GVR-4 MPI Relay clicking (no, it's not the MegaSquirt2 ECU)

[phant0mxx]

MPI Relay clicking (no, it's not the ECU)
It also did this with the original ECU, as well as the standalone.

I'm fighting a problem with the MPI Relay clicking and can't seem to find the problem.
The ECU is a MegaSquirt2, brand new hardware, engine runs off it just fine. (Until the clicking starts and it dies)
I bench tested the MPI relay and it's fine, there's no issues with it.

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Anyone have any suggestions where to look?
I don't see anything shorting out, nothing obvious stands out.

 

[luv2rallye]

What year/engine is this?
Are you sure that's not the fuel pump half of the relay?

 

[phant0mxx]

What year/engine is this?
Are you sure that's not the fuel pump half of the relay?

It's a '91 JDM Galant VR4 RS.
It cuts power to the ECU when it starts clicking

 

[phant0mxx]

New symptom; RPM gauge is erratic and stays at 0 sometimes.

I'm leaning towards CAS/PTU circuits now.

 

[phant0mxx]

Tested PTU and it checks out just fine(as per your testing guide).
This morning the MPI clicking was sporadic and now it's bouncing off the walls. Leads me to believe it's something that's shorting or disconnecting when it's hot (110f outside temperature now and hot engine)

 

[steve]

Relay clicking indicates that not enough current is flowing through the coil to keep the relay engaged. If the relay is working under test (and you're heating it to make sure it's not temp sensitive) then it could be the voltage to the relay, the quality of the ground switching provided by the ECU or an issue with the wiring.

The ECU ground it's end of the MPI relay coil when it sees the ignition turn on.

SO it's time to break out the multimeter and start monitoring the signals to the relay to see which/what is failing and work from there.

You can shortcut some of the diagnostic process by forcing a solid ground at the MPI relay at pin 8. If it still clicks check the voltage to pin 10 and make sure it's not intermittent..

https://www.dsmtuners.com/threads/1g-basic-ecu-mpi-circuit-function.435961/

 

[phant0mxx]

Relay clicking indicates that not enough current is flowing through the coil to keep the relay engaged. If the relay is working under test (and you're heating it to make sure it's not temp sensitive) then it could be the voltage to the relay, the quality of the ground switching provided by the ECU or an issue with the wiring.

The ECU ground it's end of the MPI relay coil when it sees the ignition turn on.

SO it's time to break out the multimeter and start monitoring the signals to the relay to see which/what is failing and work from there.

You can shortcut some of the diagnostic process by forcing a solid ground at the MPI relay at pin 8. If it still clicks check the voltage to pin 10 and make sure it's not intermittent..

https://www.dsmtuners.com/threads/1g-basic-ecu-mpi-circuit-function.435961/

Thanks for the reply Steve,
I messaged you on a different forum but you can ignore it since you've already replied here.

The PTU and MPI relays both check out good in the bench, over heating them and putting a load through to make it as realistic as possible.

I'll monitor voltages in a bit, when the sun goes down and post back with the results.

 

[phant0mxx]

I'm not able to monitor voltages now because I ran into another issue.
I'm dropping CPS signal for some reason and I can't get it to run.

 

[steve]

I don't want to read too much into what you've posted so far, I'll just remind you that the CAS (Crank and Cam sensor) gets it's power to function from the output of the MPI relay just like the ECU does and the signaling from those sensors is by pulling an ECU +5v signal line low, not by providing any voltages themselves.

Since you are using a MegaSquirt2 I can't do more than describe how things are intended to work.

 

[steve]

Any resolution to this?

 

[phant0mxx]

Any resolution to this?

Sorry, I forgot I had this thread open.
The fix was to completely remove the OEM MPI relay and install a couple of Bosch style relays.
It must have been a bad MPI relay but when I bench tested it it was fine, even when heat was applied to try to induce a failure.