I did a DPFI to MPFI swap,
Then replaced my 1991 DX Cabin harness with a 1989 DX cabin harness due to melted wires.



Here it says Main relay connects to ECU (A13 + A15)



In my manual it says the main relay connects to both the injector resistors and the ECU.

Where I highlighted on the manual picture is where I cannot get the connection. Within the engine harness, it is fine and the multimeter says it also connects to the ECU just fine.

I kno that when I switched from the 91 to the 89 cabin harness, there were some differences in plugs and I'm having trouble figuring out where they all hook up correctly.

 

Are you saying that the injector resistors don't get voltage?

Have you tested the main relay?

 

The main relay clicks upon ignition II.

However, I can't get the fuel pump to prime at that time.

I think it has something to do with this wiring swap.

I'm saying that the main relay's wires to the injector resistors are not connected to connector C313. Would this effect this effect the fuel pump prime upon key turn to ignition II?

 

The Yel/Blk wires at C313 must supply voltage to A13 and A15 in order for the fuel pump to prime.

1) Does the main relay connector get voltage on the Yel/Wht and Blk/Yel wire terminals?

2) If you ground the Grn/Blk wire (A12, A14) in unplugged ECU connector A with the key in ON(II), does the fuel pump run?

 

After connecting the voltmeter to the yel/wht and blk/yel wire, I instantly received 12 volts without the key even in the ignition. After turning the key to II there was no change from 12 volts, it stayed constant. Not sure if that makes a difference.

I grounded A12 and A14, and, with everything but ECU connector A plugged, my fuel pump did not un with the key at II.

 

Have you cleaned and tightened the important ground wire attached to thermostat housing?

 

I have, I just removed the entire wiring harness this afternoon to double check all my wiring on it. I just replaced it to check the main relay voltages and the grounds.

 

Unplug the main relay.

With the key off, use a multimeter to test for continuity to body ground at the black wire terminal in the main relay connector. Do you measure continuity? If so, test the main relay.

 

With the main relay unplugged I measured continuity to ground on all of the spots on the main relay with the key off. I affixed the ground continuity wire to the radio interference ground on the valve cover.

I'm getting continuity at all of these:
Black
Yellow/white
Blue/white
Black/yellow
Yellow/black

 

^Not all should have continuity to body ground. How is the multimeter set?

Test the main relay.

 

The multimeter is set correctly. The main relay is actually brand new.

All of these having continuity to ground appears to be my problem. There is a connector in the area that is highlighted in red in the initial post which I can identify as the rear cabin harness to front cabin harness connector. While I switched the (front) cabin harness from a 91 to an 89, I kept the rear cabin harness of the 91. I found out that there is a difference in connectors from these two years, and I have been forced to try and repin the 91 rear harness connector appropriately. However, even upon disconnecting this, I have found that I am receiving continuity to ground on all of the same wires.

I am very confused, and I really appreciate your help.

 

Should there be a constant 12 volts across the yel/wht and blk/yel terminals on the main relay connector?

 

Constant battery voltage to body ground for the Yel/Wht and with the key in ON(II) for the Blk/Yel.

 

But when it is not in ON(II) then I should not be reading 12 volts. When the key isn't even in the ignition, it should read nothing, correct?

 

For the Blk/Yel wire, yes.

Are you possibly testing the Yel/Blk wire terminal?