VEMS Community Forum
Technical => Wiring & Sensors => Topic started by: gunni on December 05, 2014, 04:45:52 pm
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So my fuel pump is running when the ecu is powered off, the main relay also stays on,
I´m using a 3.8 board, when I turn the ECU on the pump operates as per the software, i.e primes and then stops. serial number is 9680.
Not sure if it´s related.
At the same time pulsewidth for lambda 1.0 at idle has gone from 1.37ms to 1.42ms , no change in fuel pressure, not sure if that relates to this issue.
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So my fuel pump is running when the ecu is powered off, the main relay also stays on,
I´m using a 3.8 board, when I turn the ECU on the pump operates as per the software, i.e primes and then stops. serial number is 9680.
Not sure if it´s related.
At the same time pulsewidth for lambda 1.0 at idle has gone from 1.37ms to 1.42ms , no change in fuel pressure, not sure if that relates to this issue.
it's the protection diodes inside ecu :) if you turn off ignition and fuel pump relay is still getting +12 from somewhere it will trigger from these diodes, if you rewire relay that it wont have +12 with ignition off no problem then
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It's unwanted as i am getting 12v from a different supply then the 12v for the ecu, and I'm using standard wiring so it's not an option at all to have this happen.
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"I'm using standard wiring" you mean E36 Pin15. You did not invert the logic? so the pump relay should be on when E36Pin15 (not wired) is grounded (0.001V)? This is what I get on the bench, also pin 15 gives a floating 0V (0.08-9) when not running.
I guess that this relay stays on because of a small be sufficient current through the solenoid. I would try to reduce this leak using a resistance in line.
Of course the value of this leak and the sensibility of the relay are dependable
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No standard engine wiring, i.e oem loom.
I have and want to use the p259 outputs for relays, and it seems without proection diodes is the only way.
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I noticed that too in summer when first installed v3.8 board and I just removed the diode on the fuel pump output, left the others in place.
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In case someone finds this thread with a search:
http://www.vemssupport.com/forum/index.php/topic,2565.msg24330.html#msg24330 (http://www.vemssupport.com/forum/index.php/topic,2565.msg24330.html#msg24330)
either remove the protection diodes (but there is a reason they are there).
Or make sure your relays are not powered when the ecu is not powered, thats it, changing 1 wire from vbat+ to switched vbat seems te easiest (and recommended) route.
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In case someone finds this thread with a search:
http://www.vemssupport.com/forum/index.php/topic,2565.msg24330.html#msg24330 (http://www.vemssupport.com/forum/index.php/topic,2565.msg24330.html#msg24330)
either remove the protection diodes (but there is a reason they are there).
Or make sure your relays are not powered when the ecu is not powered, thats it, changing 1 wire from vbat+ to switched vbat seems te easiest (and recommended) route.
only few ecus were affected by this, current ones don't have this problem :)
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Hi,
seems V3.8 was changed without changing the version numbering [wow!, I was surprised!]. In beginning protection diodes was routed to EC36-25 now same diodes go to EC36-23 (flyback wire) - more reasonable solution. So it is wise to wire up relays with coil connected to this wire.
Gints
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Having this problem too, even if new ecu.
With key to OFF, Main relay and Fuel Pump relay are still getting a 4V in the relays' coils, making the Fuel Pump to start.
And they are getting the 4V from the Flyback wire, as removing it from ecu would shut the relays off.
What about connecting the Flyback to the Fuel Pump Positive AFTER the Fuel Pump relay?
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I've made this P259 amplifier http://www.vemssupport.com/forum/index.php?topic=2863.0
And it's working fine on a 3.8B board.
A small note is that I had to insert a 18V zener in front og the FET protection diodes, to ensure the power from the relays didn't run backward and powered the 12V ECU mains. But except from that little "bug" did it solve all my P259 issues.
I have plenty of raw boards, FOC for who ever need one.
Mads
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I've made this P259 amplifier http://www.vemssupport.com/forum/index.php?topic=2863.0
And it's working fine on a 3.8B board.
A small note is that I had to insert a 18V zener in front og the FET protection diodes, to ensure the power from the relays didn't run backward and powered the 12V ECU mains. But except from that little "bug" did it solve all my P259 issues.
I have plenty of raw boards, FOC for who ever need one.
Mads
Thanks, very interesting...
Anyway, any other way to fix it?
Would it be ok to connect the Injector Flyback on a switched 12v?
