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CATEGORY LISTINGS > CATERPILLAR > 3126 hard to start need help! [ REFRESH ]
Thread Title:

3126 hard to start need help!


Created On Monday April 14, 2014 04:21 Diesel Talk
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GSSign
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Joined: Apr 2013

Note Monday April 14, 2014 04:21 View thread in raw text format
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Hi all,

I have a 2000 Freightliner with a 3126 cat. It has recently started getting hard to start. When it acts up, it always starts instantly for about 2 seconds then dies. After that when I crank it over it hits but does not start. After several cranks, it starts but runs real rough for 10 to 15 seconds, smokes quite a bit then smooths out and runs fine.

When it did it today, I opened the hood, and attempted to pump up the manual pump but it was very firm.


Any ideas would be greatly appreciated.

Thank you.
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Skidd88
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Note Monday April 14, 2014 18:14 View thread in raw text format
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Hello, it sounds like you have a high pressure oil issue with a injector or injectors. This means you are loosing oil pressure to one of the injectors which causes the firing of the injector. Do you have a check engine light on the dash when this happens, if so you may possibly have a electrical problem with a injector. (the injectors are 2 part, mechanical-electrical) You can remove the valve cover(13mm socket) bolts, have someone crank the engine over and looking for oil spraying from around a injector. The injectors have seals on them and can be replaced if there is no check engine light. If you are mechanically inclined you can do this and save money with a little help, hope this helps. You said the you tried to prime up the fuel system and the prime pump was hard it sound be.

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Master ASE Tech, International Dealership Certified, Cummins, Detroit, Freightliner Dealership Trained.
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GSSign
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Note Tuesday April 15, 2014 03:39 View thread in raw text format
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Thank you for your response with my problem.

I spoke to a service dealer, he told me to replace the check valve on the back of the head. Did not offer much info to me but it is hard to expect much help from a service company when you are wanting to attempt to repair it your self. Hard to make a living giving free advice.

If the check valve was letting the fuel bypass, wouldn't my plunger be soft?

I am praying the truck starts this morning with the temps in the low 30s. I will pull the cover asap to check the oil flow from the injectors to see if one is passing more than others.

The only time it does this is when it sits over night. It can sit for hours and it fires right up. But once after is sat for a couple hours and it did smoke a little and idled rough for a few seconds.

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GSSign
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Note Tuesday April 15, 2014 04:05 View thread in raw text format
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Lucky for me, it fired right up this morning.

I will post back when I can pull the valve cover.

Thanks.
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GSSign
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Joined: Apr 2013

Note Saturday June 14, 2014 08:51 View thread in raw text format
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Hello all, I still have not found my problem.

I have been using the truck every day and on some long trips.

The truck never fails to start, it just depends on how long I have to crank it over. Some mornings, is starts like nothing is wrong but most mornings it has to crank for 15 seconds or more. It only does this on the first stratup of the day. When is starts, it smokes and the smoke smells very rich with raw fuel. It runs rough for a few seconds and smothes out and runs perfect all day. There is a direct relationship to how long the truck sits between starts. If is sits for 4 hours or so, it fires right up, smokes very faint. If it sits for 8 hours or so, it still fires up quick, but it smokes for a little longer and idles a little rough for a few seconds.

The part that is weard to me is that if it sits over the weekend or just over night, it starts instantly and runs smooth every time but only for about 3 seconds before it dies. Then I have to crank on it to get it to run. While I am cranking on it, it is trying to start, it smokes while cranking.

I pulled the valve cover this morning to check for excessive oil passing thru one of the injectors but all 6 were oiling the same, cranking and while running. I also pulled the IAP sensor first thing to see if it allowed a normal start but it seemed to make it worse.

It has been sugested to replace the fuel check valve at the back of the head. When the truck dies after the first start of the day, I have tried to pump up the manual fuel pump but it is hard as a rock, to me, it would seem that if the check valve was not holding pressure, I would be able to force feul past it easily with the manual pump. I can force fuel past the check valve but it takes a lot of force. It feels the same as it has for the past 11 years that I have owned the truck.

Is this correct or should I just replace it?

Is replacing the IAP controll valve my next best option?
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Skidd88
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Joined: Feb 2014

Note Saturday June 14, 2014 15:03 View thread in raw text format
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Hey, you may have a injector that is going bad on the mechanical side of the injector and that injector is bleeding off fuel if it is stopped on the open side of the injector. Which would give you the raw fuel smell and smoke issue. Try to use a red dot heat gun to see which injector is the coldest after first start up. Or you can loosen up the exhaust manifold bolts and slide the manifold out with out unhooking anything else and see which exhaust hole is smoking. This will tell which injector is bad, with having a computer to hook up to the engine ecm. I hope this helps!


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Master ASE Tech, International Dealership Certified, Cummins, Detroit, Freightliner Dealership Trained.
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