no spark on 98 DT150G

[Pbray21]

New to the forum, but looks like there is a lot of good advice on here.

I have recently rebuilt my DT150G efi 1998 model because a piston ring broke last summer and caused the #5 piston to be trashed. The motor was running at that point but had trouble at idle speeds after it warmed up, kept wanting to die, but ran great at 1500 rpm and up. Never had any trouble with it starting.

I have the service manual for this motor and believe it is a 98 "W" model according to the manual. I reinstalled the powerhead a couple of weeks ago and it cranks well but has no spark. I have been through all of the testing procedures in the manual and everything tests with in spec except for the CKP sensor and the Gear Counter sensor. The CKP test fine with resistance measurements but only has about 1 volt when cranking, book says it should be at 1.5 volts or higher. Measurement from the CKP to the flywheel is .758 mm, book says it should be .75mm. The Gear counter also tests fine with ohms but has 3 volts cranking, is supposed to have 4.0 volts or greater, the gap on the gear counter is .654 mm. Would either of these sensors cause the motor not to fire?


I have ordered new ones but they are not here yet.

I have been through all of the wires and grounds a couple of times and can't find anything hooked up incorrectly. Any direction or advice would be greatly appreciated

[Solarman]

Find the wires coming from the stator assy for the condenser charge coils, the is a low and high condenser charging coil, the low coil has to have a good ohm reading, by the manual for low rpm running and starting.

Post back on what you find out.

[Pbray21]

The lowspeed condenser coil measures 405 ohm and has a voltage output of 150 v green to ground and 160 v Rb to ground. The high speed coil has 14.1 ohm with w/r 25 v to ground and w/b to ground 23 volts

[Pbray21]

The only part that has resistance measured out of spec is what the wiring diagram calls pcs rectifier, has ohm reading of 17.1 on each location that shows there should be a reading spec range is 8-13

[Pbray21]

Found a bad ground connection near the key switch and one of the ecm grounds was not good. Replaced the pulser sensor and got the motor to fire. The new pulser sensor is measuring in spec by the book producing 1.5 volts, and the motor is running much smoother than it did in the past. Probably should have gone through the grounds more thoroughly the first several times, but I don't know that I would have found the ecm one without help, it was tight but not making a good connection.

[Murray]

That begs the question “What other wire connections are weak”? Good to hear that your back up and running.

[Pbray21]

I had the same question Murray, I went thru every wire and connection from the motor to the controls and cleaned and inspected all of them, found a couple more that were starting to show corrosion, Everything seems good now, will have to see how it runs on the water next week. Thanks for all the posts you guys have here to help us rookies out. I am new to this boating thing and not used to what salt water and wet conditions do to thing electrical.

[Solarman]

Pbray, we are no different than you. We own our boats. Work to maintain them, then some of us worked on motors way earlier in life. So, many of us have hung around, been offering to help those that have similar problems like you have had, just trying to help other owners. You are welcome to share in the experience to help others.

Thanks, and happy boating. Come back if still having issues. Good luck.