Maybe I'm missing something - but if it won't even crank how would it be a fuel problem (short of a leaking injector hydrolocking a cylinder)?

IMO it's unlikely to be a crank or camshaft position sensor - the ECU would not expect to get a signal from either of these until after the starter is spinning the engine.

In the car world the fact that it doesn't crank would indicate something in the battery-ignition-relay-starter-solenoid chain. It's possible that our trucks are checking for fuel pressure prior to cranking - but it would be news to me (not that that would mean much!!)

good luck with it and please keep us posted.

 

I think he meant that it won't "fire" when he said it won't "crank"

 

deesilpwr - is it your truck?

 

My bad, CRANK and START are the same to me in my animated world
Just replace Crank with Run in all of my posts and it will make more sense.

Yes, this is Deezils truck. He had the Bully Dog with Crazy Larry for about a year and has nothing except the parts mentioned in this post now for performance parts! He lives like 2 minutes from me so we have both been tinkering with this thing.

Where is th cam sensor located on this thing? It must be on the rear of the front cover on the passenger side, but I havent looked for it yet. Am I right?

 

The Camshaft sensor is located just below the CP3.
But also check the wiring running right next to the A/C compressor. Also known to cause issues because of chaffing. This harness supplies power to both the Camshaft sensor and the A/C Transducer.

MikeyB

 

Karl, did you get that? I havent talked to you in a couple of days? You still there? Karl? Karl?

 

I didn't see any posts saying if there were any codes?If there aren't any codes,& it won't START,as opposed to CRANK.Then I'd say it must be a rail pressure issue.These engines will start,& run on EITHER crank,or the cam sensor.It may be the glitch I heard my dealer tech tell me about.The ECU may set a code,& /or not start if it sees more than 800psi. rail pressure while start sequence is initiated.There is a flash for this.Or it could be a crossover tube from the rail to the injecter leaking after it heats up.Something like that.Good Luck.

 

On our Mack engines the cam sensor and crank sensor will back each other up. If one fails the other has enough input to keep the truck running although power may be reduced.

It just baffles me as to how it could be a rail pressure issue when we have replaced everything that would cause such. There are no signs of any injector tubes leaking, at least not that I can see. The ports are not full of fuel or anything. There doesnt seem to be any external fuel leaks.

If it was a rail pressure issue wouldnt the rail bleed off slowly after it sat for a while? This prblem is right the opposite. It will sit for a while and crank and run fine. When it is running and you shut it off and try to imediately crank it back, it wont even attempt to fire off. Give it a little touch of ether and it fires right up?

There are no fault codes being logged during any of this. The only faults logged were the one when the key was cycled with all the stuff unplugged.

Will these engines go to a default mode and run under reduced power if the rail pressure sensor is unplugged?

 

If it starts right away with ether, sounds like a fueling problem - as in not enough pressure when it's hot...

 

Had a F250 with powerjoke 7.3l that had a vibration sensor that would let it not crank like you are referin to here

Do our 3rd gen have such a creature?

 

It sure seems like it would be, but WHAT? I keep picking my brain at work and trying to figure it out, but I just cant.

The truck also doesnt have to be hot to do this. We have started it ice cold, let it run for 15 seconds, and then shut it off and try to restart it with no luck. It would just spin over and not crank. Hit it with a little ether and it fires right up. It wont stumble, miss, smoke or anything. Its like it needs to spin a litte bit faster to fire. That would make one believe that the C3 isnt building enough pressure and the little bit of extra cranking speed is what makes it go on and start and run. But it has a dual feed stage 2 CP3 brand new on it? I know I keep asking and saying the same thing over and over but I am trying to get my brain jogged so I can figure this thing out.

Please excuse me before I go get my .45 and suck on the barrel like a crazy straw

 

when you had the injectors done did they replace the bodies because as of last week when i talked to an injector shop that is Bosch certified their is no one who rebuilds these yet because the parts have not been released by bosch. if you didnt pay at least 250 or more per injector then you are running with the ame ones just new tips which will not fix the bypass problem. had this happen on my 03 the toys jusst enhance it

 

DmaxEter Could your problem be that you have too much fuel pressure from your Walbro pump or is your fuel shut off sticking or acting up
because of too much fuel pressure from the lift pump? The second generation trucks started hard if they had too much fuel pressure from the lift pump.

Retooc

 

Thanks Rich. That was what I wanted to know. I bet DDP just threw the tips in and nothing else. I bet the internals in the bodies are shot. Thats where all the real work goes on!! I had been thinking about that and was afraid to mention it. I bet that is what it is. I just wonder if its a wear problem or a dirty kind of problem! I wonder if some good cleaning would get this problem resolved? What are the opinion on that???????

 

But how would the injector(s) failing to bypass cause hard-to-start when hot only?