Crank No Start Frustrations
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Crank No Start Frustrations
2003 f-150 lariat 5.4 2 valve
Truck sometimes hard to start and ran but had misfires on 2 cylinders, according to autozone they said 2 coils were bad.P0302 and P0307 after changing, wouldn't start, put old ones back in. still no start
Battery is good, it's only 6 months old, swapped in a good one just to make sure,connections are tight
replaced the fuel relay, i may have inadvertently damaged the other messing with the contacts, pressure is at 35-40psi and seems to hold, thinking that should be good enough to at least start?
Pulled coils, checked ohms on both sides, all the coils came out close to each other
Checked PCM relay and diode, also checked every fuse
bought a coil on plug tester and no spark to plugs, but also have 11.9 volts at all connectors
pulled a couple plugs, they look like they were changed not too long ago. They are Motorcraft Platinum AGSF 22WM gaps were good AT .052, reinstalled and torques to 25 ft lbs with a 4" extension
Checked power at fuel injectors also had 12volts, pluged in NOIDS and they aren't lighting up with key on cranking
rechecked all connections, checked cam and crank sensors, all seemed to be fairly clean and tight, all vacuum and egr hoses reconected
Tried adding gas and beating on fuel tank with ignition on, I don't know why! Lol
Check engine light goes out when cranking, the anti theft light goes out while cranking
Pulled codes with my bluetooth code scanner and only code i get are P1000, OBD Readiness Test not complete
I did a live scan while cranking, it showed throttle position and maf sensor but zero rpms, so i thought maybe crank sensor, what a job! But no luck
tried a different key, tried jiggling key
When i spray starting fluid into the throttle body, it acts like it wants to start, i can smell some exhaust but it never catches to the point where it actually starts then dies.
My last thoughts are PCM?
Truck sometimes hard to start and ran but had misfires on 2 cylinders, according to autozone they said 2 coils were bad.P0302 and P0307 after changing, wouldn't start, put old ones back in. still no start
Battery is good, it's only 6 months old, swapped in a good one just to make sure,connections are tight
replaced the fuel relay, i may have inadvertently damaged the other messing with the contacts, pressure is at 35-40psi and seems to hold, thinking that should be good enough to at least start?
Pulled coils, checked ohms on both sides, all the coils came out close to each other
Checked PCM relay and diode, also checked every fuse
bought a coil on plug tester and no spark to plugs, but also have 11.9 volts at all connectors
pulled a couple plugs, they look like they were changed not too long ago. They are Motorcraft Platinum AGSF 22WM gaps were good AT .052, reinstalled and torques to 25 ft lbs with a 4" extension
Checked power at fuel injectors also had 12volts, pluged in NOIDS and they aren't lighting up with key on cranking
rechecked all connections, checked cam and crank sensors, all seemed to be fairly clean and tight, all vacuum and egr hoses reconected
Tried adding gas and beating on fuel tank with ignition on, I don't know why! Lol
Check engine light goes out when cranking, the anti theft light goes out while cranking
Pulled codes with my bluetooth code scanner and only code i get are P1000, OBD Readiness Test not complete
I did a live scan while cranking, it showed throttle position and maf sensor but zero rpms, so i thought maybe crank sensor, what a job! But no luck
tried a different key, tried jiggling key
When i spray starting fluid into the throttle body, it acts like it wants to start, i can smell some exhaust but it never catches to the point where it actually starts then dies.
My last thoughts are PCM?
Fleet Mechanic
Joined: Jun 2023
Posts: 1,394
Likes: 384
From: WA
I did a live scan while cranking, it showed throttle position and maf sensor but zero rpms, so i thought maybe crank sensor, what a job! But no luck
tried a different key, tried jiggling key
When i spray starting fluid into the throttle body, it acts like it wants to start, i can smell some exhaust but it never catches to the point where it actually starts then dies.
My last thoughts are PCM?
tried a different key, tried jiggling key
When i spray starting fluid into the throttle body, it acts like it wants to start, i can smell some exhaust but it never catches to the point where it actually starts then dies.
My last thoughts are PCM?
If it was mine I might check resistance at the PCM connector through the harness and sensor. There are two pins to measure across. It's a variable reluctance sensor, basically a coil that generates a voltage when the teeth of the reluctor wheel pass by. There's no external power involved the voltage is generated by the movement of the parts. Not sure what it should be but probably around 200 ohms.
If you have a good harness and sensor then bad PCM might fit. But there might be other causes too. At least you'll know that the sensor and harness should create and pass the voltage signal.
I've also read about measuring the bias voltage across the crank sensor PCM pins with the key on. You can do both with the PCM connector off. I'd have to look that number up I've never done it myself. That will tell you more about the PCM itself. Good luck.
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