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Topic: Failure to Crank - Neutral Start Relay Modification  (Read 480 times) previous topic - next topic

Failure to Crank - Neutral Start Relay Modification

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. . .

Re: Failure to Crank - Neutral Start Relay Modification

Reply #1 –
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.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Failure to Crank - Neutral Start Relay Modification

Reply #2 –
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.

Re: Failure to Crank - Neutral Start Relay Modification

Reply #3 –
Good job troubleshooting.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Failure to Crank - Neutral Start Relay Modification

Reply #4 –
I had book marked this and will make a note on my information in the coach.

Thanks for the explanation
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Failure to Crank - Neutral Start Relay Modification

Reply #5 –
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.

Re: Failure to Crank - Neutral Start Relay Modification

Reply #6 –
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

Re: Failure to Crank - Neutral Start Relay Modification

Reply #7 –
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..
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Failure to Crank - Neutral Start Relay Modification

Reply #8 –
Had the exact same problem last year which Barry helped me to troubleshoot. Bypassed the neutral start switch and no problems since.
jor

Re: Failure to Crank - Neutral Start Relay Modification

Reply #9 –
Quote from: Barry & Cindy –
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.

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?
1998 U270 34'

Re: Failure to Crank - Neutral Start Relay Modification

Reply #10 –
Quote
If I read this correctly, you are saying the neutral-SAFETY no crank function is not critical and have decided to permanently bypass it.

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