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Cat Man
Cat Man, Caterpillar Engine Expert
Category: Heavy Equipment
Satisfied Customers: 5901
Experience:  23 Years Caterpillar Engine experience.
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WE have a 2002 Freightliner FL80 Cat 3126E. We just inframed

Customer Question

WE have a 2002 Freightliner FL80 Cat 3126E. We just inframed it. It is pulling a code 72. The injectors have been rebuilt with new O rings. No oil spill over from injector o rings. Have checked resistance from ECM harness to injectors, consistent ohms. Truck had over 500,000.00 miles when brought in. Had long start. Did not have any codes at that time. Ran better after warmed up. We have changed pistons, rods/ bearings/main bearings. Rebuilt factory Cat head. Rebuilt oil pump. Changed harness to injectors but not harness from 12 pin connector to ECM. Please give me advise. Thank You, Sam.
Submitted: 1 year ago.
Category: Heavy Equipment
Expert:  Wayne replied 1 year ago.
Hi I'm Wayne,
I will help you with this,
Good evening
You sound like low fuel pressure
Your engine should maintain a fuel pressure between 65 and 85 psi at all times. I would advice installing a psi gauge on the fitting near the fuel filter and measuring the pressure. Even though you seen fuel after removing the plug, it still may not be enough pressure.
If the pressure is low I would suspect that you have a failed fuel pressure regulator. The regulator is located on the back of the cylinder head
Customer: replied 1 year ago.

Wouldn't low fuel pressure effect all the the injectors not just 1 and 2?


 


the only thing on the back of the head is a plastic return line with a compression fitting


 

Expert:  Wayne replied 1 year ago.
Hi Sam,
Thank you for that ,
you never mention #1 and #2

what is the fuel pressure between 65 and 85 psi at all times
let me know
Customer: replied 1 year ago.

I thought mentioning the code 72 indicated that cylinders 1and 2 were involved . The fuel pressure in fine 65 to 85 psi. So we still have a code 72


SID1, SID2,

Expert:  Wayne replied 1 year ago.
Hi Sam
I am going to turb thiis question to a friend oof mine fellow expert
who is very good on Cat engines

Thanks Wayne
Expert:  Cat Man replied 1 year ago.
Hi. Thanks for using JA! I will try and help you out.

So the code 72 is active when the engine is running and the yellow check engine light is on also?
Customer: replied 1 year ago.
yes to both questions and we have changed injectors injectors installed new injection harness in head and visually checked harness pins at ECM and 12 pin
Expert:  Cat Man replied 1 year ago.
I see. Thanks for the information.

If the code is active that are only 4 things that can cause the code 72.

An injector

The harness under the valve cover

The harness outside the valve cover

And the engine ECM.

To be honest it is rare for an ECM to cause this. I would suspect the outside harness since you have already replaced the injectors and harness under the valve cover. I know you have ohmed the outside harness but it could still be faulty.

Do you have any way of getting a service tool like cat ET software connected to the engine?
Customer: replied 1 year ago.

I hear you on the high voltage system it could be a stretched wire


when the truck came to shop it running bad but no engine light I drove it in


the number one injector plug was broke so we replaced the harness .


now it still runs bad we have a J PRO and cannot run a snap test on the injectors so we changed then to a different holes. no codes on those holes


so we are down to the ecm harness or ecm is there any way to check the ecm Cat tells me 50/50 chance they can check it . and as you know the ecm and programing it not cheap please give us any suggestions we have not seen a bad ecm in a cat before may be this is the first will one driver die?

Expert:  Cat Man replied 1 year ago.
Yes Cat should be able to check it easily. I have tested many of them for injector fault codes. It's pretty easy. I would let them check it. They can confirm if it is bad. I would hate to just throw an ECM or harness without having it tested.

Let me know if you need more help.
Customer: replied 1 year ago.

Will get back with you the ECM is at Freightliner being replaced and reprogramed we are installing a new ECM harness with new ECM when the ECM was pulled out it had oil in the plug . Thanks Sam

Expert:  Cat Man replied 1 year ago.
You are very welcome Sam. Thanks for the update. Let me know if you need more help.
Customer: replied 1 year ago.

