2001 DT225 looses 200-300 RPM's at around 4500

[Jetfixr]

So I pulled the VST and the can was completely clean not a speck of crap in it, Now I am stumped. Help.
Jet.

[Jetfixr]

Hello Dan and Solarman, not trying to hijack the thread however i have been paying close attention, I have a 2003 SeaPro 206cc with a very low time 1993 DT225 <100hrs, when i got the boat it had been sitting out of the water on a davit for 7 years, i changed the fuel and ran it one day it ran like a scalded dog, after that I went through and added a racor, a glass inline filter and changed to a blue ball, replaced a bunch of stuff that was just inoperative like the bilge pump, also replaced fuel lines to new CG lines. Any way i just cannot get the thing to stand up and run again, found the liner for the new fuel lines had 'melted' and was coming apart the engine just would not rev above 3K under load, no load it would bury the tach, so i replaced all the 'new' lines i put on cleaned all the filters, found trash in the glass bowl and also the last chance under the cowl, (had no idea bout the VST). So took the boat out again same crap, so now i did some more reading found out about the VST but had to go back to work. I am getting to the end of my rope with this thing and i really want to run it for a few more seasons as it is <100 hrs on the engine. I really made my boat haul the mail....when i pull the VST i will advise of the findings and the results, i cannot imagine what else, the vent line is wide open the fuel is fresh. I am at a loss. I know these DT225's are bad ass engines when they run right. Any comments would be appreciated.

[Solarman]

Dan, on some model motors they had a small cone filter inside the line just as it leaves the VST going to the high pressure pump. If your motor has this filter, remove it and clean it, then put it back just like it was, and try that.

Your stator, or CPI generally would not cause a surging problem.

Your VST float level could cause surging at higher rpms if the float is set too low (would cause motor to run low on fuel at WOT), also any trash on the back-side of the needle valve seat could cause surging at WOT, as it would be a restriction of fuel. Inspect any trash found there, it is important to know what it is.

Good luck, post back on what you find out.

[dan34685]

I agree I think its heat related. I really don't believe it is fuel related. Would a bad stator or CPI cause this? Seems like others have had similar problems. Really frustrating trying to get this diagnosed.
Thanks.

[Solarman]

After reading your posts, the primer bulb being flat could indicate a restriction of fuel getting to the bulb from the tank? Is there an anti-siphon check valve that may be giving you problems? A tank vent problem could also cause this, kinked fuel line, dirty water separator filter?

The cranking/starter being sluggish, not turning motor over could be heat related, or possibly a wire problem. Check wires from battery to solenoid, and to starter, flex them to see if any seem to crunch (possibly corroding inside insulation, reducing voltage to starter)? Also, All starters, on all motors, should not be used for more than 5 seconds at a time, as the high amperage during starting causes the starter windings to get exceedingly hot. So, too much starting, or holding the starter on too long can damage/short-out the windings, making it turn over slower and slower, until it shoots out completely.

Good luck, post back on what you find out.

[dan34685]

UPdate. Same problem today as on 4/28. Engine ran good for the first 20 minutes or so. Then I shut it down to catch some bait and couldn't get it restarted (like before). When I initially try to start the engine, I get very little engine turnover, almost like a dead battery. But after waiting 45 minutes or so I"m able to crank the starter quite a bit, but it won't start. I'm convincing myself that this is somehow related to heat as the engine runs good and then once warmed up seems to die.

[dan34685]

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[dan34685]

I replaced both low pressure fuel pumps and cleaned out the VST. Did not find anything in the VST although if their was something it may have leaked out when I disconnected the hoses.

Took it out for a spin, here's the results.

Seemed to run a bit rough when idling and then I opened it up for about 1/2 mile at WOT. Ran great. Idled through a no wake zone, then WOT again for about 2 miles. Again ran great.

Puttered around at low RPM's for 10-15 minutes scouting some fishing holes when all of a sudden, the engine started running rough and then died. When I tried to start it, it just seemed really dead, like I wasn't getting a good crank. After 2-3 tries, I primed the bulb till hard (which seem flat) and the engine fired back up. Came back to the marina without incident. Tried to replicate the problem but couldn't.

