Hard Starting After Engine Warms Up

[MAYoung]

Gentlemen:

I need your insight and advice. My 1998.5 Dodge 2500 with 263,000 miles and nearly 21 year life (owned since new), has begun to start hard after it warns up. On initial start up, it fires right up after one tap of the starter. Drive it for a a bit, and it may take 5-10 seconds before it restarts. It has been getting progressively worse for several months now.

I quietly suspect the VP44 actiing up. It behaves like previous failures. I have no trouble codes. Fuel pressure upon cranking is about 15-16 psi. The lift pump was replaced was replaced with a DDRP about 10 years ago and it maintains about 13-14 psi under a running load. The lowest psi I see is about 12.

This is the third VP44 for this truck. The first failed at about 80,000 miles, the second at 160,000 miles. This is the longest lasting VP44 I have had in this truck. After the second failure, I installed a fuel pressure gauge and watch it religiously so I believe the fuel pressures to be ok. It was replaced with a unit re-manufactured in Utah. (I forget the outfits' name but it advertised in TDR magazine.) I cannot tell you if a new electronics board was installed upon reman.

We are towing horses around regularly so I need to get this fixed. I realize that this is an old issue but I am looking for any suggestions for diagnosis and repair.

Thanks again, Mark Young

 

[DavidC]

https://www.bluechipdiesel.com/troubleshooting-1

 

[KATOOM]

There are two reasons for a hard HOT start condition. 1) The fuel pressure is too high and causes the timing ring and fuel solenoid to hydro lock until the pressure drops during cranking. This is usually something experienced after the stock VP has been replaced with a re-manufactured VP and combined with an aftermarket higher pressure / higher volume fuel pump, like a FASS or Airdog. A fuel pump delay relay solves this problem by interrupting the fuel pump during engine cranking. The way you determine if this is the problem is when the hot hard start happens you unplug the fuel pump fuse during engine cranking and see if it starts normal. Given that you havent messed with anything for a decade I'm going to guess that this is not the problem with your truck.

Or 2) the PSG electronics are getting too hot and have effectively timed themselves out as the lead free solder has begun to crystallize and the connections are becoming compromised. How to establish if the problem is the PSG electronics is to carry around a gallon oor two of water with you. Then when the hard start happens, open the hood and pour the water directly on the PSG (top of VP). This cools the PSG electronics and should cause it to start more normal.
If that is whats happening then I'm going to presume that whomever you got your reman VP's from is not supplying them with new PSG units. It is essential that your reman VP comes with a brand new never used PSG...

 

[MAYoung]

Thanks to you both for the prompt guidance. As usual, I see that there are multiple paths to failure.

I'm going to check the starter rotation first. The starter has been on there a long time (12 years?). I think that it may be ok since it starts so well on the first start of the day. In any event, the starter has a lifetime guarantee (yes, one of those) so I may go down an swap it if it demonstrates any sign of trouble. If not the starter, I'll do the cold water test on the VP44.

 

[JR]

Katoom advice is spot on, but the one time I did the water test I substituted with a couple of those soft ice packs. I didn't like the idea of pouring water over a heat soaked PSG (although im sure it would be fine).
I just threw in a couple of the softies in a cooler and brought them with me.

 

[NIsaacs]

When you start your truck hot, go instantly from off to start. Do not pause, on run, then start. See if that will help.

 

[KATOOM]

The starter has been on there a long time (12 years?)

If the factory starter was ever replaced with a "lifetime warranty" over the counter unit then yes they can crank slower over time due to drag. Simply put...the lifetime ones are horrible. The factory starters are almost bullet proof and only need contacts/plunger replaced about every 100k miles.
If a starter is dragging then it usually affects cold weather starting as a mere 50 rpm reduction in cranking speed can affect starting. But it generally doesnt affect hot engine starting for obvious reasons. So if your batteries check out by testing individually and it starts just fine cold then its likely not the problem.

 

[MAYoung]

Update: April 12, 2019

Gentlemen:

It has been nearly a month since my first post and I have been busy with your suggestions. First, I tried ice packs on the injector pump PC board. It sort of helped....I think....maybe....it didn't hurt anything. I was just not convinced and I was worrying that I would need a new VP44

I read KATOOM's post above with interest. The starter was old; it was a Auto Zone replacement. Could it be that it was just worn and I was not noticing the declining RPM's upon start? I went down to my local Dodge dealer and ordered a Dodge factory reman unit---$480 plus core, but a lot cheaper than a VP44 reman.

I just finished installing the new starter and gave it a try and WOW! It started with all the gusto of a brand new everything. One touch on the starter and that engine was back to its old Cummins self. And this was after a day of running around a lot, several hard starts and still hot everything under the hood while the new starter was installed. I went back and tried it several times and it was a single touch of the starter to start everytime.

Thanks to all. Once again, I just paid for about 25 years of TDR membership by following ideas and suggestions from the forum It was a great assist.

I've got other issues that I'm working on but that was a big one. Let's hope that it holds. I will start a new post for my next question.

 

[DavidC]

Good to hear