'89 Suzuki DT55 intermittent power loss/shutdown

[bassboy1]

I have a 1989 Suzuki PU55 Jet (factory installed outboard jet, but from the midsection up, it?s a DT55, so we?ll call it that). It?s been running fine until a weeklong trip earlier this month. It's set up as a tiller, so a key switch is the only thing hooked up, no gauges, warning lights, etc).

Over the course of the week, we developed a problem, and watched it get worse.

It started with an occasional power down. We?d lose power for a couple seconds, but then it would immediately power back up, and we?d go from there. I think this might have happened once or twice in the first half of the week. On Wednesday, we had an abrupt shut down in the middle of the bay, but it restarted immediately. 10 or 15 minutes further, we had another shut down, but it wouldn?t restart. I pulled the fuel hose from the filter to make sure the fuel pump was working, and when turning the key to test, not only was fuel pumping, the engine also fired right up on what was left in the carbs. A 2 ? 4 minute cool down was all it needed.

The next day, we had a random power loss early in the day. As if it lost a cylinder for a couple seconds, but then it came back on and we continued. Later, though, after a long run, it acted as if it lost a cylinder, then after a few seconds of that, shut down completely, no restart. After trolling the last couple hundred yards into the harbor, it of course fired right up. I was pretty confident that we are fine with fuel and this was ignition related, but this diagnoses was based on symptoms, not a spark test (didn?t have that equipment with me).

The next day, it started misbehaving horribly. After 10 minutes of running in the morning, it started losing power, gaining power, losing power gaining power. Very rapidly, as if someone was flicking a switch on and off. It died, but restarted. Then died shortly after. We decided to let it cool for awhile before trying to make it back. We fished for a couple hours, then started it up. It fired right up, but only made it a couple minutes before the lose power, gain power, lose power, shut down routine.

It allowed us to restart after a couple minutes, and we were able to run okay at lower RPMs, it seemed to really start acting stupid as we went faster. After a couple minutes of half throttle, I tried to speed it up just long enough to get on plane, then I?d back off to half throttle. Unfortunately, it didn?t like that, and died, but would not allow a restart, even after 10 and 20 minutes of waiting.

We ultimately had to troll in until we found someone to give a tow. I had assumed that whatever ignition component that had been ?dying? was now ?dead.? I had also assumed it was the power pack (based on sometimes losing one cylinder, sometimes losing the entire thing, and how abrupt the gains and losses were ? I?ve never experienced fuel delivery problems to be that abrupt), or CDI box, in this case.

After getting back in town, the boat sat untouched for a week, until a couple days ago, when I went to do a spark check ? the engine fired right up, and idled on the hose for 20 minutes, with no problem. Now I?m left with an engine that isn?t reliable enough to use, but isn?t unreliable enough to diagnose.

I was somewhat surprised at the price of a CDI box. The cheapest I?ve found yet is around $750. If that is the case, I?m not very interested in fixing this engine, as I?ve got a parts motor. My parts engine is a (presumed ?82, model number is missing) DT65. The ignition components aren?t compatible, but an entire powerhead swap is.

The previous owner had the DT65 powerhead swapped in place for a year or so, to get the extra hp, but then had a fuel delivery problem in the middle of the season, and instead of doing carb rebuilds, he just swapped powerheads back to the original configuration. I certainly wouldn?t mind throwing a little more power on the boat, but am also pressed for time, so I don?t necessarily want to do that if the fix for my current powerhead is simple.

That leads to my questions. Is the highest likelihood the CDI box, or could something simpler be the problem? My Clymer manual is not giving me what I?m needing here, and the wiring going to the ignition switch is not the cleanest.



-First, kill circuit from the key switch. How does it function? Does it open a circuit to shut the engine down, or does it close a circuit to ground? Would high resistance in a connector possibly cause these problems? Seems unlikely for it to be the culprit of a partial power loss.

-Second, oil injection. I don?t have any gauges or warning lights connected, so no help there, but if the sensor for that was faulty, what would the symptom be. Can it shut down the engine. Oil is not low, and level is dropping, so it seems to be working, but I?m curious if a faulty sensor or bad connection in that circuit could cause this, or if it only powers a light/buzzer.

-Thirdly, temperature sensors. Can they restrict or shut down an engine, or do they just flash idiot lights?

-Any other simple sensor or circuit I?m missing? If there?s a high possibility of something simple, I?ll spend the time doing some testing. If the high possibility is the CDI box, I?m simply going to swap powerheads, and chase the fuel problems on the spare.

