11 replies to this topic

[Dave_GSR1.8]

So, I have an starting problem that I think is the ECU, based on the testing I have done.

 

To set the scene, I am running ECMLink v3 Lite in a GSR ECU with standard bolt on mods (fuel pump, fuel pump wiring, injectors, EVO AFM, FMIC, exhaust, but sadly still with TD04). I have run this ECU for three years without issue, this problem started about a month ago .

 

The issue is that the ECU intermittently goes into a fault state whereby the CEL does not come on with ignition on; the engine will crank but will not fire. To fix this I have to remove and refit the fusible link for the MFI relay (no 2 in the engine bay fuse box), after which the ECU works properly again till the fault reoccurs.

 

So, I got out the voltmeter and back probed all 8 pins on the MFI relay (a new one because I was led to believe that this was the problem, it wasn’t...) and Pins 60, 36 and 12 on the ECU, with the ECU in both its "fault" state and when working normally.

 

The results are summarised in the attached PDF attachment.

 

In summary, my thinking is that:

 

The ECU is not switching off correctly when the ignition is switched off; this is an intermittent fault, but happens often enough to be an issue (at least four or five times a week).

 

This is based on;

- the voltages being read at the ECU (pins 12 and 36) and MFI relay (in particular pins 2, 3 & 6), when the ECU is in the fault state;

- the fact the battery will go flat if the car is left in this state for more than 48 hours;

- the fact that disconnecting the ECU from backup power causes it to reset and function correctly until the fault occurs again.

- the fact that there is fuel pressure at the fuel rail, when the ECU is in fault condition and engine is cranked

- the fact that there is spark at plugs, when the ECU is in fault condition and engine is cranked

- the fact that the injectors do not fire when the ECU is in fault condition and engine is cranked

 

So, has any one else ever had this issue? Or have any ideas other than the ones I have had? I am wondering if there is anything I might have missed or overlooked?

 

 

 

Attached Files

•  Voltage at MFI & ECU relay Pins 19-03-17.pdf   46.3KB   134 downloads

[Ian91]

Sounds scary, do any of the normal relays in the fuse boxes have any control over the ecu or mfi? Maybe one is damaged and sticking on. Have you checked the ecu hasn't burst a capacitor or 2?

Don't know what else to suggest.

Edit: maybe a bad earth, they can cause all sorts of random issues.

Edited by Ian91, 22 March 2017 - 12:57 PM.

[Dave_GSR1.8]

I think your comment 

 

"Have you checked the ecu hasn't burst a capacitor or 2?"

 

is a possible explanation (and so is a bad earth). I will remove the ECU over the weekend to have a look, and go from there.

 

Anyone got an old GSR ECU laying around that they are willing to sell (which is my next option to try and get to the bottom of this issue)?

[BYBY5L]

I got one ya can have for $50+ post if ya do need one
Will just need the part number as I have a few different ecu's

[Dave_GSR1.8]

I got one ya can have for $50+ post if ya do need one
Will just need the part number as I have a few different ecu's

 

Excellent! If the part number matches (MD187040) I'll take it!

 

Many thanks for that.

Attached Thumbnails

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Edited by Dave_GSR1.8, 25 March 2017 - 02:04 AM.

[Dave_GSR1.8]

Just as an FYI I had a look at the ECU board and could not see any obvious issues (to my untrained eye). It looks like the capacitors have been replaced at some point, maybe in 2007...

Apologies for the photo quality.

Attached Thumbnails

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Edited by Dave_GSR1.8, 25 March 2017 - 02:12 AM.

[leadfoot]

if the ecu was sent to ecm link for install ecm would have done the caps

[BYBY5L]

I'd be thinking the same as above, pm me if ya do want it though, just dust collecting anyway

[Dave_GSR1.8]

PM'd

[gee]

Hi, i got an evo 1 ecu 7701. the problem is, there is no fuel pump primp during turn ON switch..change another ecu able to start and running fine. Appreciate if someone can share or tell me what component inside ecu causing this problem. I already change the 3 capacitors but cant help.Thank you 

[Ian91]

Hi, i got an evo 1 ecu 7701. the problem is, there is no fuel pump primp during turn ON switch..change another ecu able to start and running fine. Appreciate if someone can share or tell me what component inside ecu causing this problem. I already change the 3 capacitors but cant help.Thank you

Did you test the mpfi relay is working?

[gee]

Yes Ian91...change new one..take out an ecu and install to other car, problem same.. borrowed friends ecu and car able to start