Updated! 2003 E 350 fuel pump stays on
After a alternater replacement it would not start. Then after pulling a coil it did, but randomly.
When i first got to it i crank it. All lights on the dash stayed on while cranking. However the fuel pump stays on while the ignition is on. Also no com with any modules. I check all the fuses and relays relevant to the pcm. Next i went to verify that there is no spark or injector pulse. I unplugged a coil to test, and when i turned the key to the on position, i had both power to the coil, and the pump turned off. So of course it runs now and all the modules are talking just fine. I traced all the wires to find a fault with no success!
I know i watched a video from eric o, or paul danner, on this kind of issue, just can't remeber what direction they went.
Any help is greatly appreciated!
UPDATE!!!!
So next time it wouldn't start i could pull up live stream. It look like no rpm data but i forgot to check the engine light to see if it went out during cranking... sorry but i rarely work on fords!!! Fuel pump prime was normal. Not wanting to unplug anything i gave a injector a quick ground to fire it. The thought was to spray some gas and see if that cylinder had spark..... well it started.
Next time the battery was a brick even though it's suppose to be rather new. Wouldn't start, no com, check engine light stayed on while cranking and no fuel pump prime. Had 5v ref at the tps and i had a crank signal from the sensor. Didn't have anymore time so i came back today to finish.
Everything is the same. Checked the 5v ref at the coolant sensor, it's 10.6 volts which is below battery voltage. Not sure what to make of that! But pressing on I checked the crank signal at the pcm which is good. It also has a single wire from the pcm which the wiring diagram reads" rmp siganal". I assume this is for the tach which it doesnt't have. It reads near battery voltage and lowers when cranking.... 4 volts i think.
Next I hit every power and ground on the pcm with a 3amp headlight bulb and they all passed. So I'm at the horrible point of calling the pcm which i truly hate. I was looking at flagship one for a replacement. The pcm comes flashed with a lifetime warranty. Has anyone dealt with them?
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- chief eaglebear
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Unfortunately i don't have a wiring diagram because it seems like unplugging a coil momentarily seems to fix it. But from what I've been told that doesn't always work!
Thanks for the response!
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The fuel pump stuck on is actually a helpful symptom, because it proves that the PCM Power Relay is working, too. That's usually my go-to with no comm Fords of this generation, but not the case here.
Do you recall why the PCM was replaced initially? Was it in response to this same condition? Or a different issue?
My initial suspicion is a bad replacement PCM. If possible, get it to not start again and check PCM powers/grounds/5V reference. This is the best way to make 100% sure the wacky PCM behavior isn't being caused by something external.
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I keep thinking that something is causing the pcm to wig out. Like a frequency feading into the pcm thru the coil. But it's a coil on plug so i would have to unplug all of them. Plus the coil i unplugged is not the one that had been unplugged before when it would start.
Found some wiring diagrams so i guess I'll do some studying. Since it's a church van i hate to see them use it and this happen again!
Thanks for your responce!
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Bucher wrote: Pcm was replaced a year or so ago by a dealer, no idea why. I went after the coil to check controll from the computer. When i unplugged the coil it was fine. Which seems to be a common theme. I am kicking myself for not trying the 5v since that is a no brainer!
Gotcha, thanks for the info. Don't sweat the 5V reference check - you were following good no start diagnostic procedure by checking for spark, IMO.
I keep thinking that something is causing the pcm to wig out. Like a frequency feading into the pcm thru the coil. But it's a coil on plug so i would have to unplug all of them. Plus the coil i unplugged is not the one that had been unplugged before when it would start.
This was gonna be my next question. If it's the same coil getting unplugged to make it start, then you might be onto something. If you can unplug ANY coil and make it start, then you're just seeing a symptom of the problem. It would seem that the act of changing a status flag for a coil driver (which typically sets a P035X code) is somehow snapping the internals back into life. :silly:
Let us know what you find!
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- Matts Auto
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I pulled the diode with the ignition on to verify a response. The pump turned off and when the diode was pulled back in, the pump turned back on. I did that several times. The terminals looked like the were 15 years old but not that bad. Having said that i wouldn't be suprised if something like that is the issue!
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- Matts Auto
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Thanks again.
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- Matts Auto
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I unplugged the coil when the ignition was off, then turned it to the on position. That's when the pump returned to it's normal 3 second prime. Wouldn't the engine need to be cranking to turn on the driver and set the code?
I did unplug the coil while running and it did flag a circuit failure for that cylinder. I would think there would be a bias voltage that would change when the driver is on. At least that's my guess as to how the pcm sets a code.
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Bucher wrote: I unplugged the coil when the ignition was off, then turned it to the on position. That's when the pump returned to it's normal 3 second prime. Wouldn't the engine need to be cranking to turn on the driver and set the code?
Nope! The PCM will flag a code based solely on the voltage present at the PCM pin, even with the driver off. It's what Paul calls an output state monitor. The PCM is watching that pin any time the key is on, and flags the P035X whenever the voltage doesn't correspond to the driver state. Driver off, voltage should be high. If it isn't (like with the coil unplugged), the PCM knows there's a circuit issue.
I did unplug the coil while running and it did flag a circuit failure for that cylinder. I would think there would be a bias voltage that would change when the driver is on. At least that's my guess as to how the pcm sets a code.
Actually, there's no bias voltage on these coils. It'd be helpful if there was! :silly:
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So if that theory is true, then unplugging the coil with the ignition on could flag a code. Maybe it's looking for voltage with ignition on and then a drop when it sees the rpm signal and the driver is working.
If so then unplugging something like the coil will flag a code and thus waking the pcm up from it's weird behavior.
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So next time it wouldn't start i could pull up live stream. It look like no rpm data but i forgot to check the engine light to see if it went out during cranking... sorry but i rarely work on fords!!! Fuel pump prime was normal. Not wanting to unplug anything i gave a injector a quick ground to fire it. The thought was to spray some gas and see if that cylinder had spark..... well it started.
Next time the battery was a brick even though it's suppose to be rather new. Wouldn't start, no com, check engine light stayed on while cranking and no fuel pump prime. Had 5v ref at the tps and i had a crank signal from the sensor. Didn't have anymore time so i came back today to finish.
Everything is the same. Checked the 5v ref at the coolant sensor, it's 10.6 volts which is below battery voltage. Not sure what to make of that! But pressing on I checked the crank signal at the pcm which is good. It also has a single wire from the pcm which the wiring diagram reads" rmp siganal". I assume this is for the tach which it doesnt't have. It reads near battery voltage and lowers when cranking.... 4 volts i think.
Next I hit every power and ground on the pcm with a 3amp headlight bulb and they all passed. So I'm at the horrible point of calling the pcm which i truly hate. I was looking at flagship one for a replacement. The pcm comes flashed with a lifetime warranty. Has anyone dealt with them?
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Anyway, you had crank signal and 5V reference, so I'm inclined to agree that the PCM is intermittently failing.
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