Long crank - continues with key off

[KVacek]

2005 Yukon Denali XL - 6.0 - over 170K. Owned since 2008 when it had 36K. Original fuel pump and sending unit assembly or at least we've never changed it.

After having the transmission pulled to replace the rear main seal and (cam?) sensor to solve bad oil leaks, there's a weird problem.

The engine cranks fine but often on the first attempt will crank long - even if you turn the key off "Start". Next try it will start normally.

I've had Jill try to turn the key on for a second and then off and then start and she says it usully starts normally after the first key on-off. Which makes me thing fuel pump of course. But she doesn't always do that and then thinks that maybe it doesn't always help. OR maybe she doesn't pay atttention or remember to do that. I certainly don't remember on the few occasions I use the vehicle.

I had this exact problem a couple years back and found the answer somewhere - I thought here - but I can't find it again. Whatever it was was simple and immediately fixed it, and seemed very logical, though not directly involved with the starter or fuel pump. But damned if I remember what it was.

It's something that senses that the engine has not started within the first second or two the computer takes over and keeps cranking for a few seconds longer. Back when it happened before I happened upon an entry somewhere after I had coincidentally already fixed whatever had been causing the issue and thought "Hmm - that was why it had those long cranks for a while".

I went through every menu I could find with my Eggroll brand fake Tech 2, but nothing jumps out.

Old age sucks - I don't cherish the memories of great repairs to modern cars - I just do what I have to and move on, hoping never to fix it again. Give me a Quadrajet or SU and a distributor or maybe an airplane engine with a Bendix Stromberg and dual magneos and I can identify with it and know/care what I'm doing.

This must sound familiar to someone???

 

[nonickatall]

I would check or replace the fuel pump relay....

 

[Fless]

I would be curious about which sensor was changed. If either the crankshaft position sensor, or the camshaft position sensor, or both, a Crankshaft Variation Relearn is recommended. Search "Crankshaft Variation Relearn" to read more about it.

It would be easy enough to do with your Tech 2, if not just to rule it out.

 

[exp500]

Starter Solenoid sticking. A hammer whack while engine still turning will usually disengage starter doing this, but you need a helper.
Should show no voltage to energise solenoid on tech2 after key off.

 

[KVacek]

Starter Solenoid sticking. A hammer whack while engine still turning will usually disengage starter doing this, but you need a helper.
Should show no voltage to energise solenoid on tech2 after key off.

This is not a sticking solenoid, but thanks. It's being electrically held on for several seconds during some crank cycles.

 

[Fless]

Not sure I understand. Is the issue a long crank before starting? Or is it a starter that seems to be commanded to run longer after the engine starts?

 

[wjburken]

I would check your fuel pressures. When I had issues with my fuel pump in our 2007, if you turned the key to START and immediately let go, or hit remote start, it would crank the motor for a prescribed amount of time. Then, the second time I would turn the key to start or hit remote start, it would fire right up. Cause was a fuel pump losing pressure. First start attempt was building the pressure back up but the start cycle timed out. Second attempt finished building fuel pressure and the motor started. Replaced the fuel pump and problem went away.

 

[Fless]

As stated above, try the easy things first, one at a time. Check and monitor fuel pressure. Swap fuel pump relay with a known good relay. Figure out which sensor was changed and do the Crankshaft Variation Relearn if either crank or cam sensor was replaced.

EDIT One other thing -- carefully inspect the starter for proper mounting, as well as for good electrical connections. You've probably already done that but thought I'd toss it in.

 

[mattbta]

Sounds like you have a cheapo camshaft position sensor. Check out my video after I had a shop do the same, RMS and cam sensor. Even went back and had them do a crankshaft variation relearn. No change. I kept kicking the can down the road and they were still willing to put an OEM sensor in, but I just did it myself and fixed that problem. Starts first time, every time now. I knew about the problems with non-OEM sensors but had fun launching a parts cannon. Before I put the OEM sensor in, I did fuel pump, filter, and pressure regulator. Ha. Good excuse and it was probably getting close to time anyway.

Good luck.

