injector's cut off - problem

[rs200]

hello
my good friend have problem with his urquattro with 20vt aan engine.
car run fine until in one moment they cut off injectors.
they are in middle of project. and everithing if fine acept this.
what can cause this problem.
tnx
Igor

[UrS4boy]

Not enough info to solve the puzzle. If it is an AAN ECU, can you pull the codes? Are they running a blade fuse or thermal fuse in the brown injector fuse holder? Is the fuel pump relay working properly? Is the G40 working properly?

AAN injector wiring:

http://forums.quattroworld.com/s4s6/msgs/90802.phtml

Above ECU Fuse Callout:

http://forums.quattroworld.com/s4s6/msgs/137287.phtml

[rs200]

I also said to him , that is very hard to explain , and imagine the problem what he have.
there is no fault codes he said. car run perfect and in one moment cut. he said it not matter if car is at 0.2 , 0.5 or 1 bar.
for example, if he drive at 0.3bar for a 5 second-cut. if they drive at 0.8bar for few second- cut . but if he drive 1. gear full gas, second full gas, nothing happend.
3. gear full pedal, cut.
the problem is based on some boost pressure for limited time (around 3-5 second). it is very hard to know what it is because they use half of ur quattro engine loom , half AAN.
only God know what they done.

[prj]

Electrical problem, probably fuel pump switching off.
I bet it's losing trigger sync because the trigger wires are not shielded and so on.

Pull fault codes.

[rs200]

they mesured fuel pump -always 3.5 bar at rail, mesured voltage on it, and they are always on 12v.
they find out that injectors loosing +12v when that cut came on.

[rs200]

there is NO fault codes.. nothing..

[prj]

If injectors lose 12V it has nothing to do with ECU.
ECU does not provide 12V to injectors, it only controls the ground.

Start looking in the wiring.

[UrS4boy]

If injectors lose 12V it has nothing to do with ECU.
ECU does not provide 12V to injectors, it only controls the ground. Start looking in the wiring.

Yes and no. The ECU does provide some power to the injectors with the ignition key to "ON" via the holding relay and pin T55/37. Paul N. and I went around (and around) on that one. http://forums.quattroworld.com/s4s6/msgs/102009.phtml

Once the starter has produced enough spin to get more than 13 RPM from the G28, the ECU triggers the fuel pump relay via T55/3 to energize the S72 fuse that feeds the injectors (and the fuel pump, etc, etc).

I think the issue is either a faulty fuel pump relay or a faulty thermal fuse in the brown S72 fuse holder. (In both cases, no codes will be thrown)

[prj]

Yes and no. The ECU does provide some power to the injectors with the ignition key to "ON" via the holding relay and pin T55/37. Paul N. and I went around (and around) on that one. http://forums.quattroworld.com/s4s6/msgs/102009.phtml

Once the starter has produced enough spin to get more than 13 RPM from the G28, the ECU triggers the fuel pump relay via T55/3 to energize the S72 fuse that feeds the injectors (and the fuel pump, etc, etc).

I think the issue is either a faulty fuel pump relay or a faulty thermal fuse in the brown S72 fuse holder. (In both cases, no codes will be thrown)

Yeah, the ECU powers all this so that in the case that you wreck your car it does not catch fire.
But it does not control it in any way except for the "IF RPM > 13 TURN ON" logic.
So if 12V is going away from the injectors it means either the RPM signal is going or something is faulty in the wiring from that relay, but it has not really much to do with the ECU's boost protection mechanisms.

[UrS4boy]

Yeah, the ECU powers all this so that in the case that you wreck your car it does not catch fire. But it does not control it in any way except for the "IF RPM > 13 TURN ON" logic. So if 12V is going away from the injectors it means either the RPM signal is going or something is faulty in the wiring from that relay, but it has not really much to do with the ECU's boost protection mechanisms.

Not sure exactly what you are saying Dmitri. Too many non-specific "it"s and "that"s.

I think we agree that the ECU will shut OFF the J17 fuel pump relay IF the engine stops, e.g. in an accident. That is the safe thing to do. If the G28 signal suddenly goes bad, e.g. a bad connection to the harness or a faulty G28, while the engine is still be going around, the ECU will go into "panic!" mode (joke) and shut off the J17 Fuel Pump relay, resulting in a "fuel cut" but also a loss of power to the injectors, etc.

We will also agree that the ECU does control the precise firing of the injectors by taking the power through the ECU to ground, triggering the solenoid inside the injectors, as requried. (More injector info for others to read: http://forums.quattroworld.com/s4s6/msgs/20441.phtml)

G28 info: http://forums.quattroworld.com/s4s6/msgs/20986.phtml

RS200 definitely needs to get his friend to review the pertinent G28 and J17 wiring and connections for faults.

[ManiacuV6]

Or you can try something simple : Feed directly through a 30 amp fuse the injectors 12V wire. If you have a lack of supply to the injectors I think you get trouble codes. Right ?


P.S>: On every injector you have 2 wires one is 12V feed and one in the command ( that goes to the ECu) . I said that you need to give 12V on every injector . So five wires (from 5 inejctors ) go into a wire next into a fuse (30 A) and after that to Battery 12V. I hope is clear

[UrS4boy]

Or you can try something simple : Feed directly through a 30 amp fuse the injectors 12V wire. If you have a lack of supply to the injectors I think you get trouble codes. Right ?

Not sure about your testing suggestion.

Faulty injectors should throw codes if there is a power issue:

•4411 (Blink Fault Code), 01249 VAG1551/2 Fault Code Number
Fuel Injector for Cylinder 1, (N30)
Open or short circuit, +12V supply circuit breaker or fuse open
Symptom: Engine runs rough or stalls

•4412, (Blink Fault Code) 01250 VAG1551/2 Fault Code Number
Fuel Injector for Cylinder 2, (N31)
Open or short circuit, +12V supply circuit breaker or fuse open
Symptom: Engine runs rough or stalls

•4413, (Blink Fault Code) 01251 VAG1551/2 Fault Code Number
Fuel Injector for Cylinder 3, (N32)
Open or short circuit, +12V supply circuit breaker or fuse open
Symptom: Engine runs rough or stalls

•4414, (Blink Fault Code) 01252 VAG1551/2 Fault Code Number
Fuel Injector for Cylinder 4, (N33)
Open or short circuit, +12V supply circuit breaker or fuse open
Symptom: Engine runs rough or stalls

•4421, (Blink Fault Code) 01253 VAG1551/2 Fault Code Number
Fuel Injector for Cylinder 5,
Open or short circuit, +12V supply circuit breaker or fuse open
Symptom: Engine runs rough or stalls

[stocious]

if the injectors are loosing 12v intermittantly, does it also mean the ecu lost its 12v also at same time?

missed a bit of thread, ignore

[UrS4boy]

if the injectors are loosing 12v intermittantly, does it also mean the ecu lost its 12v also at same time? missed a bit of thread, ignore

Shouldn't. The ECU also has unswitched power via the 5 amp fuse in the red fuse holder above the ECU. Enters the ECU at Pin T55/18. That said, the switched power to the ECU comes into it via the fuse in the yellow fuse holder (also the coil power fuse):

[stocious]

ok. what i was getting at was, could the ecu be resetting at the same time that the injectors lost 12v. thus reseting each time it happens. thats a great diagram, for the bookmarks, also line 15. switched power, what is it switched by , ignition ?