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'07 Nitro RT, Occasional Hard Starting

2659 Views 6 Replies 3 Participants Last post by  MoparNorm
My '07 Nitro (4.0, auto, 2wd) occasionally has trouble starting (cranks for 4-5 seconds before firing) when the ambient temp is above 95 degress, which is often because I live in Vegas. It's happened right after being driven and also after sitting out all night. I ran my code-checker and it didn't pull anything. It acts like its vapor locked, cranking until fuel gets to the rail then starts and runs fine. Its always fired right up and hasn't stranded me yet, but I'm not about waiting for it to die in the middle of nowhere. Anybody have any ideas?
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I'm wondering if that fuel system has a "backflow" or Checkvalve, to prevent the fuel from draining back?
That's normally a function of the fuel pump and could indicate the pump is losing prime.
Wait for Imperial Crown to respond, he will likely know the answer.
Thx MoparNorm. This is one of those questions I think I know the answer to and don't like what it entails because i thing the pump is in-tank.
MoparNorm is correct. A fuel pressure gauge can be Tee-d into the connector at the fuel rail and the pressure monitored after shutting the Nitro down. Make sure that there are no fuel leaks with this set-up before taking your eyes off it. The pressure should slowly bleed down leaving a little residual pressure in the rail. This will help keep the fuel from boiling into vapor inside the hot rail and help at the next start up.
By rolling the key between 'run' and 'off' a couple of times before cranking it over may prime the rail enough to have it start up easier.
If this is intermittant, you can tie the gauge safely out of the way under the hood for observation. The check valve is serviced with the fuel pump assembly.
Normal fuel pressure is 58 psi +/- 5 psi.
You guys are great, Thanks for the in-depth info! I'll tie-in a gauge this weekend and see what I get for pressure, then take a look at the steps required to change the pump assembly. Thanks again!
The less fuel in the tank, the lighter and easier it will be to move around. Go with ~1/16 tank if you can. It can be supported and balanced on a floor jack and flat piece of wood.
Chock the wheels, set the parking brake and mark and remove the rear driveshaft for more tank working room.
Unbolt the inboard side straps and lower the tank slightly. This should allow you access to the top of the tank, quick-connect fittings and pump retainer nut.
A service manual with pictures and methods would be very helpful.
I'll just add, wipe off the top of the tank, around the retaining nut, before removing the pump assembly, it will prevent unwanted debris from getting into the tank.
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