1986 to 1993 Troubleshooting an Engine That Will Crank But Not Start

It seems like every time I buy a car, it has set for a long time and does not start. Usually the culprit is a tank of old gas or a fuel filter. But sometimes its mice in the wiring or some other problem. While troubleshooting my 1990 Mustang GT I bought, I documented the steps I took to get it started.

Place car in neutral or park and set the parking brake

Because I usually find it is a fuel problem, I test for fuel first.

1 Turn the key on to the start position and listen for the fuel pump to build up pressure. You should hear a low whine from the tank area for about 5 – 20 seconds then it will be silent. Don’t hear the pump prime, check to make sure the inertia switch was not tripped. If it was tripped, reset it. The switch is hiddent under the plastic trim covering the driver’s side taillight. Use a voltmeter or test light to make sure you have power to both sides of the switch. To trick the fuel pump into running, find the EEC test connector and jump the connector in the Upper RH corner to ground. The EEC connector is near the wiper motor and LH hood hinge.

2 Check for pressure at the Schrader valve located on the fuel rail. It should have 20 pounds of pressure when the car is not running. Don’t have fuel pressure, change out the fuel filter. The fuel filter is located in front of the fuel tank and behind the rear axle. In my cars, it is held in with two clips that look like bobby pins. Have a spare since they do break sometimes. Pull the pins off, then pull the lines from the filter, replace the filter and the pins. Try to start the car now. if it starts you are lucky and got off cheap. If it does not start, check for fuel pressure agin. no pressure, check the fuel pump power relay – located under the driver’s seat in most Mustangs built before 1992. Still no pressure, get ready to drop the tank and replace the fuel pump. (See the tip on dropping the fuel tank).

3 Check for blown fuses on 1986-1990 models only lo9ok for a blown fuse link in wiring harness. Look for 12 volts at the Orange/Lt Blue wire on the fuel pump relay. The fuse links for all model years 86-93 can be found in the wiring harness near the starter solenoid.

You should have fuel pressure now. If it does not start with fuel pressure, check to see if your injectors are firing. Using a noid light attached to an injector harness at the injector, crank the engine. The noid light should flash. Or, you can pull an injector wire connector off and look for 12 volts on the red wire when the ignition switch is on. If you don’t get any voltage, look for problems with the 10 pin connecter (salt & pepper shakers at the rear of the upper manifold). Still 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.

Teh last thing to check is that the TPS voltage exceeds 3.7 volts with the throttle closed. This will shut off the injectors, since the computer uses this strategy to clear a flooded engine. Use a volt meter and a pair of safety pins to probe the black/white and green wires to measure the TPS voltage.

Next I check for spark.

Pull a spark plug wir from the easiest plug. Insert a screwdriver into it and while someone is turning on the key to start the engine and it is cranking over watch for spark as you hold the metal blade of the screwdriver next to the engine block. If you have spark, then it is most likely a timing problem or spark plug wires are not in the correct order. Firing order off: HO & 351 use a different firing order from the non HO engines. HO & 351W 1-3-7-2-6-5-4-8, Non HO 1-5-4-2-6-3-7-8

If you don’t get spark, make sure the engine is grounded. Using a volt meter measure for connectivity between the engine and the battery. Got a good connection, the next thing to check is the coil. Next check the TFI module in the distributor and the PIP sensor in the distributor. The PIP sensor supplies the timing pulse to trigger the TFI and injectors.

Engine seems to load up on fuel and may have black smoke at the tailpipe. Fuel pressure regulator failed. Remove the vacuum line from the regulator and inspect for fuel escaping while the pump is running. If fuel is coming out the vacuum port, the regulator has failed. Check the regulator vacuum line for fuel too. Disconnect it from the engine and blow air though it. If you find gas, the regulator has failed.

Ignition switch – Look for 12 volts at the Ignition Coil Red/Light Green wire. If it is not reading 12 Volts: possible blown fuse link or faulty ignition switch. Remove the plastic from around the ignition switch and look for 12 volts on the red/green wire with the switch in the RUN position. If there isn’t 12 volts then the ignition switch is faulty. If 12 volts is present in the Run position, then the fuse link is blown.

Bad or missing secondary power ground. This ground is located between the back of the intake manifold and the driver’s side firewall. It supplies ground for the alternator, A/C compressor clutch and other electrical accessories such as the gauges.

No ECC or Computer Power – ECC or computer relay failure or fuse failiure.

Engine fires briefly, but dies immediately when the key is released to the Run position: Pull the small push on connector (red wire) off the starter relay (Looks like it is stuck on a screw). Hold the switch in the crank position: if it continues to run there is a problem with either the ignition switch or TFI module. Check for 12 volts at the red/green wire on the coil with the switch in the Run position. If reading 12 volts, then replace the TFI. If not reading 12 volts, replace the ignition switch.

No start when hot – Press the throttle to the floor & try starting it if you get this far. If it starts, replace the ECT.

Engine that has had the heads off or valves adjusted. Do a compression test to make sure the valves are not adjusted too tight. You should have a minimum of 90 PSI on a cold engine.

Good Luck!.