Injectors not firing?

71pony

New Member
Jul 30, 2002
15
0
0
trumbull,ct
i got a 88 hatch back i've converted to a 5.0 the motor ran fine in the previous car. it has good spark, and has good fuel pressure. i tested the injectors and there getting power to them but there not spraying. any ideas? wires to check?
 
  • Sponsors (?)


A Noid light available from Autozone, is one way to test the injector wiring.

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.

There are two 10 pin connectors at the back of the upper manifold, one of them has all 8 injector connections. Pull them apart and check for damage. Each injector should ohm out at about 13 ohms +\- 1.5 ohms.

Remember that the computer supplies a ground path for the injectors. The power for the injectors comes through the ECC relay located on top of the computer. They have power to them any time the ignition is on. The computer turns on the ground and completes the circuit, making the injectors fire.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

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
 
J.R., you take the fun out of my trying to add my two cents worth. LOL J/K.

once you post, no one can add anything - excellent response as always!
 
The orange wire attached to the block is the injector harness ground.
However, when I had some problems through the winter, I experimented and noticed my car ran the same way whether that was grounded or not.

Anyone know why? :shrug: Seems to me that should be quite the important thign to remain grounded!
 
mansonozz said:
The orange wire attached to the block is the injector harness ground.
However, when I had some problems through the winter, I experimented and noticed my car ran the same way whether that was grounded or not.

Anyone know why? :shrug: Seems to me that should be quite the important thign to remain grounded!

It does not ground the injectors. It is the ground for the O2 sensor heaters.

The computer provides the ground for each injector. The injectors are supplied with power anytime the ignition switch is in th run position. The computer switches each injector on and off by supplying a ground path to complete the circuit.