# ECM diesel engines



## CalTreeEquip (Apr 26, 2014)

I would like to hear about your personal experiences keeping diesel engines with ECM's (electronic control module) running.
For example, I just spent $1,600 on a Cat tier 2 engine because there was too much resistance in some of the contacts
and fuses, inline to the ECM, causing it to send a false malfunction signal to the injector pump, preventing it from running.
I couldn't figure it out, my mechanic couldn't nor could the mobil Cat mechanic. It took the Cat shop and lots of hours to find the flaw. This is the second time this has happened. The other unit was a Perkins and cost me $900 to replace a $5 resistor.
So what are your stories?


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## dieselfitter (Apr 26, 2014)

Post a picture of this $5 resistor. I'm betting they replaced a failed VLPM. 
The Cat (Perkins) 4.4, 6.0 and 6.6 tier II engine has two computers. It uses a Bosch VP30 injection pump that has a computer. Perkins installed an ECM(computer) to control the Bosch injection pump/computer. Low battery voltage to the ECU during cranking can prevent the ECU and or Bosch computer from powering up. The two different computers have two different minimum voltage thresholds to power up so it can be hard to identify the problem. A bad connection anywhere in the power supply to the ECU and injection pump computer will cause this issue. Also a weak battery, excessive starter current draw, bad battery connections... Easy way test is supply a temporary power supply directly from the battery and monitor the supply voltage during cranking. 
Also, that thing next to the ECU that looks like a pipe bomb, it is a VLPM(voltage load protection module). That is fancy terminology for "surge suppressor". It turns out the Bosch VP30 doesn't tolerate voltage spike well, (the Perkins ECU is tough as hell). Anyhow, the VLPM has a high failure rate. One of the first things I do for a not start is bypass it as a test. There are four wires red, orange, blue black. By-pass it by connecting orange to red and Blue to black. If it will start by-passed, replace the VLPM.
Overall it is a simple reliable electronically controlled fuel system. The Tier 3, Tier 4 interim and final are, by comparison, quite complex and even more dependent on the Perkins EST(electronic service tool) for diagnosis and testing.


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