 

[bassboy1]

Not that it makes a whole lot of difference, but my spare engine is actually an '85-'87 DT65, not an '82 as previously assumed. The '82 isn't even remotely similar. The part numbers for the CDI are different, but the overall ignition system is more similar than previously thought.

 

[mphelle8vld]

I have the same jet (remote) with shop manual, what's the four digit number printed in white on your cdi?

 

[bassboy1]

The '89 jet has CDI #9472.

The spare DT65 has been narrowed down to an '85. It has #F8T09471 and 4Z26


The reading that I've been doing suggests that there is no failsafe that results in a shutdown. It appears that in a low oil or overheat situation, the engine is designed to throttle back to 3k revs, not shutdown completely. This apparently eliminates the possibility of a faulty sensor giving bad info to the CDI, as I had a complete shutdown multiple times. What I thought was a cylinder loss, however, could possibly have been a 3k restriction.

By my understanding, this pretty well puts my issues either in the CDI, or perhaps the ignition/pulser coils under the flywheel, or a shutdown circuit malfunction.

 

[mphelle8vld]

Your 89 is the K model, I'm currently running an 85 DT65 powerhead, only gives about 300 more rpm but it's noticeable. Some of the early DT's had problems with labyrinth seals so keep that in mind if you decide to swap and start chasing carb issues, strange that the PO told you that he swapped powerheads rather than cleaning the carbs. Are you using a Suzuki tiller handle? It should plug right in to the harness, post some pictures of the questionable wiring, your issue seems heat related but both the kill switch and the ignition switch ground the green wire to the CDI to shut the motor off. I don't post copywrited manuals to public websites but if you want specific tests or schematics send me a PM with your email.

 

[bassboy1]

I'm using a factory tiller handle, but it is mechanical only (throttle and shift, no electronics). Someone installed a generic key switch in one of the holes on the front of the lower cowl. No kill switch present. I do possess a remote handle with wiring harness, and I also have the dash gauge that contains the idiot lights, but none of that is in use.

There were actually two previous owners, and I personally have known both for years. First one was the guy who did the powerhead swap in lieu of a carb rebuild. He told me he fiddled with the ones on the DT65 a couple times, but had a couple repeat problems, so he didn't want to waste time waiting on a set of rebuild kits. He ran the engine remotely instead of tiller.

Second previous owner was the one who setup the key switch in the motor and put the tiller back on. I don't know why he kept the long rats nest of grey wire (it's long enough to have made it to a console) coiled up in the hood instead of cleaning it all up when he installed the switch, but that's how he left it. It has been on my short list to clean up (I've only had it in the water for about a month), but the rest of this boat has been a bit of a problem child - I've had to start by fixing more pressing issues - since that still worked, I left it.

After looking further, the mess is all outside the factory round plug, and just deals with the key switch (start, choke and shutdown). What's between that plug and the engine is more or less untouched.

I also traced everything that is taped away. Low oil reset button isn't hooked up. Coolant sensor at top of head (above #1 cyl) isn't hooked up. The 5 prong square plug that goes to the dash idiot light cluster isn't hooked up.



I can't think of any way the ignition switch wiring could give me the symptoms I had, especially since the switch closes the circuit with the green wire to shutdown (I could believe high resistance from a corroded connector giving me problems if the switch had to open a circuit to kill), so it sounds as if we are back to CDI, unless you can point out a flaw in my logic.



I have the Clymer manual that covers all Suzukis from '85 to '91. It has wiring diagrams and some test procedures. My issue is that it doesn't act up at the shop, so I'd have to do any diagnostics in the middle of the lake, after it's decided to act up, but before it decides to start working again.


My spare DT65 has a broken head bolt and the wrong carburetors (from an '83 2 cylinder 60hp). I can likely take care of the head bolt and can certainly rebuild those carbs, but that's a fair bit of work, and I'm not sure if the improper carbs will give me any issues. I wouldn't complain about the extra ponies, though.


It looks like my best option is to pull the whole ignition system from the DT65, and put it on the DT55. The pulser coils and primary coil under the flywheel have the same part number for both engines, so it really looks like I just need to swap the contents of the plastic electronics box (CDI, coils and whatever else is in there) and the ignition timing dial switch. The upside to this is it is quick and easy, the downside is that it is a more primitive system.

 

[mphelle8vld]

I'm unaware of a cooling sensor on top of no.1, it could be the gear counting coil but if it's not connected I'm not sure how it's running. The only difference between the 55 and 65 is the carbs and intake manifolds, the 1985 uses a simple dual switch on the middle carb for timing, the 89 uses a sensor to more accurately set the timing so the motor harness would have to be swapped also. Your photos don't show up.

