12v Hard to Start When the Engine is Hot

[vastan]

I am the original owner of a 1997 Dodge Ram 2500 with a 5.9 12V Cummins with 5 speed manual and 4x4. The truck has less than 130k miles on the odometer. About 4-5 years after taking delivery, I had to start lightly pressing in on the throttle to get the truck to start. Up until about 6 months ago, it would fire up every time with no issues. Now it only fires up when the engine is cold. If I try to start the truck immediately after driving it, the throttle pedal gets hard to push in and I am almost forced to push the throttle all the way in until the RPMs spike and a big cloud of smoke belches from the exhaust. This does not always work on the first try. Otherwise, the truck has no issues whatsoever once started and has plenty of power when pulling or just driving around town to the hardware store.

Over the past 2 years, I have replaced the following parts as either maintenance or to avoid future issues due to the age of the truck's original components.

• Fuel Shutoff Solenoid
• Installed fuel filter kit FFK9798
• Replaced fuel pre-filter screen, though original was clean and free of debris or deposits after over 20 years.
• Replaced turbo with ATS Aurora 4000 Turbo System since my boost was fading on the original Holset unit.
• Replaced the exhaust manifold with ATS Pulse Flow Exhaust Manifold Kit, 3-Piece
• Installed a MBRP 4" exhaust pipe with muffler.

To date, I have changed the oil every 3k miles until switching to full synthetic many years ago and now change every 5k miles. I check the valve lash about every 30k miles and just recently checked them.

However, I have never serviced the mechanical Bosch fuel pump or replaced the injectors. However, I doubt it is the injectors since the truck runs perfectly fine once started and has no problem starting when cold.

Any help in resolving this issue would be greatly appreciated.

Thanks,

 

[GAmes]

There isn't any servicing for the p-pump but there is maintenance that is required every now and then. The idle screw is adjustable. With the engine warm and A/C on the spec is 750-800. My owners manual states that when cold it may be necessary to depress the pedal a little for the first start of the day.

Every now and then I pop the throttle rod off and clean/lube the balls & sockets. The bushings in your linkage should still be good at your mileage but they do wear out over time. https://www.genosgarage.com/product/4425053-mopar-bellcrank-throttle-bushing/throttle-cables-linkage

You are correct about the injectors. 400k is the average for mine needing replacement. I don't see rubber fuel lines on your list. If yours are original they are way overdue replacing. When cold does the engine fire on the first revolution or does it take awhile?

I hope you have replaced the fuel filter more than once. After about 15k my fuel pressure starts to drop and I have adopted a 15k replacement interval.

 

[mfurrh55]

Don't know if this helps, but my son's 97 12 valve 3500 did this and replacing lift pump cured it, just a thought.

 

[Iron Duke II]

There isn't any servicing for the p-pump but there is maintenance that is required every now and then. The idle screw is adjustable. With the engine warm and A/C on the spec is 750-800. My owners manual states that when cold it may be necessary to depress the pedal a little for the first start of the day.

Every now and then I pop the throttle rod off and clean/lube the balls & sockets. The bushings in your linkage should still be good at your mileage but they do wear out over time. https://www.genosgarage.com/product/4425053-mopar-bellcrank-throttle-bushing/throttle-cables-linkage

You are correct about the injectors. 400k is the average for mine needing replacement. I don't see rubber fuel lines on your list. If yours are original they are way overdue replacing. When cold does the engine fire on the first revolution or does it take awhile?

I hope you have replaced the fuel filter more than once. After about 15k my fuel pressure starts to drop and I have adopted a 15k replacement interval.

What is your opinion of the brass version of the linkage bushings? https://powerdrivendiesel.com/product/pdd-bronze-p7100-bellcrank-bushing/

 

[Iron Duke II]

I am the original owner of a 1997 Dodge Ram 2500 with a 5.9 12V Cummins with 5 speed manual and 4x4. The truck has less than 130k miles on the odometer. About 4-5 years after taking delivery, I had to start lightly pressing in on the throttle to get the truck to start. Up until about 6 months ago, it would fire up every time with no issues. Now it only fires up when the engine is cold. If I try to start the truck immediately after driving it, the throttle pedal gets hard to push in and I am almost forced to push the throttle all the way in until the RPMs spike and a big cloud of smoke belches from the exhaust. This does not always work on the first try. Otherwise, the truck has no issues whatsoever once started and has plenty of power when pulling or just driving around town to the hardware store.

Over the past 2 years, I have replaced the following parts as either maintenance or to avoid future issues due to the age of the truck's original components.

• Fuel Shutoff Solenoid
• Installed fuel filter kit FFK9798
• Replaced fuel pre-filter screen, though original was clean and free of debris or deposits after over 20 years.
• Replaced turbo with ATS Aurora 4000 Turbo System since my boost was fading on the original Holset unit.
• Replaced the exhaust manifold with ATS Pulse Flow Exhaust Manifold Kit, 3-Piece
• Installed a MBRP 4" exhaust pipe with muffler.

To date, I have changed the oil every 3k miles until switching to full synthetic many years ago and now change every 5k miles. I check the valve lash about every 30k miles and just recently checked them.

However, I have never serviced the mechanical Bosch fuel pump or replaced the injectors. However, I doubt it is the injectors since the truck runs perfectly fine once started and has no problem starting when cold.

