Injector not spraying fuel

Hello,

It sounds like you either have no power at the injectors or the ECU is not receiving a signal from the crank angle sensor. In the electronic engine control system utilized on this vehicle, two signals generated by the distributor/ crank angle sensor which are used by the ECU in its calculations for various outputs.

First check that the injectors are receiving 12V supply.

POWER SUPPLY CHECK

Disconnect injector harness electrical connector.
Check for voltage at the B/Y wire terminal of the harness side connector.
IGNITION "OFF" - 0 volts
IGNITION "ON" - 12 volts (battery voltage)

If no voltage is present, check the main relay and wiring between the main relay and injector harness connector

Also check if there is spark when cranking the engine.

The distributor utilizes a photo-diode type crank angle sensor consisting of a slotted disc that turns with the distributor shaft and a stationary pick-up assembly. As the disc rotates past the pick-up, the slots (one for each cylinder) alternately pass and block photo-diode light transmission. Signals generated are interpreted by the ECU to determine crank angle (#1-cylinder TDC) and engine RPMs. To calculate ignition timing, the ECU uses this input together with several others related to vehicle operating conditions. Except for the initial setting, ignition timing is under ECU control.

How to use Voltmeter.
https://www.2carpros.com/articles/how-to-use-a-voltmeter

How to test a relay.
https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Please let us know.

Cheers, Boris

Hi,

I noticed you haven't been contacted for several days. Have you been able to make any progress?

As far as the injectors are concerned, they should receive power once the key is on, and I believe you mentioned that is the case. Once you crank the engine, the ECM should provide a ground path to each injector based on need. If I'm reading the schematic correctly, power is supplied via the black wire with a yellow tracer. I attached a copy of your pic below. Is this where you have the power supply to all injectors?

If you do, the issue is either the ECM isn't providing a ground path. If you have a Noid light, test the light green wire with a black tracer on injectors 1 and 2 to see if power is continued to the ECM's ground. Do this cranking the engine. Also, injectors 3 and 4 should receive a ground path via a light green wire with a red tracer. Check them all.

If you want, you could check for continuity to ground with a multimeter as well when cranking the engine.

I attached your pic below along with a schematic of the injectors for your reference. Also, if you haven't already, I recommend testing for diagnostic trouble codes. The vehicle has an OBD1 system and all you need to retrieve codes is a short jumper wire or even a paper clip. Here is a link that shows how to do it.

https://www.2carpros.com/articles/diagnostic-trouble-codes-for-1995-and-earlier-mazda-cars-obd1

Let me know what you find or if I can help. Also, inspect some of the wires you indicated in pic 1 you sent. Some look like they could have internal damage (under the insulator). Also, which wire are you referring to in your pics as loose or disconnected?

Pic 3 shows the wires I noticed appeared damaged. Inspect them closely.

Take care,

Joe

See pics below.

Hi,

First, you are very welcome. You are likely correct as far as the ECM. That is what completes the circuit. If you have a multimeter, you could check for continuity to ground on the opposite wires. That would need to be done when while the engine is cranking.

I prefer using an analog multimeter because it's easier to see the needle jump. A DMM sometimes can trick you.

Also, if I recall correctly, the ECM receives ground by being screwed to the kick panel. I don't know the condition of the vehicle, but if there is corrosion or rust, it can cause issues as well.

By chance, did you try to retrieve diagnostics codes?

Joe

Hi,

By chance, is there a single-pin green connector located there? If there is, you will ground that connector using a jumper cable.

See pic 1 below. It shows what I believe you have. Pic 2 is the directions from the manual for testing.

Let me know what you find.

Joe

See pics below.