New ECM And harness fixed it , however it set all night and would not start this morning acts like air in fuel already had checked fuel pressure before


and was okay, thought regulator on back of engine okay from prior fuel test


 

Expert:  Cat Man replied 1 year ago.
Thanks for the update. I'm glad you got that part fixed.

However is sounds like the fuel is leaking down. I have seen this before. This can be caused by two things. The regulator on the back of the head or the fuel transfer pump.

I always start with the regulator. Even though the engine has good pressure, the regulator still can allow fuel to leak down. It is the job of the regulator and the fuel pump to hold fuel in the head. If fuel is leaking out, one of these are not doing its job.


Let me know if you need more help.
Customer: replied 1 year ago.


It appears to not have come with a tranfer pump on the housing , And the regulator it not at a 10 degree tilt in the head can you get a transfer pump and could the tilt wrong cause the problem . otherwise we are putting a regulator on it .

Expert:  Cat Man replied 1 year ago.
Yes it has a transfer pump. It is on the drivers side of the engine bolted to the back of the high pressure pump.

Not sure what you mean by 10 degree tilt. Could you elaborate? The regulator is on the back of the head and it does not matter which way it is turned.
Expert:  Cat Man replied 1 year ago.
One more thing. If you have a 3126E that has a serial number that starts with HEP. The fuel transfer pump that is held on the high pressure pump with 4 bolts can NOT just be removed. It will damage the high pressure pump. The entire high pressure pump must be removed and stood up in a vice with the gear facing the floor. A special Cat bolt is needed XXX-XXXX to remove the pump. This bolt holds the high pressure pump together so the fuel transfer pump can be removed.

Let me know if you need more help.
Expert:  Cat Man replied 1 year ago.
Hi Sam. I just wanted to see how things were going. Please let me know if you need more help or have more questions.
Customer: replied 1 year ago.

Good morning .


 


we have changed the fuel pressure regulator on the head, change water temp sender because gauge did not work and changed air sensor.


drove it last night no problems , no problems on re start yesterday .


This morning it will not restart disconnected injector actuation circuit still no start , install fuel gauge have 35psi at filter , cranking speed on tach is 300 this problem comes and goes very little smoke at exhaust when cranking this problem only happens in morning it seems all injector orings have been changed new Cat reman head we used shell rotella oil 15-40 Thanks Sam

Expert:  Cat Man replied 1 year ago.
Thanks for the update Sam. If you have 35 psi fuel pressure, that is enough to start the engine.

If you are getting some some from the exhaust, the ECM is firing the injectors. Is the engine is not starting and only smoking, there are two things I have seen cause this.

The first is an inaccurate TDC signal from the engine speed timing sensors. It is rare but view happen. The engi e has two sensors one on top of the other under the HEUI pump. The lower sensor is the primary start sensor. It has a bigger magnet. I had seen them cause this. Even though the engine is getting an rpm signal, the TDC can be messed up. The only way to know would be to change sensors.

The other is a high pressure oil problem. Basically since it is smoking it has some high pressure but maybe not enough. It may be low. To verify you would need to install a 5000 psi gauge in the head and measure the pressure. It takes at least 870 psi high pressure oil to start. If it is low, you could have a leaking injector or Heui pump problem. To verify you could dead head test the pump. Just connect the 5000 psi gauge to the outlet of the pump and crank. You should make 4000 psi steady. Please be careful. High pressure oil is dangerous.

Let me know if you need more help.
Customer: replied 1 year ago.

It is trying to start like it has air so they must be trying to fire when you say leaking injector do you mean the orings or leaking from the tip into the cylinder , would the speed sensor indicate a code ? and this problem comes and goes it started yesterday morning fine Thanks for your help


 


 

Expert:  Cat Man replied 1 year ago.
You are very welcome.

When I say leaking I mean leaking o rings or an injector is leaking oil out of the spill port on the injector. This will lower the pressure. However a leak at an injector is unlikely but possible. I say this because most often when there is a leak at an injector, the problem continues while running. And you say it runs good after starting.

