Is this a forum where I can post questions?
No. Despite the name, The Diesel Forum is a troubleshooting library. Each page answers one common question; there are no accounts or posts.
Can I diagnose my diesel from this site?
You can narrow things down and do the easy checks safely. Real diagnosis needs codes, tests and service information, and high-pressure fuel and hot exhaust work belongs with a qualified diesel technician.
Which engines and vehicles are covered?
The Cummins in Dodge and Ram pickups is the main focus, with hubs for Power Stroke, Duramax, GM 6.2/6.5, EcoDiesel, Titan XD, Navistar, Detroit, PACCAR, Volvo/Mack, Isuzu/Hino, Sprinter and VW TDI, plus pages for semis, RVs, school buses, tractors, marine diesels and generators.
Do you publish specs, torque values or part numbers?
No. Those vary by engine and year. Use your service information. For Cummins engine specs and identification, see cumminsboard.com, linked from the Cummins hub.
Does Dodge Off Road sell engine parts?
No. Dodge Off Road builds suspension and steering for 1994-on Ram trucks. We link to it where front-end or towing setup is part of the story.
Does a 5.9 Cummins have glow plugs?
The Cummins B-series engines in Dodge and Ram pickups use an intake air grid heater as their cold-start aid, not glow plugs. Always confirm against your own service information.
Why will my diesel not start after a fuel filter change?
Usually air in the system. Follow the priming procedure in your service information for your engine.
Is white smoke on startup normal for a diesel?
A little white smoke on a cold start that clears as the engine warms is common. Persistent white smoke, or smoke with coolant loss, needs a diagnosis.
Is some black smoke normal?
A light puff under hard acceleration can occur on some engines, but steady black smoke means too much fuel for the available air and is worth checking.
Can a turbo cause blue smoke?
Yes. Worn turbo seals are one of the common causes of oil burning on a turbo diesel.
Can I clear limp mode by disconnecting the battery?
That may clear codes for a while, but the cause stays, and you lose the stored information a technician needs. Read and record the codes first.
Can a dirty fuel filter cause a rough idle?
Yes. Restricted flow or water in the fuel can cause rough running. Filter service and draining the water separator are easy first steps.
Can I keep driving with the water-in-fuel light on?
Water can damage injection components. Drain the separator as soon as it is safe and follow your owner's manual guidance.
How do I know if there is fuel in my diesel oil?
A rising level and a diesel smell are clues. An oil analysis test from a lab measures fuel dilution and confirms it.
Is it EGT or coolant temperature that I should watch?
Both matter, but they measure different things. Coolant temperature is the cooling system; EGT is exhaust gas temperature. Follow your owner's manual guidance for each.
Can an EGR cooler make it look like a blown head gasket?
Yes. An AERA bulletin for Duramax engines warns that EGR cooler leaks can put coolant into cylinders and lead to misdiagnosis.
Why do 6.0 Power Stroke EGR coolers fail?
Specialist sources commonly link them to a clogged oil cooler that reduces coolant flow to the EGR cooler.
Is it bad to shut off a diesel during regen?
Interrupted regenerations leave soot in the filter and, on some engines, add fuel dilution. Follow your owner's manual.
Can I add anti-gel after my fuel gels?
Most cold-flow improvers must be added before the fuel reaches its cloud point. Some products are made to help re-liquefy gelled fuel; follow the label and your engine maker's guidance.
What fuel pressure should a 24-valve Cummins have?
Use the figure in your service information for your engine and model year. We do not publish a single number here because sources quote different figures for different setups.
Does a diesel engine cause death wobble?
No. Death wobble is a front-end oscillation from steering and suspension wear or looseness. The heavy diesel engine adds front weight, but the fix is in the front end.
Does DEF go bad?
Yes. Industry guidance says heat shortens DEF shelf life and contamination ruins it. Buy sealed product and store it cool and clean.
Can a bad NOx sensor put a diesel in limp mode?
