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Troubleshooting Crank No Start on M1078A1

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akkanow

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I've been working on a crank no start issue with a M1078A1 that ran fine when shut off, but sat for a couple months. It has been stored indoors since and just cranks and doesn't even try to start. In following the troubleshooting in TM 9-2330-365-20-1, I get as far as e6 (is 24 vdc present on TL28). I guess that's where the A1 differences catch up. Is there a TM for the A1? I have searched with no success.

In looking for that fuel solenoid, I found the attached pictured device, which appears to be some sort of solenoid. It is missing the nut, so I assume it may not be working. 24V is present in the connector. Is anyone familiar with what this device is? Thoughts on if it could cause the problem I'm seeing?

In reading this thread, I see that someone said the A1 has no fuel solenoid. So perhaps I need to move on down the list?
 

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Ronmar

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Yea, wrong list… no fuel solenoid on an A1. Its EFI. I guess the first question i would ask is do you get a check engine light at initial power up, or at all? My second would be what year is it?

cranking indicates the transmission is powered up and in neutral to deliver a neutral start signal. And there should be a brief check engine light on power up From the ECU…

There are a few basic known issues. They chose to install a filter in the power circuit of the ECU and these have been known to fail. This filter is a little module in the cable at the ECU, and many have been bypassed/removed. Another issue with the early 3126 ECU’s is that they use an internal battery to maintain their programming. As these age they fail, and if service battery power is removed the computer looses it mind… when it sat for a couple months, did the batteries go flat?

Beyond that you are probably going to have to put together a computer and interface, or have someone connect to it and talk to the ECU if you can, so it can tell you whats wrong with it.
 
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akkanow

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Ronmar said:
Yea, wrong list… no fuel solenoid on an A1. Its EFI. I guess the first question i would ask is do you get a check engine light at initial power up, or at all? My second would be what year is it?
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First, a huge thank you! Yes, the check engine light comes on and flashes about every 5 seconds. As does check trans. It is a 2002.

Ronmar said:
cranking indicates the transmission is powered up and in neutral to deliver a neutral start signal. And there should be a brief check engine light on power up From the ECU…
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OK, that's great to know. So then I guess the check engine light staying on and flashing every 5s must be an error condition?

Ronmar said:
There are a few basic known issues. They chose to install a filter in the power circuit of the ECU and these have been known to fail. This filter is a little module in the cable at the ECU, and many have been bypassed/removed. Another issue with the early 3126 ECU’s is that they use an internal battery to maintain their programming. As these age they fail, and if service battery power is removed the computer looses it mind… when it sat for a couple months, did the batteries go flat?

Beyond that you are probably going to have to put together a computer and interface, or have someone connect to it and talk to the ECU if you can, so it can tell you whats wrong with it.
Click to expand...
Aha! Is that battery something I can change? It could very well be that it went flat. This is a project truck and we got pulled to a different issue for a while, so this one didn't get a lot of attention for a period. I tried to start it occasionally, but likely not often enough. I think I read elsewhere that the battery going dead would cause the ECU to lose its programming? Is that something that I can reprogram with the appropriate software/hardware? Most importantly, I guess, is the program available somewhere?

I'm happy to assemble the interface to this. Is there anything you can point me to that explains what is needed?
 

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Ronmar

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Well check engine flashing is a good sign, it is probably a sensor, or perhaps a data bus issue with its comms path to the transmission.

The ECU battery is buried in the ECU and not easily replaceable. I know someone who was experimenting with batt replacement but do not know how that turned out. I think the basic cat program as well as the tune/codeplug would have to be reloaded and I don’t imaging cat would have released that base code anywhere. If it dies the ECU must be replaced and the tune for your specific engine/application reloaded…

You will need a laptop, interface and cat ET software to talk to it. I am not familliar with the specifics. @GeneralDisorder is our resident cat ECU expert…
 
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GeneralDisorder

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It is possible to replace the ECM battery but it requires electronics skills. The ECM's are probably an 8 or 9 out of 10 difficulty level due to the way they are manufactured. Just getting them apart requires de-soldering about 45 MOSFETS and VR's that are glued to the case with heat transfer adhesive.

1000006651.jpg

1000006652.jpg

That said - I have seen a LOT of trucks and ECM's and ALL of them have a dead battery including my daily driver. None of them know the time or date and that is really the only purpose of the battery. To provide a time and date for the data logs. All of them work fine with the date reset every time your start the truck. So I doubt that's actually the issue and if it is, then you need to just toss that ECM since it would be a very old revision and probably suspect in terms of reliability.

Check for the EMI suppression box and if it's present but disconnected then look for the jumper harness and DELETE it. Cut the connectors off the chassis side and crimp the wires with standard electrical splice terminals or solder them or whatever you like. JUST BE CAREFUL NOT TO CROSS THE WIRES. One is power and one is ground and if you cross them you WILL destroy the ECM.
 
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akkanow

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GeneralDisorder said:
It is possible to replace the ECM battery but it requires electronics skills. The ECM's are probably an 8 or 9 out of 10 difficulty level due to the way they are manufactured. Just getting them apart requires de-soldering about 45 MOSFETS and VR's that are glued to the case with heat transfer adhesive.

View attachment 940238

View attachment 940239

That said - I have seen a LOT of trucks and ECM's and ALL of them have a dead battery including my daily driver. None of them know the time or date and that is really the only purpose of the battery. To provide a time and date for the data logs. All of them work fine with the date reset every time your start the truck. So I doubt that's actually the issue and if it is, then you need to just toss that ECM since it would be a very old revision and probably suspect in terms of reliability.

Check for the EMI suppression box and if it's present but disconnected then look for the jumper harness and DELETE it. Cut the connectors off the chassis side and crimp the wires with standard electrical splice terminals or solder them or whatever you like. JUST BE CAREFUL NOT TO CROSS THE WIRES. One is power and one is ground and if you cross them you WILL destroy the ECM.
Click to expand...
Wow, thanks for the info. I'm actually pretty confident reworking boards, but it sounds like it may not be worth the risk/effort.

I'm sorry to be dense, but when would I find the EMI suppression box? I guess right next to the ECM? I guess I'm not even sure where that's located. I'm definitely a newbie on this side of the vehicles.

I think I saw you had some information regarding getting the software/hardware setup for communicating with these things. I'm interested in setting something up as we have a number of these vehicles in the area. I'm just not finding a lot of (approachable) information for where to start.
 
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Ronmar

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@GeneralDisorder yea I cannot remember if it was you or Superman I had the battery discussion with, but I recall it was a little involved. I do recall being involved in quite a few dead ECU conversations typically after prolonged service power removal, One key symptom with those was no check engine light, so I suspect this is some other fault in his HEUI system...
 
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