05 4.0 sohc won't stay running - Ranger-Forums - The Ultimate Ford Ranger Resource


4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

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  #1  
Old 12-16-2015
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05 4.0 sohc won't stay running

It cranks, runs for a couple seconds and quits. Just replaced fuel pump today. Filter is good as well. Need help. Stuck at work.
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Old 12-16-2015
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Why did you change the Fuel Pump?

What were previous symptoms?

Are/were there any codes?

Have you tried removing air plenum from intake and spraying starting fluid(or gas) in to intake to see if it stays running, confirming it may be running out of fuel, if it still dies then spark is being cut off.

Unplug TPS(throttle position sensor) then try to start.
TPS gets 5 volts from computer
It sends back 1volt(closed) to 4.5volts(wide open)
If TPS sends back 4.5volts or higher(foot to the floor) with RPMs at 0 then computer will shut off fuel injectors, this is called Clear Flooded Engine routine found in all fuel injection computers.
But this would be a no start, not a start and stall.


Fuel pump relay in the engine fuse box could be going bad.
Swap it with WOT relay
WOT = wide open throttle, this relay will cut off AC compressor when you need more power, which is when you are at WOT

Does it die right when key comes back to RUN, could be ignition switch is going bad, i.e. voltage at coil when key is turned to START but no voltage in RUN, so engine starts then dies.
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Old 12-16-2015
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Quote:
Originally Posted by RonD View Post
Why did you change the Fuel Pump?

What were previous symptoms?

Are/were there any codes?

Have you tried removing air plenum from intake and spraying starting fluid(or gas) in to intake to see if it stays running, confirming it may be running out of fuel, if it still dies then spark is being cut off.

Unplug TPS(throttle position sensor) then try to start.
TPS gets 5 volts from computer
It sends back 1volt(closed) to 4.5volts(wide open)
If TPS sends back 4.5volts or higher(foot to the floor) with RPMs at 0 then computer will shut off fuel injectors, this is called Clear Flooded Engine routine found in all fuel injection computers.
But this would be a no start, not a start and stall.


Fuel pump relay in the engine fuse box could be going bad.
Swap it with WOT relay
WOT = wide open throttle, this relay will cut off AC compressor when you need more power, which is when you are at WOT

Does it die right when key comes back to RUN, could be ignition switch is going bad, i.e. voltage at coil when key is turned to START but no voltage in RUN, so engine starts then dies.
No codes from this. Just suddenly did it Monday. Then as i cycled the key from off to on several times i could hear the fuel pump loud as ever, sometimes it made a lower pitched noise as if it were weak, other times it didn't turn on at all. Stays running on ether. Already swapped the relays earlier. Run a test light to the pump and its only powered in start position. Was suggested to run a toggle switch and hotwire to pump.

Last edited by 1badwelder; 12-16-2015 at 05:14 PM.
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Old 12-16-2015
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Ford computers only turn the fuel pump on for 2 seconds when key is first turned on.
It won't start again until RPMs are above 400, this is a safety features in case fuel line breaks, broken fuel line would cause engine to go below 400RPMs, it would stall, lol, and pump would shut off instead of pumping fuel out the broken line.

If you cycle the key on and off a few times the noise should changed, as the pressure in the system builds the pump can't push anymore fuel in, so it would sound quieter more muffled.

You can pull out the Fuel Pump relay and put a jumper in there.

have a look here: Automotive Relays - Electric Circuit

All automotive relays are the same, same layout just different load ratings and voltages
You want to jump slot 30 to 87, those are the "load" contacts
85 and 86 are the coil contacts, used to CLOSE the "load" contacts
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Old 12-17-2015
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Problem solved

Quote:
Originally Posted by RonD View Post
Ford computers only turn the fuel pump on for 2 seconds when key is first turned on.
It won't start again until RPMs are above 400, this is a safety features in case fuel line breaks, broken fuel line would cause engine to go below 400RPMs, it would stall, lol, and pump would shut off instead of pumping fuel out the broken line.

If you cycle the key on and off a few times the noise should changed, as the pressure in the system builds the pump can't push anymore fuel in, so it would sound quieter more muffled.

You can pull out the Fuel Pump relay and put a jumper in there.

have a look here: Automotive Relays - Electric Circuit

All automotive relays are the same, same layout just different load ratings and voltages
You want to jump slot 30 to 87, those are the "load" contacts
85 and 86 are the coil contacts, used to CLOSE the "load" contacts
It was the daggum anti theft system. Apparently as I was cycling the key I did it in the perfect sequence to activate the anti theft system. Runs like a dream. Thanks for all the help. I love this forum.
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Old 12-17-2015
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Cancel the all clear signal

Quote:
Originally Posted by 1badwelder View Post
It was the daggum anti theft system. Apparently as I was cycling the key I did it in the perfect sequence to activate the anti theft system. Runs like a dream. Thanks for all the help. I love this forum.
She idled good for about 5 minutes then died. The wiring harness under the seat started smoldering and filled the cab with smoke.
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Old 12-18-2015
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That doesn't sound too good !!! ???

I think in '05 the anti-theft system(PATS) cuts the fuel but also prevent starter motor from activating, so not sure if that was the problem?
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Old 12-18-2015
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Quote:
Originally Posted by RonD View Post
That doesn't sound too good !!! ???

I think in '05 the anti-theft system(PATS) cuts the fuel but also prevent starter motor from activating, so not sure if that was the problem?
Well the motor, trans, ECU is '05 the chassis is '01. I found a problem. Last Saturday I removed the seats and washed down the floor board. There's no carpet or vinyl. I used a concentrated industrial degreaser to remove at least a year of grease, oil, spilt coffee, alcohol, and cokes. The degreaser got into the harness connector under the seat where it goes outside the cab. This caused the melted harness connector. It was still soaked with it when I took it apart. I plan on doing away with it and using a lot of butt connectors with heat shrink.
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  #9  
Old 12-23-2015
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there is also a issue if you carry multiple keys on your truck key set. it is possible to create a ground to your lock cylinder thus disabling your ignition key. happened to a friend because of the way he held his key set when he started his truck.
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