1983 3.0 to 3.2 conversion ?? Help

[stubble88]

I have no power to my fuel pump.
I did have power but stumbled and didn’t start. Then I effed with the wires and now won’t work.
It will start if I spray fuel into intake.

1983 fuse panel and car harness.
3.2 engine and DME harness.

1). Will the fuse panel fues relay be obsolete now? Because the DME now controls all that? I have no power to my fuel relay on the 1983 panel. But is it needed?
Thanks

2). Wires in question going to fuse panel from DME: red/green. (Power to fuel pump)???? With this wire is a black wires (power to coil)???? This black wire that’s with the other thin black wire (not confusing). But I did test this wire so it’s the right one on the DME. I don’t know what these wires are exactly or where the go.

[76FJ55]

On the Motronic harness, the Red/Green wire should come from the DME Relay pin 87b and go to the input side of the fuel pump fuse (#3 on the 10 fuse block for 1984 anyway) then through the fuse and to the pump. there is no fuel pump relay at the front fuse/relay panel for the Motronic cars.

As your car has been converted, I can't say what yours should have. they may have run the wires like the 84+ cars, or they could also have used that red/green wire to trigger the original fuel pump relay so that they didn't have to redo the wires going from the fuse box to the pump.

For the black wires, the thicker one looks like it should be going from the fuse panel to the ignition coil and the thinner black wire (also coming from the same location as the thick black wire), should go to the DME Relay (pin #86). These are picking up the 15 bus (+12V in run and start) and therefore should be switched power. to turn on the first stage of the DME Relay and supply power to the coil.

[stubble88]

Ok. So red/green sends power to 1983 red fuel relay?

Thicker black receives power from fues panel?

Thinner wire receives power from fues panel?

Ok. So I have power to fuel pump. Must be using the original red fuse panel relay.
But I only see about 10v of power at the fuel pump. I’m guessing this should be at least 12v? Maybe why the car just stutters?

Thanks

[76FJ55]

I don't know if it connects to the 1983 relay or not, you will need to determine that as I do not have access to your car to follow the wires. that being said, if you are getting some voltage to the fuel pump, you could always remove the original FP Relay and see if that has any effect on the power at the pump.

on the 84 wiring diagram the black wires connect to the 15 bus at the fuse box, but they are not fused, just connected to the bus. the ignition switch which is connected to constant 12V supplies the 15 bus of the fuse box via ignition switch pin 6 in the run and start positions. this power travels from the Ig switch via a red/black wire to the fuse box where it connects to the supply side of the 10 fuse block at the inputs for fuses #7 and 8. there are several circuits including the previously discussed black wires that connect into the 15 bus at that location.

[stubble88]

Removing the fp relay results in 0 power to the fuel pump.
So the red/green wire from the DME is energized while cranking. So I just don’t need the old red fuel relay. Should I just wire the red/green directly to the fuel pump? This is probably the issue. I’m running through two relays. I guess.

[76FJ55]

running through 2 relays shouldn't be an issue, if nothing else it should remove the high current draw through the DME Relay and therefore should greatly improve the DME Relay life.

presumably (if they followed normal wiring convention) they would have connected the Red/Green wire from the DME Relay to the 86 pin of the (1983) red FP relay. the 85 pin on the Red relay should then be connected to ground (31 bus). this is a slight deviation from the original 911 SC wiring (at least based on the 82 diagram as the WSM does not seem to have the 83 diagrams, so I must assume they are the same). the original red relay would have been controlled by a switch in the air flow sensor which would only ;make contact to ground the 85 pin when the airflow meter was pushed open. I'm not sure how they adapted this wiring, but it seems like this must have been addressed in order for the red relay to be closing and supplying power to the pump.

there are a few things that may be worth test associated with the red relay though.
first, with the relay removed you should have constant power (ignition off) to pin 30. verify this.

if you place a jumper between 30 and 87, this should supply power to the fuel pump and cause it to run. check voltage at the FP with this jumpered and see if you are getting power at the pump and if it is 12V or still only 10V like you found previously.

you should have continuity to ground for the 85 pin. verify.

check for voltage on the 86 pin in both run and crank position.

since it is still using the original red relay, I assume that they have continued with the original fuel pump fuse (fuse #19 based on the 82 diagram, but you would need to confirm using your 83 fuse chart). remove this fuse and polish the fuse box contacts and the ends of the fuse and see if this has any effecton improving the fuel pump voltage.

[stubble88]

I do not have constant power to 30

It’s getting all its power from the red/green. I guess

[76FJ55]

Do you have constant power coming into any of the pins to the red relay?

[stubble88]

Nope. It’s all powered when cranking. All from the red/green
30 never has power.
85 87 87a and 86 all get power while cranking.

[76FJ55]

Looking back at the 82 diagram I see that there is no constant 12V. that particular relay is not originally wired via the normal convention as it is a special case to incorporate engine stall fuel cutoff for crash fire protection. Can you pull the relay socket out and see what they have connected to it?

with the key in the run position do you have power on any of the pins of the red relay? based on the diagram you should have 12V on the 87a pin coming from the fuel pump fuse (15 bus, key on or crank).

It would be very beneficial to know where they have the red/green connected.

[stubble88]

Only while cranking. 30 never has power

Red/green is in #6 on the 6 pin DME connector.
It’s accompanied connected with a yellow wire

[76FJ55]

yes I understand that it is on pin 6 of DME Relay, but where does it connect to the red relay?

[stubble88]

I have it on the bottom fuse panel connected to 86? Big red wire is top side of fuse opposite of red/green.
So basically red/green is fused to red 86

[stubble88]

I feel like I should be getting power from another wire besides only the red/green.
Can I add 12v to the red/white connector? This is the wire with the black one from 30

[mysocal911]

With key-on (#30 & #15 - 12V powers), pins 1, 18, 35 should be 12V. Pins 5, 16, 17, 19 should be ground.
Pin 20 should run (ground) the FP relay contacts), and send 12V to the FP.

Troubleshooting help here;
911 3.2 No-Start Troubleshooting

[stubble88]

Pin 30 gets power from where?
There is a thicker black wire and a thinner red/white

[76FJ55]

Originally Posted by mysocal911

With key-on (#30 & #15 - 12V powers), pins 1, 18, 35 should be 12V. Pins 5, 16, 17, 19 should be ground.
Pin 20 should run (ground) the FP relay contacts), and send 12V to the FP.

Troubleshooting help here;
911 3.2 No-Start Troubleshooting

I assume these pin numbers are associated with the DME computer itself.

[stubble88]

Should 30 be fused to the red/green?
If I power 86 the pump just runs
If I jump 12v to 86 I get over 12v at fuel pump
If I add power to 30 pump just runs with key on.

Red/green sends power while cranking (with a 3.2 that’s what I want). Problem is it’s only 10v.

[76FJ55]

Originally Posted by stubble88

I feel like I should be getting power from another wire besides only the red/green.
Can I add 12v to the red/white connector? This is the wire with the black one from 30

Just to be clear "30" can refer to several references.

It is generically referred to as constant battery +12V when referring to the 30 BUS.
It can also refer to a pin designation on a relay or other electrical component "pin 30".

which 30 are you referring to above? and what black wire ( the thick and thin ones previously discussed or a different one)?

Ideally you would have either BUS 30 (constant +12V) or BUS 15 (switched +12V) power (through a fuse) connected to PIN 30 of the red relay and then connect 87 to the supply to the fuel pump. then use the the red/green wire to control the red relay via connection to PIN 86 on the red relay. and connecting PIN 85 of the red relay to ground .

[stubble88]

Sorry. 30 on the fuel relay