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Author Topic: Larger engines take long(er) to start  (Read 568 times)

Chi-Travels

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Larger engines take long(er) to start
« on: December 24, 2017, 07:24:15 AM »
Our previous 1998 coach had a Cummins 325 and it started up immediately once the key was turned.  Our new (to us) 2002 coach has a Cummins ISM 500 and, although it seems to start well, it takes 4 to 5 seconds before it kicks over; the engine has to turn over a few times before starting.  The previous coach (i.e., smaller engine) fired up within a second.  Is it normal for the ISM 500 (i.e., larger engine) to take longer to start?
2002 43' Newmar MADP w/tag-axle
500 ISM Cummins
2006 CRV Tow Car

Gary RV_Wizard

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Re: Larger engines take long(er) to start
« Reply #1 on: December 24, 2017, 08:21:33 AM »
I don't think the size per se has anything to do with it, but maybe the newer engine and/or the fact that it is a different engine model has resulted in a change.  You didn't mention the engine model for the 325, but I'm guessing it was the C engine. In a 1998, it could be the mechanical C rather than the electronic ISC, and that would perhaps make a difference.  And I think the ISM uses a air intake heater rather than glow plugs. Are you waiting for "Wait to start" light to go out?

The 2004 ISL I had started in anywhere from instantly to as much as 3 seconds.  That's cranking time, not "wait" time. I never thought the time variation was significant
« Last Edit: December 25, 2017, 08:13:17 AM by Gary RV_Wizard »
Gary
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Kevin Means

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Re: Larger engines take long(er) to start
« Reply #2 on: December 24, 2017, 11:43:17 AM »
Our 8.9 Cummins (450 horse) starts within two turns evertime. As long as yours is consistent in the way it starts, I wouldn't be concerned.

Kev
2011 Winnebago Tour 42QD
Towing a Jeep Rubicon Unlimited LJ
RVI Brake 2, Minder TM-66 TPMS, 960 watts of solar
(Can't wait to spend more time RVing)
Lakeside, California

Utclmjmpr

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Re: Larger engines take long(er) to start
« Reply #3 on: December 24, 2017, 07:12:36 PM »
 Gary may have hit it,,,The ISM being a larger engine will have a larger "grid heater", and take longer to preheat before starting.. This is especially relevant during cooler weather which will extend grid heat time.>>>Dan  (Don't try to crowd it,, when it's ready it will start)
« Last Edit: December 24, 2017, 07:14:27 PM by Utclmjmpr »
38' American Tradition 38TT/330 turbo Cummins
Jeep liberty 4 down
72 VW Baja 4 down
Cedar City, Utah
USAF vet. 59-63
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John From Detroit

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Re: Larger engines take long(er) to start
« Reply #4 on: December 25, 2017, 08:13:48 AM »
Though Gary has a point, cold weather starting is different from warm weather starting epically with Diesels as you have to wait for the heaters to heat.

But once warmed a Diseal should start within 2 revolutions. (often 1)  Gas engines likewise may take a few revolutions for fuel to make it all the way to the cylinders but with mdern injected they too should start quickly

Fuel pumps. used to be engine mounted, now tank moujnted, may take a second or two to get fuel to the engine.

When I was a small engine (Chainsaw) Mechanic we had a rule  Cold engine 3 pulls, if it was not running it needed work
Warm engine one pull

I once started a small engine (B&S horozontial) that we used on a power ladder,, one GENTEL pull. the kid acrss the street had been trying to get his lawn mower to start for like 30 minutes. . HE WAS PISSED.. I only used 2 fingers to pull that roap.
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Utclmjmpr

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Re: Larger engines take long(er) to start
« Reply #5 on: December 26, 2017, 07:55:07 AM »
 Diesel engines use heat as an ignition source,(not spark plugs) A diesel also has large compression ratio's to create that heat. When starting,, the heat created when cranking is absorbed by the piston and cylinder walls,( When air is compressed it gets HOT) and this takes TIME to do.. When the heat is sufficient  ignition will occur,, the colder the ambient air the longer the process will take.>>>Dan
« Last Edit: December 26, 2017, 07:59:49 AM by Utclmjmpr »
38' American Tradition 38TT/330 turbo Cummins
Jeep liberty 4 down
72 VW Baja 4 down
Cedar City, Utah
USAF vet. 59-63
The difference between intelligence & stupidity is: intelligence has it's limits
      Albert Einstein.

Neal

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Re: Larger engines take long(er) to start
« Reply #6 on: December 26, 2017, 07:51:47 PM »
On one of my tractors, when cold, we cycle the ignition switch, 2 and sometimes 3 times, until the WAIT lite goes off. This makes a big difference on start time in cold weather.
Neal,        2008 Winnebago Journey 39Z, Freightliner XC-S chassis,
Cummins ISB 6.7L 350 HP, Allison 3000,  2014 Honda CRV Toad.

Utclmjmpr

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Re: Larger engines take long(er) to start
« Reply #7 on: December 26, 2017, 07:55:02 PM »
In the old day's, there was no "wait" you just turned it over a few licks,,,wait for two minutes then again until it started,,,,hoping the batteries would hold out until it did.>>>Dan
38' American Tradition 38TT/330 turbo Cummins
Jeep liberty 4 down
72 VW Baja 4 down
Cedar City, Utah
USAF vet. 59-63
The difference between intelligence & stupidity is: intelligence has it's limits
      Albert Einstein.