Dt 140 no power under load

[Jigging bob]

Hello,
I have a 91 dt 140 suzuki oil injected and it is carburated. With 340hrs on it & it is very clean well taken care of. I purchased this spring from a friend that's father passed away. Her father purchased new & took extremely good care of it. Boat was fogged for winter but sat for approx. 3-4 years before she sold to me. He had professionally serviced regularly.

It starts & idles fine but when out on lake hit throttle & bogs out under load? I ran entire day at low rpms tugging around runs fine, but as soon as hit for higher rpms it just blaaa & won't plane out . Sometimes it seems to surge slightly up then down, if I hit waves it sometimes surges down, but most of the time it won't get past 2500-3000 mark. Like it's dropping a cylinder then picking it up quick then in & out. No alarms going off? It sometimes comes out of it & gets full rpm until I slow it down again then tends to go back into this. Does have a crack on the bracket that holds the choke solenoid not sure that this would effect anything? I would think that only on the starting end of things.

I replaced gas hose, bulb water separator filter twice, didn't see water in gas when dumped water seperator filter Gas into a jar, put a new fuel filter strainer kit in it, changed oil injection oil out, new gas, sea foam...has good compression had a shop put carb kits in, fuel pump diaphragm kit, they also did a leak down test & said motor was. Like new yet. They also said it is flooding 3 & 4 cyl but has good spark. They are lost.

I have had to 2 shops & all I get is we can't figure it out motor is like new? do you want a new motor? This Is not an option. Seems they don't want to deal with older suzuki. I thought suzuki dealer dealt in everything not just new motors? I am extremely frustrated & love this boat but I may have to put up for sale if can't get someone in area that knows anything on these. Getting deep in dead end trouble shooting costs.

Note the day I put fuel pump diaphragm kit in it did run very well for about 2hours? Not sure if that was by coincidence? Went back to running poor soon after.

Thank you all for the help.

[Solarman]

dt140, 91, running issues

Well there are several things to check.
If 3 & 4 plugs are wet, from flooding out, do the carbs on those two cylinders leak gas when pumping the bulb tight? If yes, would check float settings on those carbs. If no, then need to check pulse coils for those cylinders. Also check gear counting coil if not right distance from teeth throws timing out. Could swap #1 & 2 coils + plugs, for #3 & 4, just to eliminate them being the problem, might break down at higher rpms?
Another possibility would be the TPS (throttle position sensor), it could be breaking down at half to full throttle, this would affect timing, but generally should show a code?
Also, when they rebuilt the low pressure fuel pump, did they look to see if the two clear discs (check valves) were intact, they can't be replaced unless the pump is replaced.
If they did a good job cleaning carbs then I would look into those things I mentioned above.
Let us know what you find out. It is a good motor.

[Jigging bob]

That was my next question. Are these good motors? Seems like a nice one when it runs good for the 2 mins it does.

I am going to get it from dealership I have it at tomorrow. They aren't to interested in working on it? I'm going to do some testing on my own. lol boy I would sure hope between the two dealerships I brought it to they would have checked those floats but sometimes it's the obvious. However I don't remember gas ever coming out of bowls?

I will check fuel pump out that's easy enough.

I also thought about The Tps sensor. There is suppose to have adjustment according to the manual but I see know way of doing this? How do you tell if it's shot? We checked with a ohms meter and seemed in tolerance.

Thanks solar man these all seem to be tests I can handle. Really want this baby to work out for many family memories. Losing a lot of sleep over this.

[Solarman]

The tps sensor is basically a potentiometer. If you disconnect the throttle linkage, connect the ohm meter to two of the leads it should have a steady reading at lowest throttle, and as you increase the throttle slowly, the ohms should change respectively all the way to full throttle. If it jumps or changes erratically during throttle movement it should be replaced. Do not try to adjust it, unless bad. If bad it should be replaced by dealership, but you could try marking the casing in several areas once you have a replacement, so you can mark the new tps identically, as the old making sure the throttle plate is fully shut. It might also be a good idea to note the ohm reading, and see if new tps ohm reading is same when you install it (hopefully it is very close at idle stop position). Again, don't loosen the mounting screws unless you're sure it is bad. The manual can tell how to adjust it, but requires a bit to set up properly, unless you have dealer equipment.