Any help in resolving this issue would be greatly appreciated.

Thanks,

The following overflow valve helped the starting issue similar to what you described. http://www.torkteknology.com/cummins-adjustable-overflow-valve-by-tork-tek-ofv010/

 

[GAmes]

What is your opinion of the brass version of the linkage bushings? https://powerdrivendiesel.com/product/pdd-bronze-p7100-bellcrank-bushing/

I have a set on the workbench, a job I have been avoiding. More than likely they won't get installed until I install the engine I am rebuilding.

 

[vastan]

Below are my responses to all the helpful suggestions.

1) Once started, the engine idles around 800 rpm and the engine fires on the fist rotation when the engine is cold but not when it is hot.
2) I recently replaced the rubber fuel lines but have not cleaned/lubed the balls & sockets on the throttle linkage.
3) I replace the fuel filter roughly every 10k miles or at very other oil change. I sometimes let it go to 15k miles.
4) I replaced a faulty (leaky) lift pump around 60k. Hence, the current OEM mechanical lift pump only has around 70k on it.
5) Forgot to mention that I replaced the overflow valve but it did not cure the condition.

I will go back and check the throttle linkage and consider replacing the lift pump due to its age and will let you know if any of these things help.

Thanks for everyone's feedback. Most appreciated!!

 

[GAmes]

I change my lift pumps at 300k as preventative maintenance. I have never had one fail. 70k is nothing on a mechanical pump. Besides, if it was bad the engine wouldn't run perfect once started. Here is what I suggest. The next time it doesn't start easily leave the key on and look to see if the FSS is up. You might also adjust the idle a little higher. I like mine at 900 so that I have better heat in the winter and better cooling in the summer while operating in city traffic. Also, there isn't any need to apply throttle when starting with it adjusted that high.

 

[vastan]

Thanks for the helpful suggestions. I will try these and let you all know what I find out.

 

[James Robb]

So what was the solution? Really irritating when someone says "I will try these and let you all know" and then doesn't. having the same issue with my brothers 95.

 

[Thomas (Steve) Dixon]

I'd like to know what the solution is too as I'm having problems along those lines with my '96. Also a loss of power when pulling/hauling. I have a filter and lift pump to install, but it would be nice to know what fixed the OPs truck.

Steve

 

[Thomas (Steve) Dixon]

As far as mine is concerned I replaced the fuel filter, and the lift pump--twice, because the first one leaked where the hand primer is, and the power is back. I also replaced all the rubber hoses and plan to add a gauge to monitor the lift pump pressure sometime soon, it had an exhaust gas temp and boost gauge when I bought it. Next up is to get back to lockout hubs and solid axle shafts.

Steve

 

[SRath]

Last week, after an oil and fuel filter change, I put 3,143 miles on my '97 in 3 1/2 days going to Phoenix and back pulling a 32' enclosed gooseneck. Somewhere in NM after fueling, my truck did the start-die routine about six times before staying running. It was similar to when it was sucking air through the fuel preheater if parked with the front higher than the rear for more than a day. Eliminating the fuel preheater solved that issue for good over a year ago.
The difference this time was the lack of a huge cloud of black smoke when it finally did stay running. I strongly suspected either my FSS or it's relay was going belly up. It did the same thing twice more, but only when the engine was warm (fuel stops), but not when it was cold. So the truck was left running for the remainder of the trip. (Had to get back for work).
I drove it to work when I got back, did my 12-hr night shift, fired it right up in the morning at -11*, and went to buy a new relay and fuel shut off solenoid. Four blocks from the parts store, in one of the two left turn lanes at a busy intersection the truck simply shut off.
With the key left On, pulling the plunger on the FSS up didn't help, it wouldnt stay. so the HOLD On coil or the HOLD ON part of the relay was bad. The PULL ON worked. A friendly but impatient cop finally stopped and told me I needed to get it towed. I'd already called 4 towing services and, due to the extreme cold, was informed they were all too busy to get to me in less than 3 hrs.
My fingers were beyond numb but I unplugged the relay, used my Gerbers to cut a short piece of electrical wire from my snowplow solenoid wiring (I didn't have the plow on), and jumpered directly across the relay plug. LOUD CLICK as the PULL ON coil energized and slammed the fuel arm upward. Now the truck fired right up and ran. Cop was happy. But I only made it about three blocks before smoke started pouring out under the hood. That PULL ON coil is simply not designed to be held on for more than a few seconds. Way too much current draw.
But now I was able to get off the road into a parking lot. Bought some zip ties and warmed my numb fingers in the store. Still 11 degrees below zero. Finally managed to get the fuel shut off lever ziptied in the up position long enough to get the 25 miles home. There is very little room for big frozen hands to get down there!
Sure, I need to replace BOTH the FSS and the relay now, but I planned to anyway and that's still WAY cheaper than a towing bill. And now I know the very short limit of how long the PULL-ON coil can stay on to get me out of an intersection. lol.
Another response already said you should check the relay and FSS, but I thought you might enjoy hearing this very recent experience. Don't ignore the warning signs of that relay or solenoid going bad.

 

[BigPapa]

RelayS, plural. The “Hold” circuit has a relay in the relay panel under the hood. The “Pull” relay is on the firewall next to the fuel heater relay.