 

[bassboy1]

I'm unaware of a cooling sensor on top of no.1,

I lied. It's actually on top of #2. Cooling water sensor, part # 34870-94630 My photographic memory isn't as good as I thought, apparently.

The gear counter is definitely hooked up.

Not sure why photos aren't showing up. I uploaded them through the site, and they are showing up on my end. Is external hosting still necessary on iboats? That said, all they show is about 15' of bundled up thermostat wire with red butt connectors going to the aftermarket ignition switch, so you're not missing much.

I see the dual switch you are speaking of - that swap still sounds doable, so I think we'll take care of it this weekend. Not real crazy about dealing with a broken head bolt, or how ever many others are still frozen, and it certainly beats retail price for a CDI.

Thank you for the help!!



Last question while I've got someone who really knows these things:

I had based my observation of incorrect carbs off this parts breakdown from Browns Point. It clearly shows the DT65 carb as looking identical to the DT55 - hinge for the float is at the center back of the float bowl. Back of float bowl is beveled on both corners.
http://www.brownspoint.com/store/pc/pdf/DT55_65(85-87).pdf#page=9&zoom=auto,-249,41

My carbs have the float oriented 45 degrees different - hinge is in one corner, and the other corner of the float bowl is ogee shaped. As such, I thought I had the wrong carbs, and started looking at all of the breakdowns on Browns Point until I found a match. Hence why I thought wrong carb.


For whatever reason, I tried to search for the DT65 carb on Ebay, and found one that looks exactly like what's on my parts engine. Can you confirm that the breakdown in the link above is incorrect? If the carbs on my parts engine are correct, I'll consider swapping them and the intake manifolds over to my DT55 block at a later date. I couldn't figure out why that engine would have the wrong carbs.

 

[mphelle8vld]

I would tackle the head bolt and check compression before trying the swap, still not sure what's going where but the connectors from the 85 cdi won't match the 89. I sent you a PM

 

[mphelle8vld]

The carbs are most likely original to your DT65, the 1985 was the only year that used the plastic cam operated switches on the middle carb. If you rebuild them, take note of the jet sizes.

I should also mention that the throttle shaft of the 85 middle carb is not machined to utilize the 89's throttle position sensor.

 

[bassboy1]

The carbs are most likely original to your DT65, the 1985 was the only year that used the plastic cam operated switches on the middle carb. If you rebuild them, take note of the jet sizes.

I should also mention that the throttle shaft of the 85 middle carb is not machined to utilize the 89's throttle position sensor.

I was looking at moving the entire wiring harness and igntion from the parts engine to my good engine, as the parts engine is in rougher shape (may have been a salty engine), and I know the mechanical portions of my '89 are sound. I saw the same thing you mentioned about the throttle position sensor being carb specific, so if I went that route, I'd have to go ahead and swap carbs and intake manifold. Suddenly that idea isn't as desirable.

I just did a cold compression test on the parts engine, 130 - 140 on all cyls. It has spark. I pulled the cylinder head to try and tackle the broken head bolt. The water jacket has a bunch of pieces of a destroyed water pump impeller, and about half of the head bolts are very rusty (but they did come out without a fuss). I'm going to mess with the broken bolt here for a little while, and really check over the condition of this parts engine before deciding if I use it, or swap all the accessories.

 

[mphelle8vld]

While you're soaking the bolt with PB blaster, check the resistance of the gear counter coil. It should be 170-250ohm, it may read good, up to you if you want to heat it with a hair dryer to try and get it to fail.

 

[bassboy1]

While you're soaking the bolt with PB blaster, check the resistance of the gear counter coil. It should be 170-250ohm, it may read good, up to you if you want to heat it with a hair dryer to try and get it to fail.

That's a really good suggestion.

I'm getting 210-225 ohms on that, even with external heat applied, so that looks good.

Also, the engine will fire with that unplugged (accidental discovery), but only runs for a few seconds before coughing and dying. Also, with that unplugged, it will still restart (for a few seconds) after dying, so that isn't the same symptom I had on the water when it wouldn't fire at all after dying.


I built the broken stud on the parts engine up to past flush (TIG weld), and then TIG welded a piece of scrap flatbar to it to twist it out. Took multiple tries with penetrating oil sprayed in between tries (while still hot), but it finally came out.

 

[mphelle8vld]

Nice job on the bolt, I'm surprised the motor fires without the coil, good info.