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Cat 3126 Air Intake Heater
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KCinKC
Reg. Apr 2010
Posted 2010-05-03 4:20 PM (#4966)
Subject: Cat 3126 Air Intake Heater





Posts: 15

I have a 2000 Freightliner FL70 with a Cat 3126 engine. This weekend we had a couple of colder mornings and the truck was very hard to start. The intake heater indicator on the dash came on when the ignition was switched on but then went out after about 3 seconds. Typically it would stay on for 30+ seconds or so before going off. Needless to say it blew a bunch of smoke when it started and idled very rough for a good bit. Once it was warmed up it would start up no problem.

I'm suspecting the air intake heater relay to be bad since the heater grid did not sufficeintly warm the air prior to startup. But I don't know where to look for it. Can anyone tell me where to look or better yet, where to find a shop manual for this truck/engine? Thanks in advance for your help.

KC
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hogtownboss
Reg. Jan 2009
Posted 2010-05-04 10:07 AM (#4967 - in reply to #4966)
Subject: RE: Cat 3126 Air Intake Heater





Posts: 176

I will check my today and let you know. My 1998 Chevy 6500 does the samething and I have been wanting to check it instead of plugging it in.

Now tis gives me a reason too.


Let you know this afternoon.
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hogtownboss
Reg. Jan 2009
Posted 2010-05-04 2:04 PM (#4968 - in reply to #4966)
Subject: RE: Cat 3126 Air Intake Heater





Posts: 176

Here is a couple of items I found about the CAT engines I did not even know about.

The 3126B has a air inlet heater . Most likely if you have a problem with it starting it is either sucking air , the engine speed sensors arent reading correctly , or the oil in the engine is in bad shape . The IAPCV (Injection Actuation Pressure Control Valve ) will "stick" if it gets any traces of material in it . The engine's oil will be too thick and cause the relief/oil filter bypass valve to pop open when the engine is started . If the oil is trashy it will be sent through the system and find it's way to the HEUI pump which contains the IAPCV valve . If the condition persists the IAPCV will be permanently damaged and you will expect a surge , rattling noise , engine miss , stalling , and check engine light .
Then you will get the IAPCV replaced (if under warranty free) for like $190 for the valve plus trouble shoot time and R&I time . Oil changes on this engine need to be regualr . Take into account the time the engine idles towards the total time the oil has on it . Id change the oil around the 6 to 7000 mile mark .... sooner if it's in a dirty environment . If you stop by your local Caterpillar dealer they have a worksheet that they can give you a almost exact time/ mile reading where the oil for the engine should be changed to prevent failures of the HEUI system .
The HEUI system is a very good system but gets a bad rap by people who run the oil for 15,000 miles and experience problems .

http://www.newyorkbussales.com/pdfs/Cat%20Cold%20Weather%20Start%20...
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KCinKC
Reg. Apr 2010
Posted 2010-05-04 9:02 PM (#4969 - in reply to #4966)
Subject: RE: Cat 3126 Air Intake Heater





Posts: 15

Thanks for the info, I didn't know that either. It only had 875 miles since the last oil change when it started doing this. If something was stuck wouldn't I have this problem every time I start it instead of just when it's cold first thing in the morning ? Shouldn't the intake heater indicator stay on longer than 2-3 seconds on cold mornings ? If I could find the relay I'd like to test it to see if it is faulty.
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hogtownboss
Reg. Jan 2009
Posted 2010-05-05 9:29 PM (#4970 - in reply to #4969)
Subject: RE: Cat 3126 Air Intake Heater





Posts: 176

I would think it would stay on longer. My has a 150-k miles and even on a warm morning it will stay on about 15 sec..... I have mine getting serviced now, and they are going to check out the intake switch for me. I will let you know if and where they find it at.
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KCinKC
Reg. Apr 2010
Posted 2010-05-05 9:44 PM (#4971 - in reply to #4966)
Subject: RE: Cat 3126 Air Intake Heater





Posts: 15

That's what I think too. It use to stay on longer and with one morning being 38 degree it should have stayed on longer than 3 seconds. Thanks for your help.
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