the main chassis wiring harness. The power wire runs to the 14-pin connector at the front of the relay board (pin 13, the left-front pin; black/red wire). The ground wire runs to the common ground point under the relay board.

The AAR power wire is in the engine wiring harness that connects to the 12-pin connector at the right-rear of the relay board. It is a white wire on pin 12, the right-rear pin. The connection into the fuel pump power circuit is made inside the relay board. The AAR is grounded through its case; there is no separate ground wire.

--DD

[Glistre]

Originally Posted by Dave at Pelican Parts

General advice to answer your questions:

Follow the wiring diagrams. They're available in your Haynes manual, among other places.

The fuel pump wiring is in the main chassis wiring harness. The power wire runs to the 14-pin connector at the front of the relay board (pin 13, the left-front pin; black/red wire). The ground wire runs to the common ground point under the relay board.

The AAR power wire is in the engine wiring harness that connects to the 12-pin connector at the right-rear of the relay board. It is a white wire on pin 12, the right-rear pin. The connection into the fuel pump power circuit is made inside the relay board. The AAR is grounded through its case; there is no separate ground wire.

--DD

My wiring is definitely hacked. No power coming from the white AAR wire in the rear of relay board. As for the main harness connector I do indeed have the red/black wire in the left front found it goes to a grommet behind battery help hole where it is clipped and has a brown wire next to it. I assume it went to fuel pump which was relocated up front. Now the fuel pump is direct wired to fuse box. How would I check for power to black red wire? Turn the ignition key on and put a lead from a voltmeter on it and the other lead from brown wire to negative battery terminal or ground? When I do that I only get .25 volts does that mean bad fuel pump relay

[Dave at Pelican Parts]

Probably not a bad relay, though it could be.

The D-jet system controls the pump through the pump relay, in stock form at least. The system will send power for about 1.5 seconds to the pump when the key goes from "off" to "on", then stop until either the starter is cranking or until the engine is turning over faster than ~50 RPM. (Could be 150? Could be a different number, but it's very slow.)

So, the ignition switch sends power to the D-jet power relay, which sends power to the D-jet brain. The same circuit sends power to the fuel pump relay, but since it doesn't have a ground it won't send power to the pump. The D-jet brain will supply a ground to the fuel pump relay to switch it on, and that will cause the relay to send power to the pump.

Both relays have to work in order for the pump to be powered.

A quick relay test can be done by swapping the unknown relay into the head light relay socket. (Assuming your headlights go up and down correctly!!) If the headlights go up and down with the relay plugged in, the relay is generally good.

--DD

[Dave at Pelican Parts]

Time to start reading up on D-jetronic fuel injection.

https://members.rennlist.com/pbanders/

Brad Anders has compiled just about everything that is currently known about this odd analog-electric system. Read through all of that to have some understanding of what is going on.

--DD

[Glistre]

Originally Posted by Dave at Pelican Parts

Probably not a bad relay, though it could be.

The D-jet system controls the pump through the pump relay, in stock form at least. The system will send power for about 1.5 seconds to the pump when the key goes from "off" to "on", then stop until either the starter is cranking or until the engine is turning over faster than ~50 RPM. (Could be 150? Could be a different number, but it's very slow.)

So, the ignition switch sends power to the D-jet power relay, which sends power to the D-jet brain. The same circuit sends power to the fuel pump relay, but since it doesn't have a ground it won't send power to the pump. The D-jet brain will supply a ground to the fuel pump relay to switch it on, and that will cause the relay to send power to the pump.

Both relays have to work in order for the pump to be powered.

A quick relay test can be done by swapping the unknown relay into the head light relay socket. (Assuming your headlights go up and down correctly!!) If the headlights go up and down with the relay plugged in, the relay is generally good.

--DD

Switched out relay and tested and the fuel pump buzzed for 1.5secs then tried again and just “clicks “ no fuel pump

Went through step by step Jeff Bowlsby Fuel Pump and found the bad Power Relay, but unfortunately I have no power at pin 30 of the Fuel Pump relay , and I have no power at pin 1 of the 4 pin ECU connector Jeff's chart says that pin 1 is left aft, but I read elsewhere pin 1 is passenger / right front. I am guessing the bad Power Relay shorted the fuse, and in fact, I checked and the fuse was bad! Glad I don't have a bad relay board ( so far). Everything is running now.

However, how did the fuse blow? I had the brown wire grounded to battery, the one next to the Black /red fuel pump but did that somehow short and blow the fuse? What is the brown wire is it supposed to be grounded? I already have a ground for the fuel pump up front since I relocated the pump. Hopefully, no more blown fuses and perhaps the bad power relay blew the fuse but I feel like maybe wiring the brown wire to the negative battery terminla might also have caused a short.

[Dave at Pelican Parts]

If the brown wire is original, it is ground. Brown is always ground in our cars, unless someone has changed the wiring.

If the black/red wire wound up touching a ground, it would blow the fuse on the relay board. Likewise, if the white wire that plugs into the AAR touches ground it will also blow the fuse.

--DD

[Glistre]

I bet it was the AAR white wire . I will go ahead and run the brown wire to ground not sure if the relay board might need it