Diesel engines require fuel, air, and enough voltage to crank the engine to cause ignition. Gas engines operate with fuel, air, and spark. When nothing happens after turning the ignition key, or the engine starts but fails to idle, one of these main engine components is usually lacking.
Start by analyzing the situation. Review exactly what occurs when the key is turned. If nothing happens, this may indicate a low state of charge in the battery. Recharge the battery using a remote charger. Certain model RV’s are equipped with a battery boost feature designed to pull charge from the house batteries that will aid a weak chassis battery in starting the RV. You will find the battery boost switch located on the dash, or the driver’s side panel. This is a momentary switch requiring the operator to hold down the switch while turning the ignition key to the crank position. Never engage the battery boost switch for longer than two minutes. After two minutes release the switch and allow the battery to boost solenoid to cool for four minutes before any further attempts. If the engine starts once the adequate charge is supplied, have the chassis battery and alternator checked by a qualified technician.
If the engine cranks slowly or fails to crank at all, carefully inspect the starter system. An easy way to test the system is by turning on the headlights and having someone outside watch what they do as you turn the ignition key. If the headlights go out this could indicate a problem with a low battery or poor cable connections. Carefully clean and examine the connections from the engine to the chassis battery. When the headlights stay on while the ignition key is turned, the problem may lie with a bad ignition relay, loose wiring or a poor connection in the fuse box. Poor starter connections or ground cable connections may also be the reason for a no crank.
Certain diesel model motor homes are equipped with a rear start switch. If the engine fails to start from the cockpit, try cranking the engine using the rear start switch located in the engine compartment.
Chassis battery problems creating a no-start situation may not be visibly noticeable at a glance. Gaps between cable ends and the terminal or a loose connection can affect engine-starting performance. Regularly tighten cable connections and occasionally remove the battery cables to clear away corrosion.
Diesel engines may feature a ‘Wait to Start’ icon on the dash panel. This indicator will illuminate as the combustion chamber is heating. Be patient and wait for the light to go off before cranking the engine.