I had a customer bring in a 2008 LMM a couple of weeks ago that wouldn't run. The story I got was he slung a belt that ripped the cam sensor wires. He took it to a local shop that found and repaired the wires. The truck ran for a day, but after that died and hasn't run since. When the truck got to me, I verified the wires were put together correctly and they showed good continuity. I then tried swapping in a good cam sensor thinking maybe the original was somehow damaged when the belt came off. I have also verified fuel pressure and verified the ECM is getting a cam and crank signal. Datalogging with the V2 does not indicate the injectors are firing even though all parameters are met (as far as I know). I'm stuck and am struggling to figure out where to go from here. I know there are lots of smart guys here; anyone have any suggestions?
Stumped: LMM crank no start
- Thread starter JoshH
- Start date
Doesn't appear to be, and I am getting strong, consistent cam and crank signals on my scope.
maybe put a scope or light on the injectors and verify they are not triggering? did the customer say when it shut off if it back fired or made any kind of noise when it did? i assume no codes? all other sensors reading correct like baro, map, maf, and so on? will it start on an injectable and possibly keep running?
After making this post, I did a comparison to my 06 and can see the cam/crank signals aren't sync'ed up the same on the non running truck as they are on my truck. I'm assuming maybe the reluctor wheel on the LMM has moved out of position. Looks like I'll be pulling the front cover to figure out what is going on.
The scaling is off a little because one truck was running and the other was just cranking, but if you count the teeth on the crank from the gap to the step on the cam reluctor plate, you’ll see the problem. Now the question I have is why it wasn’t throwing a cam/crank correlation code.
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you sure its just not a lag issue between the two from what a running truck has verse non running? if you disconnect the injectors on the running one, might give you a more comparable scan before you start tearing in more.
otherwise, i wonder if the truck had a backfire or something and the cam pin sheared when it stopped running the second time. so now its out a few degrees.
otherwise, i wonder if the truck had a backfire or something and the cam pin sheared when it stopped running the second time. so now its out a few degrees.
I’m 100% sure the cam and crank are not lined up properly. This is what the running truck looks like cranking before it fires up. This truck had the pin for the balancer shear a couple of years ago. We fixed it and installed a balancer from SoCal that pressed on to hopefully eliminate that from happening again. I wonder if the pin for the crank reluctor was also damaged and it has finally moved after all that time. It’s weird that it happened after the belt damaged the cam wires, but that’s what it seems has happened. Regardless, the front cover will be coming off to investigate further.
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I have seen a few LMMs beat the crank reluctor pin up in stock form, without any other engine damage and cause misfires and no starts...wicked fun.
Check to see if the fuel filter will prime. I have had to replace mine twice in 300K miles and it just seems to go out a random time, once after I replaced the filter and the first time it just would not start one morning.