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Solenoids keeping ECU powered up


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Link G4+ Storm Wire In ECU

I'm having a problem where if I have either the Boost Control Solenoid or Idle Speed Solenoid plugged in the ECU will not power down fully. I have attached the wiring diagram for my setup. Boost Solenoid is connected to a switched 12V and AUX 8 at the ECU, ISC is connected to the same switched 12V and AUX 7.

Solenoid unplugged, Ignition On - AUX Ouput shows 10.8V

Solenoid plugged, Ignition off - AUX Output shows 8V dropping to 3V

post-2324-143621571115_thumb.jpg

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Hi Eoin,

As long as the 12 volt supply to the coil of the relay is ignition switched all should be good.

You may need to use a diode protected relay, but I have never had to use one.

The reason for the back feeding is when the ECU is powered down the output drivers etc are all switched low when off.

So if the coil of the relay has constant 12 volts with the aux output switched to ground when powered down the relay stays active.

Are you using a ECU HOLD POWER RELAY at all.

Regards

Dave.

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Hi Dave,

Thanks for the reply.

No ECU HOLD RELAY, only wired as the diagram I attached above.

I took the covers off the relays so I could close the switch without needing the ignition powered on. With the Boost or ISC Solenoid plugged in, the "+14V In" of the ECU and therefore the +VE side of the relay coil sees +8V dropping to about +3V. This keeps the switch closed and everything powered on.

I have my AEM UEGO Wideband powered from the "+14V In" also so I can see this is powered on too.

I have attached another diagram to explain what I mean.

Thanks for your help Dave!

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Hi Eoin,

Your diagram looks correct, this does not make sense to me, other than something else is on the circuit somewhere and has a hot feed (+ve feed ) influencing the circuit.

The voltage being 8v, dropping to 3 v does not make sense, this indicates an initial load of some description and the back fed power drains to 3 volts as that circuit cant carry the amperage to power it up correctly.

Have you swapped out the relay to make sure the point contacts haven't arched and have a pit with slight contact between both sides of the points.

I would disconnect (physically) Aux 8 and see if the issue is still there, then one at a time disconnect your Aux O/P's and see if you can isolate the influencing circuit.

There has to be another voltage back feeding somewhere, is this a standalone ECU or PLUG IN UNIT.

With the boost solenoid and the ISC disconnected does everything shut off.

Regards

Dave.

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Hi Dave,

Yes tried a known good relay and it was the same issue.

This is a standalone ECU with a custom loom I made myself.

With the Boost and ISC solenoids unplugged the ECU behaves normally, with either connected it won't power down.

I just disconnected every plug on the loom and left only the ISC connected. The ECU would not power down until I unplugged the ISC. The same with only the Boost solenoid connected.

I've left all unused wires on the loom running the full length of the loom but covered the ends in heat shrink, is it possible the ECU could be backfeeding itself with its +8V or +5V outputs?

I'm really stumped on this one!

Happy New Year to you by the way!

Cheers,

Eoin

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Hi Eoin,

there is very little chance of the power back feeding through the unused loom unless the 8v supply for the trigger PIN A6 is shorting somehow to another wire within the loom.

With the ignition turned on what power reading do you get at PIN A5 and B5 depending on the ECU you are using.

With everything connected and then with the ISC and the Boost solenoid disconnected.

Does the removal of the WIDE BAND make any difference.

Also try removing the loom connector/connector from the ECU probe every pin in the loom connector and check for any sources of power, you should only have power on A5 and B5 depending on the ECU and also any digital input used for ignition switched input, there should be no other power on any other pins unless you have a HIGH switched Digital Input that is active.

Have you tried removing the coil positive feed to your ISC and boost solenoid relay instead of getting power from the main ignition relay, have the coil positive for the ISC and Boost solenoid relay come from a different ignition switched source or just physically connect and disconnect and see if the ECU shuts down.

I have never seen a LINK or ViPEC ECU have this problem other than a back feed issue.

Normally from a device other than the obvious hence for checking all the pins for power and making sure each circuit within reason has it's own supply and relay. I use 5 pin relays and pair off devices from each relay, that way issues are contained to that circuit only.

I also make sure I have every relay controlled by the ignition switch via a BUS BAR with a fuse.

I do not have multiple relays being switched from other relays,

See how you go with the other tests.

Sorry for the delayed response and thanks for the New Year wishes.

Regards

Dave.

 

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Hi Dave,

I replied a few days ago on my phone but it turns out it didn't show here.

The issue is fixed. I ran another Ignition Switched +VE directly to the problem Relay coil and it is now behaving normally. It appears the Relays just don't like to have the coil +VE come from another Relay switch.

For reference, removing the Wideband made no difference and I did take the voltage readings at the pins with the Relay manually switched on if anyone would like them put up here.

Thanks a million for your help Dave, especially over the festive period!

Cheers,

Eoin

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I can see where the problem is as it took me ages to find the reason when my car did the same.

While you switch the ignition switch off, the power flows through the boost solenoid into the AUX8 on the ecu,

back out of the +14V in terminal of the ecu and backwards into the ignition relay.

As you have turned off the power to the ignition relay, what was the power terminal is now earth and power flows backwards through the relay windings keeping the relay on.

 

One solution is fit a diode inline with the power to the ECU, 

but that can cause low voltage issues under cranking,

or change the feed to the ignition relay so it is switched from the same feed that switches the main relay, not the output from it..

If that is a diagram supplied by link, then they have it wrong as that does not work.

 

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Hi Matt,

If you look at the schematic the power that switches the ignition / accessory relay on is supplied via the Main Relay.

The diagram is CORRECT, the Ignition / accessory relay coil winding is grounded and has no connection to the ECU .

The accessory has connection to the ECU and therefore back feeding can occur if the Relay coil positive is hot fed permanently.

The only way that the issue could happen as you explained it is if you used a  NC (normally closed) relay or a 5 pin change over relay and were using pin 87a N/C contact, when powered down which also means that accessory would not work when the relay is energised, a common fault I see a lot of.

The Relay contacts are N/O normally open and if negative was connected straight to the positive feed through pin 87 to pin 30 the fuse would blow, if the contacts were closed.

Have another look at the diagram.

I just want to make you aware that the diagram is correct.

As a side note I do use 5 pin relays dual pole dual pin 87 , not change over relays with pin 87 and 87a to power multiple relays without issues, however I try to use a relay per device if possible.

Just my personal decision.

Regards

Dave.

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Hi Matt,

Aux 8 is a negative switched output, these outputs switch to ground when the ECU is powered down as you discovered.

So in the LINK schematic it shows the positive for the device what ever it may be , boost solenoid, fan etc feed power from what would normally deemed as pin 87 on the relay, the power feed comes normally from relay pin 30.

This power can only be supplied to pin 87 when the coil of the relay is energised.

In the diagram the AUX relay is controlled via the MAIN RELAY pin 87 which is only connected to the 12 volt source when the coil is energised once again.

If the coil positive feed is hot fed and not ignition switched then what you are thinking is very true.

However these diagrams are correct as the coils are grounded permanently and the positive side of the relay coils are switched via the Main Relay or the ignition switch.

I have seen many circumstances where people have simply looped pin 30 to the coil as the positive feed, this will definitely make the coil stay energised when the ECU is powered down (or try to) as that relay has a permanent hot feed to the coil of that relay.

And in the case of the boost solenoid, AUX 8 will switch to ground and the if done this way, the hot feed to the coil of the relay will keep that relay active.

Plus any AUX output is controlled via a Transistor, these are in the circuit indirectly tied to ground,

Regards

Dave.

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