The gear counting coil is normally the first to go out, i've had to replace three on my twin 140's. All three became bloated from rust then started misfiring. This coil tells the computer how fast the crank is turning by counting every tooth on the flywheel (why it has to be proper distance to flywheel), the tps sends the signal where the throttle is, and the computer advances the timing accordingly, so the pulse coils can trigger the plug primary coils to fire at the precise time.

The coils you can swap pretty easily to test them, just make sure you hook the wires up properly. If the #1 & 2 plugs become the wet plugs after the swap, then the coils may be the problem.
read the manual for each of these items, you should be fine.

Tell us how it's going, and good luck.

[Jigging bob]

Ok Got my boat back today.
Took entire fuel pump off & squeezed ball and nothing squirted out so no leak there.
I then took fuel pump apart diaphragms seem good yet. Both the clear plastic pieces in the pump seemed to be fine.
However the back section of the fuel pump closest to the motor had black oil/gas or carbon of some sort on the inside wall that is closest to the motor. I took a clothe and It cleaned right out. Not sure why that was so dirty? I am going to order the two o rings that are on each side of the fuel pump insulator, cheap & easy to get in there.

Also I took all the spark plugs out. They were extremely oily almost like clumpy burned on oil but wet black oil/gas on them also. Wet all the way up plug thread. Cylinders also all had black oil/gas coming out of them around spark plug hole locations when removed.

I haven't ran motor do to fact that I am an hour away from the lake. I plan to go out next weekend.

Is testing Gear counting coil just an ohm test also or did you just order one & try a new one?
Thanks so very much for the help.

[Jigging bob]

One more note either the boat or the motor is reaking of gas fumes horribly. It stinks up my whole garage. I do not notice any leaks or carbs wet? I have a pretty large garage & Even with my garage door open stinks bad? I can't tell where it's coming from? I thought it was the vent this summer when it was hot but it's doing it today & it was a nice 60 65 degree day? This puzzle is making me nuts. Lol

[Solarman]

dt140, 91, running issues

The heavier gas smell in enclosed areas, may be related to evaporation of gas from multiple carbs. And/ Or, could be the gas spilled down inside Cowling from working on the motor. And if floats in carbs are set too high, gas may sit in throats of carbs. Evaporation of gas happens at all temps.

Gear counting coil is a simple ohm test, just connect the two leads to the two coil wires, turn the flywheel by hand till several teeth pass the coil. consistent readings on each tooth and space are good. Erratic readings/ not consistent - replace.

The TPS/TVS should be steady reading at lowest throttle, and smoothly change to highest throttle. If it is erratic anywhere from lowest to highest throttle position - replace.

You should check your readings several times on each.
Let us know how it's going.

[artdf175]

Having gas fumes on an enclosed space are extremely dangerous
How full is the main fuel tank?
I had a very serious situation a few years ago I brought my boat into the garage for storage. Gas expanded and dripped -a lot- out the vent. Could have been a disaster
I would be very careful where you park this until you find and fix the fuel leak
If your tank is full. Try removing a few gallons

Not familiar with the older motors but when you pump the bulb I was under the impression that fuel should make it all the way to the carbs so not understanding your comment that no fuel was getting past fuel pump

[Solarman]

dt140, low pressure pump test

I had thought he was just checking to see if fuel was leaking past the diaphragms, or around edges of pump itself. Was also thinking he had carbs still connected and pumped bulb tight to get pressure on the pump after removing from motor, 2 stroke.

[artdf175]

Fuel problem
Can I make the assumption the main fuel tank is maybe located under flooring?
If there are no visible leaks to the extent you describe i would start looking into the main fuel source. the infill side hoses - the hose the runs to the fuel filter and to the vent. There is an inspection port the fuel tank
Have you tried to tilt the boat up in the front with the drain plug removed to see there is any raw fuel in the bilge?
Unless there is fuel dripping from the carbs / filters / pump I would rule them out as the source the leak
And can only suggest the highest degree of caution working around the fumes you are explaining damn dangerous situation

[Jigging bob]

I will try to clarify I took fuel pump off the motor & squeezed bulb to see if the fuel pump diaphragms leaked. I then reinstalled fuel pump then pumped bulb to see if carbs leaked - all good. Yes carbs are all hooked up I've never had the balls to touch them. Lol Not sure if by pumping bulb fuel would get all the way to the carbs?

