Spark issue, PLEASE HELP!

[ajb399]

Hello everyone! I am new to this site but I have come to find that forums really come in handy at times. I have recently bought my first Suzuki outboard but there seems to be a problem that I just can't figure out, so I hoping that someone can point me in the correct direction. I have a 1987 Suzuki DT75 that is not getting spark in cylinder #1. When I bought this outboard, I wasn't able to hear it run due to the location but I was able to at least check the compression. The compression on all 3 cylinders was 160 psi which I know is fantastic. The only thing the guy advised me of was that the carbs needed to be either cleaned or rebuilt. I also noticed that the oil injection system or has been removed from the engine so its a premix only. The guy did give me all the parts from the systems except for the pump. There is a block off plate covering where the pump was. This wasn't an issue to me since I have always had to use premix with other outboards that I've owned. I have recently rebuilt all 3 carbs, replaced the water pump and all 3 spark plugs. The is fires up and idles but it does smoke a bit. The last time I had it running, I decided to check that each cylinder was firing by disconnecting a plug wire one at a time to see if anything changed. Of course when I pull the plug wire from cylinder #1, there was no change. When I pulled the wire from cylinder #2 or #3, the engine would stall. At this point I decided to check the coil with a test light and there was no spark from the coil. I then swapped around the coils to see if it was the coil. When I swapped the coil from cylinder #2 to #1, the coil was working fine. Then I used my test light to see if power was getting to the coil from the CDI box. The Orange wire that goes from the CDI to the cylinder #1 coil was not putting out any voltage. The Blue & Gray wires that go to coil packs for cylinder #2 & 3 were both putting out voltage perfectly. I have been trying to read through the Clymer manual I have but it's very vague on the 86/87 model DT75. The only thing that I can gather from the manual is that there are 2 trigger sensors in the timer base that send pulses to the CDI box. One sensor sends the signal for Cylinder #1 & #3 and the other sends a signal for cylinder #2. Since cylinder #3 is firing just fine, I would like to believe that the trigger sensors are fine. I am feeling like either the CDI box is bad or the issue is caused by the oil injection delete. I know that there is a sensor for oil level but no flow on the 87 model. If there is no oil sensor connected, will this put my engine in "Limp Mode" and cut out a cylinder? Im not sure how the so called "Limp Mode" works on these outboards. If it wasn't for the fact that this engine has fantastic compression, I would have normally sold it for parts and bought something different. I have always owned Evinrude/Johnson outboards with very few issues over the years. I do own a 2008 Suzuki DF9.9 that is just an awesome little outboard, so I thought I would give a larger Suzuki outboard a shot. I am open to all information or advise on what path I should take with this engine, Thanks!

[Solarman]

You could try connecting the oil level sensor back in, but tape the unit into the full level position, just to see if it makes a difference? If cylinder #1 starts firing, then you will know the sensor does matter. I didn't know the earlier models did NOT have a flow sensor at the bottom of the oil tank?

If the motor still doesn't fire on #1, then you might try and find a good used CDI?

On some of the earlier motors ('87 era?) they did use a combination heat sensor w/flow switch, and there were problems with those sensor/flow switches causing "limp mode", if the flow switch hung- up/stopped reading water flow, even though the motor didn't overheat it went into limp mode. Also, some people changed out those sensors, installing wrong parts? It might save you a CDI cost if your motor has this, or if it's not working?

Good luck, post back on what you find out.

[ajb399]

Thanks for the idea! I tinker with the oil level sensor later today to see if that has any effect. As far as the oil flow sensor, according to the parts manual for the 86-87 DT75/85, they didn't incorporate the flow sensor in the DT75/85 until 1988. The only thing that my engine should have is a $5.00 round oil filter that is supposed to be inline from the oil tank to the oil pump.

I can't seem to find anything in the parts manual on a water flow sensor. I have a temperature sensor that I did test by grounding it out and it seems to be working as it should. It's almost like the 86-87 models were experimental years in new style electronics. In the mean time, I did go ahead and order a used/working CDI from Ebay for $165.00. There were a few others on Ebay but some people wanted $400 - $500 dollars for them. I guess either way, the cost a CDI is still cheaper than another outboard.