 

[oldchev]

I have the same issue. Had to have the trans rebuilt last April. While out, they find the leaking main rear oil seal which we could see prior. They replaced it. Also found the camshaft position sensor wires baring copper. The insulation was gone. I asked and they said they can splice in a new pigtail so they did ... great. Now I have the issue you have. Not everytime but maybe 50% of the time. Cranks without start. Maybe a pop. The second attempt starts immediatly. Just like yours. Just like you describe.
I was suspecting that possibly the wiring was mismatched on the pigtail. I am not overly educated on how the cam postion sensor exactly works but I have the factory manuals and understand the sequncing of fuel/spark based on parameters of camshaft and crankshaft. If a wire was inadvertly miswired, would it do this? That I cannot yet get an answer. I have to pull the intake off to redo that pigtail. Maybe the CMP has failed at the very time they touched it? Unlikely but possible.
I can say this, it was perfect until the wires were touched/repaired. I did not go back there with this problem because I am leary of what could happen. The trans works fine and the rear oil seal is tight. Just this. I am putting up with it for now, but irritating.
Maybe someone has additional info that can help us?
-Oldchev

 

[mattbta]

I have the same issue. Had to have the trans rebuilt last April. While out, they find the leaking main rear oil seal which we could see prior. They replaced it. Also found the camshaft position sensor wires baring copper. The insulation was gone. I asked and they said they can splice in a new pigtail so they did ... great. Now I have the issue you have. Not everytime but maybe 50% of the time. Cranks without start. Maybe a pop. The second attempt starts immediatly. Just like yours. Just like you describe.
I was suspecting that possibly the wiring was mismatched on the pigtail. I am not overly educated on how the cam postion sensor exactly works but I have the factory manuals and understand the sequncing of fuel/spark based on parameters of camshaft and crankshaft. If a wire was inadvertly miswired, would it do this? That I cannot yet get an answer. I have to pull the intake off to redo that pigtail. Maybe the CMP has failed at the very time they touched it? Unlikely but possible.
I can say this, it was perfect until the wires were touched/repaired. I did not go back there with this problem because I am leary of what could happen. The trans works fine and the rear oil seal is tight. Just this. I am putting up with it for now, but irritating.
Maybe someone has additional info that can help us?
-Oldchev

I posted the same response when you asked the same question in another thread months ago. If you're pulling the intake to inspect the pigtail, put an OEM sensor in it. Then do a cam/crank variation relearn for funsies! (My chinesium cam sensor still exhibited problems even after relearn, OEM fixed it!)

Unlikely the truck would run well at all if the wires weren't correct.

 

[KVacek]

I've been a little under the weather so haven't worked on this much. It's very likely past time for a fuel pump now when it's optional rather than after it dies completely. Gauge sender has been flaky for years too.

That said, I did take the Tech 2 out there the other day and did the crank relearn (that's how this model syncs the cam and crank sensors).

Still does the crank itself long first try, then fire right up second try about half the time. When I feel better and it gets cooler I'll see if there's any way to get to the cam sensor without other disassembly. Otherwise I'll drop the tank and do that fun job first, and see if that's it.

 

[oldchev]

2004 Yukon Denali Update: Today, I used my boroscope to look at the pigtail and connector to the CMP. The CMP bolt bolt looked pretty clean compared to the other parts around it. That said, I re examined the invoce on the trans work including the pigtail connector. The Ah Ha moment occured when I saw they stated replacing the pigtail and the CMP. So, I have the GM 19420911 coming from Rock Auto.
I'll update when installed. I am pretty sure this will fix it. (fingers crossed). Stay tuned.

 

[Fless]

2004 Yukon Denali Update: Today, I used my boroscope to look at the pigtail and connector to the CMP. The CMP bolt bolt looked pretty clean compared to the other parts around it. That said, I re examined the invoce on the trans work including the pigtail connector. The Ah Ha moment occured when I saw they stated replacing the pigtail and the CMP. So, I have the GM 19420911 coming from Rock Auto.
I'll update when installed. I am pretty sure this will fix it. (fingers crossed). Stay tuned.

I don't have the whole history of this, but... has a CASE learn been done to see if that would fix it with your current issue/sensor? I know @mattbta recommended doing one. If you do change the sensor, it's recommended to be done anyway for the new sensor.

 

[oldchev]

Yesterday 9/08/23, I replaced the CMP with GM19420911.
Instantly started. It now starts first time, everytime, with the GM sensor.
As stated by several on this forum, the other types of CMP sensors could be faulty. Using the correct GM sensor eliminated my issue. BTW, it never had a start issue until after the trans work, so replacing the "good one" with a new, incorrect one caused it to fail. I have 30+ starts on it now, so calling it good.
Oh, btw, this is a difficult access repair, at least for 60+. Once you feel what you have to do, it becomes easier. You have to make room by removing top eng cover and side covers. Then I had to sit aside of the eng, on top. I could elaborate but several already have.