Engine Shutoff Solution
Q: In the “Engine Shuts Off” inquiry that appeared in the October 2004 issue of FMC magazine (page 30), Carl Kummer, F272373, indicated he was having fuel valve shutoff problems on an 8.3-liter, 300-horsepower Cummins engine. I had the same problem on my coach and found the following.
The fuel shutoff valve has two coils: one that activates with the starter circuit to pull the valve in, and a second “holding coil” to keep the fuel shutoff valve energized while the ignition is activated. If the circuit that holds the fuel shutoff valve is interrupted for even a very short time, the valve will drop out and the engine will stop. But it will work once again when the engine is restarted. I found a faulty solenoid that would drop out momentarily when I was driving, allowing the fuel shutoff valve to close. So I added a wire from the fuel shutoff valve holding coil all the way to the front of the motorhome to bypass all connectors and solenoids. This solved the problem. Later, the faulty solenoid failed completely and was replaced. However, I did not rewire the coach to use the original circuit.
Carl has two choices. One is to replace the solenoids in the fuel shutoff valve holding coil circuit; the other is to run an extra wire to bypass all of the connectors and solenoids in the RV. I think that the second choice is preferred, as it wires around possible problems.
Bill Zebrow, F140955
Corona, California
A: Thanks for your possible solution to Mr. Kummer’s problem. To make sure your suggestion didn’t lead to further problems or interfere with proper engine operation, we asked a representative of Cummins’ Service Engineering group to take a look at it. Here is his response.
“I’m not sure exactly what this is describing. It appears as if Mr. Zebrow is bypassing the OEM (original equipment manufacturer’s) hold-in coil wiring, but I’m not sure if that terminates at the key switch or at another relay or something else. A large percentage of shutoff solenoid failures are due to low battery voltage and poor/degraded wiring. The pull-in coil has experienced the highest rate of failure due to the large current draw. The hold-in coil requires much less.
“The hold-in coil must be wired to deactivate when the key switch is in the off position. If the bypassed wiring is done correctly, it should be okay, but my first choice would be to correct the OEM wiring.
“Cummins’ recommendations for externally switched dual coil solenoids are as follows:
- Isolate the fuel shutoff solenoid from the starter motor circuit through the use of a separate dedicated relay. The relay must be properly rated to carry the current required, 65 amps of continuous current, for the fuel shutoff solenoid pull coil under all starting conditions.
- Do not connect the fuel shutoff solenoid pull coil to the “S” terminal on the starter solenoid or to the starter relay that is connected to the “S” terminal.
- To minimize voltage loss and resulting solenoid force degradation, select the proper wire gauge based upon the total wire length from the battery to the solenoid and back to the battery.
- To protect solenoids from permanent damage, include an overload protection device such as a fuse or circuit breaker in the system.
“Externally switched dual coil solenoids must have a limited on-time for the pull coil. Maximum energizing of the pull coil must not exceed three 30-second cranking attempts with two minutes of rest between each attempt. After the third 30-second crank attempt, the solenoid must be allowed to cool to ambient temperature before more cranking attempts.”
A Long, Long Tow
Q: I have a 32-foot motorhome and tow a Jeep Wrangler. Do you know of a Web site that lists the states that will allow me to tow a small boat behind the Jeep? The total package will be the motorhome, the Jeep, and a boat.
Charles Yole, F342555
Traverse City, Michigan
A: The “Motorhome Regulations” chart that appears beginning on page 114 in the January 2005 issue of Family Motor Coaching magazine provides the combined towing length limitation for each state and province, but it does not address the issue of double (or triple) towing. We don’t know of any Web site that lists this data, but AAA’s Digest of Motor Laws does provide such information. Call your local AAA office to see whether this book is available. If not, it can be purchased from AAA Government Relations, 607 14th St. N.W., Suite 200, Washington, DC 20005; (202) 942-2050.
Of course, before towing you will need to determine whether the combined weight of the motorhome, towed vehicle, and boat exceeds the motorhome’s gross combination weight rating (GCWR). If you don’t use a supplemental braking system already, we would suggest that you seriously consider using one should you decide to tandem or triple tow.