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I have a CAT 308E that won't start. It was running fine and…

I have a CAT 308E...
I have a CAT 308E that won't start. It was running fine and then all of a sudden died on me. The only notable item I saw was that the temperature gauge because inaccurate when it died.Had a CAT technician look at it and he couldn't come up with a reason why it won't start.How can I verify that the ECM is fine?
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Answered in 2 hours by:
7/2/2021
Mechanic: catmastertech, Technician replied 1 year ago
catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 3,965
Experience: Field service technician for CAT 19 years.
Verified

Hey, sorry to hear you are having these problems. I know that can be frustrating. Hopefully, we can get you back to work quickly.  I see no one could help you earlier, and I hope this is not too late to be helpful. Please note that I am not set up for phone calls, you can ignore the site pop-ups. We can post to this chat as much as you like to work through this issue. All experts are not employees, and we work from home in our spare time to answer questions.

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Please post the complete machine serial number (PIN) so I can research the correct information to help you.

Have you checked the circuits from the key switch to the relays?

Why are you suggesting it is an ECM failure?

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Customer reply replied 1 year ago
FJX05510 is the last 8 of the serial.What happened was thef excavator was running and died all of a sudden. When I tried restating it other then the starter there were no signs of life.One more thing I noticed was the temp sensor was inaccurate when it died. Engine was hot but it was showing cold. That makes me think that it might have something to do with ecm. I can't point my finger to anything else.Let me know what wiring you were talking about that I could check.It was also really hot that day. Had thoughts that the heat had something to do with it.When the technician read the codes he wasn't able to see anything jump out at him. He would sometimes loose communication.
Mechanic: catmastertech, Technician replied 1 year ago

Thanks for the serial number.

The first thing to check is the battery, it must be in top shape and provide 12 volts to circuits.

The ECMs will turn off if the voltage is too low.

Since you have cranking ability, the machine ECM is working and the engine is ECM is working. They are both used to crank the engine.

The next issue I would check is the Main power relay which is the first relay in the panel beside the battery. It has to 60-amp fuses and they send power out to the cab and accessories.

The key switch power turns on the relay and that will send power to the top of the fuse panel.

Let me know what you find and if you need further help.

Thanks, Don

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Customer reply replied 1 year ago
That all works. Theres power to the cab.What would prevent the temperature gauge from showing an accurate reading?Thats the only other thing I notice beside it not starting.
Mechanic: catmastertech, Technician replied 1 year ago

The sensor is read in the engine ECM and then data link signal is sent to the monitor to display the readings.

If that is the only gauge not working, I would check for a reading in CAT ET. Maybe one of the sensor wire is broken.

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Customer reply replied 1 year ago
The technician checked and the only relevant code dealt with the ecm and it was intermittent. Seems like either the ecm or a bad connection somewhere. Too bad there's so much going on... Not sure how to diagnose.
Mechanic: catmastertech, Technician replied 1 year ago

CAT likes to say, it's never the ECM! (Until it is the ECM!)

I would check data link connections first.

What were the ECM codes? Power, data link, or something else?

I doubt it is power related since it does crank.

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Customer reply replied 1 year ago
Unfortunately I'm not sure what the exact code was. Wasnt able to obtain that information.Where are the data link connections? How can I check it? Are you referring to the actual connections going into the ecm?
Mechanic: catmastertech, Technician replied 1 year ago

Yes, these are the twisted pair of wires to each ECM and device on the CDL and CAN networks. You can test the voltage on the network to see if the high and low lines total 5 volts or you must identify all components used on the network and disconnect them to ohm out the wiring to check for short circuits.

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Customer reply replied 1 year ago
Can you help me find the pin diagram from the ecm? Both inputs and outputs. I'd like to be able to test myself if the right pins are producing voltage.Also where is the temperature sensor on the engine?
Customer reply replied 1 year ago
Thanks so much. Do you know how the temp sensor works? Does it provide a certain voltage to the ecm that then is interpreted as a specific temperature? Is there documentation about the details of what voltages and currents those pins expect to see?
Mechanic: catmastertech, Technician replied 1 year ago

The manual doesn't have details on the sensor. It is connected to the engine ECM and is a digital sensor. The purple wire is the signal and the black is a ground (floating ground to ECM not to chassis). A digital (data link) signal goes to the monitor. The monitor performance screen will provide a digital reading of the gauge.

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Customer reply replied 1 year ago
Thanks for the info.Any idea how to test that the signal for the ecm is going to the injectors to open them while I crank. Should it be 12volts coming to each of the injectors from the ecm?
Mechanic: catmastertech, Technician replied 1 year ago

The battery voltage is raised to about 110 V by a high-voltage generating circuit inside the ECM and that voltage is supplied to the injector to actuate it.

I have seen a tester is available for the fuel shops but, I haven't seen any way to test them in the machine. CAT ET can do a cutout test but, that is all I have done. Older versions electrical connector would break when trying to disconnect the harness. These older engines also had a harness issue and some required new harnesses.

Yours may be new enough to be beyound these problems since you don't have codes.

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Customer reply replied 1 year ago
Hi. I found a blown 20amp fuse by the battery where there are 60amp fuses. What is that fuse?
Mechanic: catmastertech, Technician replied 1 year ago

It is the battery feed to the Engine Power #3 relay and is switched on to power the multiple ECM battery connections and also the air flow sensor as well as the EGR valve.

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Customer reply replied 1 year ago
I chwnged fuses and the machine started and ran! Wonderful....Except we decided to just run a test for our selves for future. Disconnected the fuel pump solenoid connector and were checking voltage... And tried to crank it. After reconnecting my starter won't work now.If I jump the starter directly, it starts and runs.This is a separate issue, but what could it be? Ecm telling the starter to not go? Probably need to read and clear codes?
Mechanic: catmastertech, Technician replied 1 year ago

Clearing codes does not fix problems with most CAT machine. The only exception is a few EPA emissions lockouts.

Let me see where this could be related.

The 30 amp fuse beside the 20 is to the start relay. Did you check that fuse? Could it be damaged?

Other circuits are not fused but run between the key switch and the machine ECM and the start relay and engine ECM.

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Customer reply replied 1 year ago
Yeah we swapped them temporarily and that was the issue. Got it all working. I strongly appricate your prompt responses and your knowledge. You've been tremendously helpful.
Mechanic: catmastertech, Technician replied 1 year ago

You're welcome! Glad I could help.

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Thank you for using JustAnswer, if you do need further help, please let me know.
If you are satisfied with my service, please take a moment to provide a rating.
Thanks again, Don
CATMASTERTECH

catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 3,965
Experience: Field service technician for CAT 19 years.
Verified
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