Question1994 N14, that I have owned since new. Original ECM and all ECM wiring. Only the oil pressure and engine position (twice) sensor have been changed. ECM updated to let eps sense twice per revolution...had developed a long crank-to-start problem. Tech found that engine had been built without anti-drain-back valve in fuel supply line (just prior to filter). Long crank-to-start problem eliminated. Engine has had 2 injectors fail, one at a time. Last January had all 6 injectors replaced, Jake tuneup, recon turbo, recon air compressor. Couple of months ago, 2 injectors were replaced at the same time. That Cummins Distributor had a dyno and at first they replaced #6 injector, then let me know that it still had a miss and was also still producing white smoke. Tech asked if I had any Jake problems...Jake staying on with switch off, etc..no. They then replace #3 injector, no more miss or smoke. Engine ran fine for a day, then it sounding like it was barking at the exhaust stack at idle, power seemed to be fine. Did that 3 or 4 times and no longer barks. Odd intermittent idle has occurred since then. It varies from a mild miss to a truck shaker. No rhyme or reason for duration of odd idle, sometimes it is brief and sometimes will act up for 10 minutes. Took it to Cummins Distributor that has done everything on it since new, except the last 2 injectors. They spent 3 hours on it, would not act up and no fault codes showed.
Seems to me that it only acts up with very damp or wet weather. Most recent oil change, I had a oil analysis done...nothing unusual, no fuel dilution. Engine uses no oil between changes. Has small front cover oil leak.
I am suspecting a wiring problem...I noticed during a wiper motor exchange that the wiring connectors are brittle...'95 White GMC---the wiper motor is above the area of the rearward head...so it does get some heat from the engine. I can only imagine how brittle the ECM connectors are on the harness at the block.
My distributor wants to "simply" sell me a new ECM. I have read where there can be an internal moisture problem with the ECM, and of course the old wiring can easily be at fault.
Been thinking of taking a spray bottle of water or maybe a bucket of water to it and see what happens. I can't see replaced the ECM just for the sake of swapping parts and hoping that is the problem.
Have you seen any specific wiring problems with a N14 or White GMC WIA tractors ? Any ideas on what I can troubleshoot without a diagnostic tool (no fault codes anyway) ?
Answer I havent heard of anyone replacing the ECM for that problem.Usually it will always misfire on a cylinder & stay misfiring because a driver is bad.I would not replace it until it fails.They are very expensive,like $2500 plus labor & calibration charges.Water might be causing it.We have had some problems with moisture in wire harness at ECM on some trucks.We took the ECM connectors off & got some windsheild sealant to put on the backside on the wires to keep moisture out.Make sure the small orange "o" rings are still in place too.
