rusefi.com

Hey all, I m a college student that is restomoding his Peugeot 205 GTX, changing the original carburetor to EFI. I m running into a bit of a problem and I was hoping someone could help me solve it.
When I power on the ECU (microrusefi) and I connect my laptop to it, Tunerstudio shows that the voltage received by the ECU is very very low (5-9V) and very unstable, but my battery is at 13V aprox. The engine is off and the battery is on a charger. However, if I use my voltmeter directly on the ECUs PCB and I touch a point that says "12V" and "GND" on the PCB, the measurement is 13V. Also, this problem I think is messing with my TPS because it gets constantly out of range and is incredibly unstable
Any idea why the ECU is reading such a low voltage?
Thanks in advance

What connector pin are you using to supply MRE?
MRE measures Vbat using pin 1. But can be powered by pin 1 or pin 5. Please check this.

I m supply the ECU with 12V with a relay conected to the ignition key to pin 5 and with the main relay to pin 1. With a voltmeter I measure 13V on both pins on the back side of the ECU.

Cucuye wrote: ↑

Mon Mar 06, 2023 8:42 am

voltage very unstable

bad soldering during PCB fabrication?
bad connection somewhere?
bad connector?

When this picture was taken, Tunerstudio said the ECU was getting 7.6V
I bought the ECU directly form the online store preassembled.
Where do you suggest I search for the problem?

I see two separate issues

* wrong reading - this we can deal with later
* jumping reading - let's focus on jumping

please upload log https://github.com/rusefi/rusefi/wiki/HOWTO-upload-log

I have uploaded the tune and log. I calibrated the tps 2 min ago and I didn't touch it in the log.
It doesn't show in the log, but sometimes the tps value shoots up to past 100% and the Vbat increases at the same time a bit (1V)

Tunerstudio shows that the voltage received by the ECU is very very low (5-9V) and very unstable

AndreyB wrote: ↑

Mon Mar 06, 2023 10:49 am

* jumping reading - let's focus on jumping

This log does not show very unstable voltage. Please link a link with very unstable voltage since that sounds like the most important issue.

I have posted a new log. This time the voltage is higher ever though the battery voltage is still the same

Cucuye wrote: ↑

Mon Mar 06, 2023 6:22 pm

I have posted a new log. This time the voltage is higher ever though the battery voltage is still the same

Please provide exact log URL. I've attempted to located and there is only one log while it looks like two logs are expected.

The last upload failed. I have reuploaded it. In this log, the voltage is all over the place. I'm not touching anything and the TPS and MAP are uncontrolable but should be steady.
https://rusefi.com/online/view.php?log=1188

Cucuye wrote: ↑

Tue Mar 07, 2023 4:21 pm

https://rusefi.com/online/view.php?log=1188

Interesting! Your VBatt swings from 9 to 15v with a somewhat reasonable line, it's clearly not noise.

Can you please provide more pictures of the overall setup? Do you have small jumper wires to hook directly to male pins on MRE connectors? Do you have some other source of 12v or 15v or 19v?

I have all the connected cables in the crimped pins inserted in the connector. The ECU is supplied with 12V from the battery with pins 1 and 5.
I made this diagramm to create the wiring harness If I check the voltage as I showed in the picture in a previous post, in the last log the voltage was rock solid at 12.45V.
Also, the TPS voltage is constantly changing, but when I put the voltmeter directly on the pin of the ECU that receives the TPS signal,it remains constant at 4.05V.
Something very similar happens with the MAP.
It seems as all the voltage readings are wrong.

Please ignore MAP. Please ignore TPS. Please focus on VBAT.

Please post photos of your test setup.

malfunctioning voltage regulator? does it happen during cranking? bad battery? what software do you usually use to view .mlg files? megalogviewer is limited just to 500 values.

It seems as all the voltage readings are wrong.

AndreyB, why do you say ignore MAP and TPS. They are clearly coupled to VBAT.
Could be broken adc in the chip itself?

puff wrote: ↑

Thu Mar 09, 2023 12:24 pm

It seems as all the voltage readings are wrong.

AndreyB, why do you say ignore MAP and TPS. They are clearly coupled to VBAT.
Could be broken adc in the chip itself?

Because I have limited abilities and I was hoping for harness issues. A screenshot of good relevant log selection would help

puff wrote: ↑

Thu Mar 09, 2023 12:17 pm

malfunctioning voltage regulator? does it happen during cranking? bad battery?

The engine is stopped and I'm not cranking the engine. I'm checking the sernsors and actuators of my EFI system and found this issue when I connected the ECU.

Do you connect laptop to the MRE's internal USB connector or through main connector?
Do you have AC charger connected to your laptop? If yes - can you try without charger?
Please show us you MRE to car chassis/body connection. Please show us your battery to chassis connection.

My laptop is connected to the main connector. I have tried with and without charger. I have not changed the original battery to chassis setup and it worked perfectly. I have meassured the continuity of the ECU grown to the chassis and it shows a great connection. This is my connection to the wiring harness As you can see in this image, the Vbat is not the same as meassured with a multimeter directly on ECU board. Battery is at 13.29 and stable and Vbat is at 12 and unstable. In the next picture you can see that Vbat registered a change from 13 to 12V. In this picture you can see the difference between rawTPS and the TPS voltage measured directly at the pin.

Do not see where is GND connected to digital multimeter. I see not the "official" white latch pigtail and I know how tricky those harness connectors are.

Please divide and conquer, please simplify the testing apparatus:

In my opinion next step is to remove microRusEFI from bench, hook up only three wires: pins 1, 2 and 5 to some sort of bench power and see if VBatt swing would reproduce.

I have done exactly what you have showed me in the picture.
This battery is at 12.5V.
https://rusefi.com/online/view.php?log=1193
Watch the TPS meassurement. There is no TPS connected of course, just the 3 wires. I m using the internal USB to connect.

Almost a volt of swing, sounds like time to assume unit is physically damaged.

Please return unit to me, let me ship you a replacement.

Perfect, thank you very much.
What do I have to do next?