No RPM? Relay drivers not working? Perhaps you have a dead P259

[rob@vems.co.uk]

A dead P259 is caused by the grounding rules not being followed, or misunderstood;)

To get testing again you need to remove the P259, you can cut pin 21 (4th pin from the top on the right) and test the crank trigger, I use some very small sharp side cutters.

It is easy to bridge the cut with solder if the P259 is not dead. But to replace it you will need to remove the chip in its entirety:

Cutting the pins then de-soldering the bits of the pins that are remaining avoids possible damage to the PCB.

[Sprocket]

Interesting Rob.

I did the exact oposite to the grounding rules and now the relay output chip has smoked, however, Its still picking up an rpm signal. Would this loss of rpm signal depend on VR or Hall, as the hall needs a 5v supply and pull up, where as the VR generates its own voltage?

[laine_16v]

Is there someone in the UK that can do this?

I think mine has blown as im not getting an RPM reading.

Also you are saying you can cut pin 4 and it will make it work again, but cutting this pin, what will it disable, i.e. if you cut it and it started working again, why would you have to then buy another chip?

[Bat]

Hi,
You cut the pin off the chip to allow the RPM signal to work again.
However the chip, which is used to switch the fuel pump & cooling fan relays aswell as driving the tacho, will not work so therefore will need replacing. 
Does the fuel pump run when you switch the ignition on? Assuming it is switched on by the VEMs ECU
Cheers,
Gavin

[laine_16v]

I see,

Well thats good i suppose becuase.... the fuel pump on my car is directly wired to an ignition live at the moment, and the fan uses the standard care relay setup, so the VEMS is controlling neither. So i may well snip that pin and just run it like that

[PeepPaadam]

Yes, but you should investigate the reason why did the P259 chip blew in first place!

Where did you connect the ground wires? In case you didn't read the manual, these have to be connected to engine block or head and not to chassis, battery etc. This is the most common reason why P259 chips blow (2nd most common seems to be using rude battery chargers when VEMS is connected).

[laine_16v]

I have a prebuilt V3 Harness, that has just 1 earting lead on it, and the ECU is in the passenger footwell of the car, i earthed it too a place in the footwell on the chassis (it seems a very good place), had no idea you couldnt do that though? i dont have any instriuctions as i bought it all 2nd hand.

[Bat]

Hi,
Manual....
http://www.vems.hu/wiki/index.php?page=MembersPage%2FPhatBob%2FUserGuide
Cheers,
Gavin

[rob@vems.co.uk]

If you're using a VEMS harness, and the thing about the reading occasionally coming back  ( http://195.159.109.134/vemsuk/forum/index.php/topic,802.msg8306 ) then I really doubt that you've got a problem with the P259 as the ground connections are text book - but that doesn't always mean that you have a good connection to the car's chassis

It is bloody odd though, thats for sure - what sort of voltages are being shown when you're cranking - strange things can happen when a battery is put in the boot for example...

Have we tried changing the connection on the sensor's plug?  Swapping the wires at the sensor end NOT at the VEMS end.

[laine_16v]

Lol your right its REALLY odd.

I was playing around with it and a mate came over and gave me a hand, ive been testing it with the injectors and coi dissconected, but we put them in anyway, sometimes it would fire every now and then, and it probably saw 400rpm or so once on the reading before dieing.

ANd then would shoot off the aboslute loudest bang you've ever heard after youve stopped cranking out the exhaust lol.

Ive unravveled the prebuilt loom a bit and jiggled the earths around while cranking, does nothing.

OTher sensors read fine, the coolant and air temp are both reading 18 degrees C today, so suggests a good earth for them to be reporting properly?

Um i have to jump my car off another car to crank as my battery is dead, but it shows like 12v while cranking, and the other car running, its all normal and fine.

BAttery is in the normal place. Is it possible because im jumping off another car its screwing with the crank signal?

The connections everywhere are solid and read a consist resistance when moved around and jiggled. Help me before i shoot myself or lob this ECU in tbe bin and buy an emerald.

[rob@vems.co.uk]

Starting with a bad battery is going to give problems but jump starting it shouldn't effect the ECU's ability to read the RPM.  As it came from a running car, and known good loom then I'm thinking that there has to be something different on the car.  You've tried your ecu in another car, what happens if they try their ECU in yours?

I'm a bit concerned when you said that you'd jiggled the earths around - you've not disconnected them have you?  It sounds like you've moved them around to see if theres a dry-joint in there somewhere.

Have you definately tried swapping the crank sensor wires?

I'd advise against shooting yourself or binning the ECU, if you were to spend money on an Emerald then you might be no further forward if theres something up with the crank sensor setup.

Also connecting the injectors isnt a good idea, if you've got any cranking signal at all you'll get injector pulses and that will put fuel into the engine - without a spark you're going to get fuel all over the place and possibly contaminate the oil - meaning you wipe out your crank bearings when the engine finally does run up.

[Sprocket]

What about the possability of an inverted VR signal?

Funny story. Matty over on EFi Minis managed to get his engine started, all be it very badly. I went to help tune it, but couldnt get the engine started, even though it had been running earlier in the week. We spent hours looking at all the connections and the trigger set up, but still there was no rpm signal. I suggested we try and swap the wires over on the sensor even though none of the wiring had been changed. Turn of the key and the engine spluttered to life with a strong rpm signal.

[laine_16v]

I have not tried their ECU in my car, but i shall do that over the next couple of days.

I did jiggle the earths around but didnt get a lot of joy, i didnt cut or move any of the looms joints i kept them intact.

Yeah have disconnected coil and crank for the time being.

Swapping crank sensor wires is the only thing ive not done, but i will do that tonight so i can tick off another thing ive tried.

[laine_16v]

OK guys, i got home straight away and changed the polarity of the wiring on the sensor, and its made it a lot better i get quite a few more RPM readings now and it tried to fire, but it still wont quite catch.

All i did was solder the connections over and this happened...

http://www.youtube.com/watch?v=JUdXt4w1fhM&feature=channel_page

So then i thought hmmm what if i resolder the connections back to how they were and again it was just like the video above so it seems it doesnt matter what way the sensor is.

But ive localised the problem to a small bit of loom for the crank sensor.

The backfire at the end only happens on cylinder 1, for some reason as soon as the ignition is turned on the VEMS hold the injector on CONSTANTLY in cylinder 1? any ideas?

[Sprocket]

Does this car have the exact same injectors fitted?