I've recently replaced the 2.2 L 4-cyl. engine in my '89 Ford Probe GT, but when I go to start it, it runs for 2 seconds, then the computer shuts down the injectors.


I've replaced all the fuel system components, including the gas tank, and I've replaced all the electrical ignition components, including the electronic control module, but no difference. What would cause this computer to shutdown the injectors: oil pressure? The gauge slowly moves to normal pressure by just turning on the ignition. Apparently, the computer needs reprogramming or is getting undesirable input. The 'check engine' light has never come on.

 

I would check for crankshaft and camshaft sensor signals to the pcm. Most systems prime the fuel pump for 2 seconds and then wait for these signals as an indication that the engine is running/starting. This is something that can be easily verified with a scan tool.

 

It might be a little tough to get that info with a scan tool due to the age of the system , it just may not be available.
I believe they had a distributor that provided the RPM signal that the computer required to keep the fuel pump relay closed. It's been a while and I would need to check further if that is the case.

 

Just a couple more things to throw your way...Have you actually verified your fuel pressure? You didn't mention anything about actually replacing the fuel pump. If you did replace the fuel pump, it's not the first time I've seen a new pump be bad. Also, have you verified the operation of the IAC? This little bugger will cause the same start/stall scenario you're having.

 

Sorry for my slow response. I've been trying to figure out how to reply to a thread on this site.

The engine never loses spark to the plugs and the fuel pump continues to run after the engine dies. I've checked the fuel rail pressure and it is at spec. The problem is that the ECA is shutting down the fuel injectors. I listen with a stethoscope to the injectors clicking as the engine starts and the clicking stops just as the engine dies, but my timing light shows the plugs are still getting spark.

The throttle position doesn't seem to make any difference when starting the engine, it only idles. I disconnected the coolant temperature sensor, which is wired with the throttle position sensor, barometric pressure sensor, EGR valve position sensor and vane airflow meter, and the throttle position sensor seemed to be working when I tried to start the engine, but alas, the engine still only runs for about a second. I've replaced the vane airflow meter with no change.

Something I forgot to mention; it happened so early in this process: I accidently shorted a wire when I was testing the fuel pump continuity and had to replace the ECA. Apparently, the short caused damage to the original ECA because the engine fan would run as soon as the ignition was turned to the 'on' position. I bought 3 ECA's (It was a good buy! ) for this Probe Turbo and when I hook up any of the 3 ECA's they all shut down the injectors. So I'm wondering if something might have shorted out in one of the fuel system components of the electronic persuasion.

Would a shorted barometric pressure sensor (I think it's better known as the 'MAP sensor') cause the engine not to start?

 

'Use Common Sense', I don't believe this vehicle has an "IAC"; instead, it has an "Electrical Load Unit" that does the same thing as the IAC. I've replaced that unit with no change.
I took the vehicle to a Ford mechanic; people say the best in this area. He had it for several days and finally gave up. He couldn't figure out where to plug in his computer.
I'm beginning to think it has something to do with the EGR components or the MAP sensor. I've tried about everything else!

 

this vehicle uses group bank injection so each injector fires at the same time once per crank revolution. I have not been able to view an injector wiring diagram.
I am wondering if one injector is shorted. the control module may be picking this up and shutting down all output.
why don't you disconnect each injector and ohm check each one and them ohm check the wiring harness while its disconnected for short to grd. each injector should measure 11-15ohms.

if I can find more info on system operation, I will pass it on.

 

When the engine is in the cranking mode, fuel is supplied to all cylinders simultaneously by providing one injection per crankshaft rotation (2 injections per cycle). Therefore, one injection period supplies half of the fuel necessary for ideal combustion.
Between idle and 6,000 rpm, fuel is supplied through a 2-group injection per two crankshaft rotations (one injection per cycle). At the completion of the first crankshaft rotation, fuel is supplied to cylinders No.1 & 3 by determination of the cylinder identification sensors signal created by the distributor. After the completion of the second crankshaft rotation, fuel is supplied to cylinders No.2 & 4 by determination of the cylinder identification sensors signal also created in the distributor. - quoted from Shop Manual.


The injectors are reading 13.5-13.7 ohms; the specs call for 11-15 ohms for the Turbo engine, according to the Shop Manual. I sent the injectors in to be rebuilt before I installed them. When I start the engine, I can hear (with a stethoscope) all the injectors 'clicking' until the computer shuts them down.


Once the engine starts and dies, you have to shut the ignition switch off, then on to start it again; otherwise, it won't run at all. Apparently, the computer is being reset when the ignition switch is turned off.

 

some modules have built in protection that will shut down when they sense a short to grd. the module with run normally for a few seconds until the short to grd is pick up at the high side driver. did you check for short to grd on the wiring harness

when the power is supplied by a module, it must do this as there are no fuses outward from the module.

 

With the ignition off and the wires unplugged from the injectors, I checked each of the injector wires of the harness for continuity with the ground and none have continuity with the ground.