Fuel injectors not working

[GNX106]

I have 12volts at injectors with key on no pulse 

i can pour a little gas in the throttle body. Starts right upi

 

thanks for helping

[psu_Crash]

What year is the car? Did this happen all of the sudden or has it been not running? Can you hear the fuel pump run when the key is turned on?

Edited March 23 by psu_Crash

[tux]

Check each injectors resistance to make sure they are within spec.  I think it was 2-3 ohms

[GNX106]

It’s an 88 model. Happened all at once. 
 

fuel pump is running while trying to start 

 

[GNX106]

I will check the resistance 

[psu_Crash]

From the service manual. Could be a bad resistor I suppose. I have heard of them going out before. If it runs on spray then it must be getting a tach signal to the ECU. Probably a wiring issue if I had to guess. 

[TexasQuest]

Check you injector pigtails

[kev]

injectors are known to stick especially if the car has been sitting awhile.   Pull them out on put the tips in a cup of carb cleaner for a few hours.    I usually do a quick test using a large syringe connected to the injector input, via a piece of tubing, with denatured alcohol.   Energize the injector (using an old injector clip connected to a 12V power supply, or even a 9V battery, and push down on the syringe to make sure they spray.   If they open and spray, then you the car should at least fire up.   If not, it is something prior, such as wiring (including the clips) or the resistor.

It's usually the primary injector, black top, that sticks.  When this happens to me, I usually can get the car to fire up and chug by pumping the gas pedal during cranking (i.e. the secondary, green top, injector is energizing when pumping the pedal).  

 

If this is indeed the problem, and the car fires up and runs semi-decent after a quick cleaning, I'd recommend sending your injectors out for a professional cleaning/inspection.   It's pretty cheap and fast (around $15-20 an injector).  They do an initial flow test, clean the injector out thoroughly, inspect for internal and external leaks, clean the contacts, and do a post flow test.    

kev

 

[GNX106]

On 3/23/2024 at 3:53 PM, GNX106 said:

I will check the resistance 

both test at 2.1

[tux]

Then the coils in the injectors work!

 

Now that we know the injectors are good electronically, follow the additional suggestions from the thread

[GNX106]

what makes the infectors fire the ecu or the eci 

[admin_JAinsworth]

This is a write-up by Mike_C

 

Injectors not firing

 

Is the tach moving too - just "having spark" isn't enough. If the tach is wiggling though then the signal wire from the ignition coil to the ECU & tach is working. Without that wire the ECU won't command fuel. It wants to verify ignition is present before it will flow fuel - this is a safety thing in case the car was in a wreck... don't want fuel being sprayed when the fuel lines, injectors, etc. could be busted wide open.

To command the injectors, the ECU:
* needs to see the signal from the ignition coil "-" post; this is the tach signal I just described.

* wants to see pulses from the airflow sensor. The airflow sensor (aka "MAS" or "AFS") is the single most important input to the ECU for the fuel calculations; all of the other engine sensors just add or subtract from the AFS based value.

* ECI fusible link must be intact. This powers the fuel pump, injectors, etc.

* ECI relay (actually 2 relays in one housing) powers the fuel system and fuel pump. The ECU "holds" the fuel pump side ON as long as the ECU sees those ignition pulses ("engine is still running, go ahead and send power to the fuel pump..."); the ignition key START position also trips this relay to power the pump while you're trying to start.

Some simple tests:
1: verify the tachometer wiggles. If not, find out what's wrong with the ignition system or your wiring. The wire from the coil "-" post to the tach and ECU is a skinny coax cable (skinny cable TV wire: a wire inside a braided shield, then encased in rubber) and it's possible for the inner conductor to short out to the shield if the wire is pinched, crushed, or bent tightly. Often it gets shorted right at the ECU connector. There are TWO of these shielded coax wires at the ECU - one is for the ignition, one is for the oxygen sensor. If you hook up an air/fuel guage to the wrong one you could screw things up.

2: Look for basic power to the injector while cranking: using a voltmeter red/positive lead probe either injector wire on the primary injector (the one closer to the fender on 87-later cars, or just pick either injector on earlier cars) and ground the voltmeter's black/negative lead. Now try starting... you should see 10 to 12 volts. No? Try the other post on that injector. Still no 12 volts? Then your ECI fusible link is shot, the ECI relay isn't ON, wiring is bad, or the ballast resistor is shot. The ballast is the silver prism-shaped thing bolted to the bulkhead between the air filter and passenger side headlight. +12volts goes in one wire, the resistor is actually two resistors that split this +12volt line... each resistor feeds one injector. Bad resistor = no power to injector.

3: Hook a noid light to the primary injector - the one closer to the driver side fender. It should pulse/blink if the ECU is completing the ground to fire the injector.

mike c.