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 Freightliner with Cat c7 Hard Starting
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Mark23290
Senior Member

United States
96 Posts

Posted - 01/09/2019 :  3:23:49 PM  Show Profile  Reply with Quote
Have a 05 Freightliner Cat c7 Engine. Starting hard even when it’s plugged in all of a sudden. Don’t have diagnostics/software. Runs fine once it’s started. Tomorrow going to change the fuel filter and water separator filter as a starting point. Intake heater seems to be cycling as normal. Power at the block heater as well. Has had fuel additive and premium winterized diesel. Want to pick the real mechanics brains.

Mechan1c
Top Member

USA
853 Posts

Posted - 01/09/2019 :  5:13:13 PM  Show Profile  Reply with Quote
Would "cranks normally/won't start" describe what's happening? Like an extended crank but at normal RPM? Brought on by colder weather? If that's the case try letting the Cat system go through its sequence without interuption. Wait to start light goes out, (may need to sequence the intake heater twice before cranking) and then let the bus run without messing with the throttle and let the ECM make its injector and fuel adjustments. You'll hear the engine making changes on its own. I've found that doing this helps after a few days. My old Cat PSSR guy swore by this because every winter he would get a rash of calls about 3126/C7's not wanting to start. He would go out and do a quick driver training class for winter starting and operations for his school districts. I run 17 I6 Cats daily 2000-2004 M/Y.

Check valve at the back of the head for fuel return could be faulty. Usually it will not run smooth with air in the system though...

If it's more of a "cranks slow, barely starts," I'd be looking for marginal batteries, bad connections, corrosion, big voltage drops where there should be none.

There's also a pair of engine speed sensors tucked in behind the air compressor, and one of the 2 could be bad. It'll fire on one, but when the second one goes out, it turns into a complete cranks won't ever start situation. P/N 245-4630; Sold as a pair.

Did this just start with the cold weather? Does it only happen on the first cold start of the day? Sounds like you have your fuel squared away...how's the engine spining over?

That's what comes to mind.




Edited by - Mechan1c on 01/09/2019 5:51:47 PM
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Bluenozer
Top Member

Canada
640 Posts

Posted - 01/10/2019 :  09:39:34 AM  Show Profile  Reply with Quote
just because the "intake heater" light is on does not mean your grid heater is actually operating, whats the resistance of the block heater itself just because it has power to it does not mean its working either
If other units are fueling at the same depot with no issues and regular maintenance is performed then changing filters is a waste
since you threw in "all of a sudden" probably one of those components has STB
any sensors should illuminate the CEL on the dash also

OEM trained in wiring and all engine platforms for over 20 years
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Mark23290
Senior Member

United States
96 Posts

Posted - 01/16/2019 :  08:46:18 AM  Show Profile  Reply with Quote
So far replaced the fuel filter and fuel separator filter. Still giving a hard start. Good pressure from the fuel pump. They found some slimy gunk in the seperator. Replaced filters again and going to blow the lines out and see today. Also in the mean time replaced the batteries checked the intake heaters.
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Mark23290
Senior Member

United States
96 Posts

Posted - 01/16/2019 :  12:35:49 PM  Show Profile  Reply with Quote
So far replaced the fuel filter and fuel separator filter. Still giving a hard start. Good pressure from the fuel pump. They found some slimy gunk in the seperator. Replaced filters again and going to blow the lines out and see today. Also in the mean time replaced the batteries checked the intake heaters.
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wwinters
Senior Member

USA
114 Posts

Posted - 01/16/2019 :  2:24:59 PM  Show Profile  Reply with Quote
If it is a slime type gunk, it could be algae, we had that several years back lots of additive and filters to clean it up, but I would think it would affect other units as well unless they fueled on the road somewhere

Edited by - wwinters on 01/16/2019 2:26:24 PM
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Poolguy7250
Active Member

USA
11 Posts

Posted - 01/16/2019 :  7:06:15 PM  Show Profile  Reply with Quote
At one time I operated 30 Chevys with Cats. The intake heater solenoid failed all the time. They get hot and melt the terminals. They still would sound like it was working but no current would get threw them. I started replacing them with 100 amp Blue Bird body solenoids.
Also does this Cat have a hand primer pump.
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Mark23290
Senior Member

United States
96 Posts

Posted - 01/18/2019 :  07:32:16 AM  Show Profile  Reply with Quote
The intake heater light comes on as normal when it’s not plugged in. They said it seemed fine. As for the hand pump yes it does have one. The bs I only have 3 and I don’t think I got bad fuel. I fill at a Meijer.
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Bluenozer
Top Member

Canada
640 Posts

Posted - 01/18/2019 :  10:23:40 AM  Show Profile  Reply with Quote
it should come on everytime inside, outside , plugged in shouldn't matter it comes on and temperature dictates the length of the cycle
It measure intake air temp. not coolant temp.
Cycle the key and use a heat gun to measure rise in temp. to make sure it works

OEM trained in wiring and all engine platforms for over 20 years
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66glide
New Member

6 Posts

Posted - 02/02/2019 :  7:28:00 PM  Show Profile  Visit 66glide's Homepage  Reply with Quote
Voltage drop test across the grid heater relay when it is operating. If you see more than .2V, it will hard start cold. A new one will be less than .1V drop.
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