83 cranks but won't start (SOLVED)

[Odoyle]

Was doing some errands and parked the car, come back an hour later and it cranks but won't fire. Tow it home and figure its the ignition control module. Replaced it and nothing changed. Confirmed I have spark by putting the spark plug connected to the wire on the valve cover and cranking. Car is very original and wiring looks to be untouched. Fuel pump was replaced less than 500 mile ago so I know that's working. I also checked in AFM door for free movement and its fine and turns on the fuel pump when activated. Tested the fuel pressure with a pressure tester teed off on the cold start injector hose per the factory manual recommendation and pressure was 38psi and held pressure (spec says it should be between 33-39psi). So I know the fuel pressure regulator is fine. Also has a new coolant temp sensor and checked the resistance on that and it was approx 2000 ohms (spec calls for 2000-3000 ohms at 68 degrees F). So I figured its the double relay that's faulty, replaced it with genuine Bosch, still cranking but wont start, it backfired at one point and blew the air hose off the AFM air box. Checked that injector 1 is getting 12V, have yet to used a noid light while cranking. Not really sure what else is wrong, checked all fuses, even the one if the fuse holder, all good, all the ground connections are good, chassis ground, ones on the intake mani, under the dash, one in the trunk all good. Thoughts or suggestions ? Thanks you guys.

[RRoller123]

Backfire like that suggests a Timing belt slip, check valve timing? (amhIk)

[tima01864]

I would try backing off on the Throttle Positioning Switch. I have set my idle and set the switch the engine will not start, An idea.

[spider2081]

Just some thoughts:
you have verified you have spark and fuel pressure
Have you checked the engines static timing?

Often the valve cover can not be used to check for spark because the cover is not making an electrical ground to the engine. The face of the cover is insulated by the gasket to the cam box and the retainers also have a fiber washer insulating them from the cover. I like to use the hood latch on the firewall for the spark plug when checking for spark.

I like to remove the black plastic cover from the fuel flow meter so I can watch it's operation when the engine is cranking. The flap should move quire a bit when cranking and the wiper on the resistor can be seen moving about 3/4 of an inch if the flap is free and there is not a massive air leak.

The FI troubleshooting manual (available to Mirafiori.com members in their library) suggests measuring the resistance of the temperature sensor from the ECU connector. Measuring from the ECU connector is also checking the cars wire harness integrity and and the connector to sensors connection.

Often fuel pumps fail from contamination in the tank and fuel lines. Many owners install a filter before the pump to extend Fuel pump life. Have you removed the fuel tank sender and inspected your tank for rust and water? Did you cut open the removed filter to inspect the element?

All 4 injectors fire at the same instant. Have you used a long screwdriver or automotive stethoscope to listen to the click each injector makes when it operates? The screen filters inside the injectors can be contaminated restricting flow through the injector. If I remember correctly with out cranking the engine move the AFM flap to activate the fuel pump observe the pressure. Then crank the engine and observe the pressure. The fuel flowing through the injectors when the engine is cranking should cause the pressure to drop

[Odoyle]

I will check the static timing tonight. Yes I did install a pre pump fuel filter along with new bosch fuel filter and fuel pump about a year ago. When would I be listening to when the injector clicks? When cranking the motor? . So if I check the resistance from the ecu plug for coolant temp sensor, if the resistance is different than just testing it at the coolant-t would that indicate that the connector and or wire needs to be replaced?

[spider2081]

The injectors make a distinct clicking sound when the engine is cranking and/or running.
Its not too uncommon for the pins in the temperature sensor connector to corrode and they then require cleaning or replacement. The wire harness is seldom an issue unless someone modified it or did something to it.

[kilrwail]

Have you checked the gap on your ignition points? Even when properly adjusted, they can drift off spec to the point that the engine won't start, even if it was running.

When you said you were running errands and turned the engine off and then it wouldn't start, that immediately reminded me of an ignition switch failure I experienced. If you turn on the ignition switch and then directly connect the starter to 12 volts, it should start, bypassing the vagaries of the switch.

[ORFORD2004]

Have you checked the gap on your ignition points?

No points in a 83.

[kilrwail]

I wondered about that.

[Odoyle]

Ok update, I replaced the duralast ignition control module with an original AC Delco control module, car started up, let it run for 10 minutes. Shut it off, try to start 20 minutes later, cranks won't start.

[spider2081]

I replaced the duralast ignition control module with an original AC Delco control module, car started up,

I have seen a number of the newer ignition pick-up connectors that mate with the ignition control module defective. Some have had the female pins installed too far back and unable to make proper contact with the ignition control module pins. Others do not have the the female pins locked in place to they move away from the ignition control module as the plug shell is pushed into place. You might want to inspect that connector and its pins mating with the ECM carefully.

[Odoyle]

Second update, car started up last night, went for a short drive, back home idling in driveway, shuts off. Now I'm figuring its the battery or alternator. Call AAA today and car started right up when they tested battery and alternator. Battery tested good, but voltage output was 11.60V at alternator and was barely charging system. So something is wrong with the alternator. Thinking of starting with a new voltage regulator considering the current one looks to be original. Should I just look at replacing the alternator?

[kilrwail]

Yes, replace the alternator. The new one will have a built-in voltage regulator, so you'll have one less component to worry about.

[spider2081]

From following this post I think your car is a 1983 Spider
This car would have a Bosch 65 amp alternator from the factory. Does the alternator out light in the tachometer light when the key is in the on position and the engine not running?? Then does the light go out when the engine is running? IF the light never illuminates is the black/violet wire connected to the alternator?

The Bosch alternators have a voltage regulator/brush assembly mounted to the back of the alternator. It is held in place by 2 straight slot screws and can be removed and changed with out removing the alternator.

[ORFORD2004]

No relation between cranks but won't start and your alternator except if your starter is too slow.