Cranks but no start, then starts immediately

[WA5LTA Bill]

I have a '99 2500 with 330,000+ miles that I use as a work truck. It still has the original fuel pump. Had output pressure checked and was ok. It starts relatively well the first time of the morning--temps in high 60's low 70's. However during the day after the engine gets hot, it normally takes 3-4-5 times to start. Sometimes on the 2nd try. I can hear the fuel pump operate when key is turned on. I have no other problems with its operation--runs great at highway speeds and has good power. It doesn't have any symptoms of a VP problem from what I have read. Batteries are a year old and major wiring was replaced last year. Starter seems to spin at required speed.

 

[KATOOM]

Bill what you could be experiencing is a hot PSG (computer on top of VP). If everything is still factory stock then you're doing great. But what happens is over time that old PSG solder crystallizes the from heat cycles which can cause a whole slew of problems. One particularly being hard hot starts. What you can do to test this is to bring along a couple gallons of water in jugs with you and when the hot hard start happens, open the hood and pour the water directly on the top of the VP. This cools the PSG and should allow for a normal start.

If you didnt say everything was still factory stock then I would have asked if you had an aftermarket fuel pump and remanufactured VP at some point in time. Because there is a hot hard start problem which is created by excessive fuel pressure during engine cranking, which causes hydrolocking of the timing ring and fuel solenoid. But this cant be whats causing your situation...

 

[WA5LTA Bill]

Katoom, Thanks for your reply. I will try the cold water on the VP and see what happens. I don't remember if I have had the VP replaced (will need to check my service notes). I was thinking that it could be an electrical issue, like a plug/jack connection not making when hot or something like that.

 

[WA5LTA Bill]

Have tried pouring ice water, but not 2 gallons, on VP44. Didn't seem to make any difference. VP44 was replaced at 151,793 miles. It is a remanufactured unit and was replaced by the local Dodge dealer. Have 339,234 on truck now. Last Friday, it wouldn't crank after several tries and had to jump with my '08 3500. I did notice that the starter seemed to spin faster with the jump. I have cleaned the battery posts/cable connections about two months ago. I am using the Larry B's post connectors and had new cables fabricated at a parts house. With the weather getting hotter here in SW Arkansas, looks like I need to determine what the problem is, as I use it as a work truck and have multiple starts per day. I have had the starter replaced several times. I think the mechanic got the starters from the local NAPA parts house. What rpm should I see when starting?

 

[KATOOM]

Hmmm... The VP replaced by the dealer means its likely an OEM part and not one from a reman company, and it could be just fine too since you may have discovered that your starter is the culprit. Starting RPM is critical on diesels as the compression heat is what ignites the fuel and mere 50 rpm drop in cranking RPM can prevent starting.
The OEM starters are amazingly stout units but generally need the contacts replaced about every 100k miles or so. Thats when unfortunately some people turn theirs in for a "lifetime warranty" unit at the parts store and those are garbage even though they look the same. They last only so long and eventually spin slower and slower, causing starting issues. You can get another but it'll be doing something similar in time.

OK, all that said, voltage issues can also cause similar starting issues. If the batteries are not in perfect condition and/or corrosion has compromised connections or cables then the voltage drop when its really hot or really cold will be enough to prevent the VP fuel solenoid from moving and cause starting issues.

 

[WA5LTA Bill]

Revisiting this thread with questions. Will a faulty/intermittent TPS and/or CPS cause the hard/long starting when engine is hot? Sometimes it will start immediately on first try, especially first start of morning (ambient temperatures in mid 70's). As the day progresses and gets hotter most of the time it takes multiple start tries. I have been told not to "pump" the accelerator for a diesel, but I do, which seems to help somewhat in the hard starting times. Another question is about the ignition key lock/switch assembly. If the switch is not making good connections on all contacts, would this affect the hard starting? What test procedures should a knowledgeable mechanic need to use to diagnose the actual problem. A couple of mechanics that I have talked with both say it "could" the VP44. If it can be diagnosed as such, ok. I don't want to have it replaced just because someone "thinks" it is defective and it not be the actual problem.

 

[KATOOM]

Good for you for not throwing parts at it because that can get costly...

A bad CPS can definitely cause a starting issue, and a random one too. I've never heard of a bad APPS (TPS) causing a starting issue, and pumping the throttle does nothing since you're only moving a rheostat which has no affect on the actual "throttle" position until the engine runs. These trucks are drive by wire with a cable going to the electronic wire.

As for the ignition, I would say that yes, if there was a problem in the assembly that it may affect something. Not sure how it would cause a hard start though. You could take note if the ECM system is booting up correctly by watching the dash lights. All the lights should illuminate and then turn off before starting.