1G Another MPI question

[bigplans1g]

So I cleaned up the ECU and still had the same issue. Now I understand the ECU could still be faulty however after some more investigating I decided to open the MPI so I could observe it's contacts operation. What I found was one side depending on your perspective closes and the other does nothing.

Does anyone know whether both are suppose to close with key in on position? Because only half of mine is doing so.

I imagine if the ECU is only getting half the power it's supposed to have would have a huge difference. I did some looking around and haven't found a solid answer so if you are educated on the matter please take me to school. I don't want to manually switch it and cause myself more problems.

Thanks fellas the one on the left is the one that's got action.

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[pauleyman]

So I cleaned up the ecu and still had the same issue. Now I understand the ecu could still be faulty however after some more investigating I decided to open the mpi so I could observe it's contacts operation. What I found was one side depending on your perspective closes and the other does nothing. Does anyone know weather both are suppose to close with key in on position? Because only half of mine is doing so. I imagine if the ecu is only getting half the power it's supposed to have would have a huge difference. I did some looking around and haven't found a solid answer so if you are educated on the matter please take me to school. I don't want to manually switch it and cause myself more problems. Thanks fellas the one on the left is the one that's got action.

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If memory serves the other side is for fuel pump and that doesn't close with key on. On a 2g I think it does momentarily but that looks a 1g emblem in the background?

 

[Drewpy Dawg]

Correct, one side closes with key on to power ECU, etc. Other side only closes during cranking and running to power the fuel pump. It’s powered by the starter relay during cranking. Once the engine is running it’s powered by the ECU.

 

[bigplans1g]

So if you saw my post yesterday I found corrosion on the ECU due to moisture from leaving the computer on the floor. I cleaned it pretty well but obviously it could still be my issue. Anyone have anymore suggestions on potential problem areas I should look at or more information as far as how these systems are designed?

I have no problem doing my homework or rolling my sleeves up I just appreciate knowing there's knowledgeable people I can consult and I'm truly grateful for the help.

And yes it's a 93 manual. I'm really wanting to back probe the ECU and find out what's going on here. Other than the ECU issue nothing has changed. I have a tendency to overlook simple things often.

Anyway thanks again.

Andrew

 

[19Eclipse90]

Steve’s article is a knowledge goldmine and will be a great resource during your troubleshooting:

1G basic ECU MPI relay circuit function

 

[steve]

As mentioned one relay inside the that MPI relay box is for power to the ECU and most of the engine bay and the second one is for the fuel pump. On 97 and up 2G there are actually two identical relays mounted together to do pretty much the same thing.

I couldn't really tell what the problem was you were trying to diagnose in the other thread?

If you're getting the CEL to turn on for five seconds and turning off and getting power to pins 102 and 107 on the little ECU connector it would seem like the ECU is activating it's part of the MPI relay and the problem with the gauges a different issue. Maybe. Can you connect and talk to the ECU with DSMLink?

You did have corrosion on the pins in that area inside the connector but like I said it's not clear to me what exactly the problem is that your chasing.