Long crank, no faults

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Jimmy Brooks

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Ok so over the past couple weeks I’ve been able to narrow it down to a leaky fuel rail. Every time I open the driver door I hear the low pressure pump prime and the car has no trouble while running or driving (doesn’t stall no hesitation no weird misfires) so it can’t be high pressure either. After the car turns off I notice fuel rail pressure desired goes to 1450PSI and the fuel rail pressure begins to climb to that amount. Once it reaches over that desired pressure it seems so leak out around 500psi per hour until finally settling to around 50 psi while the car is not in used thus making a cold start difficult. The only time I smell fuel is when I’m doing a long crank. Is it safe to say that it’s most likely fuel rail if I were to tell my shop to look at it? Again no codes or anything just the long crank on only cold starts, starts right up othet wise
 
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Nechaken

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Ok so over the past couple weeks I’ve been able to narrow it down to a leaky fuel rail. Every time I open the driver door I hear the low pressure pump prime and the car has no trouble while running or driving (doesn’t stall no hesitation no weird misfires) so it can’t be high pressure either. After the car turns off I notice fuel rail pressure desired goes to 1450PSI and the fuel rail pressure begins to climb to that amount. Once it reaches that desired pressure it seems so leak out to around 50 psi while the car is not in used thus making a cold start difficult. The only time I smell fuel is when I’m doing a long crank.

Wait, do you mean once the car is ON, " fuel rail pressure desired goes to 1450PSI and the fuel rail pressure begins to climb..." ?
 

Jimmy Brooks

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Wait, do you mean once the car is ON, " fuel rail pressure desired goes to 1450PSI and the fuel rail pressure begins to climb..." ?
No. Heres the whole run down, when the car is idoling normally fuel pressure fluctuates from 418-425 psi. While the car is running the “fuel rail pressure desired” reads 0. Only when the car turns off does it desire 1450 psi which tells me the car is supposed to build to at least that amount of pressure while it’s turned off. When I turn off the truck I see the fuel pressure start to climb to way higher then that desired amount (around 2000ish). After it’s satisfied it will stop pressurizing. Over time I am able to see the psi drop (around 5psi for every 10 seconds) until it drops all the way down to 50psi. When I go to start it again it will crank until it has built enough pressure and then turn over. Car runs perfect after that and will fire right up u less you leave it for a 4ish hours. I checked the high pressure fuel lines and they all seem dry, no gas smell coming from the engine bay. Almost makes me think it’s an internal leak. Am I missing something? Is there a pressure regulator that could be stuck slightly open?
 

jlglr4

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Finally got a chance to look at fuel rail pressure. My car was sitting all weekend without being started. When i put on the ignition, before starting, fuel rail pressure read 650 kpa, so about 95 psi. It started immediately, as always. I wouldn’t expect to see much pressure, but maybe you are losing a little too much. Not sure if that is helpful to you or not. Fuel smell on the long crank is a bit inconsistent with this theory though. That would suggest you are getting fuel to the cylinder but no combustion.
 

jlglr4

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As for the pressure regulator, I believe the regulators are built into the HPFP, not separately replaceable.
 

Jimmy Brooks

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Finally got a chance to look at fuel rail pressure. My car was sitting all weekend without being started. When i put on the ignition, before starting, fuel rail pressure read 650 kpa, so about 95 psi. It started immediately, as always. I wouldn’t expect to see much pressure, but maybe you are losing a little too much. Not sure if that is helpful to you or not. Fuel smell on the long crank is a bit inconsistent with this theory though. That would suggest you are getting fuel to the cylinder but no combustion.
Now that I think about it I might have been smelling a little bit of exhaust and mistaken it for fuel upon first start up. Do you think the 40psi difference would be enough to make the difference of a 3 second crank and a 10 second crank? Or do you think it’s not fuel system related? Starter sounds healthy and the battery was replaced last year. Also does your fuel system have similar behavior when turning off the car? Does it pressurize the fuel rail like mine does when you turn it off and then go away as the hours go by? Just want to rule out the fuel system if the behavior I’ve observed is normal.
 

Nechaken

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No. Heres the whole run down, when the car is idoling normally fuel pressure fluctuates from 418-425 psi. While the car is running the “fuel rail pressure desired” reads 0. Only when the car turns off does it desire 1450 psi which tells me the car is supposed to build to at least that amount of pressure while it’s turned off. When I turn off the truck I see the fuel pressure start to climb to way higher then that desired amount (around 2000ish). After it’s satisfied it will stop pressurizing. Over time I am able to see the psi drop (around 5psi for every 10 seconds) until it drops all the way down to 50psi. When I go to start it again it will crank until it has built enough pressure and then turn over. Car runs perfect after that and will fire right up u less you leave it for a 4ish hours. I checked the high pressure fuel lines and they all seem dry, no gas smell coming from the engine bay. Almost makes me think it’s an internal leak. Am I missing something? Is there a pressure regulator that could be stuck slightly open?

Interesting. When its not 4 degrees outside, I'm going to compare this to my car's behavior. Also just saw you're in Pasadena. Small world, I used to live on Orange Grove Blvd.
 

ftillier

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Slightly below freezing this morning, after sitting over 12hrs, ignition on values:
Screenshot_20230131-085304.png

And shortly after turning the engine on:
Screenshot_20230131-085320.png
 

Jimmy Brooks

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Looks like what I’m observing is pretty normal then. Is there a live value for the low pressure fuel pump that I can see? Is it possible it’s not priming enough? would that make sense even if it was driving perfect apart from cold starts?
 

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