Resolved Want to know 1G MPI Relay Resistances

[Laika]

I was wondering if someone with a working 1G MPI relay could do me a huge favor and test the coil resistances for me. It should be MPI pins 10+8, 3+7, and 9+6. Below is a diagram (from https://projectzerog.com/wiring_info.shtml) that shows the pin locations for the connector.

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Thanks!

 

[Vegas Smith]

I'll try tonight.

 

[Laika]

I'll try tonight.

Thanks, I appreciate it!

 

[steve]

I thought I had a 1G MPI relay handy but I can't find it.

The FSM doesn't list resistances for the 2.0 version and the 1.8 version doesn't make sense 35 ohms for one of the FP coils and 95 ohms for a bunch of pins that shouldn't connect. Note that there is a diode in-line with the 10 to 8 coil so you'll only get a resistance in one direction and only if your meter exceeds the diode's forward voltage drop.

Are you trying to to test a MPI relay or come up with relays to replace it?

MPI pins 10+8 (ECU MPI Coil)
MPI pins 3+7 (ECU Fuel Pump Coil)
MPI pins 9+6 (Starter Fuel Pump Coil)

 

[Laika]

I thought I had a 1G MPI relay handy but I can't find it.

The FSM doesn't list resistances for the 2.0 version and the 1.8 version doesn't make sense 35 ohms for one of the FP coils and 95 ohms for a bunch of pins that shouldn't connect. Note that there is a diode in-line with the 10 to 8 coil so you'll only get a resistance in one direction and only if your meter exceeds the diode's forward voltage drop.

Are you trying to to test a MPI relay or come up with relays to replace it?

MPI pins 10+8 (ECU MPI Coil)
MPI pins 3+7 (ECU Fuel Pump Coil)
MPI pins 9+6 (Starter Fuel Pump Coil)

That's a good note about the ECU MPI coil, thanks. I'm working on replacing the relay with universal ones, so I'm trying to make sure I'm getting relays that are going to work. Unfortunately only the starter fuel pump coil reads a reasonable value on my MPI relay (27 ohms), I think the other two are toast or at least I'm not going to trust those readings for this.

 

[steve]

The simplest solution might be to get a replacement factory MPI Relay. Finding a dual coil relay for the fuel pump might prove difficult. You can't use a single coil since one input is active high (Starter) and the other active low (ECU).

 

[Laika]

The simplest solution might be to get a replacement factory MPI Relay. Finding a dual coil relay for the fuel pump might prove difficult. You can't use a single coil since one input is active high (Starter) and the other active low (ECU).

Getting another MPI relay is my backup plan but I'm going to try having three relays so one can be triggered by the fuel pump signal going to ground (MPI pin 7) and the other by the starter signal (MPI pin 9). I'll just have to pay attention that I set up the relays correctly but don't see why it wouldn't work otherwise.

 

[Vegas Smith]

Wasn't able to get the readings but I did find this:

MPI relay schematics?

Long story short, I am having a problem with my MPI relay and/or wiring. I am going to try to put in a new relay and see what that does but in case that doesnt work, I am going to end up testing each wire to figure out what one is making my car act up. My car is not driveable at this time as it...

www.galantvr4.org

 

[Laika]

Wasn't able to get the readings but I did find this:

MPI relay schematics?

Long story short, I am having a problem with my MPI relay and/or wiring. I am going to try to put in a new relay and see what that does but in case that doesnt work, I am going to end up testing each wire to figure out what one is making my car act up. My car is not driveable at this time as it...

www.galantvr4.org

I saw that earlier too and suspect that the VR4 relays are different from the DSM ones since the pins are different from the 1G DSM one in the diagram they give. This makes me question relying on those resistance values they give too since I have no way of knowing if they are different as well. I appreciate your help though!

 

[steve]

After 12 years I'd forgotten that thread. I don't think there is anything there that isn't in https://www.dsmtuners.com/threads/1g-basic-ecu-mpi-circuit-function.435961/

 

[Laika]

Just wanted to post an update for you guys - I decided to just go for it and test my idea for replacing the MPI relay with 3 bosch-style ones. Car started up and idled so it looks like it was successful. I'll be posting a guide on here soon. Thanks for all your help!