Hello, I purchased a 95 turbo'd 420a. Its running very rich even with a new set of 24lb injectors. I have a error code 42 which is a no MFI output at ECU. I did some inspection and found that there is only 1 relay for the fuel pump. The other relay was removed with 2 wires connected and a 3 wire by itself. My thinking is that this is causing the ECU not to be able to adjust fuel or timing and a result is the rough running rich mixture. Can any please tell me what the wires are going to the ASD and MFI and at what position on the relay they attach so I can put it back to the way it was. David

here is the 95 ECU pin out:

http://www.2gnt.com/index.php?d=1995_ECU

I am a little confused on what you are asking. The car would not run if the ASD relay was missing as the coil and injectors receive power from that relay.

You say that it is running rich: what do you have for fuel control? AFPR? WBO2? Missing link? FCD? what tuning device do you have?

Please give details on the setup. Running rich is not related to a missing relay. It is more than likely that it needs to be tuned.

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2012 2500HD LML

Sorry for the confusion I just looked at the wiring and here it is. I have Black/Red soldered to Red/Black, Red/White wire open!
To a relay I have White/Red, Red/Blue, Black/White, Black/Blue.
My thinking is that the ECU is not seeing a connection(Red/White wire) to a relay and sending the error code 42 no MFI output. The car runs, but very rough and rich. It has a Walbro 255pump with FPR set a 20. I was setting it low so I can eventually add fuel with the SAFC to reducing timing a little for the turbo.

I just downloaded a schematic of the ASD relay and it looks like the person tried to hot wire the coil pack with the Black/Red to Red/Black connection to produce spark. The problem is that the Red/White wire which comes from the ECU #58 is not hooked up and the ECU thinks that there is no ASD Relay(Error 42)and might be messing with the Fuel Injectors and Ignition Timing? I would like to put it back to stock and would like to know if someone can look at there Relays and tell me which wire goes to the selected relay positions.

For the most part, all automotive relay wiring is the same.

Pins 85 & 86 get the low current switched circuit where 30 and 87 are the pins for high current/load circuit.

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2012 2500HD LML

Thanks very helpful. Now I need to figure out the wiring setup.

ASD Relay
86: Black/White power source from Ignition Switch
87: Red/Black power to coil pack
30: Black/Red fused power
85: Red/White ground from ECU

Does this look correct?

Question with the Black/White wire as it is being used for the Fuel Relay right now. Is it split into both relays?

Have you ever seen the Black/Red soldered directly to the Red/Black for coil power?

Would the Red/White wire not hooked up cause the ECU not to control the injector pulse width and timing, since it is not seeing the ASD relay and throwing a error code 42?

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2012 2500HD LML

If the ECU is throwing a Error code 42 No MFI, how would it still control fuel and timing if it thinks that there is no spark?

I just looked at the Fuel pump Relay that is hooked up
86: White/Red
30: Red/Black
85: Black/White
87: Black/Blue

You have to love Modified Cars and Wiring! Other wise life would be to simple.

I also belong to a local gun range. Love Guns, mainly Pistols.

As long as the fuel injectors and ignition coil are receiving a +12 volts, the ECU will continue to fire them appropriately by the ground triggers. It does not care how the devices get the +12 volts, as long as it gets them. I do not the specifics of how the circuits work, I just know that it works that way.

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2012 2500HD LML

But with a Error code 42 wouldn't it go into Limp Mode, causing a rich condition

Not necessarily.

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2012 2500HD LML

Ok, Thanks again for all your help and will post another message when I get it all figured out.

Well I thought I could wire the Red/White wire(MFI output) into the White/Red wire(Fuel Pump output) that goes to the relay. That fixed the error code 42 no mfi output, but produced another error code 43 ignition coil circuit.

Here is a Great Schematic of the 95 420a ECU
http://www.columbusdsm.com/forum/attachment.php?attachmentid=3196&stc=1&d=1206413335