Post 19, idle at 600, very low, 13K desired and actual furnished by the CP3. Are you saying that the ECM has upped the demand pressure because the idle needs to be raised to 700/750? Ignore this as being the cause of the engine running poorly?
L5P will barely start, then die Please Help
- Thread starter Rdomeck
- Start date
If the idle is not getting to were the ECM wants, or it's having to inject more fuel to maintain it, then the ECM will also raise fuel pressure. If you look over the fuel pressure maps, you'll see the pressure increase at higher mm3 even for the same RPM
Hey guys, sorry for the lack of response. I have been racing the last few days in the Ozarks. Had to bring my 1996 3/4 with 420,000 miles on it.
I have to give up on this trip for the Duramax. I'll be checking more things out next week.
Are you guys saying I shouldn't be worried about the high fuel rail pressure at the moment?
The only code I have is the P0016. I had this code since day one and was able to drive it without issue. I have not been able to find the cause of that code. My new even more expensive scan tool was able to reset the crank to cam correlation. The code is still present.
The only thing in this mix I have not replaced is the ECM. I have a new HP Tuners ECM that I can install, but I need to buy the OBD interface to do that.
I just had to stop work on that and prep the race car and maintain the 420,000 mile truck for the journey.
I have to give up on this trip for the Duramax. I'll be checking more things out next week.
Are you guys saying I shouldn't be worried about the high fuel rail pressure at the moment?
The only code I have is the P0016. I had this code since day one and was able to drive it without issue. I have not been able to find the cause of that code. My new even more expensive scan tool was able to reset the crank to cam correlation. The code is still present.
The only thing in this mix I have not replaced is the ECM. I have a new HP Tuners ECM that I can install, but I need to buy the OBD interface to do that.
I just had to stop work on that and prep the race car and maintain the 420,000 mile truck for the journey.
So, do I need to be worried about the high fuel rail pressure or start really chasing down the P0016?
I have not verified wiring between the cam and crank sensors. I have replaced both sensors. I can watch the counts on my scan tool and see that the ECM is seeing the sensors and they have the correct counts per rpm for the crank and half that for the cam.... So, I can say with reasonable certainty, the sensors and wiring are not the issue.
I have replaced every other parts minus the ECM. I have a new unlocked ECM from HP Tuners. I have verified with them that I can use their software and an interface and replace the ECM with a stock tune.
Is this my next thing to do?
Thanks for all the help and suggestions so far.
I have not verified wiring between the cam and crank sensors. I have replaced both sensors. I can watch the counts on my scan tool and see that the ECM is seeing the sensors and they have the correct counts per rpm for the crank and half that for the cam.... So, I can say with reasonable certainty, the sensors and wiring are not the issue.
I have replaced every other parts minus the ECM. I have a new unlocked ECM from HP Tuners. I have verified with them that I can use their software and an interface and replace the ECM with a stock tune.
Is this my next thing to do?
Thanks for all the help and suggestions so far.
I think the high fuel pressure is a result of something else being off. Not a direct issue. Things like a bad coolant or intake temperature sensor can cause higher then normal pressure. Same for little fuel making it into the cylinders causing the ECM to demand more fuel and thus fuel pressure. Or high exhaust back pressure, low cylinder pressure, bad valves or rockers, etc. basically anything that the ecm would normally use or command higher fuel MM3 can come with higher fuel pressure
I don't recall if you posted it earlier, but what is the main rate mm3 when you do manage to get it running?
I'm wondering if you have the cam gear out of time or if the gear has slipped on the crank. If that P0016 code is persistent, it tells me there is an issue there that needs to be addressed. Perhaps the problem was always there, but maybe it has worsened to the point the cam timing is making it not be able to run. There is definitely something going on there. Since you know it's a problem and it is something that was worked on during the rebuild, that's where I would start.
I have removed the cover on the front of the engine to verify the cam timing and that the pin has not sheared off on the crank gear. All is in time there.
I have two videos. One is recording a popping sound come through the I take. The other should show the mm3 rate. I am controlling the idle up and down. If I let off too fast, it will die.
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It does not do it all the time. Just a little on warm up. Goes away within a minute.
I should also add that the popping just started for the first time today after I put the exhaust back on.
Unless for some reason the keyway sheared on the camshaft?
This is what they are referring too.
Popping thru intake is usually a bent push rod or bad rocker unless as suggested the cam has sheared and is out of time.
Any way to verify this without removing the front cover?
You can sort of get a vague idea by carefully measuring the pushrods or rockers in relation to the piston. But you'll still be second guessing until you open the front cover and actually look
I’d check the rockers and push rods first. There is a fairly common issue with L5p rockers coming apart and causing the thumping from the intake.