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Old 06-28-2022, 01:34 PM   #1
Junior Member
Monaco Owners Club
Join Date: Jun 2022
Location: Wichita, KS
Posts: 12
2009 Monaco ISM500 Starting Issue

Hello, everyone. I am new to the group. I purchased my coach a couple of years ago with 13,500 miles on it from a great couple in Texas. They purchased it because they needed a tax write off in 2008 and were too afraid to drive the bus. I couldn't be happier, but am working out some bugs.

I thought I would share an issue I have been dealing with at the end of last season and during my last couple of times out this season. I was able to fix the issue last night.

Issue: I was having issues with my 2009 Monaco Dynasty with a Cummins ISM500 turning over at enough speed and for long enough to start the engine. I keep the coach plugged into 50A in my shop. I would not be able to start the coach with the house battery boost either. If I started my generator and watched the charging monitor above the passenger seat until the amp charge was down to 25 amps, the engine would turn over with enough speed to start the engine. I had 4 AGM 800 CCA chassis batteries.

Process of elimination:

1. I isolated all batteries and checked volts conducted a load test on each battery at the end of last season. All carried a "GOOD" load according to the tester.

2. I did not have a spare Big Boy. So I replaced it with a new one and rebuilt the old one for a spare. It was due to be rebuilt. No change in the Issue

3. I verified voltage at the batteries was what the charging monitor in the coach was reading. I verified the voltage at the positive terminal at the starter matched what the batteries were.

4. I cleaned all ground terminals on the starter and chassis. No change in the issue.

5. I isolated each battery again last weekend and 1 of the batteries was bad and the other 3 batteries were weak. I replaced the 4 batteries with 3 AGM 800 CCA batteries (2,400 CCA), which is more than the 1800 CCA requirement from Monaco's Owners Manual. All connections at the batteries were cleaned. No change in the issue.

6. I cleaned all terminals at the lugs on the inside of the battery compartment and the other side of the lugs on the outside of the batter compartment. I cleaned the positive terminal on the starter. Issue is fixed!!!

I wanted to post this to hopefully help someone else out who searches "must have the generator started to turn over the engine", "ISM 500 will not start without generator running", "ISM 500 will not turn over unless generator is running" . I figured it was a poor connection somewhere, causing the issue and the generator gave the batteries enough help to turn over the engine. I just did not find the correct connection to clean until last night.

I have a couple of questions for the group.

My ISM 500 must crank for 10 seconds or so (as fast as the original OEM starter will crank) before it will start. Many times I will just stop cranking at 5 seconds and then it will start on the next try. But it really seams hard to start to me. I have read that this can be fixed by having Cummins do a software update. I am sure there have been no updates since the coach was new. Do any of you have any experience in this and do you recommend this?

Also, I don't think the starter spins as fast as it should with the CCA required by Monaco/Cummins. I read (on one of these forums) that it is highly recommended going to a Denso 428000 Series starter to solve this issue. I would like to do this. But I am not sure which starter I should buy between the Denso 428000-4430 and the Denso 428000-4420. I reached out to Denso, but have gotten no response yet. Do any of you have a recommendation for the best choice for my Monaco between the two?

Thank you. I really look forward to learning from the group.

Trae Jones
2009 Monaco Dynasty
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Old 06-28-2022, 02:09 PM   #2
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Join Date: Oct 2009
Location: Tucson, AZ
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Wow, a 2009 Dynasty is a great find. That's one of the last of the large Monaco coaches.

For us the gear reduction starter was the key for easy starting on our last two coaches. It now turns over much faster and starts up much quicker even without the Boost switch.
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Old 06-29-2022, 03:53 PM   #3
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If not the starter are you sure you are getting fuel pressure to your injector pump with just the key on?

Full Time 2000 Dynasty Regent FD, 8.3, Banks Turbo, 5" Diameter Exhaust, 475 HP 1425 Torque, FASS system, towing 05 Pilot 1100 Watts solar 800ah lithium & E-Bike
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Old 07-01-2022, 09:01 AM   #4
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Thanks for the great report.

Two posts to your credit and this one is out of the park.

Chasing weak connections can be a real challenge as you have found and finding the voltage drop at the starter can be incredibly difficult.

In many cases where getting a voltmeter to a connection where things are moving and possibly dangerous I run a wire from that point so a meter can be safely monitored and use a very good analog meter versus a digital one.

Of course, the act of making that connection can fix a problem so you need to be acutely aware of (the last thing you touched).

