Long crank, no faults

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jlglr4

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You raise some good points about there being no misfires (though it seems like you might have had a couple in that last post). Could be that the leak is small enough not to cause much by way of drivability issues, but still letting pressure escape when setting long enough. But you would think the leak would get worse with high pressure with engine running and you’d see some kind of fuel trim issue.

If fuel rail pressure is the problem is the check valve in the hpfp, which would also explain why there is no misfire or other problem when driving.

As for hydrolock, I don’t think you need to worry about that yet. If you had that bad of a leak, I think you would be completely flooding the cylinder and have a massive misfire problem and fuel odor - likely both in the engine bay and the tailpipe.

One other thought - check your purge valve with the engine off and make sure it’s closed. I think its sufficient to just pull the end of the line off the throttle body and blow into it with your mouth. It should be closed tight. Also - check the air filters to make sure they are clean if you haven’t already.

This thread is getting long enough that I’m forgetting what has been checked, but you could still be dealing with something like a bad plug (or plugs) or intermittent problem with a coil, and I don’t think we can conclusively rule out the ECT sensors or even the MAFs without more logging of values - the sensors could be failing intermittently. Since injectors are a pain (and fairly expensive), I think I would probably do the following:

(1) Each morning for maybe a week or so, before starting but ignition on, log the fuel rail pressure and coolant temp sensors and then note whether the cranking was long or short.
(2) If that doesn’t give you any clues, replace the plugs (assuming you didn’t just do this recently). If you do this, you might consider doing it after letting it set for a few hours or overnight, and putting a borescope down into the plug holes to see if any of the cylinders appear to be more “wet” than others. Just be very careful not to drop anything down in there (i.e., make sure your borescope doesn’t have any loose lenses or other parts that might come off).
(3) Replace the fuel rail pressure sensor (I understand this is pretty easy, and they do go bad).
(4) If all else fails - consider the fuel injectors or hpfps. Honestly not sure which I’d try first. Could also be throttle body - easier to change out, but might be more expensive to buy.
 

jlglr4

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I guess the last thing to add…could take it to a mechanic and pay a diagnostic fee of $100-200 to see if you get any different advice before throwing money into parts. I‘m going to feel pretty bad if you start throwing money into parts based on my advice, and it turns out to be something different entirely.
 

Jimmy Brooks

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You raise some good points about there being no misfires (though it seems like you might have had a couple in that last post). Could be that the leak is small enough not to cause much by way of drivability issues, but still letting pressure escape when setting long enough. But you would think the leak would get worse with high pressure with engine running and you’d see some kind of fuel trim issue.

If fuel rail pressure is the problem is the check valve in the hpfp, which would also explain why there is no misfire or other problem when driving.

As for hydrolock, I don’t think you need to worry about that yet. If you had that bad of a leak, I think you would be completely flooding the cylinder and have a massive misfire problem and fuel odor - likely both in the engine bay and the tailpipe.

One other thought - check your purge valve with the engine off and make sure it’s closed. I think its sufficient to just pull the end of the line off the throttle body and blow into it with your mouth. It should be closed tight. Also - check the air filters to make sure they are clean if you haven’t already.

This thread is getting long enough that I’m forgetting what has been checked, but you could still be dealing with something like a bad plug (or plugs) or intermittent problem with a coil, and I don’t think we can conclusively rule out the ECT sensors or even the MAFs without more logging of values - the sensors could be failing intermittently. Since injectors are a pain (and fairly expensive), I think I would probably do the following:

(1) Each morning for maybe a week or so, before starting but ignition on, log the fuel rail pressure and coolant temp sensors and then note whether the cranking was long or short.
(2) If that doesn’t give you any clues, replace the plugs (assuming you didn’t just do this recently). If you do this, you might consider doing it after letting it set for a few hours or overnight, and putting a borescope down into the plug holes to see if any of the cylinders appear to be more “wet” than others. Just be very careful not to drop anything down in there (i.e., make sure your borescope doesn’t have any loose lenses or other parts that might come off).
(3) Replace the fuel rail pressure sensor (I understand this is pretty easy, and they do go bad).
(4) If all else fails - consider the fuel injectors or hpfps. Honestly not sure which I’d try first. Could also be throttle body - easier to change out, but might be more expensive to buy.

I turned the tuck on to move it into the garage today and it did it’s normal long crank, no sputters or anything. Plugs were done at either 125 or 130k (can’t remember but it was some time early last year) and I’m at 143k now. I believe coils are original. Purge valve was done I believe at 133 or 135k. When I was having purge valve issues I was getting rough starts after fueling but nothing else. I’ll still check it. Air filters were done by me a bit ago I think at 135k. MAFs are reading temperature properly and voltage was reading normal when cold. Now that I think about it I don’t believe I’ve checked the fuel rail sensor voltage when it’s cold so I’ll do that. I’ve tracked coolant sensors and they all seem normal as well and didn’t see any correlation to the engine starting weird or not. I’ll check the purge valve today and make sure that is sealed shut. Not sure if I’m going to have enough time to check in the cylinders through the plugs.

The fuel rail pressure seems good while driving and while idling. How would I check the hpfp pressure valve?

Also if the hpfp pressure valve was the issue wouldn’t that mean I’d have to completely replace the hpfps
 

alldazed

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Did you recheck that 419f external temp reading you had ? I think it was warm when you read it initially and you were going to check at cold.
The other thing I think you mentioned way back in the thread was a fuel system cleaner. I was thinking more of one that would specifically absorb moisture though you could just add gas line antifreeze as it’s cheap. I have had issues over the years in other vehicles and it has helped on the odd occasion I’ve filled up with poor quality gas as it is otherwise hard to remove the moisture.
 

