01 Yukon random no crank

[Beau F.]

Hello everyone..Im at my wits end...2001 Yukon. Starts,runs fine for undetermined amount of times. Then out of the blue , no crank. All the dash components work. Door dinger works. Security light flashes until door closes ,then it stops. I have tried the passkey/passlock key relearn sequence to no avail. I have replaced the ignition cylinder, checked the battery and all wires, connections and grounds. Replaced starter and ignition relays as well as ignition 20 amp fuse. Pulled starter, checked wires for breaks and bad connections, cleand up the starter and put it back in. The truck cranked up fine for five or six starts and then no crank again....I had this happen on the paking lot of a grocery store, disconnected and reconnected the battery, tried the key pattern etc...had it towed to a mechanic. They started it right up and couldn't find anything wrong,,,no error codes no nothing...it started up multiple times while at the mechanic...picked it up and had no issues for about 4 days and then one morning it wouldn't crank....its a vicious circle of uncertainty. From looking at the internet and other forums it seems to be a common issue, but yet no one has an answer for my situation...any help would be awesome...thanks

[riverbanks]

What's the chance it's the neutral safety switch on tranny?next,no crank,foot on brake,hold in start position,run down thru the gears till?crank hopefully

[Doug_Scott]

Well first thing to do is stop letting your wallet from teaching you that simply opening it up and tossing money at the truck is not the solution to your problem.  The time to troubleshoot the issue is when the truck won't star.  If it does not happen when the mechanic is their, what is he supposed to do?  Just guess and install some part that may or more like will not fix the issue.  I have had customers tow their car who arrived before their car did, and they came into the shop to talk to me to explain the issue.  The car I was working on was a buddies 66 Nova pro street car, which when started eliminated conversation.  my buddy tapped me to tell me their car was just pulling up.  I got the tow truck driver to just drop into the empty bay next to mine.  Just as the wheels hit ground I stuck my arm into the window to put it into park, but instead I tried to start before putting it in park. I turned the ignition to see what would happen.  Car started right up, and idled just fine.  I put the car in park and told the customer that since it started right up and it would very likely be expensive.  The odds of catching the solution in less than an hour is slim to none.  Personally I would do all the single issues.  By singles I mean all items that can operate on their own.  

[Beau F.]

@riverbanks..Thanks for the response..Neutral safety switch had been suggested by a friend..I did hold it in start and cycle thru the gear selections..no results...

 

[riverbanks]

Pop the cover off the relay center, give that a good look over,they are a good nest spot

[Beau F.]

@Doug_Scott..Thanks for answering...I understand that "tossing money" at the problem wont solve it. The things that I replaced were at the suggestion of a friend who is a mechanic. We tested from the ignition cylinder all the way down to the starter solenoid and found no issues. Thinking it might be security system related due to GMs passkey/passlock/VATS issues, and reading about cylinder pin wear over time a, cheap and easy replacement of the cylinder was not a big deal. Since the tests showed no apparent issues and as the ignition switch and starter replacement would be in the hundreds of dollars just to see if it would solve an undetectable and random problem, I figured I would ask around to see if anyone could relate to my issues...

[Beau F.]

@riverbanksI checked in there when replacing the relays and checking the fuses...no lizards,birds or mice..lol...although I have seen rats nesting in a fan shroud before....haha

Edited October 21, 2019 by Beau Fish

[riverbanks]

Hmm,so what's in the circuit, ignition switch,then neutral safety switch,then starter relay,I think I have them in order,so,at safety switch,your going to have to test that,output,when it quits starting,stinks,but you gotta go down the line,and my test isn't perfect for safety switch,so I'm thinking test there?

[Beau F.]

@riverbanks...Didn't get to test it today..will try tomorrow...But if my relay points test good, wouldn't that show the neutral safety switch isn't an issue...as its before the relay..

[Doug_Scott]

27 minutes ago, Beau F. said:

@riverbanks...Didn't get to test it today..will try tomorrow...But if my relay points test good, wouldn't that show the neutral safety switch isn't an issue...as its before the relay..

When you tested "your relay points test" did that test with the vehicle in Park or D?

[Beau F.]

@riverbanks..With the truck in park there was power to the relay...

 

[Doug_Scott]

12 hours ago, Beau F. said:

@riverbanks..With the truck in park there was power to the relay...

 

There should be power to at least 2 wires, one with the key in the on position, the second wire will become active only when the key is turned to the start position.  You can quickly test the rely by simply swapping the relay next to it.

[Beau F.]

@Doug_Scott..Thanks for replying..I swapped the relays and also bought new ones before it was tested... A friend of mine assured me that there is power coming to the relay. The problem is intermittent...so it seems testing would have to be done when the fault presents...other than testing the relays themselves after removal, but thats a moot point if they are new and nothing changes when switching with other relays. It started right up this afternoon with no problems....Ill see what happens tomorrow...

[Beau F.]

Alright..got it figured out...Started from scratch and began testing from the ignition...power up to the starter relay...so from key to relay is good...got light when testing key in start position,  found power all they way to the starter on the main line...but no power on key turn at the starter solenoid. Went back to the relay, pulled it out and jumped the circuit (Starter should power up) got power at the solenoid, but starter wont engage...Take jumper wire off and put the relay back in...nothing....Tested before the relay and got power again at the key turn....tested the relay again and it seemed fine but replaced it with a another one just to be sure....then I noticed that when having someone turn the key , that the relay wasn't clicking under power...so I wiggled it a bit and it clicked...turns out the socket the relay fits in was wallowed out so the contact pins weren't making good contact...that's why it would show as good one time and not good the next...which also explained the intermittent starter failures..so I wrapped a small bit of copper wire around the posts and pushed it back in..it was nice and tight and had power all the way to the starter and at the solenoid at key turn. But still no starter engagement....(starter engaged fine a few days ago, but now just spun and Bendix didn't thrust out and engage...replaced the starter and all is good....so apparently the combination of the loose socket for the relay and the failing starter were the culprits....

[Doug_Scott]

If "wallowed out" means "melted away"  you have not fixed it.  It will return again, and likely a lot faster than it took the last time.

[Beau F.]

@Doug_Scott...Well, my understanding of "wallowed out" means a space or hole has been forcefully stretched beyond its original size or depth...and "melted away" would most likely refer to an overheating of some sort that would surpass the melting point of a substance resulting in the deformation of the space or hole....In this instance three of the four slots that the contacts pins of the relay fit into were somehow forcefully stretched beyond their original size or depth. It could have been either a test probe jammed in there or maybe just forceful wiggling trying to remove the relay, I dont really know what caused it. I do know that there was (is) no melted, discolored or burned plastic and no smell of anything electrical or heat related, so I would rule out "melted away" as the culprit....thanks for the heads up though.