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ECM Discussion....


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I know there has been talk about how few times an ECM goes out, not to worry about the engine heat and where it's mounted and so on. Except isn't it getting harder to find a good reliable one? Getting it flashed properly can be a problem also, I've heard. Then you have a few ECM rebuilders/ repair companies sending off faulty units. Sometimes being a crap shoot trying to get a good one. Some have reported bad experiences while their truck sits for days sending units back and forth till they get one that works.Now I have been Googling engine heat, ECMS and problems... finding reports about how heat does affect them. One ECM supplier reporting that the engine heat is the biggest enemy to the ECM. On a truckers forum they discuss how to keep it cooler with running fuel lines near or around it. I think I remember reading how Cat engine already does this for their ECM's. On the Cummins forum there was a guy complaining about his 24 valve was acting up always after it was up to full engine temps. He then moved the ECM off and away from the engine, mounting it on the original fuel pump bracket no longer used and his trouble went away.So if you are like me and want reliability for the long haul doesn't make sense to move the ECM away from the block? I'm wondering too, if I can ground the ECM housing directly to the battery after it's moved?Thanks for any thoughts

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When I had to replace my ECM, I opted for a new Mopar part. It really was a no brainer, as they had a 2 year unconditional warranty on it and at the time I had a Chrysler mechanic buddy who flashed it for me for $20. If my ECM goes out again, I will still likely put in a new Chrysler part. In my opinion, the biggest killer of ECMs is electrical noise and spikes. Making sure your alternators diodes are good and making sure you don't have any solenoids, relays, or other switches backfeeding into your system are key. I went through 3-4 Edge Juice modules, an ECM, a radio, and a VP44 computer thanks to a bad relay putting 20+ V spikes into the system when my Air Dog cycled. In short, there should be minimal AC voltage in your system when measuring with a multimeter. Personally, I am comfortable with .2 V or less, though MoparMan has a standard he found (likely from the service manual!) :thumb1:

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I was under the impression you can no longer buy a new ECM for the second gens.So CSM, your bad relay crossed the ECM circuit and the lift pump power from the batteries. Yikes... I'll see if I can do a test for that.98, I can move the F/Filter further away so I'm interested in that pic when you have time. I already isolated the F/F housing off the intake manifold (Special phenolic resin block used in electronics) because the filter housing was getting too hot Heat from contacting the intake manifold. It heated the fuel just before the VP.

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I was under the impression you can no longer buy a new ECM for the second gens. So CSM, your bad relay crossed the ECM circuit and the lift pump power from the batteries. Yikes... I'll see if I can do a test for that.

I didnt know that. That could suck. The Air Dog solenoid was wrapped tightly with other wires. Basically that made a transformer and every time the solenoid would cycle it would make a 13-20V measurable spike in the whole electrical system.
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I know Mopar is still selling new units from the dealer but price is premium for them. What is strange is the few people I've talk to about getting rebuilder to do the work on a ECM about 90% of the time I keep hearing about a chip that is no longer produced or can't be purchased. That still get me stratching my head about that. Why is it that Mopar is still selling new ECM's but a rebuilder can't purchase the same chips to rebuild it? :think::shrug:

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The Air Dog solenoid was wrapped tightly with other wires. Basically that made a transformer and every time the solenoid would cycle it would make a 13-20V measurable spike in the whole electrical system.

That's amazing. I don't understand it :think: but, I have heard something about bundling wires too tightly together. Did you just loosen up the bundle to fix it and put in a new Relay?

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I know Mopar is still selling new units from the dealer but price is premium for them. What is strange is the few people I've talk to about getting rebuilder to do the work on a ECM about 90% of the time I keep hearing about a chip that is no longer produced or can't be purchased. That still get me stratching my head about that. Why is it that Mopar is still selling new ECM's but a rebuilder can't purchase the same chips to rebuild it? :think::shrug:

Good question, good to know.... wonder if it's something to do with exclusive vendor rights that Chrysler paid for

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I used a longer bolt and an aluminum spacer I got from ace hardware.

98, Thanks for the picks :thumbup2:.... looks like I will need to space the F/filter further out/ away like you did. Glad to know it all fits. I'm probably going to find a way to insulate between the engine and the ECM just cause I'm an anal Cummins owner :whistle:
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As one of the ones who have had a bad experience with rebuilders and weeks waiting for a rebuild of the rebuild, I finally got one from Dodge. This happened 2 years ago and I was under the impression that remans were all you could get then. Could be wrong. Personally if mine were to go out again I would go with the Dodge, or Cummins, who ever had the best warranty and or price. I would agree with electrical spikes and heat would be just as bad for the ECM as any other electronic component. Would the wiring harness be long enough to allow you to move it very far with out having to modify it? Does anyone know how hot it gets on that side of the engine?

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I unwrapped the wires and all my problems went away. It looked neat and orderly, but electronically, it was anything but!

That is interesting. I suppose due to the amount of low voltage electronics means things are more sensative. This is a good thing to note and share this problem. Thank you.

As one of the ones who have had a bad experience with rebuilders and weeks waiting for a rebuild of the rebuild, I finally got one from Dodge. This happened 2 years ago and I was under the impression that remans were all you could get then. Could be wrong. Personally if mine were to go out again I would go with the Dodge, or Cummins, who ever had the best warranty and or price.

I would agree with electrical spikes and heat would be just as bad for the ECM as any other electronic component. Would the wiring harness be long enough to allow you to move it very far with out having to modify it? Does anyone know how hot it gets on that side of the engine?

Dripley, I imagine it can get pretty hot with summer heat and heavy towing. It is really close to the engine block (cannot get finger tips behind it) not enough space for me to think it stays cool that way.

I can't tell how much the wiring harness will let you move it. The harness is running in front of the ECM, with a branch going up to the plug above and is attached very tight to the engine block just forward of the ECM. I have to cut that band so I can move it and tell. I think the limiting factor though is going to be leaving enough room for the F/filter. Cap and filter has to come off and go straight up. Got to clear the oild dip stick tube as well.

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I stand corrected, Cummins did give it some cooling space of about an inch, now that I have the ECM off I can see the spacers cast into the block. However it would be better to at least have some isolation washers in there. Something like nylon washers would telegraph/ transfer less heat. Then run a ground to the battery so the housing is grounded again.

Dripley, the wire harness band is held by a bolt 10mm.

The bottom ECM bolt was corroded so that I had to use a cheater bar. Probably a good idea to use some dielectic grease on the plug being it's down there too.

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Relays are not the only ones that produce this issue too. How about the vacuum valve on the Jacobs exhaust brake. That solenoid has enough surge to blow up LED lighted switches or standard bulb lights switches in about 10-20 cycles of the exhaust brake. So relay is one spot but not the only.But still with all this I've never had a ECM/PCM issue as of yet? I've got cooking summer heat like other areas of the country yes I've seen 112*F in Riggins, ID already this summer at a friends place. My ECM is mounted like every one else's. Just like I've only lost one VP44 to fuel pressure back at 50K miles. But never lost a VP44 to electronic failure or heat failure as of yet.Food for thought...

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YankNeck, Thanks for the links. They are very informative. I had no idea.Micheal... you better knock on wood after bragging how yers never goes out :lol:I'm putting a heat shield and spacers behind mine. He he I need things to keep busy anyhow:hyper:.A side note... the ECM housing is all aluminum. I think that conducts heat more than most other metals.

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