Archived Not completely 'broke down' but getting there - fueling issues?

[KCramer]

Good morning, all -

I am suffering an intermittent starting problem, which mimics a VP44 problem. The timeline:

Last Thursday, I parked nose-up on a hill, and the truck cranked but would not start. Fuel pressure on the transfer pump ~13psi initially (before the lift pump shut off). This repeated itself for 5-7 start attempts - not even a hint of fire. It acted like I was out of fuel, and I didn't have another alternative, so I added 5 gal. and the truck immediately fired. I drove to the station, and filled the tank with 12 gal.

No MIL, no codes noted after I got home.

I drove fine, no starting issues on Friday, but Friday night, I got a crank position code and MIL. I did not note the tach dropping out, or any driveability issue. The MIL cleared Saturday, so I believe it to be limited occurrence (so far). I did not clear the codes.

Drove fine Sunday, Monday, Tuesday morning.

Tuesday afternoon, fired fine - drove to the hardware store, and upon leaving, the truck would not start (one try). I immediately connected to the ECM, and noted only the stored CPS code, which I cleared. Truck started fine.

Any thoughts what might be going on? VP44 on its way out, without throwing a code? This pump has ~75k on it.
Mechanical pressure gauge between the filter and the VP44 is reading fine. No performance mods to the truck (other than the muffler seems to have fallen off).

Thanks in advance for any opinion, speculation, or other ideas....
klc

 

[JR]

P0336 I believe is the crankshaft position sensor code. Truck will not fire if the sensor is bad. Sounds like it's intermittently failing.

 

[petersonj]

I wouldn't be ready to condemn VP44 yet. You may have two separate issues here... or not. Your description of the first symptoms (nose of truck pointing uphill, but no codes or MIL) may indicate fuel leaking back to the tank while the truck is parked. Do you have the stock lift pump on the engine block, or has it been relocated to the frame, or inside the fuel tank?

If the problem occurs again under above situation, try bumping the starter once, then leave the key in the run position for at least 20 seconds (the lift pump should run for approximately 20 seconds in this situation and you should be able to hear it run). You may even want to do this a couple of times before trying to start the engine again to ensure the lift pump is supplying air-free fuel to the injection pump.

If by chance this turns out to be causing your starting problem, you will have to find out why the fuel is draining back to the tank. Sometimes a small leak a supply hose won't leak fuel externally, but can draw air into the line while under a slight vacuum (like when the truck is parked with the front end pointing uphill).

Hope this helps.
- John

 

[JR]

Could also be sheer coincidence as the truck has failed to start twice after that and produced a crank position sensor code both times. If you can duplicate the no start by parking on a hill there may be something there, otherwise generally if a CEL is produced repeatedly it's a good indication of a problem in that circuit. I'd start where the truck is telling you there's a problem and go from there.

 

[Bob4x4]

Crank sensors do go intermitant before they die in many cases

 

[KCramer]

Thanks to all who replied! I have had the opportunity to replace the crank sensor previously (and condemn the local auto house replacements) but had not ever experienced a starting problem. I noticed 'burps' in the injection and the tach bouncing as the sensor errored. This led me to believe the cause of this issue was something different.

That said, JR's post led me to pick up a locally available sensor (as well as order one from Geno's) 'just in case'.

Just in case came true Wednesday night, as I was swapping the sensor at 11:00 to get home from the jobsite.....

Problem solved - the truck is driving better, and starting! I'm guessing the sensor has been misbehaving for a month or two (I blamed winter blend).

Again - thanks to the TDR community for the help and suggestions.

 

[JR]

That's great to hear! The less expensive the better, LOL.

And yes, I learned a long time ago that when it comes to sensors your better off spending the extra coin on a Cummins replacement part. The box store sensors are a real crap shoot.

 

[crabman]

The following site is a very good place to bookmark if your truck has a VP44.
http://www.bluechipdiesel.com/vp44diagnostichelp.html