Injectors not firing...

I think your have a connection problem on the ground side of the injectors. Maby Jrichker will chime in...

Your meter might be averaging readings. There is a constant 12 volt feed from the EEC relay to each injector. Then computer pulses the ground to each one (this pulsed ground is how the computer varies the injector pulsewidth). I would grab a noid light from the parts store (3-5 bucks) and use it since it has very quick on/off dwell.

If you really dont have a ground pulse, the car obviously wont fire. At that point, we would need JR, Tom, etc.

Also make sure you dont have a pegged TPS reading, as that will kill the injector pulsing.

Good luck.

Make sure you have no wires pinched anywhere. Try it with the TPS disconnected. You obviously have power to the ECM, but the TFI module doesn't seem to be getting the necessary info to the injectors. I think pins 12(#3),13(#4),14(#5),15(#6),42(#7),52(#8),58(#1) and 59(#2) are the grounding signals for the individual injectors, if it comes to that. Also make sure the ECM is fully grounded.

Next, get a can of starting fluid (ether) from your local auto parts store: costs a $1.30 or so. Then pull the air duct off at the throttle body elbow, open the throttle, and spray the ether in it. Reconnect the air duct and try to start the car. Do not try to start the car without reconnecting the air duct.
Two reasons:
1.) If it backfires, the chance for a serious fire is increased.
2.) On Mass Air cars, the computer needs to measure the MAF flow once the engine starts.
If it starts then, you have a fuel management issue. Continue the checklist with emphasis of fuel related items that follow. If it doesn’t, then it is a computer or timing issue: see Step 4.


Fuel pressure OK, the injectors are not firing.

A.) A Noid light available from Autozone, is one way to test the injector wiring.
B.) I like to use an old injector with compressed air applied to the injector where the fuel rail would normally connect. I hook the whole thing up, apply compressed air to the injector and stick it in a paper cup of soapy water. When the engine cranks with the ignition switch on, if the injector fires, it makes bubbles. Cheap if you have the stuff laying around, and works good too.

a.) Pull an injector wire connector off and look for 12 volts on the red wire when the ignition switch is on.
b.) No power, then look for problems with the 10 pin connecter (salt & pepper shakers at the rear of the upper manifold).
c.) No power and the 10 pin connections are good: look for broken wiring between the orange/black wire on the ECC relay and the red wire for the 10 pin connectors.

Follow JB66's instructions and use an ohmeter to check out the resistance btween the injector wires and their respective computer pins. There should be less than 1 ohm resistance.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-90 wiring

http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif