I've got a 94 F350 xlt With 5.8 that will not run. Problem 1...it sat for a couple of years...changed out old fuel for fresh...will not start...hooked up fuel pressure to rail and found around 40+/- psi...tried fuel directly into TB and it would start and run as long as fuel was fed into it. Have replaced injectors, ECM, and cleaned every ground I can find still no injector function. What else could cause the injectors to not function...(noid light steady burn and flickers but does not flash.)?

 

when you said the noid light is steady, that makes me think that the injector(s) are getting power from the ECM and if you are getting this far, you probably have a proper ground so the ECM is working properly in that respect. If the injectors are getting the power from the ECM, then start by figuring out what triggers the ECM to fire the injector. Mine is probably similar to yours in that you probably have something inside your distributor that picks up the signal of what cylinder it should fire and then that signal is used by the ECM to fire the proper injector. That would be where I'd look next

Also try pulling the codes to see if anything is there.

 

Injectors are fired by the computer once it receives a pulse from the TFI module signifying the engine is turning over. Spark is also generated from the same source... the TFI module, so start with that and check that you have continuity across the spout plug and from the distributor to TFI and TFI to computer.

 

OK now I'm really getting frustrated. changed out the ICM and Stator new dist cap and rotor. Checked with noid light again and....while turning over the noid light seems to flash but is pretty dim when fuel is fed to the TB it will start and the noid burns much brighter and while using starter it flashes...once the engine runs on the fuel fed to TB it burns almost steady with a fast flicker. Tried wiggle, push, twisted and tugged on all harnesses while turning over hoping to find a faulty wire...no luck. I did get a code 111 and a code 126 the 111 should be system pass while the 126 should be "Manifold Absolute Pressure/Barometric Pressure Sensor Higher Or Lower Than Expected". (Shouldn't stop it from running) Where to go from here? something is obviously is preventing the signal to the injectors from triggering them to open.

Anyone with clue that could help me out with this deli-ma before my thinning hair is completely gone would be appreciated.

PS tried replacing all the relays using known good ones from another vehicle.

 

Hard to say as we can't see the noid light in action however based on what you've stated sounds like it is firing the injectors nothing is preventing it from doing so.

How much juice do you have to the injectors? You state you have a weak light during

Good strong battery motor turns over strong on attempt to start it?

Do you have battery voltage to the injectors key in start and run positions KOEO? and to all of them? did you check?

Try the noid light on more than a single injector and making sure to check at least a couple of them from each batch?

Do you have battery voltage to the injector while cranking the engine attempting to start it?

Battery voltage = 12+ volts, but anything steady 10v or better should suffice.

Check grounds, short cable from battery to drivers side fender and top of core support top left side of radiator make sure both are clean and tight also main ground right side of engine block. Should be a smaller gauge blk-wht wire in with the large main ground cable at the negative battery terminal, verify its there clean and tight.

If you have reason to doubt the noid light feel something is preventing fuel even though you state it does flash (sounds iffy at best reading it though, like you see it but have serious doubts about it), WOT shuts injectors off to clear flooded engine for example. Try unplugging the TPS try and start it see if has any effect to noid light reaction and or measure throttle fully closed position voltage druing KOEO as well as during attempt to start. If it reads 4.5-5v its causing the computer to hold injectors closed. Should be anywhere between 0.6-1.0 volts fully closed throttle. Sounds unlikely as you do state the noid light flashes but thought I'd at least mention it.

 

Check and re-establish your grounds. It's the simple things that are often overlooked which can wreak havoc on your operating system.

 

bassenator
This sparks a thought...You say the noid light is weak. When I read that I think insufficient ground. The injectors work on a duty cycle that receives constant power (from the PCM) and sends a ground signal to the injector to fire it.

The main wiring harness has a 48 pin, square connector between the PCM and the motor. This is what carries the wires for most of the sensors and injectors from your motor to the PCM. You haven't mentioned drying that out. It has a 10mm bolt on the back that holds the two sides together and if you've ever disconnected this connector, you'll see how it could stay wet for a long time. Maybe try disconnecting that and drying it out (I'd use the brakekleen that comes in a can - spray on to clean, dries fast and leaves no residue).

 

By the way the injectors do not get any power from the PCM.
The power comes from the power relay that is operated (closed) by the Ignition switch.

Also a test light with a 200mA or less bulb works much better than a NOID light for checking the injector circuit. It will also tell you if the injector has an open coil or not and a NOID light will not tell you that.
A NOID light will only tell you if there is power to that injector plug and if the driver transistor is working in the computer. A 200mA or less bulb will not hurt the driver transistor as the injector will put a bigger load on the driver transistor than that.

 

Thanks so much for the responses.

I work out of town during the week, but this coming weekend I will try to check as many suggestions and try to answer some of the questions posted. i.e. TPS, test light vs noid, etc. maybe try and post a video of what the light is doing during the attempts.

P.S. subford - would that test light be connected to the neg battery term for testing with prob in the wires while injector is plugged in? (don't mean to sound like a complete dummy here but just checking)

 

You would use both the NEG (ground bolt) & the POS post of the battery depending on the test:


By the way here is a 30min video using both the NOID light and the test light. Note that there are tw videos on right after the first. The second one is a sales pitch.


/

 

Well today I worked on this truck again and I'm still in a quandary.

Subford your help has been great...when I used the test light method I found that their is NO flash. When key is off it shows grounded...12 volts to positive terminal...key on it's 12 V to neg term...with injector pluged in I get 12.1V on red and 11.9 on tan...checked wire on both sides all the way back to ECM and they have complete continuity all the way...disconnected ALL harness plugs and recleaned along with checking continuity and ALL check good. I have checked with the same results 3 separate ECMs the grounds at the ECM also test good.

Any ideas what would tell the ECM to not send the signal to open the injectors?

Can the key switch cause an issue?

Thought maybe the inertia but I thought that shuts off pump.

danr1

How much juice do you have to the injectors? You state you have a weak light during
Key off 12V to pos term key on 12V to neg term
Good strong battery motor turns over strong on attempt to start it?
Very strong turnover while cranking keeping a good charge on Battery
Do you have battery voltage to the injectors key in start and run positions KOEO? and to all of them? did you check? Cant reach them all but at the ones I can reach yes strong power

Try the noid light on more than a single injector and making sure to check at least a couple of them from each batch? Yes

Do you have battery voltage to the injector while cranking the engine attempting to start it? Yes

Battery voltage = 12+ volts, but anything steady 10v or better should suffice. dropped to around 11.8V at injector while cranking.

Tested the TPS and found about 5.9 volts and that the voltage raises and lowers with throttle movement (not as smooth as I would have expected but none the less)

 

Try pulling all the injector leads off the injectors (get someone with small hands as necessary), then pull the connector at the computer and check for continuity in the connector beteween pin 58 and ground, and pin 59 and ground. There shouldn't be any. If there is, then one or both of those circuits have been shorted.