Problems installing DUI Distributor from Performance Distributors

[iceman510]

From the diagram Skib posted, it looks to me like pin 108 of the ECU controls the ground for the fuel pump relay.  The power to trigger the relay and to supply the fuel pump power come from the ignition switch on/start source shown in the upper right corner.  Seems like you need to substitute for that ECU ground.

 

The two inputs or outputs from the CAS (I don't know from the diagram) are pins 8 and 17.  As mentioned maybe they only fire the injectors, but the internal connections are not clear from the diagram.

[1984]

12 hours ago, iceman510 said:

From the diagram Skib posted, it looks to me like pin 108 of the ECU controls the ground for the fuel pump relay.  The power to trigger the relay and to supply the fuel pump power come from the ignition switch on/start source shown in the upper right corner.  Seems like you need to substitute for that ECU ground.

 

The two inputs or outputs from the CAS (I don't know from the diagram) are pins 8 and 17.  As mentioned maybe they only fire the injectors, but the internal connections are not clear from the diagram.

Hey thanks for the input.

 

I tested the wires with a volt meter from the bottom of the relay box. With the ignition on, 3 of the 4 wires have battery voltage. That fourth wire has battery voltage when the pump is running. I think this means that there is no ground from the relay. On the diagram there's a ground at the pump. I really don't have a good understanding of electrical stuff so correct me if I'm wrong.

 

I also unplugged the ECU and tried to start the truck. No voltage going to distributor from original wiring so no start. 

 

But if I ran a new ignition controlled wire to the distributor and have the fuel pump switched on by the oil pressure switch as recommended by datzenmike, then the ECU wouldn't be needed to run the truck. I think. Maybe...

[1984]

On 10/29/2022 at 6:12 AM, datzenmike said:

You could also ground a relay through the oil pressure switch with the fuel pump connected to the NO (normally open) terminals. Pump is only on when there is oil pressure. In an accident, heaven forbid, when the engine stops so does the fuel pump.

 

On 10/29/2022 at 12:09 PM, datzenmike said:

The tach output is a series of on off pulses across the coil. I don't think that would be good for the pump and if a relay it may chatter on and off.

 

 

The oil pressure sender is only at ground when the pressure drops below about 8 PSI and this turns the red oil light on in the dash. Many relays when off have a normally closed set of contacts and a normally open set.

 

 

The + is to the battery, the - to the oil pressure sender. When running and there is oil pressure there is no ground at the - terminal. The C and NC are connected to the fuel pump. When engine stops and pressure drops a ground condition at the - terminal energizes the coil and the NC connection is opened shutting the fuel pump off

Hey so I wired things up as you described but the fuel pump wouldn't turn on. After a lot of fiddling and madness I found something that worked. I temporarily wired things up with twist connectors and drew up a diagram to try and make sense of things. I'm curious of your thoughts on it as it is baffling for me to think about.

 

 

The oil pressure switch is on the - and the + is connected to the battery with a fuse. C is ignition and NC is the fuel pump.

So the only thing different from what you said is the addition of ignition power. 

Does this make sense?