ECU woes and confusion!

Hi guys, hope this is in the right section.

Anyway, after a few days googling and coming across various existing threads on here which were very useful I have had to resort to registering here and begging for help.

The background is that a friend of mine has had a 2.5 PRV Turbo engine fitted into his Delorean, and I volunteered to take a look at getting it running for him and sorting out the electrical side of things. After an evening spent tracing wires and checking everything against wiring diagrams it didn't look like it was going to be too difficult, especially as he has the renault loom pretty much all intact. After checking every single pin on the ECU and verifying it was wired up correctly (with the exception of the fuel flow meter (which I am hoping it doesn't require to run) and the AirCon pins, we sorted the power to the fuel pump relay and the ignition feed to both relays also.

So, we powered up the ECU and the injector relay clicked, which sends current down the brown wire into pin 19 (IIRC) of the ECU, but I understand at this point that the fuel pump relay should also click to prime the fuel pump, which it does not. Whilst investigating this we found that there was 3V coming out of the negative injector wires on the ECU (pins 20+21 IIRC), this voltage dissapears if you remove the injector relay indicating that it is coming through pin 19 on the ECU, and sure enough when checked there is a short (200 ohms ish IIRC) between pins 19 and the 20/21 that provide the negative switching for the injectors.

I hope this makes some sense, I guess my questions are is this 3V to the negative side of the injectors normal? I can't imagine it being, but you never know. And should there be a resistance between pins 19 and 20/21? My multimeter only measures the resistance one way around so there must be a diode in there somewhere. Also, what might cause the ECU to not trigger the prime sequence for the fuel pump relay? There is live to the other side of the relay, and the relay works, it's just that the ECU doesn't do it's bit in earthing the pin that it should.

I suspect that there is a fault in the ECU, possibly caused by the people who fitted the engine trying to hotwire it anyway they could, but it's hard to be certain without any other parts to try/test.

Also, while I am at it, the small plug on the coil unit, two orange wires coming out if it, pin 2 is the trigger signal from the ECU, but pin one doesn't seem to have anything on it on any of the wiring diagrams, though there is a wire coming out of it on this loom. Anyone know what that is for?


Would be so grateful of any help or info, short of blindly buying another ECU we are out of options otherwise at the moment.

Tommy.

[stephendell]

Presumably before doing this testing you removed all of the plugs from all the injectors otherwise you will just get a short showing when testing with a multi meter while the injectors are closed.

.
Well actually that's a good point, as the ecu monitors the current loop, and if the injectors are not connected - none, it won't pull the relay in as a basic safety function / system integrity fault check.

The only signals you need to run the engine / ecu as a bare minimum and look-see test are:

Air inlet temp
Water temp
TDC sensor
MAP sensor
Injectors connected, and low impedance
Coil pack signal connection

idle pot nice to have, but can get away without it

Have you tested to see if you have sparks anyway, you should.

I would be tempted to shunt the relay down, and turn the key, see if you can get any life first, as you should be able to get it to fire up

Regards,
Martin

thanks for the write up Tom

yeah we have checked the injectors but our biggest issue is this 3v that is coming from the ECU and we are trying to figure out why.

The mechanics that had their hands on the car i suspect might have tried to fire it up and maybe naffed something in the ecu to cause this lack of fuel pump relay and mysterious 3v

I just wondered if anyone has heard of similar problems

Dan

also we do not have a spark

Thanks for the responses,

I have confirmed that the 3V is coming out of the ECU down the negative (switched) feed to the injectors, not coming from the fuel pump relay down to the positive, through the injectors and back out up to the ECU. You can actually remove the fuel pump relay and the 3V is still there.

I have considered manually triggering the fuel pump relay, but I struggle to see it improving things and I didn't want to risk causing any damage. Perhaps it's something to try next time I look at it.

It is true that we don't have a spark. I have not yet tested whether we have the 5V pulse from the ECU to the coil module when cranking, but I am not too concerned about that for now, it may well be the same fault causing both issues. If the ECU isn't priming the fuel pump then I don't expect it to send a signal to the coil module either.

If anyone happens to have a spare ECU kicking about, if they could check to see if there is any short between pin 19 and 20/21 that would be very useful.

Once again, any advice is much appreciated.

.

the ECU code is S100802103 B, Renix

This evening we have disconnected all the injectors and also the idle air control valve as there was also voltage leaking through that.

It seems now we have 3.6 volts coming out of pins 20 and 21 on the ECU, and 2.57 volts coming out of pins 23 and 24 that go to the idle air control valve.

We also fitted a jumper wire across the fuel relay, obviously this stuck 12v down everything that is attached to the white wire from it, but no change in things afterwards.

At some points we have also heard the idle air control valve making a buzzing noise, but we can't get it to do it any more.

This is driving us a bit nuts now, any help appreciated as always!

Small update...

It seems that with the jumper wire instead of the fuel pump relay, it obviously provides 12v to the centre pin on the idle air control valve and when you power the ECU up the idle air control valve will buzz for a few seconds and then stop, almost as if it is moving to a default position or something.

.

[BIG_MVS]

I'd like to meet the dodgy geezer you bought this lump and ecu from Dan.

Welcome by the way, glad you made it in the end!

I did have a problem similar to this once but I'm pretty sure the injection relays didn't click and it was cured by replacing the ecu (Faulksie I sent the ecu to you if you remember not sure if you ever fixed it?).

Put the other pic up Dan of the back of the engine for other peeps to look at.

[BIG_MVS]

Oh and lets see some pics of your Time Machine in particular pics for us PRV pervs of said lump in situe!

ha ive only just remembered your user name on here, my memory is useless.

We were pulling our hair out last night and decided we have gone as far as we can without starting to swap everything, i think our next option is to get our ECU plugged in to an already working car so at least we know then for sure if it is an ECU issue.

MFaulks, that would be a great help.


I would take some pictures of the car but it could not be in a worse state to look at now! Engine has bits pulled off and bits of pipework not yet mounted, after weekend it should look alot nicer.

Best picture i have is Tommo at the beginning of the "help dan out" stage, to quote him "its all going well actually"

[BIG_MVS]

Where are you again Dan, Huddersfield is it? Just trying to think who is in your area with a Turbo that would be willing to plug your ecu in. A trip to Derby might be your best bet...

It was working originally as I tested it in the Grey GTA we had at the time.