Wednesday, May 2, 2012

A Rough Start to the Season

Last fall I was finishing up my winterizing routine when the engine on Seapickle suddenly died out and would not restart. At the time I wasn't too concerned, figuring I just flooded the engine while fogging it. Well what seemed like no big deal in the fall has blossomed into a big problem this spring. With our launch date fast approaching we needed to figure out what was wrong and fast.

 A quick test revealed that the engine cranked over fine but had no spark or injector pulse. I decided that the crank sensor was most likely the culprit so I focused my attention there. The test meter showed the sensor receiving the required power and ground from the ECU, but without my oscilliscope handy I couldn't perform an accurate test on the sensor output. With my patience wearing thin and a parts store in an almost too convenient location I decided it was worth a shot replacing the sensor.
Let the fun begin
Of course the new crank sensor made no difference and I found myself right back at square one. Armed with every wire schematic and test procedure I could get my hands on, I spent my evenings for the next 2 weeks testing and tracing wire after wire, and sensor after sensor. I finally concluded based on my testing that the engine computer, or ECU had failed. I decided this early on in the testing that this was the failed part, but when I say Volvo Penta is very proud of this part it is an understatement, and they have priced it accordingly! With the new ECU on order I decided to open the covers on the failed ECU hoping to see conclusive evidence of failure.
Evidence of a failure!!
I was actually relieved to see the potting jelly blown apart where the inputs for the crank sensor enter the computer. We waited anxiously for UPS to deliver the new computer and as soon as it arrived we raced up to the boat with only the computer in hand and a 6 pack on ice to celebrate our newly repaired boat.

Crank,crank,crank....nothing!! I ended up drinking the 6 pack that night, but I promise you it was NOT in celebration. I probably owe poor Seapickle a formal apology for all the nasty things I said about her that night.

Well back to square one again but my testing still showed a problem in the crank sensor circuit. Since the ECU and crank sensor were new, the problem has to be in the harness, but it had already passed all the factory recommended tests. I decided to start inspecting the harness inch by inch, and as luck would have it I found my problem less that a foot away from my starting point.
Wires unwrapped and placed to show original routing
Pinched Wires

When tracing the harness I found the wires were pinched in between the knock sensor and the engine block. Once I removed the electrical tape I found two of the three sensor wires badly damaged and the sensor power supply to the sensor rubbing on the bare block. I can only assume this direct short to ground is what wiped out the old ECU. I repaired the wires, she fired right up,and the celebration that ensued was epic to say the least!!

C'mon summer!


  1. Nice work - I've been down this road before myself....and it's one of the reasons I rewired my 340's engine room. You did some good work locating the problem, and I'm sure you learned a lot about the boat while doing it. Enjoy your summer!

    Dale (Masterfab)

    1. Thanks Dale! I did learn an awful lot about our boat,it's wiring, and especially the fuel/ignition control system(Mefi-4). That's all great info to know if there's ever a problem while out on the lake! I'm just happy this failure occurred while the boat was on blocks and not in the middle of our trip!

      I can't believe how much you've accomplished on Mustang!! When you first started the project I thought it looked like quite the uphill battle, but now it looks like your almost done! Great Job!! Will there be another big project after this one?