hard start after a hot soak

GregKneupper · April 7, 2009

I have a 2006 lcf that will have a very hard start when hot. It is not a high pressure oil leak. Everything has been torn apart and inspected just to make sure. It is losing a crank signal for some reason. I have tested all the harnesses and replace crank sensor with know good sensor. Sometimes it will start right up and other times it will crank for a good 15 to 20 seconds before it starts. While watching the rpm pid it will stay at 0 and then all the sudden it starts getting a signal. I am getting a 143, 145, 553, and 554 codes. The 143 keeps coming back the most. I am thinking that this thing has a bad wire harness but I cannot prove it. Does anyone else have any insight to this particular issue?

Alex Bruene · April 7, 2009

I've had to replace a harness on a 4.5 for that reason. But it was on an '08 with the rubber cased harness. It was a biotch to figure out... After replacing the sensor, dropping the oil pans to check the trigger wheel (really easy on an LCF) and swapping PCMs with a stock vehcile, there was really only one option left. And luckily it was the right option.

Aaron · April 7, 2009

Do these things have wobbly crank trigger wheels sometimes, like a six-o?

Edit: I'm not tryin' to be a wiseass, I've never worked on a 4.5

GregKneupper · April 7, 2009

I have heard that there have been reports of a few of those. But the thing is that once this truck does start it runs perfectly fine. It has plenty of power and never stalls or anything like that. It only has 58000 miles on it. I have not actually inspected it but I do not feel that is my problem. If it comes to it I will pull the pan and check it. The other issue is this truck does not fit in the shop and I am having to work on it in the parking lot.

robp823 · April 9, 2009

wire harness on lcf's suck ass

GregKneupper · April 9, 2009

Well I think I have diaged it as a bad pcm. I have a crank signal going to the pcm but the pid says 0 rpm. I have one coming for it in the morning. We will see.

GregKneupper · April 10, 2009

No luck on the pcm. I have been in contact with the hotline on this one and now they would like me to try an idm on it. I am not sure of anything anymore on this vehicle. I am now completely lost on it. It still does the exact same thing. Both cam and crank sensors have been replaced, the wire harness, and the pcm. Everything has been replaced. I get no crank signal at all but only after a hot soak of about 20 minutes. Nothing makes sense. I have an idm coming for it in the morning, but I do not think it will fix it.

LARRY BRUDZYNSKI · April 10, 2009

Have you checked the body for pinched wires or anything else that the outfitter could have done? It sounds like you have all of the bases covered but could it be a ground or something else on the body harness or body???

Maybe the ignition circuit, anything spliced into???

Alex Bruene · April 10, 2009

Do these things have wobbly crank trigger wheels sometimes, like a six-o?

Edit: I'm not tryin' to be a wiseass, I've never worked on a 4.5

They have the same trigger wheel... I have personally never seen a wobbly one on a 6.0 or a 4.5, but it had to be ruled out...

GregKneupper · April 10, 2009

I have inspected the harnesses multiple time and I cannot find anything wrong with them. The only add on that it has is a refrigeration unit and it is connected directly to the battery except for a control unit that is inside the cab. I cannot find anything wrong with any of it either. Nothing is spliced into anything that I can tell. I replace a ficm on it today per hotline and of course it did not fix anything. The fse will be here next week to look at it. Unfortunately I will not be here to look at it with him because I will be on vacation. I do not know where else to go with it. The funny thing on this truck is that it only does it after sitting about 20 minutes or so. If you drive it and shut it off just for a few minutes at a time it fires right up no problem. Also cold it has no problems. Just after a 20 minute or so soak. I do not understand why it does that. Any ways I am done with it at the moment. I guess I will find out what is wrong with it when I get back. Does anyone have any other advice or things to possibly check before I leave today? Any other advice would be greatly appreciated.

Kimani · April 11, 2009

Have you tried to update your calibrations thru NETS? Might be a software issue or the IDM.

Bruce Amacker · April 11, 2009

This is a bit out of the box, but there have been bad starters that generate enough EMI/RFI to upset the crank sensor signal and cause a no-start or hard start. I've only heard of it and never seen it first hand. I've heard of it twice on Ford gas engines and I know it is a pattern failure on some Nissan engines. The only way to diag it is to scope the CKP and CMP while cranking or sub another starter in.

Real far fetched: what do you know about fuel quality and FP pressure? This sounds like a gasser with a weak fuel pump and the gasoline is boiling in the fuel rail after a hot soak. I've seen it many times, sometimes the pressure will be fine but the volume is low. When this happens on a gasser (with a return system), the FP can't flush the vapors out of the rail and back to the tank that occur after a hot soak. Cold start, OK, immediate hot restart, OK, but go into the store for 20 minutes and it won't start. A new fuel pump fixes it.

Could this happen on a diesel with poor fuel quality? Have you checked the fuel pressure, quality sample, or filters?

Does this truck have the fuel pressure sensor update? Have you tried the injector test light tool to verify the injectors are not receiving a signal while cranking?

Could the CKP/CMP codes be false from extended cranking?

I know these are a stretch, but it's all I could think of.

Good Luck!

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GregKneupper · April 11, 2009

Bruce, fuel pressure is good at 52 psi. Both fuel filters have been checked and are clean. I have scoped the crank signal while the concern happens and it looks clean to me. Although I do admit I do not have a lot of experience with the scope to know for absolutely sure. All I can tell you is that while it happens the pattern is not jagged or dropping out. I have hooked up an injector tool to check injector pulse and they are not receiving injector pulses. I have also pulled the oil pan and inspected the trigger wheel and there is nothing wrong with it. Now I know this concern is a strange concern. During the concern the rpm says 0, the ipr does not move and stays at 29.9%, and there is no injector pulse. This data tells me that there is no crank signal. If this was a high pressure oil leak the ipr would rise during cranking. It does not. If it was fuel pressure the icp and ipr should still rise during cranking. It does not. I am for sure that this thing has some strange crank sensor issue. The only last thing that I could think of as well was a starter. I guess I should just throw one on it and see what happens. Now I am quite sure that the cmp codes are caused by extended cranking. But the crank code reappears quickly and is the one that comes back the most and at times will not even clear, even after the engine is running.