98 DT 115 intermittent power loss

[Mlkurtz]

First thank you for all of the great information on this site. I've read hundreds of posts and it that's got me pretty far.

I have had the motor for about two years and averaging 50-60 hours per month.

Symptoms:

Started a few months ago with what appeared to be a failing battery, turned out to be not charging at idle, only charging at speed. Tested battery, fine. Found melted wire insulation to rectifier (red and yellow wires only) replaced rectifier and wires.

Charging returned at idle, intermittent power loss continued.

Starts fine every time. Idles fine, tach fine at idle. Sometimes runs to plane, 3k rpm, sometimes won't get passed 2k. If I back it down to idle and pick it up again, it will run fine for a time, averaging 2 minutes to 20 and then bogs down again. Seems to be progressing in frequency.

Tachometer won't read much over 4600, although WOT speed seems to be holding when I can get it there (what used to read 5600+ at same WOT position).

Ran it 60 miles yesterday, both running and trolling, without noticeable frequency in power loss events, seems completely random.

4th cylinder (bottom) appears to run more intermittently than the others. Evidence to this is the condition of the plug, fouls faster, wet with fuel this morning, no evidence of water in the cylinder. Also if I pull the plug cap at idle, no change in engine idle. Other three yes. I have swapped the coil, with #3 with no change (3 runs fine with both coils).

Other known items:
New plugs.
Been through fuel system with no evidence of water or leaks, HP pump fires everytime with ignition start. Prime ball oriented correctly, there is no anti syphon valve. New fuel, ethanol or not, same result.
No water in fuel separator
New fuel tank with build two years ago.
Checked all connections for corrosion and bad plugs.
Compression even, 120 all four cylinders.
Water pump serviced regularly. Always pumps water.
Battery bench tested healthy.
New wires, leads, connections when I built it two years ago. Same with fuel lines.


My best guess is leading me to stator and coils, any other input would be appreciated. Here is what I know about the coils.

Shop manual is inconsistent with wiring colors from one page to the schematic so here is what I have: (note, I did invest in a quality multimeter, thanks again for the posts)

Resistance tests
Gear Count Coil: 218 Ohms (only test within range, does not change with position of flywheel)
Pulser Coil: 337
Condenser #1 Charge Low: 485 (0.485k)
Condenser #2 Charge High: 48 (forty eight)
Injector power source coil: 17.5
Battery charge coil: 0.00 true (yellow to red)

Attempts to connect pulser wires individually to ground, as manual states and another member here tried, without reading (ol), as it should since the circuit remains open. Perhaps I've misread something?

I could use some help with The coil test numbers and if anyone sees any connection between the forth cylinder firing and the coil numbers.

I will keep posting here all changes made and my goal is to post what actually solved the issue as it seems lots of others, with similar two strokes are having the similar issues.

Thank you.

[Solarman]

Ok. The gear count coil should fluctuate when a tooth passes in front of it, check distance to flywheel. Recheck this reading. It has to count each tooth, if not fluctuating when a tooth passes in front, should replace.

Also need to check low pressure fuel pump(s). Check diaphragms and look closely at the 2 clear discs (check valves), if cracked/ broken, need to let us know, you can't buy Suzuki kit, doesn't have check valves, have to get mikuni kit with check valves.

If you suspect #4 cylinder not running equally, are there any codes flashing on monitor?

As far as I can tell, your motor has only one pulse coil for timing, so if working for other cylinders might try a different plug in that cylinder?

Do you have a timing light? Connect to #4 and verify intermittent spark? Can committee to other cylinders to see.

The high condenser charge coil seems like a low reading, what does book say it should read?

We appreciate your thoroughness in trying to work this out, and all the info you have provided.

Is your manual a Suzuki shop repair manual, or a different manual?

Post back what you find, when able. Thnx for keeping us informed. Good luck.

[Mlkurtz]

Solarman, thank you for your input.

