My 1990 F250 5.0L EFI will not start.
I am a novice mechanic but have determined
that there is no fuel injector activation.
Wiring checks good. I have 12V on one lead
to ground and about 10V on the other. It
does not move an analog meter toward 0V
when the engine is cranked.
I can't tell if the Engine Control Module is
bad or some input to it is keeping it from
activating the injectors.
Help !

 

I am not sure what you mean. Is the engine turning over just not starting? If so the first thing I would suggest would be to check all the relays. Specificaly the high presure fuel pump relay. In my experience they are most often the cause of a no start situation.

JJ

 

JJ,
I could hear the fuel pumps run when the ignition is turned on but I replaced the fuel pump relay anyway. No luck, so I tried depressing the pin in the Shrader valve and fuel squirts out (I don't have a pressure tester).
I'm sorry my description was not very clear, I don't know exactly how to word it. What I was trying to describe is that there is power to the fuel injectors but no pulse.

 

If you are measuring voltage on the 12V side of the injector, there will be no pulsing. The computer turns the ground on and off to fire the injectors. Do you know for sure that you are getting good spark?

 

There is no pulse on either injector wire. I went one step farther a few minutes ago and grounded the lower voltage side through a current limiting resistor and I could hear the injectors click.
Also I tried cranking the engine and that set of cylinders fired a couple of times (until they had no fuel again). So I'm pretty sure everything is working except the signals from the ECM to turn on the injectors.

 

I'd check the TFI module. The computer gets its timing signals for injection and ignition from the TFI. Timing information under a certain rpm is passed directly to the coil. Pull the codes from the computer and see what that turns up.

 

Sorry for the long delay in the reply but had to go vote, etc.

The only codes I get are 11 11, I guess because I had the negative battery terminal off for a while.

Will any of the sensor inputs to the ECM (if the sensor was totally bad) keep the ECM from opening the fuel injectors ?

 

The only time I can see that happening would be if there was no timing signal to the computer. Other than that, the problem would be in the output to the injectors. Having the negative cable unhooked reset everything. Make sure that the computer is getting a good solid ground too - bad grounds can create a lot of headaches.

 

This morning I have replaced both of the ignition control modules. (The ECM itself and the Hall Effect pickup inside the distributor). The fuel injectors are still the same but I have a new indication. Now I have no spark unless I remove the SPOUT jumper . This is turning into a can of worms. Too bad the nearest Ford dealer is 30 miles form here.

 

Thanks to a very accomodating Kragen's, I now have replaced the ECM and Hall Effect sensor for the second time at no additional cost and I still have the same indication. No spark unless the SPOUT jumper is removed. Injectors are still the same.

Where is the ground for the computer ?

 

There is one ground on the fender just above the computer harness. There may be another going through the main harness as well, so double check the negative side of the battery while you are checking.

 

OK.
Just to be sure I removed, cleaned, and reinstalled all the ground connections I could find.

What is SPOUT ? I see in my Chilton there are error codes for it being being bad but whether I
leave the jumper plugged in or not it doesn't set any error in the computer. It definately affects whether or not I have spark though!

 

Have you tested the TFI module? You said you replaced the ECM (computer?) and the hall effect sensor. Did you mean ECM or TFI? The TFI is the module that is on the outside of the distributor that the wiring harness plugs into. From what you are saying, the timing signal is not reaching the computer for some reason. When you unplug the SPOUT connector (it should be in the harness near the TFI module) it sends spark signal straight to the coil from what I understand.

 

Sorry about the mix up in terminology. My mistake.
I have not replaced the ECM (Computer) but I replaced the TFI module on the distributor (twice) and the pickup inside the distributor (Hall Effect sensor) twice. I replaced them twice because after the first time, I got no spark and I thought maybe one of them was bad out of the box. What you describe for the SPOUT signal makes sense as to why I get spark when the jumper is unplugged. Kind of points to the ECM being bad doesn't it ?

 

Possibly a bad ECM, and at this stage, it might be a good thing to see if you can get it tested somewhere. Or if you can find another one for real cheap try to replace it. However, before doing that, double check that the wiring from the TFI module has a good circuit to the computer (<1 Ohm). You'll have to get a wiring diagram to check which pins at the computer connect to the TFI module and start probing with a multimeter. Back probe the connectors, and try not to puncture any insulation either - that will create headaches years down the road.