It can. On SCR-equipped engines, NOx sensor faults are among the faults that can lead to a staged derate.
Why do diesel EGR valves clog?
Exhaust soot and oil vapor build up as carbon, especially with idling and short trips that keep exhaust temperatures low.
Is a turbo whistle normal on a diesel?
Some turbo noise is normal. A sudden change, a hiss, or noise with lost power is worth checking for a boost leak.
Can bad fuel make a diesel knock?
Yes. Low cetane fuel increases ignition delay, which can cause harsher combustion noise.
How do you prevent wet stacking?
Run the generator with adequate load per the manufacturer, avoid long unloaded runs, and use a load bank for testing if needed.
Do Cummins pickups have glow plugs?
The Cummins B-series in Dodge and Ram pickups uses an intake grid heater instead of glow plugs. The GM 6.2/6.5 and many other diesels use glow plugs.
Does tow/haul mode prevent transmission overheating?
It changes shift points and helps hold gears, but heavy loads, heat and grades can still overheat a transmission. Watch the gauge and downshift.
Does the 6.7 Cummins have a real exhaust brake?
The factory exhaust brake on 6.7 Cummins pickups works through the variable-geometry turbocharger rather than a separate valve.
How often should I change diesel fuel filters?
Follow your owner's manual. Severe service, dusty conditions and poor fuel call for more frequent changes.
Why does my diesel stall after a fuel filter change?
Usually air in the system. Prime per your service information; if it continues, look for a suction-side leak.
Is oil consumption alone proof of worn rings?
No. Leaks, turbo seals and crankcase ventilation can all consume oil; measured testing tells you which.
Is the oil cap test a good blow-by check?
It is a rough sign at best. Shops measure crankcase pressure at set conditions for a real answer.
Do diesel pickups get liner pitting?
Cavitation pitting is mainly a concern for wet-liner engines, more common in heavy-duty and equipment engines. Check what your engine uses and follow its coolant spec.
Do diesels need special oil?
Use the oil grade and specification in your owner's manual. Many engines with DPFs require low-ash diesel oil.
When should I add anti-gel?
Before the fuel gets cold. Most cold-flow improvers do not reverse wax that has already formed.
Should I buy a diesel with the DPF deleted?
Be very cautious. EPA treats removing emissions controls on road vehicles as a Clean Air Act violation, and the truck may fail inspection or registration.
Is a DPF delete illegal?
For road vehicles, EPA treats removing or defeating emissions controls as tampering under the Clean Air Act.
Are head studs a fix for the 6.0?
Many specialist shops replace the factory head bolts with studs during a head gasket job, along with addressing the oil and EGR coolers.
Does the 6.4 Power Stroke have a DPF?
Yes. It was the first Power Stroke to use a diesel particulate filter with active regeneration.
Which trucks use the CP4 pump?
Sources list the LML Duramax, the 6.7 Power Stroke and the 3.0 EcoDiesel among pickup diesels with the Bosch CP4 family pump.
Can I stop a tractor regeneration?
Manuals allow inhibiting regeneration only for specific situations, and repeated inhibiting can lead to dealer service. Follow your operator manual.
How often should I change a marine diesel impeller?
Follow the engine maker's schedule. Many operators replace it on a regular schedule rather than waiting for failure.
How do I clean a diesel pusher radiator?
Owner guidance favors a regular garden hose and mild detergent from the correct side, never high-pressure washing that bends fins.
Does EPA recommend turning off school buses?
Yes. EPA idle-reduction guidance recommends turning off engines as soon as possible and not restarting until ready to depart.
How do I know if my Sprinter is covered?
Check your VIN on the Mercedes-Benz Vans BlueTEC update site.
Did Navistar switch to SCR?
Yes. Trade press reports Navistar abandoned its EGR-only approach in 2012 and adopted SCR.
Last reviewed 2026-10-19. General information only: confirm with your service information and a qualified diesel technician.