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Cat Man, It’s not a truck, it’s a Tamrock rock drill with a…

Customer Question
Hello Cat Man, Mechanic's...

Hello Cat Man,

Mechanic's Assistant: What's the make/model/year of your truck? Engine type?

It’s not a truck, it’s a Tamrock rock drill with a Cat 3126b engine 2005 model, with a no start problem

Mechanic's Assistant: Sometimes things that you think will be really complicated end up being easy to fix. The Heavy Truck Mechanic I'm going to connect you with knows all the tricks and shortcuts.

Thanks

Mechanic's Assistant: Are you fixing your truck yourself? What have you tried so far?

Yes we are doing the repairs ourselves, we have checked for codes using Cats Electronic Technician but found none.

Mechanic's Assistant: Anything else you want the truck mechanic to know before I connect you?

Injection Actuation pressure at 276 psi when not cranking and going up to 1325psi when cranking

Submitted: 7 months ago.Category: Construction and Road Equipment
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Customer reply replied 7 months ago
Could it be an issue with the injection actuation pressure control valve and is there a way to test if it’s working properly?
Answered in 53 minutes by:
11/23/2017
Mechanic: Cat Man, Cat Engine Expert replied 7 months ago
Cat Man
Cat Man, Cat Engine Expert
Category: Construction and Road Equipment
Satisfied Customers: 9,395
Experience: I am ASE Master Certified.
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Thanks for asking your question. I will try and help you out.Since the yellow check engine light comes on, this indicates the engine ECM is receiving power and functioning. There are several things that can cause a crank no start on this engine.The first is a low or no fuel pressure condition. The engine needs at least 25 psi to start. If it is low, the injectors will not get filled and it will not start. If the engine has a hand priming pump, and it gets stiff when operating it, the engine has enough pressure to start. If there is no hand priming pump, I would connect a psi gauge and measure the pressure. If the pressure is low, I would change the fuel filters first if you haven’t already. If it is still low, I would suspect a failed fuel pressure regulator on the back of the head or a weak fuel transfer pump. The pump is located on the back of the HEUI pump.Second is a low injection actuation pressure. This is the high pressure oil system that activates the injectors. The engine needs at least 870 psi to start. If it is low, you have either a failed Injection actuation pressure control valve in the HEUI pump, a weak HEUI pump, a high pressure oil leak at an injector, or a faulty Injection actuation pressure sensor. To test the sensor, just unplug it. If the engine starts, the sensor is bad. It has 3 wires and is located on top of the engine near the front and screwed into the head.Third is a failed engine speed timing sensor. Your engine has two. They are located on the driver’s side of the engine on the back of the engines front cover under the HEUI pump. The bottom sensor is the primary start sensor. If it has failed, the engine will be hard to start. The top one is the primary run sensor. They come as a pair.Next is low battery voltage to the ECM while cranking. The ECM must have at least 7.5 volts DC to operate. I have seen weak batteries or a poor connection cause low voltage. You could have a poor connection at the batteries or starter.Next is a faulty engine ECM. The ECM has an injector driver module inside. This is what powers the injectors. If it fails, the ECM will log injector codes for all the injectors.Lastly are worn injectors. Over time the injectors can wear if they have a lot of hours on them. To verify, I like to check AC to the injectors while cranking. You should have between 20-40 AC while cranking. If you do, and you have good fuel pressure, the injectors are worn.Most often when these things are happening there will be diagnostic codes in the ECM. If your engine has cruise control switches, you can pull the codes. If you have never done this, let me know. I can get you the procedure.Please reply back if you need more help or have more questions. I am happy to assist.
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Customer reply replied 7 months ago
Hello,I have attached a picture of the Cat ET screen which shows some of our readings we have found. The unit is a 2005 Tamrock Ranger 800 Drill rig 6,250 hours. The engine is as follows:
CAT 3126B
Serial # DCS01876
Arrangement #(###) ###-####
It had done this before when it was in the yard, wouldn’t start and the a few days later it fired up with nothing being done to it.It’s had all fuel, air and oil filters changed since no start issue.Disconnected the Injection actuation pressure sensor and it doesn’t fire.What should we do next.Thanks
Mechanic: Cat Man, Cat Engine Expert replied 7 months ago
it has rpm and 1300 psi actuation pressure while cranking?
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Mechanic: Cat Man, Cat Engine Expert replied 7 months ago
Hey. I just wanted to see how things were going. Please let me know if you need more help. I am happy to assist. If my information was helpful, please leave a good or higher rating so that I receive credit. Thanks.
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Customer reply replied 7 months ago
We still haven’t had any luck getting it to fire up, we have 254 rpm when cranking and the actuation pressure goes to a max pressure of 1325 psi when cranking
Mechanic: Cat Man, Cat Engine Expert replied 7 months ago
Thanks for the information. I would try checking AC power to the injectors while cranking. Should have 20-40 AC
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Customer reply replied 7 months ago
The injector actuation current max was 79 when cranking.
Mechanic: Cat Man, Cat Engine Expert replied 7 months ago
That’s dc current to Heui pump. I’m referring to AC to injectors.
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Mechanic: Cat Man, Cat Engine Expert replied 7 months ago
Hey. I just wanted to see how things were going. Please let me know if you need more help. I am happy to assist. If my information was helpful, please leave a good or higher rating so that I receive credit. Thanks.
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Customer reply replied 7 months ago
I have tried to send a few message to you but for whatever reason they wouldn’t go through. We checked the AC to injectors and had a reading of 34 when cranking. The plug and 2 wires that are exposed out of the protective loom and going to the injection actuation pressure control valve were in very bad shape. The protective cover on the wires crumbled and falls off with just a touch. We have ordered a new plug with pig tails, but I have to peel the protective loom back and see how far the wire is rotten. It’s also in a very tough spot to access the engine is mounted crossways in these drills and there’s multiple air & hydraulic hoses along with air receiver tank plus a bunch of air values. Hope this goes through and I’ll be in touch once I get the wiring cleaned up.
Mechanic: Cat Man, Cat Engine Expert replied 7 months ago
Thanks for the update. Please reply back if you need more help or have more questions. I am happy to assist.
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