Also, when an engine speed timing sensor does this, it does not set a code.

Let me know if you need more help.
Expert:  Cat Man replied 1 year ago.
One more thing. I have seen the injection actuation pressure sensor cause this too. To test you can unplug the sensor and try to start. If it starts, the injection actuation pressure sensor is faulty.
Expert:  Cat Man replied 1 year ago.
Hi Sam. I just wanted to see how things were going. Let me know if you need more help. I am happy to assist.
Customer: replied 1 year ago.

We changed all the injectors to Cat remands it start right up now We still have problem when you first drive off it smokes, after driving a block it clears up


then after letting it idle after driving it will smoke again when you drive off and will clear after a block . we have change the all sensors and the orings on the injectors are new. Thx Sam

Expert:  Cat Man replied 1 year ago.
Does the check engine light come on when it smokes?

Also, have you tried cutting off one injector at a time to try and isolate the smoke to one cylinder?
Customer: replied 1 year ago.

No engine light , and our J pro tool does not let us cut off the injectors do not fee any mis fire. No codes


 


These Reman injectors are straight from Cat

Expert:  Cat Man replied 1 year ago.

Thanks for the information.

 

Yes i have used J Pro before, I wish it had cylinder cutout diagnostics. But it does not.

 

The reason I always like to cut each cylinder out is I may be able to isolate the smoke to one of the cylinders. If I can, I know that the one I find smoking has either a faulty injector or something wrong in the cylinder.

 

However I know you have inframed the engine and installed new injectors.

 

When you did the inframe, did you just replaced the pistons and rings? Or did you also have the block re sleeved?

Customer: replied 1 year ago.

Piston and rings and rods came loaded from Cat Block as you know is dry sleeved, checked with dial bore gauge all within good tolerance deglazed cylinders


 


We have followed vehicle down the highway zero smoke, 50 miles on it since inframe

Expert:  Cat Man replied 1 year ago.
I see. Thanks for the information.

I assumed the block was not re sleeved. But I wanted to be sure.

The good news is the block was within specs. If the cylinders were out of specs, the smoke would never clear up. I have seen 3126 engines inframed before and smoke. To stop the smoke, the engine will need to be heavily loaded. I have had to out several of them on the dyno to get the smoke to stop. The new rings will need to seat in the block and puttin the engine under a good load will help accomplish this. I know you said you drove it for 50 miles but if it was not under load, putting it under load will help seat the rings.

Expert:  Cat Man replied 1 year ago.

Hey Sam. I just wanted to see how things were going.

 

Please let me know if you need more help or have more quesitons. I am happy to help.

 

If my answers were helpful,. please leave a good or higher rating so I receive credit.

 

Thanks.

Customer: replied 1 year ago.

The Truck has been out on runs it cleared the smoke up alot with a oil change the oil must have gotten some diesel in it from the injector change


it still smokes on acceleratiton but clears up, could we have a bad turbo?


 


oil level is stable


coolant system holds pressure. Thanks Sam

Expert:  Cat Man replied 1 year ago.
Thanks for the update Sam. I'm glad to hear it is running better.

And yes. It is possible a turbo can cause the smoke during acceleration. The tough part is there is really no way of testing the turbo. I wish there was.

Let me know if you need more help.
Expert:  Cat Man replied 1 year ago.

Hey Sam.

 

I hope you had a great Thanksgiving!

 

Please let me know if you need anymore help. I am happy to assist.

 

If my answer was helpful, please leave me a good or higher rating.

 

We can still continue our conversation even after leaving a rating in case you still need more help.

 

Thanks in advance for leaving a positive rating. Have a great weekend!

Customer: replied 1 year ago.

Hi we have sent the truck out now for several thousand miles ,


we still have smoke at acceleration then clears .

Expert:  Cat Man replied 1 year ago.

Thanks for the update.

 

Could you get me the part numbers of the injectors you installed and the engine serial number? I just want to make sure they gave you the correct injectors.

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