2002 kenworth with a CAT 3126 engine- crank no start. I am looking for schematics for engine and OEM side as well.

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Customer: 2002 kenworth with a CAT 3126 engine- crank no start. I am looking for schematics for engine and OEM side as well. Noticed with key in on or off position there is no power at fuel pump actuator. Cranking puts power to it. Cuts out when cranking released. Does not attempt to start
Answered by Nich1019 in 2 mins 1 year ago
Auto Mechanic

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Specialities include: Auto Body Technician, Heavy Equipment Repairs, Heavy Duty Engine Repairs, Brake and Transmission Repairs

Hello and welcome to JustAnswer! I'm Nick and I'll be helping you out today. I'll be back within 30 minutes with some diagrams for you.

Awesome thank you!!

No problem. I'm working on this now.

Here's the Cat diagram.

Here's one KW harness.

Here's another KW diagram.

Both of those diagrams came up under OEM engine harness.

Ok great , are you familiar with this no start condition as far as what I should see at the fuel pump actuator? And what I should see from the ECM

No, sorry. I'm more familiar with HD engines. I will see if I can get some more specific information for you from Caterpillar.

Ok, so it looks like the control valve will only have current when running or cranking. It's job is actually to bleed excess oil pressure. Try unplugging the injection actuation pressure sensor and cranking the engine. It's on the top driver side of the engine near the front.

Do you have Cat software?

I do have cat software. Didn’t have it with me today but Saturday when I get back to this truck I will have it. Any information you can offer for diagnosis would be much appreciated

Ok, I'll make a document together this evening and send it to you.

Thanks so much

No problem.

Here's an overview of reasons why the engine may not start. I'd start by monitoring engine speed/timing sensors with CatET. Then check the power, ground and ignition supply to the ECM. Make sure the voltage doesn't drop too much while cranking. Make sure the batteries are in good condition and the cables are clean, tighten and corrosion free. Remove the rear ECM plug and check for corrosion or damaged wiring. From there move on to monitoring the injection actuation pressure as the document suggests. After all of that is verified I'd move on to fuel system checks. I'll send some separate documents for checking the timing sensors, power supply circuits and fuel system if necessary.

Here's the speed sensor troubleshooting. The illustrations are missing, but use the Cat wiring diagram if you need to check wiring.

Here's the ECM power supply information. Use the KW diagrams if necessary.

Here's information on the fuel supply pressure.

It's very likely that you have a failed high pressure pump. If the fuel supply is good, but the injection actuation pressure is low you'll need to replace the pump. If the pump has failed you should replace all 6 injectors also. There are large plugs on the front and back of the cylinder head where the high oil pressure rail is. If the pump has failed use a telescoping magnet and check the rail for metal shavings.

Awesome thank you so much

No problem. Let me know what you find or if you need further assistance.

Going to check out this afternoon. Keep you posted
Here’s an update, with the truck now. Cranking engine speed detects 200rpm roughly. Injection actuation pressures around 870. But injection actuation output stays under 100psi
Disconnect actuation pressure sensor and still does not start. Forgot to start with codes found: nothing active but logged:
-1-11 cyl 1 injector current fault
-2-11 cyl 2
-3-11 cyl 3
-4-11 cyl 4
-5-11 cyl 5
-6-11 cyl 6
-41-4 8volt supply voltage low
- 164-2 injection actuation pressure signal erratic2 codes I believe I caused while testing the other day:
-42-11 injection actuation pressure output fault
- 164-3 injection actuation pressure voltage high both from unplugging sensor and driver while cranking.Logged event code:
-164-11 injection actuation pressure system fault

Ok, with the 6 injector current faults the issue is going to be the ECM. But give me just a minute to pull up that 8 voltage supply shorted low. I'm not too sure if that would be related.

Ok let me know. Even though all codes are logged you suspect ecm? Nothing is active

Yes, the inactive injector faults are common for an ECM failure in any Cat engine. Most of the time they are inactive. If I see that I'm automatically replacing the ECM. No checking or troubleshooting anything.

The 41-4, 8 volt supply, is the supply for the throttle position sensor only. If you have disconnected the throttle or disconnected the ECM connector with the key on I would ignore it.

Ok I will see if I have a sister truck here where I can swap ecm. What about all the actuator codes and test results I reported?

The 42-11 and 164-11 could be anything from a plugged fuel filter or an issue with the fuel pump. Once you get the engine running you can perform some tests on the fuel system.

Okay I will hopefully have a good ecm to test with and go from there.
Real quick I cleared all codes and cranked engine. All injector codes came back as well as 8 volt supply code.

Ok, I'll send the troubleshooting for the sensor supply fault. It may be the ECM causing that too though.

But that code wouldn’t cause the engine not to start correct?

Right, it would cause the throttle not to work. It wouldn't cause it to not start.

Roger that. I will push customer to find a sister to swap or they can send out ecm their choice. And once ecm is replaced I can return and confirm high oil pressure system operation. One more question I have, when doing the injection actuation pressure test, the pressure reach 870 which is the minimum. But where it shows output it wouldnt rise past 100. Does that indicate a weak pump?

Yes, that may indicate a weak pump. Make sure the oil is in good condition. If it's degraded it won't be able to raise the pressure easily.

if the pump had failed it wouldn’t cause the ecm to throw those same injector codes to keep engine from firing due to lack of oil pressure?

No, it wouldn't.

Ok understood. Thank you very much for your help it’s been very much appreciated.

No problem.

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