Just ran through the following:

The gear count coil does fluctuate with the manual turning of the flywheel. The gear count coil does show a little rust at the base and is reading at the highest resistance. Reading fluctuates from 220 +\- 30 as it turns and returns to roughly 220. Perhaps I'll add one to the list.

I pulled the low pressure pump and disassembled. The small clear check discs look flawless. The large black diaphragms appear worn, but in working condition. I would replace if I had the parts on hand. the rear two o rings and springs appear in good condition. It's is oriented on the motor with the intake at 7:00 and the supply at 11:00.

It was a bear to re prime and start, however, back up and running. I did notice some fuel fast dripping from the small hole inside the base of the air intake when it did restart. I've never noticed that before. I put my finger over and revved a few times and it stopped. Lucky? Perhaps prime related. Engine idled high and low for roughly next ten minutes while I checked with a timing light, result next, without fuel drip happening again. Seems isolated.

No codes flash on the monitor, I don't trust it's doing much though. Timing light showed all four cylinders misfiring, top seems most reliable, bottom least, but all pretty close. Tried at idle and fast idle, above 1000 with similar results.

I repeated the test swapping the bottom ignition coil, three for four again, and had the same exact result as above. All cylinders missing, guessing it fires 18 out of twenty flashes at 1000 rpm. The bottom will sometimes skip 5 or more in a row. I rechecked the leads and ground connectors for each coil.

The plugs were replaced a few days ago, I pulled them all, cleaned and replaced. All lightly fouled from last 15 hours or so.

The book says all of the readings should be between 170 & 220 ohms, excepting battery charge which should be between 0.1 & 0.3. Not sure the brand of manual, appears to be Suzuki as the format is simialr to an older print manual that was given to me with the engine. it's an online download of about 400 pages covering multiple models including mine, and the correct model year.

Currently working on pulling the flywheel to inspect underneath. So far it's proving stubborn even with a hammer tap to the center bolt. I'm setting it up with some penetrating blast/wheel puller tight and will try again in a bit.

I'll keep you posted.

[Solarman]

Ok. If all cylinders off time, would consider closer look at gear count coil, and timing pulse coil(s), also check magnets under flywheel, if any signs of cracking epoxy, replace. Also tps can throw timing out. See next paragraph.

Gear count coil, tells ecm speed of crank (must be close enough to read each tooth); timing pulse coil(s) tell ecm/ cdi when & what plug to fire; tps adjusts (advances or retards) timing for position of throttle (must be set according to book, or timing on all cylinders will be off).

Careful that you don't thread puller bolts too deep into flywheel, it can damage the magneto (~$750). The tapered shaft of crank holds the flywheel tight. Once you have tightened main puller bolt as tight as able, one good solid wack on puller bolt should free it. Leave nut on crank so crank doesn't flare out from pulley. Check key on crank to make sure it is in good condition, had a couple damaged, half sheared/ & sheared throwing timing out too.

Good luck. Post back when able.

[Mlkurtz]

The flywheel did come off. I did it exactly as you described.

The magnets and epoxy look fine which brings me back to stator resistance readings. Also there was some light surface rust along where the Pulser would read from. I have cleaned all surfaces.

I will check the TPS, which I believe is the same as the throttle valve sensor on top of the air intake.

Funny enough, from my manual, the resistance readings for a dt 150-225 are more inline with my findings, however the battery charge still reads a "0" not "ol", the original melted yellow and red wires, which tells me I have to replace the stator which houses it all anyway; would you agree?

[Solarman]

Should have an ohm reading on coils in stator. if no reading, generally means broken wire in windings of that coil. Make sure rectifier/regulator is not the problem for no charging. But if no ohms from stator charge coil, it could have burned the windings.

Check by book, your stator and coils are different from my dt140's. But burned yellow & red wires does say something.

Don't move/ loosen any timing or other coils, as they may have to be adjusted to give accurate readings again. If have to replace stator, just remove it if possible.

Yes, I think it is TVs, not tps -carb model. My mistake.

Good luck.

