Some more thoughts on ground you may have already covered...
Fuel pressure OK, the injectors are not firing, OR one or more injectors stuck
open
Do a cylinder balance test: Warm the car's engine up to normal operating
temperature. With the Engine Off, Key OFF, use a jumper wire or paper clip to
put the computer into test mode. Start the engine and let it go through the
normal diagnostic tests, then quickly press the throttle to the floor. The
engine RPM should exceed 2500 RPM's for a brief second. The engine will shut
off power to each injector, one at a time. When it has sequenced through all
8 injectors, it will flash 99 or the number of the failing cylinder such as 22 for
cylinder #2. Quickly pressing the throttle again up to 2500 RPM’s will cause
the test to re-run with smaller qualifying figures. Do it a third time, and if the
same cylinder shows up, the cylinder is weak and isn’t putting out power like
it should. See the Chilton’s Shop manual for the complete test procedure
The red wire on each injector is powered up whenever the ignition switch is
in the Run position. The computer provides a ground to complete the circuit
and fire the injector. The injector
must have a ground to squirt fuel on
command. A short to ground in the injector return wiring can cause one or
more injectors to be continually open or triggered
A.) A Noid light available from Autozone, is one way to test
the injector wiring. If the light stays on constantly, either the wiring has a
short to ground or the computer has failed
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 An injector stuck open will release a continual stream
of bubbles. Cheap if you have the stuff laying around, and works good too.
The same trick works great to find leaking injectors too.
The wiring for the injectors may have some bare spots in it causing the
injector to computer control wire to ground out. This would cause the
injector to remain on anytime the key was in the Run position. Remove the
injector wiring connectors from the injector. Note that each injector has one
red wire for power and a non red wire (wire some color other than red) for
computer controlled ground. With the key off, disconnect the computer
connector from the computer. Use an Ohmmeter between the non red wire
and ground. You should see more than 100000 (100K) ohms resistance.
See the following website for some help from Tmoss (diagram designer) &
Stang&2Birds (website host) for help wiring
http://www.veryuseful.com/mustang/tech/engine/
Diagram courtesy of Tmoss & Stang&2birds
Using the above diagram, check the resistance between the injector and the
computer. Clean and check the 10 pin connectors since they are a potential
trouble source. Any resistance greater than 1.5 ohm between the injector to
computer wire and the matching pin on the computer connector is a problem.
See
http://fordfuelinjection.com/?p=6 for more help
Here's the link to dump the computer codes with only a jumper wire or paper
clip and the check engine light, or test light or voltmeter. You’ll need it to do
the cylinder balance test
See
http://www.troublecodes.net/Ford/
IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.
89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.
, it helped me get my engine in shape after fretting over it for a LONG time.
