starting issues

[J4aday]

I have a 91 Ford Ranger with 2.3L. It will not spray fuel into the cylinders. Here is a list of what I have done, troubleshooted, and found.

1. Engine was missing. I found both coil packs were cracked. replaced them.
2. Plugs and wires were corroded. replaced all 8. gapped the plugs to .044

ran about 3 days and was missing again.

3. replaced ICM module, Mine was corroded and was not telling the coils to spark.
4. I verified I have a pulse with my crankshaft sensor and cam sensor and I do have spark! Yay
5.pulled the plugs again. DRY, BOO!
-So I checked the fuel pump. It works!
-Put the fuel pressure guage on the Schroeder valve and have 38psi.
-I also replaced the fuel filter.
6. I can fire the injectors with 12V from the battery and they all switch.
SO. I put a test lamp on the injectors while trying to start it but I dont see it flicker like they are turning on and off. It only dims slightly.

I am leaning towards a computer problem. Seems like it is not switching the negative sides of the injectors like the computer should. I also was able to start it with starting fluid but it would not stay running.

Any thoughts?

 

[RonD]

Ford Fuel injection(and almost all others) give all the fuel injectors 12volts when key is turned on, but they have no Ground so stay closed.

The computer Grounds the injector to open it.
In your '91 4 cylinder the computer Grounds two injectors at a time, this is called Batch Fire, 1 and 4 will open then 2 and 3 will open.

If you added 12volts to injectors and they worked, then I would trace the RED wire(daisy chained to each injector) back to the EEC Relay(brown base) that is where the 12volts comes from.

 

[J4aday]

Yep, I do have 12v at each of the injectors. However I dont think the negative side is being switched. I forgot about the relay so thanks a bunch. for some reason I kept thinking it went right back to the EEC. I'll check the relay out next.

 

[RonD]

If you have battery voltage(12v) at the injectors then EEC relay is working.

Check grounds at EEC(PCM, computer)
Good wire/pin diagram here: http://www.auto-diagnostics.info/ford_eec_iv

You can also pop the top on the computer and look for any discoloration on circuit board.

 

[J4aday]

Again thanks for the info. I finally found the relay under the fuse box. I believe it is working but I need to check the grounds. Aargh! there is a bunch of questionable looking wires in the area. I may have to repair some of the other wires as well. Starting a fire in the garage this afternoon for some heat. It's Fracking cold out man.

 

[J4aday]

I found that the wiring was all corroded on the bases of both the fuel pump relay and the EEC relay. I had to wait for parts so its been a while since my last post. I now have the relay bases changed, Soldered and shrink tube. The truck still will not start. Still no fuel to the injectors. Im now seriously thinking the computer. Anything else I might be missing?

 

[RonD]

If you manually add fuel to the intake, gas or starting fluid, will the engine fire up?
If so then yes it could be computer problem, assuming fuel pump is working as it should and you have pressure at the fuel injectors.

If engine doesn't fire then there is no spark, and no spark means no fuel injectors.
The Crank position(CKP) sensor is connected directly to the ICM(ignition control module), the ICM controls spark plug firing order based on CKP sensor pulse, and sends that pulse to Computer to time fuel injectors.
If computer doesn't get that pulse then it doesn't know that you are even trying to start engine, so never starts injectors.

 

[94RoadkillRanger]

Like your 1991, I was at the same point with my 1994 Ranger. It's either the Computer or the Crank Sensor. There are two parts to the Crank Sensor as it also controls the spark (unless you have a 94 California Ranger). My spark side was working but the injector side had failed so I replaced it. Funny thing is that the computer was cheaper! CKP replacement fixed mine.

 

[J4aday]

As I stated above. I do have fuel pressure 38psi, and I do have spark. I have both the crank and cam position sensor otherwise I would not have spark. I was able to fire it up with starting fluid but it would not stay running. The fuel pump does work, I can hear it. If I look at my wiring diagram the other side of the injectors are switched at the EEC. Pin 58 is injectors 1 and 4. Pin 59 is 2 and 3. EEC switches the negative sides, -12vdc of the coils inside the injectors. EEC relay provides the power to the injectors wire#361 red.

 

[huh?]

Im now seriously thinking the computer. Anything else I might be missing?

in RonD's link to the eec-IV wiring information, pin numbers 16, 20, 40, & 60 are ground wires that need a good solid grounding connection to the negative post of the battery.

you already diagnosed this as an injector grounding issue.

for injectors to get grounded:
1) wiring from injectors to computer>
2)computer switches ground>
3)ground wire from computer to negative of battery.

before the ECM is condemned, make absolutely sure that:
1) the wiring from the injectors to ecm connector pins 58 & 59 have continuity
2)in RonDs last post he said ICM signals ECM in regards to injector timing. posted by RonD : "the ICM controls spark plug firing order based on CKP sensor pulse, and sends that pulse to Computer to time fuel injectors. If computer doesn't get that pulse then it doesn't know that you are even trying to start engine, so never starts injectors." i don't know which wire(s)/pin number(s) need to be tested to see if this communication is occurring
3)the ground wires(pins 20, 40, 60) from the ecm connector to the negative battery cable clamp show a complete circuit. i recommend you get a long jumper wire to test for continuity directly at the negative battery cable clamp and these pins.