[Mlkurtz]

Thanks again.
Parts ordered. I will post again when I get them in and update thread.

[Solarman]

Ok, we'll wait to hear how it's going.

Post back after parts are in, good luck.

[Mlkurtz]

Getting closer...

I replaced the stator with a new, not used, part.

I ordered the two other coils, used (at a significant discount to new) but visually clean, gear counter coil and pulsor coils online, as I was not confident about my manuals stated test readings.

After doing a resistance test on all ordered parts, I found the readings to be nearly identical to those posted earlier and would confidently say for someone checking the resistance on this motor that these are correct, except for the battery charge coil, which did read 0.1 on the new stator, 0.0000 for the old.

I did not replace, or move the gear counting & pulser coils from their positions, because the resistance readings were the same as the used parts I received. I had previously replaced the rectifier with a new one.

Started motor...

Instantly you could see the voltage meter rise at true idle, change with rpms, and the voltage when running was +/- 14. Clearly an improvement.

Test runs still yield wot at 4400-4600, slow to get there, and its sluggish to get on plane. (Last year same prop, high 5) The power did not drop out like before. At fast idle under load, 1800 rpm, it feels as though there is a slight pulsing in power, very subtle but consistent.

Timing light is much more consistent, occasional skip, but nothing like before. Appears consistent across all four plugs.

I am going to pull the injectors today, visually inspect and bench test with a power source. I still suspect #4. I also received the replacement diaphragms for the LP fuel pump and will change those (the clear discs looked great).

Perhaps I'll pull apart the vapor separator if the injectors don't reveal anything enlightening, but I will start with the injectors and go from there.

[Solarman]

Before you pull the injectors, can you run a fuel rail pressure test? Look at the manual, it will show where to connect a pressure gauge. You need to know if pressure is consistent, by manual. If pressure isn't where it should be, then suspect the regulator - maintains pressure on high pressure side of pump.

Post back, when able. Good luck.

[Mlkurtz]

Water in cylinder 4

Solarman,
Just got your reply, I can test the pressure but think I've found the main remaining issue. Water in cylinder 4, the bottom.

First here's what I've done for anyone else troubleshooting...

Fuel injectors:

First I loosened the top two bolts on the oil reservoir bracket to get better access to the fuel injectors, and set slightly aside (still connected). I ran the engine at idle and pulled the injector plugs only, one at a time. All but number #4 (bottom) made a difference at idle. I also tested the voltage to each plug while running, 2.7 volts +\-, consistent.

Next I stopped motor and killed power. I pulled each injector carefully and inspected. They had clean screens, no debris of any kind; testing resistance across injectors found the same on all four. They look new.

I flipped the ignition and the fuel pump showed fast volume of delivery to the rail, which is common, fuel delivers to bottom and returns to pressure valve from top. Next I swapped the injectors from top to bottom, ie injectors 1-2-3-4, were replaced 4-3-2-1. I left the top one out momentarily and tested/bled ignition again, fuel delivery to top injector hole was instant, high volume. I replaced top injector, blew out electrical connectors and replaced oil reservoir.
Started motor and tested each plug again. Same result, #4. Then turned off.

Ignition coil (again) for the main purpose of testing power from ECM:

I pulled ignition coils #1 and #4 and swapped places. I tested the voltage delivered to each coil at idle from the ECM, ruling out ECM power delivery, consistant across all four. Then test ran boat again. Same results, 4600 +/- at WOT, sluggish to plane and speed. No more dropping out though. Guessing this issue was stator related.

At idle again I pulled all four plug caps one at a a time, still number four, definitely spark power to all plugs.

Next I killed the engine, pulled plug #4 and disconnected power to ignition coil number four (I did not want spark and open cylinder, thought that might be bad...). I started the motor taking care not to give any gas, ie no load no speed and found water, light mist ejecting with every cycle from #4. Definitely water. I'm guessing a blown gasket, or in the process of getting worse.

