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Fuel pressure drop ?

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  #1  
Old 05-15-2012, 10:58 PM
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Default Fuel pressure drop ?

Please help need facts from mopar techs!
For about 1 week 04 qc ram 5.7 hemi 4x4 is giving me extended cranks before start up.
Some time fires right up some times 3 to 5 sec crank is required
Seems to act up more when warm when just shut off recently
And I ask it to start shortly after it just ran. I put a new fuel pump in it in December( got truck in nov) because plastic at top of sender rotted and leaked. Fuel pressure drops to 0 key off instantly , pulled fuel rail up because brand new pump but no leaking injectors . ? Should fuel pressure hold after shut off to a degree .
Does pump have check valve?
Thanks for help
 
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Old 05-16-2012, 03:10 PM
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Anybody have opinion
 
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Old 05-16-2012, 04:05 PM
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Any codes thrown? Not for sure about the fuel psi; but hot/warm restarting issues is often a sympton of a crank or camshaft position sensor. Did you change the fuel filter after replacing the pump?
 
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Old 05-16-2012, 04:42 PM
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No cel no filter
 
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Old 05-16-2012, 06:54 PM
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Back in the day when I was a full time mechanic fuel injected engines were supposed to hold 80% fuel pressure for 24 hrs does this
Therory not apply to 04 hemi?
 
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Old 05-16-2012, 07:10 PM
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My dakota does this too, strarts right up when cold, has trouble when its warm

Whatching Post!!!

Sorry I was of no help
 
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Old 05-16-2012, 09:44 PM
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Not trying to b pushy but if anybody has 04 hemi and a fuel pressure gauge It would b awesome if u could check to see what fuel pressure does when u go to key off. Thank you thank you thank you
 
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Old 05-18-2012, 02:46 PM
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I think it's vapor lock due to bad check valve in fuel pump
But not 100% anybody know if total fuel pressure drop key off is normal ?
 
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Old 05-18-2012, 07:28 PM
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There would still be slight fuel pressure with the key off. Anyone who has changed a cam and pulled the engine apart can verify this because when you push the Schroeder valve a little fuel does come out. However, it does not gush or spew out so it is not a lot of pressure
 
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Old 05-18-2012, 08:35 PM
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I mean a readable pressure
Running 62
When I shut mine off going by fuel pressure gauge it goes from 62 to 0 in 1 sec.
Shouldn't it drop to like to 40 then just a gradual drop from there. Ram acts up on hot days when engine is brought to temp then shut off and you try start 5 to 10 min later. If you star it right back up before gas has had a chance to boil it starts fine.
 


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