Failure to Crank - Neutral Start Relay Modification
After driving long distance, stopped to dump tanks and for the first time we experienced the dreaded failure to crank engine syndrome.
Pulled out our Ignition & Starter Wiring Circuit spreadsheet documentation page, and with a meter quickly figured out that the neutral start relay was not being energized from Allison ECU neutral signal wire.
This relay is near the bottom of the stack of relays on the right side of the large 12-volt breaker panel located behind padded dash cover in front of co-pilot chair.
Pulled out relay and with the pointed ends of a long nose pliers stuck into relay socket, jumpered electrical connection from ignition switch start position and aux start solenoid. (solenoid is located on our isolator panel behind streetside rear tire). Cindy was driving and started engine while I temporarily held pliers.
Today, made a permanent fix by making a jumper wire with male spade ends, simulating the prongs on the Bosch relay. Discarded the relay and inserted the jumper wire ends into the relay socket terminals:
Socket-30 wire-122 from ignition start position
Socket-87 wire-E9 to-Aux-Start-Solenoid
Our modified wiring diagram is attached. . .
A lot of the relays are the same. Maybe rob Peter to pay Paul from one not as important. Good information if needed though. I bookmarked it.
Chuck, We carry several spare new Bosch relays and swapping relays was not considered.
Foretravel uses this start circuit design in many coaches and some owners have had similar failures.
I think the problem is in the voltage flowing from bay wall 30-amp breaker wire-B69 to 10-amp breaker wire-C6 on front breaker panel to Allison ECU wire-136, back to relay wire-123 that I removed.
Failure to crank can be devastating, so with a simple solution that bypasses our problematic non-critical circuit, it makes more sense to us at this time to make this mod and not be concerned of a repeat.
Good job troubleshooting.
I had book marked this and will make a note on my information in the coach.
Thanks for the explanation
Cindy told me our initial posting on this thread did not share our panic when turning the ignition key yielded nothing and that diagnostic steps were many.
With voltmeter, first checked batteries which were ok, then finding no voltage on small Aux Start solenoid terminal when ignition was turned to start, brought me to neutral start relay. All this took time, but without being sure what was going on, was pleased that ignition cranked engine ok with relay bypassed by the long nose plyers.
Also did not mention that many years ago we had a hesitating / slow crank starting issue that took over a year with many changes that did not resolve it until finally we installed a new Delco starter.
During that year-long diagnosis experience, we inserted the leads from three tiny 12-v lights into the neutral start relay plug contacts so I could visually see if transmission, ignition & relay were operating as they should.
These lights were still in place and also aided in fixing last month's no crank problem.
Barry
Great work Barry, on my motorcycle key ring I have a paper clip to bypass the clutch switch, or the kickstand switch. Both eqaul a non crank/start condition. Bend to fit..
Had the exact same problem last year which Barry helped me to troubleshoot. Bypassed the neutral start switch and no problems since.
jor
If I read this correctly, you are saying the neutral-SAFETY no crank function is not critical and have decided to permanently bypass it. To me, the neutral-SAFETY start interlock is one of the most important safety functions on the drive-train.
There are other ways to do an emergency start, especially on the mechanical 8.3. This can even include running a jumper wire to the solenoid on the starter directly to +12VDC.
But why for the life of me would one not correct the problem to begin after finding the failed circuit?
I don't believe this is a safety issue. The Allison defaults to neutral. Turn the key, always in neutral. In my case, the Allison CPU worked fine except it sent only 11.2 volts to that relay (neutral safety switch).
jor