Fox T-Bird/Cougar Forums

No Start due to No Spark

Needed Tools/Chemicals:
12-vdc Test Light
Carburetor Cleaner Spray Can
½" combination wrench
TFI Ignition System Wiring Diagram

To start trying to identify if it's a fuel or a spark problem, place ign key in on, check for the fuel pump priming sound, if OK or NOK, remove the breather hose from the throttle body and spray some carburetor cleaner through the TB port.

Attempt to start engine, if engine starts for a couple of seconds and dies, the problem is a No Fuel 
 condition....if the engine doesn't start at all, the problem is a No Spark
 condition...

NO Spark
 
  Loosen distributor holding bolt with ½" wrench, remove plug from coil, turn ign on, while holding the coild plug ~ ¼" away from the coil tower, rotate distributor left-right-left....spark doesn't arc from coil to plug = next step...spark arcs from coil to plug = check condition of distributor rotor and cap, and replace.

  Place ignition key in on, with the 12-vdc test light connected to a good ground, probe the (+) terminal at the coil (Red/Lt Green wire)...test light off = usually an ignition switch or 20 GA fuse link problem....test light on = next step.

  Place ignition key in on, with the 12-vdc test light connected to a good ground, probe the (-) terminal at the coil (Tan/Yellow wire)...test light off  = replace coil, test light on = next step.

  Place ignition key in on, with the 12-vdc test light connected to a good ground, probe the (-) terminal at the coil (Tan/Yellow wire), rotate distributor left-right-left and check test light...test light blinks  = replace coil....test light on = next step.

  Ign On, backprobe or disconnect TFI and check with test light, pin #4 (ICM Power)...test light on = next step, test light off = open problem in wiring that needs tracing and repair.

  Up till now the problem is either a TFI module, or a stator sensor failure. Your options are to either replace the module and check if it starts, or follow this testing procedure to rule out/id the module as the culprit, and replace the stator sensor, TFI module, or both....I usually recommend the latter one for these cases anyway.....

 
A No Fuel Condition is either caused by a lack of fuel pressure, or absence of fuel injectors pulsing.

Tools/Equipment/Diagrams Needed:

Ignition/Power Distribution Diagram
'88-'91 Wiring Diagram
'94-'95 Wiring Diagram
12-vdc Test Light
Volt/Ohm Meter
½" combination wrench
Noid Light (if not available, the 12-vdc test light works also)

NO Fuel

  Attach fuel pressure gauge to the schrader valve at the fuel rail or fuel line.

  If you were able to notice the fuel pump prime buzzing sound, turn ign on and check pressure gauge reading, you might want to repeat the ign-off-on cycle a couple of times, or attach a jumper wire to the FP terminal at the VIP/Diagnostics connector, and ground it. As long as the wire is grounded, the fuel pump should turn on. Pressure reading should be between 30-45psi.....OK = No Fuel Injector Pulse
  ....NOK = next step…fuel pump not heard = Fuel Pump Circuit Problem

  Since pump activation is confirmed, but pressure is lower than 30 psi, the fuel tank must be dropped. Remove the fuel pump assy., check the small hose that connects the pump to the feed line for leaks/ruptures....No leaks/ruptures = replace fuel pump.

No Fuel Injector Pulse 

  The no fuel condition could be caused by an injectors not opening problem…turn ign on, check voltage at the Red wire of any of the injector connectors with the test light…light on = next step...light off = the power feed wire to the injectors needs to be traced and repaired for an open, you should also check and perform the salt & pepper connectors fix + recheck for injector power ign on.

  Using a noid light, or the 12-vdc test light, used as a jumper between the injector harness connector pins (clip and point ends), loosen the ½" holding bolt of the distributor so it can be rotated....turn ign on, and rotate the distributor left-to-right back and forth… you should hear the fuel pump prime, and the test light should blink…blinks OK = injectors need replacement…test light blinks NOK = check and perform the salt & pepper connectors fix.... recheck for injectors pulse....if test light doesn't blink = test the injector pulse signal wire for continuity between the injector connector to the ECM connector. The resistance reading should be less/equal to 5 ohms…OK = ECM is kaput, needs to be replaced…NOK = trace and repair wiring harness.

12-vdc Test Light made into a noid light

Fuel Pump Circuit 

  Since the fuel pump is not activating, make sure the fuel pump inertia/cutoff switch is not tripped...tripped = reset and repeat fuel pump pressure test....OK = next step.

FYI: The inertia switch is located in the rear lights inside panel...check the pic below.

  Locate the fuel pump relay (for ’86-’90 Mustangs, its location is under the driver seat, for ’91-’93 Mustangs, its location is in the front of the RH strut tower in the engine bay), use the wiring diagrams for your Mustang linked to, in the "Tools" list above. Confirm the relay is not activating by turning ign on,  check for the relay to click …clicks = probe back of relay connector fuel pump output wire with the test light, turn ign on, if light is off = next step...if light is on = FP wire needs to be traced for an open to the pump....doesn't click = step after the next one.

  Make sure the “always hot” or 12-vdc power supply wire has voltage with the test light, ign off…light on = replace fuel pump relay…light off = trace and repair open wire or fuse link.

  Check the Ign On voltage wire at the relay, probe back of relay connector, turn ign on…light on = next step.....light off = trace the Ign On wire for an open if it's OK = step after the next one.

  Attach 12-vdc test light clip to a 12vdc source, probe FP signal wire with the test light, while you turn the ign on for priming 2-4 sec pulse, test light should blink...it blinks = replace FP relay....doesn't blink = next step.

  At this stage of the tests, the reason the FP relay is not activating, could be caused by a faulty EEC relay, faulty wiring, or fubar'ed ECM.
 
NO Start - ECM NOT Turning On Condition

Another reason for an EFI No Start, is that the ECM is not turning on when the key is cycled to the IGN ON position. First you have to ID this is the case. In order to confirm if the ECM is not activating, notice if the fuel pump primes when the key is rotated to IGN ON, if it does prime.....the ECM is turning on.....if it doesn't.....measure for 5 vdc VREF voltage at any of the 3-wire sensors (EVP, TPS or MAP/BP), we will use the TPS for this explanation.

Notice the color of the TPS sensor wires to the sensor side.....GREEN = TPS output signal, BLACK = SIGRTN ground reference and RED or ORANGE = 5 vdc VREF

 Check for 5 vdc, IGN ON between the RED/ORANGE wire and a good ground like battery (-)......if 5 vdc is present, THE ECM is turning on.....not present.....next!

 Check the EEC ground near the battery, it should be attached to the battery (-) or the frame.

 Check the EEC relay located on top of the ECM in the passenger kickpanel, make sure it has 12-vdc "always hot" at one of the relay terminals....if not, you need to trace the "always-hot" wire to the correspondent fuselink located in the starter solenoid.

 Make sure the IGN ON relay terminal switches to 12-vdc when you turn the ignition key....if not, you either have a wiring open, a bad ignition switch assy., or an open fuselink.

 Make sure pin #1 at the ECM connector has 12-vdc "always hot", and that pins 37 and 57 have 12-vdc when the key is switched to IGN ON otherwise, you have an open fuselink, or an open wire between the EEC relay and the ECM connector.

 Also check pins 20, 40 and 60 at the ECM connector to ground (resistance check).....if you have >5Ω resistance to a good ground reference point, the ground wires have an open somewhere.

 If all the above checks OK.....the ECM is fubar.....