Over the last week I've noticed some strange behaviors from my truck and want you all's opinion on whether I'm being paranoid, I just need some maintenance, I'm about to have a serious truck breakdown to deal with, or something else altogether.

 

Background:  I'm in Minnesota, and my fuel tank is full of local "Premium" diesel.  Temps are ranging from the 20s to even a few days in the 60s.  Fuel from the same station I've used a lot in the past, newer station, sells lots of diesel.  Other guys I work with fuel here, too, no problems.  I'm running my Quad on Level 2 for MPG, as I have for a few thousand miles.  Fuel pressure is unchanged.  Can hardly tell about MPG changes as sometimes I fight a 40 MPH headwind on the interstate, and by the return trip don't get the benefit of a corresponding tail wind.  Also, except for 100 mile round trips to a "neighboring" town, most of my driving is just putting across town to the local pork plant and back to the hotel.  I've been keeping over 1/2 tank of fuel.

 

Symptoms:  I have had my "Turbo Timer" set for 300 degrees and until this week (after getting fuel the last time) the engine would run maybe 10 seconds after shutoff, even when 60 degrees out.  The past few days despite it being in the 30s to 40s my truck would run for well over a minute before finally shutting off.  I have since bumped the shutoff temp to 325 so it actually shuts off before I make it into the hotel from across the parking lot.  This is even with a coolant temp of maybe 150 degrees (drove to hotel for lunch from the plant, which is just a couple miles of flat ground).

My EGTs had seemed to be higher than normal despite same route, driving style, tire air pressure, etc.  I have not noticed any excessive smoke, and boost pressure seems same as always, though I admit I don't usually pay a lot of attention to that.

I thought maybe the thermocouple was just going bad until I had some rough starts the last two mornings, and even sputtered some at lunch today.  This morning it hardly wanted to start, acting like it had an abundance of air in the fuel system, belching unburned fuel and running like crap.  Once it ran for 10 seconds, it seemed normal, leading me to believe it's not a fuel gelling issue.  Used to be when I flipped the key to Run to let the grid heater do its thing the fuel pump would run its couple of seconds, the pressure would come up a little and SLOWLY bleed to zero if I sat there long enough.  Now, the pump still does its ~2 seconds of prime and the pressure just falls to zero FAST - actually, as I type this I'm not 100% certain the pressure comes up much, but I do here the pump run, and like I said above the fuel pressure is otherwise same as always.  There is not a puddle of fuel under the truck, though I swear I have had a small leak from near the VP44 dripping down the front of the engine; however, I can never find it!

 

Air in fuel causes delayed ignition, does it therefore also contribute to higher EGTs?  Is this just a simple case of needing some fuel plumbing maintenance, or...?  Not sure if if it's in my signature, but I run a stock "formerly engine mounted" pump, relocated to near the fuel tank, draw straw, 3/8" Parker fuel hose, stock filter housing, no banjos on the supply side.

 

Would love to read your thoughts on the matter, thank you in advance.  I will not likely be able to read or respond until tomorrow (Tuesday) evening.

You could very possibly have two issues, failing thermal coupler I had that happen, and the weak fuel pump or something going on with it. 

This is definitely the case of forewarning of doom by paranoia 

 With the fuel pressure dropping fast as you said I would think it could be a fueling problem there. The turbo timer problem could be an unrelated issue. I would address the fuel pressure problem first since that will quickly kill a VP44. Just my $.02 since I myself am new to these trucks but I have read ALOT trying to gain knowledge.

 Let us know what you find and what's done to correct it.

You might check and see if you have any trouble codes. The truck might be giving you a hint. 

As far the fuel pressure dropping quick after the prime, if you have needle valve on it just close it a bit. The pressure in fuel system bleeds of almost imediately anyway. The needle valve is just holding pressure between it and the gauge. The more closed it is the slower it it bleeds off. How is the pressure when the truck is running?

Edited April 14, 20205 yr by dripley

10 hours ago, dripley said:

How is the pressure when the truck is running?

Fuel pressure is same as it's been for tens of thousands of miles, 10-14 PSI.

 

If air is leaking in through the fitting at the back of the head, could that screw up my starts?  I sure wouldn't think so, but I'm not 100% versed on how Dodge engineers (or summer intern, Rube Goldberg disciples?) thought the system should work.

 

Dripley, I suppose you're right that it could be the needle valve has just worked out of adjustment, it just seems very  suspicious th pressure drop coincided with the rough starts.  Could the VP44 pressure relief valve be weak, or a piece of trash stuck in it?  I run Donaldson fuel filters, but don't remember the exact part number or specs.  The relief valve has been externally dry every time I've looked at it.

If your fuel pressure while running has not changed i dont fhink that has  anything to do with it. If the return fitting on the back of the head is letting air into the fuel system it can most certainly cause hard starts like you are experiencing as can a y other fitting that lets air in.

@dripley you were on to something with the needle valve!  At least that's where I needed to look more closely.  Turns out the fitting tapped into the elbow at the VP44 had finally shaken loose and was letting in air while the truck was off, and letting out fuel while the grid heaters were on.  I tightened it while the truck was on high idle, and the difference in engine noise was quite noticeable!

Doubt that has much to do with my strange EGTs, but who knows.  At least now it should start better in the morning.

4 hours ago, LorenS said:

@dripley you were on to something with the needle valve!  At least that's where I needed to look more closely.  Turns out the fitting tapped into the elbow at the VP44 had finally shaken loose and was letting in air while the truck was off, and letting out fuel while the grid heaters were on.  I tightened it while the truck was on high idle, and the difference in engine noise was quite noticeable!

Doubt that has much to do with my strange EGTs, but who knows.  At least now it should start better in the morning.

Good to hear. Simple are the best.

Edited April 15, 20205 yr by dripley