That is if you loosened the starter connection to place a temporary wire connection for metering that could easily clean the connection and all of a sudden the problem appears to have cleared. Remembering this is (the last thing you touched) will enlighten you.

Even though you have resolved the issue it would be nice to know what the voltage is on the starter when cranking. It could still be too low. A new cable on the positive run as well as the ground might help.

You should also measure the voltage on the block of the engine while cranking. Using the starting battery negative post for the meter side versus the frame of the RV.

Twelve volts is wimpy and when vehicles were six volts the size of the wiring was huge. Talking about automotive stuff here. Converting a vehicle from six volts to twelve volts made a lot of improvements and I was able to leave the 12-volt starter in place. It spun like crazy and got me out of an intersection once stalled in. Put the jeep into second gear, clutch out, then used the starter to run me right out of the problem area.

I have seen trucks use 24 volts on their starters long ago. They had a 24/12 system. It would not apply 24 volts to any 12-volt components but would turn the starters nicely. I do not know if the starters were designed for 24 volts. Most likely were in any case.

So as I digress. Cable connections and wiring size are crucial and with the number of complaints matching yours, it would be very interesting to have some real voltage numbers. The geared-down starter replacement solves it of course.

As for the "Flash Upgrades". It would be a great idea to get that done. I suspect you have DEF or at least DPF and they had a lot of issues with the DPFs early on.

The updates they did on my 08 when the DPF plugged surprised me. I also lost a bit of mileage after that. Probably .5 mpg. Don't know why.

Recently I had my 400 ISL Uprated to 450 HP. No more torque but it accelerates much better now. It was a simple flash upgrade. You might be able to have that hp of yours uprated a bit at the same time.
Certified Senior Electronic Technician, Telecommunications Engineer, Telecommunications repair Service Center Owner, Original owner HR 2008

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Old 07-01-2022, 02:25 PM   #5
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Location: Mapleton, IL
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Turn the key to the accessory position ( one step before starting ) and wait five seconds. Now try to start it.

If it starts better that way, it is a sign of weak fuel pressure or lift pump.
Don Higgins
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Old 07-01-2022, 02:50 PM   #6
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Congratulations for your coach, you'll love it!

you seem to have a Yorkshire like mine with a 500HP ISM. So we're exact twins.

I'll let you know what I did because when I bought it, it was hard to start.

I found that our ISM
- Don't have DPF
- Don't have Glow plugs or Intake pre-heat. So it'll turn longer when starting.
- Have only EGR as they were pre-2007 EPA

I went to Cummins to have a Software upgrade and it solved the starting problem.

Also, I turn the ignition at the first click untill I hear two cycles from the engine. Then crank it. It always starts within 10 seconds.

It's really the best coach money can buy!

Have a great day!
Michel & Nicole
2009 Monaco Dynasty Yorkshire 45
(ISM 500HP, Scangauge D, Eeze tire TPMS, Working Truecenter) 20' trailer and a race car
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Old 07-02-2022, 08:50 AM   #7
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Hello. Thank you for the great information!

My coach is actually a Regal IV. We couldn't be happier. I am going to have the software update. That sounds like a no-brainer.

Take care.
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Old 07-02-2022, 08:52 AM   #8
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Thank you!
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Old 07-02-2022, 09:00 AM   #9
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Thank you, Vito.a. I am going to install one.
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Old 07-02-2022, 09:03 AM   #10
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Hello, Timaz. I don't think this is the issue, but I will look into it. Thank you!
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Old 07-02-2022, 09:06 AM   #11
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Hello, 05 American Eagle. This does not help. I am going to do the software update and see what Cummins says. I will send an update after I get it done. It might be a couple of months. We have the next 7 weekends booked.

Thank you for your help.
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Old 07-02-2022, 09:09 AM   #12
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Thank you for the great information! I plan to upgrade the starter and get a software update. I will see what that does and let everyone know.
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Old 07-04-2022, 06:13 AM   #13
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Sometimes the updated also includes latest improved software version for that motor. Owners mention getting ECM backup copy, if you ever needed a replacement ECM.
95 Monaco Crown Royale
M11 400hp, 4060 trans.
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Old 07-04-2022, 07:24 AM   #14
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An 09 with an ISM. You are one lucky guy. Must have been a motor that was found in the Monaco warehouse. A little off topic but was your unit built by Monaco or Navistar?
2008 Dynasty 42' Diamond IV
1988 Bluebird PT38
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