V88 ground issue

[DaneilC]

Hello!

I bought a standalone v88 in secondhand. I used v44 on a engine before and liked it alot, so why not again.

But not to the issue, a for me very strange one!

I am using some aux ports for fuelpump, enginefan etc, it works exellent when the ignition is on. (lowside/negative)

But when i turn the key off and cut the power to the ems everyting still is on, the fan the pums.. the injectors going crazy.

I have checked the wiring 3 times and there is no error.

When i only have the ground cable conected and nothing else and measures betwen 12+ and the aux ports they are "ground".

When i try to start the car i get rpm and ign, but the injectors will not open.

Some background info,

Engine; Bmw m50

IGN; VAG 115 COP Directfire

FUEL; 990cc low ohm Peak and hold

Is the ems "burned"? Or what have ia done wrong?

[Simon]

You have a back feed issue.

Avoiding Auxiliary Output Back-feeding

A large number of technical inquiries are received regarding problems due to incorrect wiring of auxiliary outputs. Incorrect wiring of solenoids and relays to auxiliary outputs can result in the following symptoms:

· ECU not powering down when the key is turned off.

· Accessories such as engine fans coming on when the key is turned off.

· Repeated clicking of relays when the key is turned off (machine gun sound!).

· ECU draining the battery over a few days.

The root cause of these problems is the wiring of hot fed (direct from the battery positive terminal) or ACC fed (key in accessory position) solenoids or relays to ECU auxiliary outputs.

Each auxiliary output basically consists of a low side driver and flywheeling diode. A low side driver is a power transistor that can switch a load to ground. Flywheeling diodes are required for the driving of fast switching devices such as ISC solenoids and VVT solenoids. Flywheeling diodes are also essential for reducing radio interference noise.

Unfortunately, the placement of flywheeling diodes means that if power is applied to auxiliary outputs through a solenoid or relay when the ECU is powered down current will flow through the flywheeling diode causing the ECU to power back up.

As solenoids have some resistance, the current that flows back into the ECU (back feeds) is not usually enough to power the ECU up properly resulting in the ECU powering up and down continuously. This causes unusual behavior by the offending solenoid and possibly other solenoids as its current is switched on and off.

This does not apply to Auxiliary Ignition or Auxiliary Injection outputs as they do not have flywheeling diodes fitted. For that reason solenoids that require flywheeling can not be wired to these drives without an external flywheeling diode fitted. This will only usually apply to ISC solenoids.

This problem will not occur on loads wired to be High Side driven.

Engine fan relays are often fed from the ACC circuit. These should be wired to non flywheeled outputs such as Ignition or Injection channels. Alternatively their power supply should be changed to one that is disconnected when the ignition switch is turned off.

[DaneilC]

Okey so you still think its my wiring, i will continue tonight and cut one wire a time until it stops, just to find the problem.

I have problem with the injectors, they wont open at all.

Not even on injectortest.. just a smal "ticking noice" So i maybe have a problem there.

[DaneilC]

The problem remains without any wires, i have cut all wires so nothing is connected. It´s the same on all AUX ports.

As long as the ground cable from the ems is connected in the body of the car the box will ground the relay.

[Simon]

This is correct, But at key off the Relay should not have power to it and so should then not switch on.

For the injector issue check your peak and hold currents. And that you have no ballast resistors fitted.

If the current settings are too low or ballastes are fitted you will get no injection.

[DaneilC]

Thanks for the help, of some reason bmw has the relay connected as "hot at all times" so there is always power from the battery.

Now i connected it to ign power insted and it works exellent.

The injector problem seems to be jammed injectors, one of them works.. they havent been used for a year and been laying in the garage. Doesent seem so unusal when using e85 fuel.