Technical VVT valve voltage

[Redlight]

Hello, does anyone know what the voltage on the VVT valve power connector should be? I measured just over 10V. The battery was fully charged. Voltage drop to ground was over 2V. Anyway, the valve should be powered from the engine control unit, so I’m not sure what voltage to expect there. I measured the voltage with only the ignition turned on.

Engine: 1.4 8v 57kw

 

[ZaphodB]

Hello, does anyone know what the voltage on the VVT valve power connector should be? I measured just over 10V. The battery was fully charged. Voltage drop to ground was over 2V. Anyway, the valve should be powered from the engine control unit, so I’m not sure what voltage to expect there. I measured the voltage with only the ignition turned on.

Engine: 1.4 8v 57kw

Which ground were you referencing with your meter?

Battery 'earth' isn't always engine 'earth' ....down to a poor engine 'earth' strap.

You can quite easily lose a couple of volts across a poor condition strap (and it's associated end connections)

 

[Redlight]

Which ground were you referencing with your meter?

Battery 'earth' isn't always engine 'earth' ....down to a poor engine 'earth' strap.

You can quite easily lose a couple of volts across a poor condition strap (and it's associated end connections)

First, I measured the voltage on the two pins in the connector. There I measured around 10V. Then I measured pin 1 (GND) against any other ground on the engine, chassis, or even the battery. The ground on the VVT valve (pin 1) is switched by the ECU, meaning it’s only active when the ignition is on or the engine is running. That’s why I’m wondering whether such a voltage drop is normal.

 

[ZaphodB]

First, I measured the voltage on the two pins in the connector. There I measured around 10V. Then I measured pin 1 (GND) against any other ground on the engine, chassis, or even the battery. The ground on the VVT valve (pin 1) is switched by the ECU, meaning it’s only active when the ignition is on or the engine is running. That’s why I’m wondering whether such a voltage drop is normal.

Even if the ground is switched wih a FET that's a fair chunk lost...

Sorry I can't give you any more info, think you'll need a fellow owner to confirm the same voltages

 

[GrandePunto PL]

First, define the problem. Your thread starts with vague question about voltages. Wrong approach.
Do you have an engine problem, for example it lacks power, has fault codes etc.?

Basic diagnosis can be done via FES or MES. Timing should be about 106 degrees (VVT1 position), camshaft positions real and desired very close while control is zero (0%) at idle. That's all. VVT starts to operate from about 2000-ish RPM. Example data (test drive).

Most control circuits are ground side switches (not always true but in general).
Means the device under control is "hanging" on the positive rail, ECU completes the circuit to ground.
Normally you don't care what the voltages are on the open circuit. Plug the VVT solenoid valve and then check if it gets power!

Control circuits for inductive loads must have some "kickback" protection (overvoltage), making the circuit more "complicated" and messing with the multimeter readings (due to high input impedance, typically 1 or 10 Mega ohms). Some circuits have also a feedback (they are monitored), that will introduce some voltage shift (or "drop") too.

Some sensors are "floating" too. For example crankshaft sensor (classic, 2-pin) has "weird" voltages on the pins while unplugged. So what? Nothing!
We care about the signal produced by sensor, not open circuit readings. Same with actuators (solenoids, motors, coils, relays).
Testing under load is the proper way (only then we can draw conclusions).

PS
Czechosłowacja? Check this Polish forum: https://fiatpunto.com.pl/forum37.html A lot of detailed Guides like that (VVT, timing, and so on).

EDIT: Voltages.
When ignition is OFF, voltages are close to zero (single mV) on both pins.
Ignition ON gives about 2,4 V on one pin. Negative multimeter lead on the battery negative pole of course.

Other pin shows 12,0 Volts. Which is exactly battery level (yes, mine needs a charging, like NOW). There is no drop! You have a problem.

Voltage directly between the pins will be a difference (12,0 - 2,4 = 9,6 V).

How the VVT proportional valve moves. Adjustable "PWM" source (you can test it also using direct 12 Volts, check if it moves).

 

[GrandePunto PL]

OK, you have very similar results (you didn't check 3 voltages as me, only first and the last one). So your VVT circuit is OK.
Which proves my point even more, that you don't know what you're doing there (what are you "checking"?).
Answer the question: what's the problem with the engine? Does it even start?
Don't do any more "tests" like that.
And if you do, check the other sensor (3-pin camshaft), it has solid ground (0V) and +5V supply. Third pin is a signal out.

By the way "mate"... You have Punto_2012? They should have both sensors (crank and camshaft) as 3-pin!
Are you "repairing" a car after accident (and someone has put there wrong wiring loom and/or ECU)?
There you go. Polish television show about cars. Exact same issue (EVO/2012 "repaired" using parts from Grande).

"Bifuel" - CNG or LPG (factory of aftermarket conversion, added later)? It can cause non-start condition.

GRANDE:

EVO / 2012:

 

[GrandePunto PL]

Is this a follow-up, continuation of your previous thread? Same car?
https://www.fiatforum.com/threads/fiat-punto-iii-p0351.515808/ ?
Finish/update old thread, then start new ones.

PS
Factory LPG can be equipped with old style crank sensor (2-pin), according to eLearn... But the thread was about VVT (now I'm mixing things a bit - the point is, some open circuits are "floating" and that's normal).
https://aftersales.fiat.com/elearnsections/main.aspx?nodeID=199024922&languageID=2&markID=1&modelID=199000000&valID=199000001&prodID=199000000&modelName=Fiat - 199 - Grande Punto&langDesc=English&sectionName=Impianto Elettrico&validityName=1.4 8v

Now it's your turn. Clarify what's the problem. Still coils (as in old thread), VVT, other issues?