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Steve n Jan · 11-12-2016, 02:42 PM

I'm a CAT guy posting here on behalf of my friend who has a 1999 Country Coach with an ISC 350 HP Cummins in it. We've changed the fuel filters, filling each new one with clean diesel. When the engine starts, it runs for about 2 minutes and shuts off. We've pulled the filters back off and found them nearly empty of fuel. We refill them, re-install and the same thing happens. Are we missing something or doing something wrong?

Mr_D · 11-12-2016, 02:50 PM

The ISC has an automatic pump to fill the fuel filter on the engine. The one at the engine should not be prefilled according to the ISC manual. You turn the key on and leave it on for 30 seconds, turn key off and do it again like 5 times. That should fill the filter or it did on my ISC.
However, by now you may have pulled air into the injectors and be in trouble. At that point it's beyond me.

dennis45 · 11-12-2016, 02:57 PM

Like Mr. D says, the secondary filter should be filled by turning the key on and letting the lift pump run until it stops (you can hear it running).
Turn the key off and back on to start the pump again. Do this about six times and you should be good to go?

Steve n Jan · 11-12-2016, 04:32 PM

Thanks for the replies, we tried this, after doing this about 7 times, the engine started and ran about 2 minutes and died. I'm guessing from him filling the secondary filter by hand that we have excess air in the system. Can we purge the air by opening the drain valve on the bottom of the secondary filter and turning the ignition on and off to pump the air out and keep doing this until we get just fuel coming through?

dennis45 · 11-12-2016, 04:38 PM

Quote:

Originally Posted by Steve n Jan

Thanks for the replies, we tried this, after doing this about 7 times, the engine started and ran about 2 minutes and died. I'm guessing from him filling the secondary filter by hand that we have excess air in the system. Can we purge the air by opening the drain valve on the bottom of the secondary filter and turning the ignition on and off to pump the air out and keep doing this until we get just fuel coming through?

You could try just cracking the fitting on the outlet side of the secondary filter with the pump running to see if there is any air. Once the air is purged at this point, close the fitting and run the pump again a couple times. Then start the engine. If it stops, go back and run the pump some more and restart. Do this until all the air works it's way through the system.

mackwrench · 11-12-2016, 05:48 PM

Are filters being changed for routine maintenance or was there an issue before? Can you hear lift pump running?

Fill them again,
When it starts, hold throttle wide open for a minute...or so.

Opening the drain fitting at the secondary filter will not purge any air... these engines don't really have a means of "bleeding" fuel system.

dennis45 · 11-12-2016, 05:56 PM

Quote:

Originally Posted by mackwrench

Are filters being changed for routine maintenance or was there an issue before? Can you hear lift pump running?

Fill them again,
When it starts, hold throttle wide open for a minute...or so.

Opening the drain fitting at the secondary filter will not purge any air... these engines don't really have a means of "bleeding" fuel system.

Oopps, my bad. The pump is on the wrong side of the filter.

twinboat · 11-12-2016, 06:02 PM

If you fill the filters and they are draining, air is getting in, in the lines before them. The pump is pulling the fuel out and more fuel should come in.

The system MUST be air tight from the tank to the primer pump, including any filters along the way. It's that simple.

Suck on a straw with a hole in it. It don't work.

If this is a problem that occured after changing filters, look real hard at the filter and lines, just worked on, BEFORE the lift pump.

If this is an attemp to fix a problem, check all the way to the tank for a point where air can leak in. Fuel will not leak out, until after the pump.

mackwrench · 11-12-2016, 06:33 PM

Dump question to ask, but it ain't out of fuel is it?

Steve n Jan · 11-12-2016, 06:53 PM

Filters are being changed as routine maintenance, no previous problems. Fuel tank is nearly full. Will try again tomorrow and give it some throttle once it starts.

ltcolmac17 · 01-16-2017, 07:47 PM

Can you update what was found, or any final remedy? I had the same thing happen today with lube, oil, and filter service at Speedco. Had to be towed to Cummins for diagnosis and hopefully a remedy tomorrow. Mine is a '98 ISC 325.

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funjnt · 01-18-2017, 06:35 AM

Can you hear the lift pump running? Ours only take two or three key on off cycles to full the empty filters and she it good to fire. You should have vacuum sucking fuel into the first filter and pressure at the second filter thus squirting fuel out. Check the first filter or primary and see if the O ring wasn't removed with the first filter. There is a rubber O ring that goes around the threaded stud and sometimes sticks to the housing. It isn't easy to notice as the filter housing is below eye level. If you put the new O ring on the new filter you will have an air gap thus not properly sealing the filter to housing.

RKins · 01-18-2017, 02:15 PM

Quote:

Originally Posted by funjnt

Can you hear the lift pump running? Ours only take two or three key on off cycles to full the empty filters and she it good to fire. You should have vacuum sucking fuel into the first filter and pressure at the second filter thus squirting fuel out. Check the first filter or primary and see if the O ring wasn't removed with the first filter. There is a rubber O ring that goes around the threaded stud and sometimes sticks to the housing. It isn't easy to notice as the filter housing is below eye level. If you put the new O ring on the new filter you will have an air gap thus not properly sealing the filter to housing.

Are you saying that you don't need to fill the fuel filters prior to doing the key cycles? (Newbee here)

ltcolmac17 · 01-18-2017, 02:30 PM

Quote:

Originally Posted by ltcolmac17

Can you update what was found, or any final remedy? I had the same thing happen today with lube, oil, and filter service at Speedco. Had to be towed to Cummins for diagnosis and hopefully a remedy tomorrow. Mine is a '98 ISC 325.

Just got off the phone with Cummins Atlantic service rep. They said because this '98 8.3 ISC is purely mechanical, a hand-prime of the fuel delivery is required after filter change, and that filling the filter is sometimes not sufficient. Their tech hand-primed a push pump valve on the engine and said it's running fine. I don't know exactly how that's done, but I will ask them to show me how to do that when I pick it up.