POST MOD ISSUES - HELP
Thread Starter
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Senior User
Joined: Oct 2013
Posts: 128
Likes: 0
From: NW Arkansas
So, I pulled the oil filter and cranked. Fills up fine. Still no movement on gauge during long cranks. Low ICP pressure as well. Still don't know why it runs for a while after having it all apart and then won't restart!!!
Thread Starter
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Senior User
Joined: Oct 2013
Posts: 128
Likes: 0
From: NW Arkansas
So, let's say I have a HPOP leak. The only thing preventing running/starting should be the ICP... Correct? I unplug the ICP and verify PCM is seeing more than enough to engage injectors. Still no fire. WHAT THEN???
Lead Driver
Joined: Feb 2011
Posts: 8,241
Likes: 155
From: L.A. (Lower Alabama)
Wow, this one sounds like a headache! 5.56MPa is 822.3psi. Plenty to start. I assume the IPR isn't killing it's self making that pressure? With IPW showing it would seem everything is syncing up (cam, crank, FICM) Sounds like somthing else is going on. Cranking RPM good? I know you verified fuel filter fill but maybe a fuel pressure or flow problem?
Don't mean to overstate the obvious but with pistons going up and down and valves working at the right time, if it gets some fuel in it, it should at least try to fire.
Don't mean to overstate the obvious but with pistons going up and down and valves working at the right time, if it gets some fuel in it, it should at least try to fire.
Thread Starter
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Senior User
Joined: Oct 2013
Posts: 128
Likes: 0
From: NW Arkansas
It's no longer making that. ICP is showing maybe 2.6 mPa. Doesn't jive. Air test showed no leaks. If my IPR is weak, will it cause the no start? It was able to shut off 100 psi of shop air, but maybe not hold 500 psi of oil? Shot in the dark, but I'm out of options.
Lead Driver
Joined: Feb 2011
Posts: 8,241
Likes: 155
From: L.A. (Lower Alabama)
So when the screenshot with 800+ was taken truck would start, now it's less than 400?
Yes, a weak IPR can cause a no start. We mostly think of it binding or getting the screen stuck in it but the electrical side is subject to fail also. Her's a way to test it.
IPR TESTING WITH A DVM
Pull out the middle PCM connector and ohm out pin #2 of the PCM connector (yellow with red stripe coloured wire) to the positive terminal of the driver side battery at key-on/engine-off. A good IPR should read about 6.0 ohms
Yes, a weak IPR can cause a no start. We mostly think of it binding or getting the screen stuck in it but the electrical side is subject to fail also. Her's a way to test it.
IPR TESTING WITH A DVM
Pull out the middle PCM connector and ohm out pin #2 of the PCM connector (yellow with red stripe coloured wire) to the positive terminal of the driver side battery at key-on/engine-off. A good IPR should read about 6.0 ohms
Fleet Mechanic
Joined: Aug 2012
Posts: 1,760
Likes: 21
Did you have the IPR valve out? What did it look like?
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Lead Driver
Joined: Feb 2011
Posts: 8,241
Likes: 155
From: L.A. (Lower Alabama)
Think of the pressurized oil as the "power" that opens/closes the injectors. if you have a HPO leak anywhere, there is less force to work the injectors.
The systems pump makes more than enough pressure to power the injectors so under normal operation the IPR bleeds off to match the electrical signal (FPW). If the leak is small enough, the IPR raises pressure (actually volume) and compensates for the leak. Too large of a leak (or stuck IPR) and it can't keep up, pressure drops, FICM sees low pressure and quits squirting injectors.
The IPR valve is only an actuator that defaults to the nomally open position. This means it exhausts most (or all) of the high pressure oil pump output to the crankcase sump when it's not energized. When the engine is started, it is COMMANDED by the PCM to increase duty cycle (to close), in order to increase ICP as needed. Remember, it is only an ACTUATOR. If a small piece of debris lodges up inside to jam it up, it can/will prevent it from closing.
The systems pump makes more than enough pressure to power the injectors so under normal operation the IPR bleeds off to match the electrical signal (FPW). If the leak is small enough, the IPR raises pressure (actually volume) and compensates for the leak. Too large of a leak (or stuck IPR) and it can't keep up, pressure drops, FICM sees low pressure and quits squirting injectors.
The IPR valve is only an actuator that defaults to the nomally open position. This means it exhausts most (or all) of the high pressure oil pump output to the crankcase sump when it's not energized. When the engine is started, it is COMMANDED by the PCM to increase duty cycle (to close), in order to increase ICP as needed. Remember, it is only an ACTUATOR. If a small piece of debris lodges up inside to jam it up, it can/will prevent it from closing.
Thread Starter
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Senior User
Joined: Oct 2013
Posts: 128
Likes: 0
From: NW Arkansas
Ran it hard for an hour. Start, stop, and 85 on interstate. Made sure oil rail under ICP was full. Started and ran great. Shut off. Waited an hour, no start and low ICP. How else to bleed?
Debris in IPR wouldn't let it run as good as it did first time, right?
Debris in IPR wouldn't let it run as good as it did first time, right?