Hesitant Start

[GaRamGuy]

Holding the pedal down when starting is the fuel cutoff mode. Used when flooded. If it instantly fired up.. it points at injectors. What do the spark plugs look like? Do you have a cylinder that is running rich?

I changed all of the plugs about three weeks ago. Looked fine. I did remove all of the injectors and placed blue shop towels below and pressurized fuel rails. None of them leaked. Did not notice any leaks from o-rings prior to removal. Mechanic performed an injector service after replacing fuel pump.

 

[dl2011ms3]

Could also be a TPS(Throttle Position Sensor) problem. I had that happen on my 02 4.7

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[GaRamGuy]

Could also be a TPS(Throttle Position Sensor) problem. I had that happen on my 02 4.7

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It is integrated into the throttle body with the 5.7 litre hemi. Good thinking.

 

[madtrucker2016]

Been chasing this problem for awhile. Very first start of the day is great. Wait an hour and it hesitates. Fuel pump pressure is good. Checked for leaking injectors by pulling and checked for leaks while priming. I installed new:

battery
throttle body
crank sensor
Starter
IAT sensor
Egr valve

Cleaned all ground connections. Inspected all fuses. Truck has 42K mikes owned since new. No codes thrown ever. Alternator passes charging test. Charges at 14.2 volts with AC and headlights turned on. Any help would be appreciated.

could be a messed up sometimes stuck open relay for the fuel pump I had that and took the tank down and changed the fuel pump. But it wasn't that it was a 10 dollar relay messing up on times. Maybe you have another relay as a spare and pop it in and see how she runs

 

[GaRamGuy]

could be a messed up sometimes stuck open relay for the fuel pump I had that and took the tank down and changed the fuel pump. But it wasn't that it was a 10 dollar relay messing up on times. Maybe you have another relay as a spare and pop it in and see how she runs

Several relays are the same. I swapped it out with the truck starting and running the same.

 

[madtrucker2016]

Several relays are the same. I swapped it out with the truck starting and running the same.

OK maybe disconnect the battery and let sit over night and retry it just a thought

 

[Redtruck-VA]

If you startup cold, run for a couple minutes and turn off. Will it startup again or drag?

 

[GaRamGuy]

It will start up perfectly.


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[dl2011ms3]

I had to replace my TSB twice. A brand new Bosch sensor from O'Reilly was clocked wrong and putting out a wide open throttle signal on startup.

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[dl2011ms3]

TPS* not TSB....,..[emoji17]

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[Redtruck-VA]

How long does the engine need to run before the restart issue begins? Full warmup?

 

[GaRamGuy]

Driving within the hour. It will crank slowly as if the battery is weak, which is not case. When resume starting, it will crank easier but struggles lacking fuel or spark? If I step a little on pedal, it starts right away.


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[Redtruck-VA]

This really sounds like a heat soaked starter motor. But i would replace the starter cable along with the starter motor. And check engine/ battery chassis grounds. Just by chance, engage your trip odometer and see if it reverts back to it's odometer sitting after the starter drags during startup.

 

[GaRamGuy]

I replaced the starter motor this past December but did not replace any cables. I did remove ground cable attached to block near starter, and used Emory cloth to clean surface. Reinstalled ground with some dielectric grease. In fact, I checked all grounds in engine bay. Loosed and re-tightened. I wonder if using an ohmmeter will help with detecting resistances?


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[dl2011ms3]

Driving within the hour. It will crank slowly as if the battery is weak, which is not case. When resume starting, it will crank easier but struggles lacking fuel or spark? If I step a little on pedal, it starts right away.


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With your info about the pedal, I'm leaning towards the TPS. Could have been bad from the get. Check the signal voltage on startup when it's giving you problems. Pressing the pedal changes that voltage and thus "fixing the issue" to help it start.

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[GaRamGuy]

Do I need a scanner to check voltage at start up? Or hooked up to on board computer?


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[dl2011ms3]

You'll need an extra set of hands and just use a voltmeter. Press the probes onto the back of the plug trying to hit the pins or bare wire. I don't know which wires they are, but try to find the ground and signal return back to the ECU.

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[GaRamGuy]

Looks like I’ll need a wiring schematic. Should be able to find one online. I agree signal voltage should be checked.


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[dl2011ms3]

Check it while cranking, foot off the gas. And with foot on the gas the same way that works. You'll see the voltage difference. Also pull you fuel pump relay while doing this so it doesn't accidentally start while you're under the hood.

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[GaRamGuy]

That’s a good point. Should be able to see voltages.


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