Cdi problem? Dt55 1990

[Diverjon]

I have a 1990 suzuki 55dt that starts ok and runs fine for 10min or so at high rpm and then slowly automatically slows down rpms so that i have to idle back to the dock. If i let the engine cool awhile it will run fine again for awhile and then repeat the same thing. I'm thinking CDI.
thoughts? If I need a new CDI they are no longer available from Suzuki. Buy used? Or is there an aftermarket source?

[Solarman]

Why think CDI if it starts, runs, and then idles back to dock? If it had to cool to run again, is the motor getting too hot? What temp is the motor at the heads, and do you have any gauges indicating it might be overheating? Had the motor been sitting up for any length of time? When motor slows down, did you try pumping the fuel bulb, just to see if it needed more fuel?

We can't see/hear it run, so you have to give us as much info as possible to help identify what's going on.

Good luck, post back on what you find out.

[Diverjon]

As far as why suspect the CDI? I have attached a screen shot of the troubleshooting manual. The fifth item down fits my scenario...oil level ok, within rpm range , no buzzer, over rev limit on. The listed likely problems are defective reset switch and CDI. I have experienced problems with a bad CDI on another engine and the problems only showed up once the CDI warmed up.

I did take out the thermostat(which was bad) and ran it .....same issue. I do not have gauges or a portable temp gauge...however the overheat buzzer is not going off. I know the buzzer works.

yes the engine had been sitting for several years prior to this.

Also, I did squeeze the fuel bulb to no avail. The bulb was not contracted and the fuel vent was open.

The engine came with the boat I recently bought and the seller knew little history of the engine since he was selling it for a friend on his deathbed. So I knew I was taking a big risk and that the engine may only be worth whatever parts I could sell off of it. The compression is good. But if I can get it running without major expense then it may be worthwhile.

Thanks for your help!

[Solarman]

Ok, the rev limit is on.
And did you check the reset button, to see if it checks out, per manual? Also check the oil flow sensor, per manual before cdi change. Is the cdi getting hotter than normal?
I think I'd replace the stat just to make sure motor isn't getting too hot/cold, and borrow/buy (about $25) a infrared temp gun to check areas around the head, and cdi unit. It is not unheard of for water pas-sages to get blocked, and those areas get hotter than normal.

Post back when able. Good luck.

[Diverjon]

Well I assume the rev limit is on since the engine automatically slowly decreases rpm until just idling .
no I have not yet checked the reset switch or oil sensor.
and no the cdi does not seem to get excessively warm.
as far as I know there is no instruction as to how to check the reset switch in the repair manual. I assume one can simply attach a continuity checker and push the switch and see if it makes continuity...I'll do that now.
if I have time I'll check the oil sensor per the manual instructions
Thanks again.

[Diverjon]

Ok. I checked the reset switch with continuity. Its fine.
I checked the oil level switch. It's fine. I checked the oil flow unit. Its fine.
I dont know about the oil filter. I'm not sure where it is. I believe it's part of the oil flow switch. It doesnt appear that it can be taken apart without destroying the flow switch.

[mphelle8vld]

When you say idle back to the dock, do you mean an idle speed of around 800rpm or limp mode speed of around 3000rpm? Do you have the suzuki monitor gauge hooked up, and what are the numbers printed in white on the cdi?

[Diverjon]

I dont have an rpm gauge but I would guess idle rpm going back to the dock. I dont have a Suzuki monitor gauge either.

[mphelle8vld]

If the motor had been sitting for a long time, I would first say to clean the carbs. Since your problem is repeatable and related to heat, I suppose you can't rule out the cdi. When it fails, does the idle rpm remain constant regardless of throttle position? Let me know about the cdi numbers, I may have some parts for that motor. Where are you located?

[Diverjon]

The CDI part number is: 32900-94711.
When the engine automatically slows down the rpm remains the same regardless of throttle position.
thanks

[mphelle8vld]

Never saw one with a part number on it, here is a photo of an 89 cdi.
89 DT65 cdi.jpg

[Murray]

The CDI part number is: 32900-94711.
When the engine automatically slows down the rpm remains the same regardless of throttle position.
thanks

Check out the parts section on the site, plug in your year and HP, scroll down to the bottom of the page an you will find a list of other years and models that use the same part. Might help you if your looking on the used market.

[Frazys]

If this is still an issue or anyone else is finding these common symptoms, i would suggest dissconnecting the following switches at the bullet connectors one by one when the fault occurs to test for faulty sensor or switch and for some sort of change. (firstly) engine temp sensor, oil warning switch, the oil warning reset switch, oil sensor, oil pump valves and oil level switch. Depending on your model.