Country Coach Won't Start?

GUEST POST BY BRIAN KEYS, Former Systems, Training & Resources Manager at the former Country Coach, LLC.  ...Shared from several years back, written by an excellent technical writer I always enjoyed reading...Country Coach motorhome owners enjoy.

Won't Start?

Most starting problems are caused by a tripped breaker, blown fuse, or sticking solenoid, and once the fault has been identified, it can typically be corrected (if only temporarily) within a matter of minutes.

Let’s begin by taking a look at the various components of the system and how they are connected. The circuit starts, of course, at the chassis battery itself, as shown on the diagram below and from there chassis power goes directly to the starter motor and to the chassis battery disconnect switch, followed by the chassis breaker which in turn allows power to the chassis fuse panel, ignition solenoid, and start solenoid.

When the key is turned to the ignition position, the ignition switch receives power from the chassis fuse panel on wire #50 and passes it onto the ignition solenoid on wire #34E. This signals the ignition solenoid to close and pass power from the chassis breaker through to the ignition fuse panel and also to the ECM (engine computer) through an inline fuse (located at the solenoid on Allures or Intrigues and in the electrical bay on Magnas, Affinitys and Lexas) and an ‘Engine Kill’ switch located in the engine compartment. With the key in the start position, power is supplied from the ignition switch to the neutral start relay on wire #33 and, assuming the transmission is in neutral, this power is forwarded to the start solenoid on wire #33A which signals it to close. Once closed, the start solenoid will pass power from the chassis breaker to the starter solenoid on wire #33B through a breaker or fuse, depending upon the model of your coach.

Now that we know where all the components are located and how they are connected,let’s take at look at the four most common scenarios that you might experience should your coach fail to start.

1. Nothing happens when you turn the ignition switch to the ignition or start positions.

Make sure that the chassis disconnect switch is turned on and reset the chassis breaker if it has tripped. Check for loose or corroded chassis battery terminals or cable lugs and use the battery boost if your chassis batteries are severely discharged. If this does not solve your problem then check for power on the yellow wire #34E at the ignition solenoid. If wire #34 has power then check the large terminals on either side, if only one of these has power then the solenoid is sticking and must be replaced. Gently tapping on the solenoid should allow it to close but it may now stick in the closed position meaning that your engine will continue to run when the key is turned off. Tapping on the solenoid again with the key off should release it. This should only be considered as a ‘get you home’ measure.

If wire #34E does not have power at the ignition solenoid then check the fuse for wire #50 in the chassis fuse panel and make sure that the wiring at the ignition switch is intact.

2. Dash and other ignition systems power up when the key is turned to the ignition position but nothing happens when the key is turned to the start position.

With the ignition on, verify that the transmission is in neutral, and then check for a tripped starter breaker or blown starter fuse. Check for power on blue wire #33A at the start solenoid behind the rear bumper on the passenger side. If wire #33A has power, then check the large terminals on either side of the solenoid. If only one of these terminals has power, then the solenoid is sticking and must be replaced. Gently tapping on the solenoid should allow it to close but it may now stick in the closed position meaning that your engine will continue to crank when the key is turned off. Tapping on the solenoid again should release it but as before, this should only be considered as a ‘get you home’ measure.

If you hear a loud clunk when the key is turned to the start position and both sides of the start solenoid have power, then the gear on the starter motor is probably unable to ‘mesh’ with the gear on the engine flywheel. Although extremely rare, this can and does happen, with the only cure being to manually turn the engine a little using a large socket and bar on the crankshaft pulley or to momentarily spin the starter motor by bypassing the starter solenoid on the motor itself. The latter should only be done by a professional mechanic.

3. Dash and other ignition systems power up when the key is turned to the ignition position and the engine cranks but will not start.

Assuming you have not run out of diesel, then the first thing to check would be the engine kill switch on the right side of the engine compartment. If the engine kill switch has not been activated, then check the inline fuse that provides ignition power to the ECM or Electronic Control Module. This fuse is located at the ignition solenoid on Allures or Intrigues and in the electrical bay on Magnas, Affinitys and Lexas. If the ‘Check Engine’ light on your dash is illuminated or flashing, then there is most likely an engine fault that you will need to have investigated by a Cummins or Caterpillar dealer. Earlier coach models used an engine kill relay located on the right of the engine compartment next to the engine kill switch and this relay can prevent your engine from starting, especially if the engine kill switch has been used recently. The relay is available at most local parts stores and can be changed in a matter of minutes.

4. Engine starts but will not continue running when the ignition key is released.

This situation is unheard of on current models with ECM’s or Engine Computer Modules. If you have an earlier model coach, however, with a non-electronic engine, this condition could indicate that the coach’s Engine Protection Module is preventing the engine from running. This is generally caused by a critical condition such as low oil pressure, hot coolant, or low coolant level triggering that device. These coaches have been provided with a foot-actuated override switch located near the driver’s right foot. Depressing this foot switch will allow you to start and drive the coach long enough to pull safely off the road. In these cases, it is prudent to check the obvious things first, such as coolant and engine oil levels. If the problem is caused by a temporary overheat situation, you may be able to wait until the engine cools down sufficiently to re-start and then continue on your way. In the case of low coolant level (one of the most common culprits), replenishing the coolant level and cycling the ignition key off and back on should allow the coach to start and run normally. In addition to these situations, a failed fuel solenoid can cause this no-run symptom, but this is an item that will require the skills of a professional mechanic.

Hopefully, you’ll never have to encounter a disabling scenario like those discussed above, but having a bit of knowledge about your coach’s chassis electrical system may save you some grief and expense.