2.3L ('83-'97) New engine is in, no start ?


iPandaBar

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1993
Replaced the engine, hooked everything back up, now it won't start.
Engine cranks and tried to start once.
There is some kind of issue in the wiring I think but I am unsure on how to proceed.
Injectors would not fire despite fuel to the fuel rail so I called it a night. The next day I tried to trouble shoot and there was no fuel to the fuel rail, so I went to the relays.
If I wiggle the PCM power diode with the KOEO the relays click on and fuel goes to the fuel rail.
Wiggling just the fuse box does nothing so I don't think it is a short. But the diode is working, I dont know if its in spec because I can't find the specs, not even in the Ford service manuals, but voltage does go across it in one direction.
I have ordered an aftermarket diode because Ford no longer carries them (obsolete) and I have ordered a new PCM relay and I'm hoping this will correct the issue.
Is there anything else I should be looking at?
Thanks guys, I'd be lost with this truck without this forum!!!
 


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RonD

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For now you can just short the diode to see if relays click with key on
The power diode prevents push back voltage when PCM relay's coil is activated, so OK to short for testing

If Crank sensor is working it should still have spark without PCM Relay, so spray some fuel into the intake and crank engine to see if it starts and then dies

The Spark Module(ICM) and coils are powered on by ignition switch, not PCM relay
 

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If I understand what you mean by short the diode (keep in mind I'm an idjut) then no the relays don't kick on. I can see in the electric/vac troubleshooting service manual that the start circuit is separate from the PCM circuit.
The start circuit is definitely working and I'm getting spark.
After multiple attempts to crank I pulled a plug and checked for spark and for fuel in the combustion chamber.
Plug was sparking, but bone dry. That's when I started looking at the injectors and the eec circuit. From what I can tell from the wiring diagram the injectors are directly wired to the PCM, my clutch pedal safety switch is good, the fuel system is running and pressure is good at the Schrader valve as long as Ive wiggled the diode and PCM relay.
The injectors are silent.
When I get home from work I will snap some photos of the wiring diagrams if you think that will help.
I appreciate the fast response!
 

RonD

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Turn the key on and look for the CEL(check engine light) to come on, this means the PCM relay worked and the Computer(PCM) is booting up
If CEL doesn't come on then no PCM so no fuel injectors, so that would be first issue to solve, PCM relay powers up the PCM

Power diode activates the PCM relay, but doesn't power the PCM
 

scotts90ranger

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stupid question and I am not sure it's the same on the newer engines, but did you plug in the harness connector for the fuel injectors? On my '90 it's a I think 6 or 8 pin connector that's round and white and behind the intake manifold by the joint where the two halves bolt together. Knowing me that's something I'd do...
 

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stupid question and I am not sure it's the same on the newer engines, but did you plug in the harness connector for the fuel injectors? On my '90 it's a I think 6 or 8 pin connector that's round and white and behind the intake manifold by the joint where the two halves bolt together. Knowing me that's something I'd do...
Not a stupid question at all!
You would be amazed at the dumb things I do, and I'm well "educated" ???
I even stabbed myself in the eye with a screwdriver last week, that's just how educated I am!
I know that I did connect that specific connector, but now you have me paranoid and I'm half tempted to go check it in the dark. And if I do that I will be 100% tempted to try and start it with no exhaust system installed at 0100. Which will give my already wonderful neighbors even more reasons to love me!

I did not use dielectric grease however, and I'm worried that may be my problem as well.
 

scotts90ranger

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connections on higher amperage circuits are somewhat less picky, just unplugging it and plugging it back in on a swap shouldn't need dialectric grease, we don't use it at work and we build a fair amount of engines (several hundred a year, turn key engines for boats and equipment) and don't have connection issues, but don't have any computer controlled engines over 20 years old either... Plus, chances of all 4 injectors not working because of a bad connection in that connector are slim, unless you are missing the power to the injectors.

Which brings me to an important question, with the key on, does one of the two wires to an injector have 12V? I believe they have constant 12V and the computer switches the ground side.
 

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Which brings me to an important question, with the key on, does one of the two wires to an injector have 12V? I believe they have constant
That one I'm not sure of, I'll have to check tomorrow after Church. I'll double check the wiring diagrams as well.
 

RonD

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No, with key on only the RED wire at each injector will have 12volts, the other wire goes to the computer and is Grounded only when computer wants to open that injector
 

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No, with key on only the RED wire at each injector will have 12volts, the other wire goes to the computer and is Grounded only when computer wants to open that injector
So if I connect my meter up to the red wire and touch the engine block I should get 12v? And if I don't my harness is disconnected somewhere?
 

RonD

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With key on, yes

The 12v for the injectors comes from the PCM relay
 


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