I repeated the test, turning off power, disabling respective ignition coil, and repeated test for #1 and #2. Both dry. (Note engine favors cylinder 3 without 4 firing, won't keep idle with plug or injector pulled so I didn't try this test for 3.

I would have thought the compression test would have shown a bad seal/crack, perhaps it wasn't bad enough yet?

Could it be more than a bad gasket seal? Could be surface corrosion or a crack, I guess I'll find out when I pull it. Thoughts?

[Solarman]

I would expect a bad head gasket, but compression test showed good?

The only other possible explanation might be a pinhole leak squirting water directly at #4 exhaust port from exhaust cover water jacket.

A leak down test on #4 (top of compression stroke, flywheel locked) could tell you if head gasket is leaking. It can't be a real bad leak, or compression would be off.

Good luck. Post back what you find.

[Mlkurtz]

Heads off

I pulled the cylinder covers/ head. They will require a little tlc, but look pretty good, the head covers looked worse than the cylinder head which was pretty clean. The cylinder sleeves themselves look great. Some carbon buildup on the piston heads. One of the small bolts sheared off removing, I only mention it because it's on #4, but not in a position to get water into the cylinder, all else came out clean.

The bottom cylinder was milky from water, cleaned and oiled.

There is a buildup of corrosion almost completely blocking one of the two horizontal coolant holes between #3 & #4 in the head. Suspicious but hard to see anything obvious with the naked eye. To be cleaned.

What I didn't notice before was a missing bolt on the engine exhaust cover. Is it too far down the line to cause a problem? I've attached a picture.

image.jpg

The missing bolt is the bottom center of the exhaust case. There are four bolts in a row from top to bottom, but it's not the bottom perimeter bolt, it's 1/2" above bottom. There is a little corrosion coming from it. I can slip a bolt in as far as the first seal but not beyond, and it won't thread. It's not hitting metal, rubber perhaps. It's in the area of my problem so thoughts?

Also, should I try to clean the piston heads more aggressively or leave be? Light solvent on rag has no effect on build up.

[Solarman]

I would investigate the missing bolt. All of those bolts are installed for a reason. The middle bolts prevent warping of the separator shield (exhaust cover plate) inside. The separator shield separates the water chamber from the exhaust chamber. This could cause the water to get in to #4 exhaust Ports.

I'm guessing someone sealed the bolt hole, maybe silicone, the rubber you feel. I'm also concerned there could be other damages?

The carbon on pistons can scrap lightly, or plan to run some carbon cleaner in future. Tank of fuel.

Good luck, post back what you find.

[Mlkurtz]

Success, fingers crossed

I'll sea trial her this weekend, but after a long idle alternating both fast (2k) and slow for about 20 minutes, it appears to be running per spec.

All four definitely firing now. Smooth and steady.

So the two main issues were the stator, and the water in cylinder #4, from a bad head gasket seal and corrosion between the cylinders.

I pulled the heads (2 cylinders per head) and cleaned off the old residual seals by placing the parts on a large sheet of fine sand paper, 320, atop a small sheet of 3/8 glass (flat surface). Worked like a charm.

I did make a trip to the local machine shop for help with the previous bolt mentioned. I managed to shear it off trying to extract it and figured I better take it in before I made it worse. For less than fifty bucks they drilled it and tapped a new aluminum sleeve into the head so it would take the same screw back. Money well spent.

Parts ordered included both new cylinder head seals, thermostat and seal, bottom plug, interior zinc, both rubber grommets and tubes between the heads for coolant. I finger tightened all bolts and then followed the bolt tightening sequence and torque.

When I pulled the heads there was no thermostat present. I did reinstall all missing parts. I left the old temp sensor port open on the head cover when I started it back up and waited for the engine to come to temp and the thermostat to kick water through. Appears to be working perfectly now. Started right away.

Note the four thermostat cover bolts are a different length than the others so keep them separated.

I also printed the bolt tightening sequence and taped it to my bench to keep the bolts organized. Also a big help.

Thank you for all your help. I will post back after sea trial to confirm.