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Old 06-29-2020, 09:06 AM   #1
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ISM Hard Start

My ISM 500 requires a 2nd or 3rd try to start. Hot or cold it's the same. Once started, it runs and performs normally. Several years ago I replaced the OEM started with a Delco geared starter so the engine turns over fast and easy. I've tried turning on the key and waiting 15-30 seconds before cranking but that doesn't seem to help. Each cranking cycle is about 5-7 seconds and sometimes longer, but longer doesn't seem to help. Only multiple tries seems to work. Any service or technique suggestions?
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Old 06-29-2020, 09:50 AM   #2
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Are you talking ambient temps that are warm enough to not require the grid heater?

Even if it seems to be spinning fast i would clean all the battery connections and check the cables
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Old 06-29-2020, 10:04 AM   #3
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Yep, room temperature or hotter. The engine cranks at great speed. Absolutely no problem with the cranking since I installed the geared starter motor. (The OEM motor was slow and failed completely.) Starter batteries and connections are pristine.
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Old 06-29-2020, 11:00 PM   #4
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Almost sounds like a fuel delivery problem that takes several turns of the engine to get the fuel from the filters into injectors(?). Filters in good shape?

You could intercept the line out of the second filter, and test to see what kind of fuel pressure is being delivered when you first turn the engine over.

Will follow the thread, as I'd like to no the outcome.

Best of luck to you, hope it's a easy solution,
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Old 06-30-2020, 05:28 AM   #5
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Final filter change?

Injectors next?
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Old 06-30-2020, 05:47 AM   #6
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Check the fuel line fittings for cracks where the hose presses onto the fitting. Look closely at the fuel hose that comes off the back of the ECM cooler then goes to the fuel filter. This could be letting air get into the system.

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Old 06-30-2020, 09:08 AM   #7
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Thanks all! I have but one filter and it's fresh with no change. It certainly does seem like a fuel delivery issue. I'll go over the supply hoses, both suction and pressure and look for leaks.

I don't know if it tells anyone anything but seemingly, I can crank the engine as long as I want on the 1st try and it's not going to start. So my startup game is to just crank for a few seconds on the 1st try, a little longer on the 2nd. And on the 3rd (if necessary) I crank until it starts. This routine works but is certainly annoying and I'm sure it's not right.
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Old 06-30-2020, 06:54 PM   #8
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If you don't find a bad hose then, with this latest info you need to check the oil pressure sending unit for the ECM (not the one for the dash gauge). If it is faulty/slow reading this could cause the ECM to not open the fuel valve. The ECM has to see oil pressure prior to opening the fuel valve.

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Old 06-30-2020, 08:30 PM   #9
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Thank you for that insight 4T. I suppose it's also possible that my ISM is slow to build oil pressure. I'll give it a look.
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Old 06-30-2020, 08:56 PM   #10
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I can guarantee that you could entirely remove the oil pump and it would have zero effect on the way it will start. The oil pressure sensor has zero effect on opening the fuel valve. What is your engine serial number?
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Old 06-30-2020, 10:01 PM   #11
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Sounds like the lift pump is not operating. It only runs for about 1 minute to prime the filters and provide initial fuel pressure to the injector pump then no longer operates. Have some one turn on the ignition key while you are by the engine listening for the pump's small 12V electric motor to run. This lift pump is behind and lower than the injector pump and may be seen from underneath.
Look in this thread for a reply BY IMNPRSD and read his replies, he is an expert on the Cummins fuel system.
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Old 07-01-2020, 10:06 PM   #12
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Quote:
Originally Posted by randomledder View Post
I can guarantee that you could entirely remove the oil pump and it would have zero effect on the way it will start. The oil pressure sensor has zero effect on opening the fuel valve. What is your engine serial number?
My Silverleaf shows something like
"6M3U07D110000000035222347"


It's my understanding that I don't have a lift pump in an ISM. Am I wrong?
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Old 07-01-2020, 10:30 PM   #13
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Quote:
Originally Posted by BonS View Post
My Silverleaf shows something like
"6M3U07D110000000035222347"


It's my understanding that I don't have a lift pump in an ISM. Am I wrong?
I'm wrong, I was thinking ISL.
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