Jimmy Brooks

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So I checked the purge valve and it was sealed shut. But I also checked a couple of other what I believed to be vacuum lines in the engine. Now on if I’m not wrong (I’m not a genius when it comes to engines I’m just learning the ropes with this truck) there is a vacuum line that comes out of the back of the driver side cylinder head and leads into the intake duct and then another vacuum line that comes out of the back of the passenger side head and leads into the intake manifold. The drivers side line was dry but when I pulled the passenger side line out of the manifold it was saturated in oil. Not sure if you can see how much b it when I stuck my pinky into that hole it came out with oil dripping off of my finger. Is that normal??

Hopefully don’t sound like a noob here but just want to make sure.

In the second photo you can see that there is a ring inside of hole in the intake manifold that kind of disappears, that’s because it’s underneath a little puddle of oil.
 

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jlglr4

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The fuel rail pressure seems good while driving and while idling. How would I check the hpfp pressure valve?

Also if the hpfp pressure valve was the issue wouldn’t that mean I’d have to completely replace the hpfps

The hpfp has a pressure modulation valve that controls the amount of fuel being pumped, and a check valve that prevents backflow of the fuel. It’s the check valve I’m thinking might be malfunctioning. No way of testing them that I know of, and yes - it’s integrated into the pump, so you’d just have to replace the pump. Also can’t really tell which pump, so you’d probably be replacing both.

there is a vacuum line that comes out of the back of the driver side cylinder head and leads into the intake duct and then another vacuum line that comes out of the back of the passenger side head and leads into the intake manifold. The drivers side line was dry but when I pulled the passenger side line out of the manifold it was saturated in oil. Not sure if you can see how much b it when I stuck my pinky into that hole it came out with oil dripping off of my finger. Is that normal??
I believe you are looking at the crankcase breather hoses. The driver‘s side hose is the “full load” breather, and the passenger side is the “partial load” breather. The partial load breather is connected to the PCV, which acts as a valve to balance the engine vacuum against the crankcase pressure when the throttle body is closed. The system on these cars is notoriously bad and a lot of oil gets sucked up through the partial breather hose and into the intake. But, if your PCV is going bad, you are likely to get a whole lot more oil up through there. If you haven’t replaced the PCV diaphragm in the last 60K miles or so, you might just do it. It‘s a cheap and easy repair - especially on the V8. You just buy the diaphragm kits (you need two) with the rubber diaphragm and spring and new covers, pry the little round covers off the valve cover, replace the parts and put the new covers back. Just two pieces of advice: (1) wait until you have the kits in hand as the tabs on the old covers will break off, and (2) be careful not to break the valve cover itself or the little hooks on the valve cover - you don’t want to turn this simple repair into a whole valve cover replacement.

But - I don’t think the PCV is your problem as a torn PCV diaphragm gives you a pretty major vacuum leak, which would show up as large positive fuel trim.
 

Jimmy Brooks

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here to bring you guys an update, started checking fuel rail voltage with ignition on before a cold start and I’m getting a reading from the high range sensor at .5 Volts. When the car is started it jumps into the normal range of .8-4v (usually settling at 1.2v when my other sensors normally like sitting around 2.3v.
 

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Jimmy Brooks

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ok, if I go about replacing the fuel rail pressure sensor how should I go about doing it, should I remove the whole rail and then replace it or should I reach all the way back and try to replace it with out removing the rail? Also what should I use to retorque the sensor, to my understanding it doesn’t look possible with a regular socket.

Also just checking again, below .8 volts with ignition on while the car is cold means the sensor is shot right?
 

jlglr4

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Just went out and checked my high range sensor and low range fuel rail pressure sensor readings. Screen shot attached. About same as yours (0.5 v). Low range sensor is higher (about 2v). Did you check your low range sensor? I’m guessing that the high range sensor is bottomed out when the hpfp is not running, and the low range sensor takes over at those lower pressures. Not certain though.

I came across this website that has some LR diagnostic routines. They seem to say that the high range sensor should be 1.0, but they also seem to say that a faulty sensor (either high or low range sensor) will be showing 4-5v engine off. So, not sure that 0.5-0.8v means that it is bad.


Could still be the sensor though - might be just a faulty reading on the low range. If it’s not difficult or expensive, might just try swapping it out. Looks like it should not be too bad to get to. Maybe someone on here who has done it can chime in.

As for torque - manual says 38nm. You might be able to get on it with a crowfoot on the torque wrench. Here’s a calculator to adjust the torque based on the angle of the crowfoot: https://www.tekton.com/blog/how-to-accurately-use-a-torque-wrench-with-a-crowfoot-wrench.
 

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Jimmy Brooks

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Just went out and checked my high range sensor and low range fuel rail pressure sensor readings. Screen shot attached. About same as yours (0.5 v). Low range sensor is higher (about 2v). Did you check your low range sensor? I’m guessing that the high range sensor is bottomed out when the hpfp is not running, and the low range sensor takes over at those lower pressures. Not certain though.

I came across this website that has some LR diagnostic routines. They seem to say that the high range sensor should be 1.0, but they also seem to say that a faulty sensor (either high or low range sensor) will be showing 4-5v engine off. So, not sure that 0.5-0.8v means that it is bad.


Could still be the sensor though - might be just a faulty reading on the low range. If it’s not difficult or expensive, might just try swapping it out. Looks like it should not be too bad to get to. Maybe someone on here who has done it can chime in.

As for torque - manual says 38nm. You might be able to get on it with a crowfoot on the torque wrench. Here’s a calculator to adjust the torque based on the angle of the crowfoot: https://www.tekton.com/blog/how-to-accurately-use-a-torque-wrench-with-a-crowfoot-wrench.

Low range was about 2.3 V. Starting to look like HPFP, again just odd it runs fine with good fuel trims
 

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