Long crank, no faults

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greiswig

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It’s just odd. I was up in mammoth for a couple of days while it was 20 F and the car started fine the whole trip. Yet when I was up in Santa Clarita aftwr it rained it cranked for the longest time and finally turned over. Just did it again this afternoon after it had sat for about 5 hours. I just can’t seem to tie it to the weather other then the fact that it “coincidentally” (most likely a coincidence) started happening as winter rolled around. Seems to be more common when letting it sit for a while.
I'm guessing here, but...if it doesn't happen when it's very cold but dry, but it does happen when it's been cold and then turns wet, I'd be wondering about an ignition issue. In a vehicle with a distributor cap and long ignition wires, condensation can form on those and conduct the spark away from the plugs until the condensation gets burned away.

I'm not sure there is a similar HV path that is available on an LR4 but it's maybe something to consider.

That said, I would start with checking for poor fuel delivery after sitting. No idea why cold might affect that, though.
 

Jimmy Brooks

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I believe it has Fuel Rail Pressure and Desired Fuel Rail Pressure in there.
Ok so came back to the car after letting it sit and the first thing I did was check the live values before starting the car. With the battery on I was able to see that my current fuel rail pressure after letting the car sit was 53.7 psi while the desired fuel pressure was 1450 psi. When I started the car it had a couple of extra cranks, fuel pressure was around 400-600 psi then went right up to 2090 on warmup idle at 1.5k RPM. Should my psi be 1450 before starting the car? Would this means I have an issue with the HPFP? Here’s a screen shot of the live values before cranking.
 

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ftillier

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HPFP is mechanical, so if the engine is off, there's nothing that will bring things up to pressure like that until you start cranking. Is the low pressure pump reaching its target?
 

Jimmy Brooks

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HPFP is mechanical, so if the engine is off, there's nothing that will bring things up to pressure like that until you start cranking. Is the low pressure pump reaching its target?
Not sure, couldn’t really find a live value for the low pressure, only the desired. Is there one under a different category or one that I missed that will show live low pressure data.
 

Jimmy Brooks

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I can tell as time goes on it’s getting worse, every time I leave the truck out side for over a 3 hour period of time the truck cranks for 4ish seconds in 61°F weather. Still couldn’t find any low pressure fuel pump live values. Any other suggestions on how I should track this issue down. Do you think fuel cleaner would be helpful to my issue?
 

jlglr4

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I was thinking the fuel rail is supposed to maintain some pressure when the car is switched off, and it might be leaking down in this case. So, when you crank after leaving it set, the pumps need to fill the rail again before you get fuel to the cylinders. It’s not going to be nearly the same kind of pressure as with the HPFP cranking, but I think the rail should stay full and should have some pressure in it.

Looks like you were able to get a live reading on the fuel rail with the engine off. Maybe check it right after shutdown, and then at a few time points afterwards. See if it changes. I’ll try to remember to do the same on my car and give you some values for comparison. I’ve never tried the fuel rail pressure live value with the engine off.
 

alldazed

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I thought that when you opened the door it ‘woke’ the engine up and activated the fuel pump to make sure there is fuel in the rail ?
 

jlglr4

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When the car wakes up, it powers up the low pressure fuel pump. But I was thinking that just pushes fuel up to the HPFPs, which then pump it into the rail. But I might be wrong.
 

Jimmy Brooks

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I was thinking the fuel rail is supposed to maintain some pressure when the car is switched off, and it might be leaking down in this case. So, when you crank after leaving it set, the pumps need to fill the rail again before you get fuel to the cylinders. It’s not going to be nearly the same kind of pressure as with the HPFP cranking, but I think the rail should stay full and should have some pressure in it.

Looks like you were able to get a live reading on the fuel rail with the engine off. Maybe check it right after shutdown, and then at a few time points afterwards. See if it changes. I’ll try to remember to do the same on my car and give you some values for comparison. I’ve never tried the fuel rail pressure live value with the engine off.
When I turn off the car the fuel pressure tends to build up a bit but by the time I get into it aftwr it’s been sitting for a while the car only has 50ish psi of pressure
 

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