Help with 3406E

Hey guys, long time reader . My mechanics and I are very stumped on this issue with a 3406E 5EK. (97 Freightliner Fld120).

Will give a quick background. Truck started to roll blue smoke and stutter lightly taking off from a light. Once wound up, would run fine. Did this for maybe a week.

Brought it home, changed fuel filters, truck would barely start. No throttle response, wouldn’t come off 500rpm, shuttered and shook. Thought maybe fuel filters were bad (CAT) or I bumped some dirt into them changing. Started up, same thing.

Codes on laptop showed a fault In injectors 1, 2 and 6. Took off valve covers with engine off performed injector test and saw that each one was receiving power.

Computer showed a 41-4 code I believe for low volt Ecm . Our Ecm specialist I deal with said Ecm is scrambled and that was the issue.

Purchase a used Ecm out of a 1995 peterbuilt 5EK, have tech match parameters from my old Ecm and load with a 550Hp cat file.

Install Ecm and fire truck, runs beautiful. Run the truck for the day, no stuttering or blue smoke. But engine fan is stuck on. Take to shop thought maybe it was something in the tune that was telling truck to keep fan on. Mechanic tests fan and wiring and all is fine. Decides to try loading a different tune, same issue. Tests truck for 8hours , returns Ecm back to the 550 tune so I can leave for the day.

Fire truck, TONS of blue/white billowing smoke, stuttering on throttle increase. Smokes shop out. Let it high idle for abit, no change.

I have a local company float my truck home after it sat at the shop waiting on another ECM as we thought from flashing the “new” one , scrambled it or something.

Friend of mine removes a completely stock , 475hp 5EK Ecm out of a perfectly running truck. Plug it in, truck smokes for a bit then smooths out and runs beautifully. Shut it off. Fire it up after mounting ECM and take it down the road, smokes the road out (blue), stuttering, popping out the exhaust , very little power . Limp truck back to my shop. (Still billowing blue smoke) .

Shut truck off, fire it up, no smoke , runs mint (can hold it to the floor and no smoke whatsoever). Try to take it for a drive, not even 5km down the road, smoke begins , let off throttle and let truck coast (60km/h), lay lightly back into throttle, TONS of blue smoke, stuttering popping.

I’m at a total loss here guys no idea TF is going on. My next step is to take it to CAT but they are backlogged and can’t afford to have truck down for another couple weeks.

Did these ECM a wreck something else or do I need to buy a brand new one from CAT and start from scratch ($7000) ?

Any insight is greatly appreciated at this point .

Thanks very much

Neil

 

Thanks for the quick reply! The wiring all looks in good shape, as well as the pins and connectors . With truck running I tried wiggling the harness and plugs to see if any change to no avail. I did notice that with the current ECM in the truck the tachometer is way off and doesn’t register even close to the trucks RPM. Of course that could just be coincidental as well .