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Help with building your Speeduino, installing it, getting it to run etc.
By Sagal89
Hello guys, i need your help as i don't have more ideas what to check...

I will explain all story to get context. In 2019 (First firmware used 1903) i build my own clio williams with speeduino and don't have major issues so i'm runing it and very happy with it.
Now i'm installing a speeduino on a clio williams (same year '91 like mine) so i thought i won't have any major problem, but i have 2 problems i can't solve.

First issue - Fuel pump is not stopping after the delay with engine stopped and key on. I have checked several things about this issue. With arduino alone (without speeduino shield assembled), using tester and giving 5v via USB i see PIN7 (boost) that gives 5v and after the delay it goes down to 0v, so this is OK.
Checked also powering with 12v with speeduino shield assembled and the same, works fine.
The problem is when giving the 12v source assembled on the car, giving from key on. So the difference is that boost output is grounding the FP relay. What i see then is that arduino pin 7 doesn't go down to 0V, it keeps 5v ever. So this i what i can't understand.
I was trying one long week checking all and finally i decided to try my speeduino board. So what a surprise, when installed my ecu (my speeduino shield and arduino, but using friends .msq and also IDC cables, because we have minnor difference because i run wasted spark and my friend runs oem single coil and distributor) fuel pump works properly, stopping after the delay.
We thought that assembled speeduino we bought was failing and decided to buy a component kit to make personally a new one...
New surprise, with the new board and also new arduino i'm having the same issue than before!!!!!!! Fuel pump is not stopping after delay with engine off.....
Want to cry :\


2ond issue (can be related?) - With first board we haven't readings of o2 sensor (using my own spartan2 controller with a FAE 4.9 lambda sensor). So when tried my board, 02 sensor also doesn't work properly, having strange readings for a while but major time reading 10 AFR (so 0 volts on 02 output pin). Now with this new speeduino also bought a TINYWB from DIY-EFI and also the same, only reading 10AFR all the time, except for a while it had steady value of 15AFR but never seen again after disconecting power. Last chance about that is to try my 02 sensor that came with the spartan 2 kit (it hasn't reference marked to buy another similar, only has marked 14point7 but not a reference). Do you think i need a more specific sensor than a 4.9, because FAE has crossed reference with BOSCH 4.9.
By now, i'm thinking problem should be related because i don't think lambda sensor to be a problem.

Thank you very much
Last edited by Sagal89 on Fri Jan 22, 2021 10:40 pm, edited 3 times in total.
User avatar
By Chris Wolfson
So there is one more option to check: Take the problematic Speeduino(s) and install them in your car. If they work, the installation in your friends car is the problem. Which would put you in the situation to find the fault from what you build there...

My first check would be the grounding. This is a constant problem with old cars and installers not taking ground connections serious. They do not understand the concept that the return wire is just as important as the feeding one.
Has been a major problem in century´s of home made car stereo installation, now it is the same same with the ECU DIYS.

Run 3 carefully made auxiliary ground wires from Batt negative to chassis, to engine and engine to chassis. I do not like how the battery terminal looks in your picture. Check/fix that on both sides. Check the alternator charging and battery voltage for perfect condition. Have a charger at the battery connected permanently during installation / fault finding.
If the car had any problems before the new install, chances are high they will remain.

Next is the positive feed: Do not run anything directly from the ignition lock. Use a fused new wire connected to the battery, do not use any of the stock connectors in the car. Fuse it very close to the battery, less than 10cm from the terminal. 2.5mm wire is fine and 20A fuse. Run it to the main relay, that is switched by the ignition lock near the ECU.

Anything for Speeduino is connected to this positive feed directly or by additional relays. ECU, injectors, fuel pump, ignition, lambda controller and any other ECU gadget. Use a fuse for any of them, so you can disable single items separately and in case always know what part blew the fuse.

Fuel pump: Run a new wire from the fuel pump relay directly to the pump. Replace its ground wire. Often there are problems with hidden installations, connected to the cars stock wire. Shock sensor for example, so you may only think you feed the pump directly.
Stock fuel pump wires are often quite small and age, the new wire will in many cases increase the fuel flow, making a bigger fuel pump obsolete.

This leads to the lambda sensor. Use a relay that switches on with ignition. Makes your live much easier during set up, as you do not cut it off with the fuel pump timer.

If possible, check each circuit / item alone before connecting it to the final installation. Wiring anything up and turning the key in most cases will not work if you do not do that for a living as a pro. Pro´s will not do that, because it get´s very expensive when the whole sh**t burns out.
By connecting one thing after another to the ECU and checking the response you may need one hour more during installation, but will save you days or even weeks with fault searching.

Check the alternator´s output on a an oscilloscope, sometimes defects with it go unnoticed a long time, inducing AC in the system. Some stock installations don´t care for such a fault! So the car may have run with it.

Hope that helps. Good luck!
By Sagal89
Hi chris, these are very good advices. But what i can't understand is why with my ecu doesn't fail. 02 is not working so i will have to check with new wires bcause maybe my ecu only solves part of the problem.
many thanks for your comment
User avatar
By Chris Wolfson
So that solves one part of the puzzle if the shield got a problem. I´m not so far in the circuit of the Speeduino to guess what might be defective to get such a fault of a fuel pump output switching permanently on.
What I know of and have experienced, are that fuel pump relays can easily be wired to stay on after being powered once. A quite common fault when you use parts of the old wires in the car. Schematics often don´t show all connections of your specific loom. Manufacturers like to save a few feet of wire and combine long runs if possible.

Even as the idea of using the old loom looks good on first sight, it may give all kinds of problems. I prefer to build them from scratch, as the modifications and fault finding my be even more work.
Taking the old loom apart and then reassembling it works well, too.
There is a good chance you break something on the electronics if you made a mistake in the loom / relays stuff.

If you put a diode between shield output and relays you can protect it from accidental voltage running back into the output. Did you try this? You may be lucky and still be able to use the defective Speeduino if you use another output. Off course, only if you do not repeat the mistake.
Your working Speeduino max have a safety part build in the others don´t have and be more tolerant to abuse, did you consider this option?
Basically with any connection you make, you can ruin the Speeduino. Hundreds of combinations are false, only one way to do it is right. One mistake and the whole board may be toast. This is a very bad situation for most DIYS car guys, which have learned to do mechanical things by try and error. Imagine to change a complete engine on a car and not even once drop a tool, bolt, washer or nut. That is your situation seen electronically...

For you wide band O2, check it out of the car. There are many Chinese LSU copies and compatible products around that work only for a few minutes. 14.7 is a very good source for real Bosch. I know of no Chinese quality sensor. The controller has to be for the right LSU, 4.2 and 4.9 need different controller, at least a changed programming!
By Sagal89
Chris, i told my ecu works on friends loom so i was sure it wasn't any connection error. your comment "That is your situation seen electronically.." its not apropiate and offensive
don't care

anyways, the problem was a defective new vrconditioner. i never thought that theorically this can cause this problem. But it is.

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