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I think your magic trick will be to insert a 18V zener diode. They work in a way, that current will flow in one direction, and no current the other way (like a normal diode works) but when the reverse voltage exceed the zener level (eg. 18V) can current flow in both directions.
In your case, where a protection diode potentially make current flow from a relay power back toward the FET, throu a protection diode, and back to a mains somewhere, can a zener allow the spike protection, but stop the reverse current a normal voltages (12-14v).
It's a common issue when the design controls the electornics on both the positive and negative side. Even I thougt that I was carefull when I designed the complete loom for my TVR, did I end up with the nice feature that turning on the long beam, with the key out... made the ECU power up..... a couple of hours and a few diodes later, did it work as expected :-)
Injector flyback, that is powered from the injector +12V should normally not have power without the ECU is on power, Either by using the same relay for both injector + ignition + ecu power, or by powering the injector and ignition with the fuel pump relay
Br Mads
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What about connecting a resistance to drop this 4V Under the threshold voltage of the relay? Or else you could upper the thereshold with a diode.
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What about connecting a resistance to drop this 4V Under the threshold voltage of the relay? Or else you could upper the thereshold with a diode.
why just not make relay supply die when ignition is off? :)
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yes, it dépends on how things can be wired
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What about connecting a resistance to drop this 4V Under the threshold voltage of the relay? Or else you could upper the thereshold with a diode.
why just not make relay supply die when ignition is off? :)
I already tried to install a 2nd relay (activated by the Main Relay) on the Fuel Pump relay Positive, but even the 2nd one just gets activated by the Flyback!
And if I move the 2nd relay activation wire from the Main Relay to another switched source, then the engine will not start because during cranking the relay will get off.
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What about connecting a resistance to drop this 4V Under the threshold voltage of the relay? Or else you could upper the thereshold with a diode.
why just not make relay supply die when ignition is off? :)
This is what I did on my 3.6 board since having problems of this nature with my (um...fried) 3.3 board. Nothing in the car gets power until the main OEM power bus relay is switched on by the key. So, there are cascading relays in order to get power: Turn key > main OEM power bus relay ON > VEMS unit power relay ON > fuel pump relay ON. Fuel pump relay is in the boot with its fuse and not on the main (aftermarket) fuse panel, so the pump draws straight from close proximity of the battery with its own heavy cable and chassis ground when the relay is ON and only when all the other stuff is on. So, if I blow the 1 amp VEMS fuse, fuel pump turns off.
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I think your magic trick will be to insert a 18V zener diode.
And it was! It worked wonderfully, thanks!!!
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Bringing this back from the dead - I have the same problem. Where was the zener diode installed to fix this? Ahead of the fused 12v to VEMS? or elsewhere?
thanks!
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Bringing this back from the dead - I have the same problem. Where was the zener diode installed to fix this? Ahead of the fused 12v to VEMS? or elsewhere?
thanks!
I think your magic trick will be to insert a 18V zener diode. They work in a way, that current will flow in one direction, and no current the other way (like a normal diode works) but when the reverse voltage exceed the zener level (eg. 18V) can current flow in both directions.
In your case, where a protection diode potentially make current flow from a relay power back toward the FET, throu a protection diode, and back to a mains somewhere, can a zener allow the spike protection, but stop the reverse current a normal voltages (12-14v).
It's a common issue when the design controls the electornics on both the positive and negative side. Even I thougt that I was carefull when I designed the complete loom for my TVR, did I end up with the nice feature that turning on the long beam, with the key out... made the ECU power up..... a couple of hours and a few diodes later, did it work as expected :-)
Injector flyback, that is powered from the injector +12V should normally not have power without the ECU is on power, Either by using the same relay for both injector + ignition + ecu power, or by powering the injector and ignition with the fuel pump relay
Br Mads
In the injectors Flyback wire
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Thanks,
To clarify, where exactly in the Flyback Wire?
(http://castledb.me/images/2019/09/15/0C3F749D-F2B8-4239-878E-25DF0D370ADA.md.jpg) (http://castledb.me/image/NCPb)
A, B, C or D?
And if A, which direction should the power flow go? Toward or From the ECU?
Thanks again,
Ben
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A, and likely from the ECU, after all, the purpose of flyback is to drain inductive power spikes from outputs, using diodes to isolate FET outputs from 12v, at the same time allowing voltage spikes from injectors to flow to cars electric system.