It stinks with full tank or half tank or near empty tank. Motor is on a 1992 crestliner phantom 19ft boat with a floor. The access ports don't get me in very far to see what the Heck is going on under there. Don't worry i won't stick my head in there with a cigar. Lol I may try and take part of the floor out if I can get time after work one of these nights.

Just past the bulb on fuel hose / connector close to motor I did find that there was a pretty good hose leak at the fuel hose connector- the hose clamp that clamps down on the fuel hose was not sealing tight on the fuel hose connector barb. When I Pumped the ball and blew a lot of air and spit gas out. Easy fix. Not sure if this would cause all these running problems until this weekend.

Thanks guys, I'm going to keep trying to wear this problem out.

[artdf175]

That could sure explain the reason for power loss at full throttle as it would be pulling in a lot of air
This may also be draining out fuel when motor is not running. Could leak out a full bulb of gas and maybe more
If this connection is not good would for sure check all connections to be safe
Good luck and keep us posted
Art

[Jigging bob]

Was bored and redid all hoses going to the gas tank under the floor all the way to the motor. However, I Did not redo the vent hoses they seemed fine. I also made sure all gas lines to carbs were routed correctly the dealership had the fuel pump gas lines going to wrong carbs compared to the manual. Fixed all these made sure no leaks in all other hoses in motor going to carbs pumps... Also put new o rings on the front and back of the fuel pump isolator. I felt good about things.

got out Sunday had to just keep strapped on and ran on trailer with motor dipped in water. To choppy and cold lately up here to take out on lake.

So started right up ran for a bit at idle but had a tick at same time every time ever so often. Motor would almost die every tick. Got less and less but it was Like it went around so many times and would tick and cut down for a split sec then back running fine again then tick would nock it back down again. Randomly but consistently if that makes sense. Not sure if it's a sneeze seems more of a tick to me?
Thru all this the oil alarm kept going off if I let off throttle it would go away then rev it would come back on. Not sure if motor or I did this on a sneeze but while I was messing around trouble shooting But did end up actually blowing the number 3 carb hose off along with a oil check valve hose off same 3 carb. but I was aggressively messing with the bulb, pumping it hard not sure if that did it?

I put all back on and decided to take the in line oil flow sensor filter apart it was very plugged and caked with sludge. We cleaned all out made sure oil was flowing thru this and the oil injection tank and put back together. Oil alarm stopped going off but motor still had that damn tick or hick up. Ran even better.

When tick hits it actually makes the bulb hose and fuel pump hose going to number 3 carb jump at same time this tick hits. I put in gear revved up and it would still do it but started to get less and less to point barely did it but still would sneak in every here and there. Slowing down to lesser rpm made worse. It ran just great until that tick would come thru again? Then great for 2 seconds sometimes 10 seconds sometimes 30? Random. Sometimes I also had to choke to get started if it died at one of these ticks.

As whole is running better. But still not great. Plugs are all burning on all 4 cyl so that's farther than both dealerships got that I brought it to.

So tick? We thought maybe timing or counting coil? messed with counting coil but now runs worse. How far should that be away from the gear should this be?

I was reading another post and it ended up being a cooling water sensor? We removed and It seemed to work mechanically when removed but not sure testing elect of it?

So in a nut shell we are making some progress but I am running out of time "winter" coming soon and ideas.
Thanks again

[Jigging bob]

Reeds? One mechanic I had do carbs said he checked reeds but not sure guy could check what way up is Lol are these reed symptoms not sure what they even do?

[Moonlighter]

Look, im no expert on these engines, but a "tic" accompanied by a stumble of the engine could be as simple as a bad spark plug lead, boot, or indeed a plug itself, shorting out every now and then. You can often see a mark on the lead when this has been happening so worth a look. If you can get it going in the dark with the cowing off, a spark in the wrong place soon becomes obvious as well.

Good luck, you are getting closer!