Power to injectors

[DC871F]

82 NA 280ZX.

I have fuel, spark, but no power to fuel injectors. Crank angle sensor seems intact(wiring). Car has been sitting many years, has fresh fuel, no blockage in fuel rails.

Other than Control Unit, what else will power fuel injectors? It seems hasty to pull the trigger on a new ECM, but as far as I can tell that seems to be the issue.

I pulled the ECM out, seems clean, no obvious issues.

Any thoughts? 

[Zed Head]

The injector power exits through the ECU but does not start there.  You're looking at the wrong end IF the injectors really don't have power.  If you mean that the injectors aren't opening though, the ECU is a possibility.

And 1982 non-turbo (NA) engines don't have a CAS.  Kind of reads like you're new to auto electrical.  Don't replace until you do a few tests.  Make sure you're working from the FSM, EFEC chapter.

http://www.classiczcars.com/files/category/14-280zx/

 

[DC871F]

There's no power at the injector plugs, good ole Fluke and a home made tester with a light bulb confirms. If the ECU is not the beginning power for the 6 injector plugs, where would the beginning be?

 

 

Edited April 14, 2017 by DC871F

[Zed Head]

Are you on a phone, smart or not?  Here's a smaller snip of the picture I posted.  From my computer.  I labeled the picture "the battery".

Edit - I finally got a smart phone and understand how the big pictures get lost on the tiny screen.  It's not smart to use a smart phone to look at big wiring diagrams.

 

Edited April 14, 2017 by Zed Head

[DC871F]

So you are saying that the power comes from "the Battery"?

Now I feel like maybe your kind of messing with me at this point, no? 

Thanks for the help.

[Zed Head]

Yes, you want to examine the circuit FROM the battery to the injector connectors/plugs if there is no power at the injectors.  The ECU is on the grounding side of the circuit, the very end.  There is power (voltage) in the wires and injectors all the way to the ECU as soon as you turn the key On.  When the ECU grounds the end of the circuit, current flows and the injectors open.

Fusible links are notorious for corroded connections.  The will also blow if the wire between the injector connector and the fusible link is shorted to ground.  Becuase the resistance of the injector is not there to control current.

Take your Fluke, find the fusible link for the injector power and see if there is power on both sides of the link.  If there is then work your way up to the injector connectors until you find the break n the circuit.

[Zed Head]

Forgot to say, it's not uncommon for people to measure voltage or use their test light across the connector pins.  That's the wrong way and will show zero.  Measure voltage from the pins to ground.  The block or manifold or some other path back to battery negative.

[Patcon]

He is not messing with you...

[240260280]

Think of the circuit being like a charged storm cloud:  The wire and the injectors stay at +12V DC, as they are always connected to the +12V feed when the FI system is powered. The injectors typically stay at +12V nearly all the time.

When the engine rotates, the distributor sends a signal to the  ECU (as well as sparking the plugs). The ECU uses this impulse determine when to fire the injectors and for how long.   The ECU fires the injector by shorting the +12V charged injector line through a transistor to ground. This causes a large current to flow through the injector.  (It is like a storm cloud suddenly having a path to ground and discharging).  The duration of the current flow is proportional to how long the injector stays open. (The injector is simply a solenoid).  There are 6 "current limiting resistors" upstream from the injectors that prevent too much current from burning up the injectors.

If I recall correctly the ECU fires all injectors at the same time and twice per 4 crank strokes.

Edited April 15, 2017 by 240260280

[DC871F]

2 hours ago, 240260280 said:

Think of the circuit being like a charged storm cloud:  The wire and the injectors stay at +12V DC, as they are always connected to the +12V feed when the FI system is powered. The injectors typically stay at +12V nearly all the time.

When the engine rotates, the distributor sends a signal to the  ECU (as well as sparking the plugs). The ECU uses this impulse determine when to fire the injectors and for how long.   The ECU fires the injector by shorting the +12V charged injector line through a transistor to ground.  (It is like a storm cloud suddenly having a path to ground and discharging). 

If I recall correctly the ECU fires all injectors at the same time and twice per 4 crank strokes.

Until I had seen the FSM here, all I had was a Haynes book to guide me, not much there for troubleshooting my injector problem.

Thanks.

Edited April 15, 2017 by DC871F

[DC871F]

7 hours ago, Patcon said:

He is not messing with you...

Saying power starts at the battery was a little primitive for troubleshooting purposes, I thought it was funny.

[DC871F]

Great thanks. When I check voltage its constant when engine spinning with starter . I read where its supposed to cycle to show voltage only when firing the injectors, hence light check on both pins at plug.

Fusible links all good.