Attached a link to a few videos which may help.

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Available until May 28, 2020

https://www.icloud.com/attachment/?u...OV&sz=71798778

I didn't experience any drop in RPM's or surging (which was previously occurring along with the rough idling)

So at this stage, I"m not sure if I fixed anything at all. Could it be a vacuum issue or faulty spark plug/wire? Really don't know where to turn right now.

[Solarman]

I'm still thinking a low pressure fuel pump may be bad (a rebuild kit does NOT include new check-valves, you have to replace the pump to get them.), or the TPS could be acting up at higher rpms, but that was why I suggested cleaning the VST (especially the needle valve seat, to see if any debris is reducing the fuel flow, this could cause the surging). I would start with the VST (identifying any trash found- very important), then go for the low pressure fuel pump(s) closely inspecting each diaphragm and check-valves.

Your motor sounds like it is running slightly low on fuel at WOT. This is why i suggest these steps. Your low pressure pump(s) should provide plenty of fuel, surging only at WOT indicates low fuel in VST bowl, a restriction if fuel going into bowl, or a weak LP fuel pump(s) not sending enough fuel.

Electrical problems (TPS included) are possible problems, but they are more "on & off", not really a surging action.

Good luck, post back on what you find out.

[dan34685]

Couple of updates.

I decided to take another look under the cowling and discovered two things. One, I had a spark plug wire that was disconnected (although this may have come off when I removed the cowling) and two, the fuel filter I installed was leaking (noticed it when I pumped the bulb.) So needless to say, I thought I solved my problem when I replaced a faulty filter or fuel regulator, but caused two more problems in the process of fixing it.

Long story short, I got the boat out again, and although it ran great for the first 30 minutes, I experienced the same surging and drop in RPM's again. So, the problem still exists. The mechanic at my marina refuses to work on the old Suzuki 2 strokes but said he believed it was probably an electrical issue (bad ground?) since the problem was intermittent? I guess I can add that to my list of potential problems.

So... time to regroup. What do you think I should try next? Thanks so much for your input.

[Solarman]

Dan, I believe you could find some Suzuki service manuals online, Google your motor name, year, size, with service repair manual. It is worth the investment if you plan to keep the motor?

Cleaning the VST is not a bad idea, but always remove the float needle valve and seat to check and inspect for any debris lodged on the backside of the seat (There have been numerous situations where one or more low-pressure fuel pumps have broken-down, and pieces have lodged/ interfered with fuel entering the VST, causing a surging situation during WOT? As if the motor was running out of fuel type attitude?). When re-installing the float and needle valve assy, you must always reset the float level by the manual. If float level is too high, you may have fuel leaking out of the throat of the VST when running, if the float is set too low, the VST will run out of fuel when running at higher rpms.
ALWAYS INSPECT ANY TRASH FOUND WHEN CLEANING. It could identify/ tell you if something else is breaking-down, needs to be inspected/replaced. If you can't identify the trash, take a couple of good, clear pics on white paper towel and post them here. We may be able to help?

Good luck, post back on what you find out.

[dan34685]

One other thing, when I pumped the ball, it seemed easy to squeeze (not hard).

[dan34685]

Replaced the Fuel Regulator, problem still exists. It seems as if the engine runs great for the first 20 minutes. I pumped the ball after stalling while idling and the engine restarted but the performance was poor. I headed for home and the RPM's gradually got a bit better but not anywhere near what it was when i started. I also experienced some surging today as the RPM's went from 4 to 4.4 on their own. Still had a drop from 5 to 4.4.

So maybe my next step is the Throttle Position Sensor?

[Solarman]

Although many parts may look bad on the outside, the insides may still look new? It only matters if the parts do not work. The service manual usually will tell you how to test these items, including the pressure regulator.

Good luck, post back on what you find out.

[dan34685]

Replaced the fuel filter (15410-87D01) and fuel injector filter (15410-92e02). Ran great at first, then stalled out while idling around chasing a bunch of Cobia (dang). Got it restarted after a few attempts, and then it had the same problem as before on the 10 minute ride back to the marina.

Ordered a new Fuel regulator as the one on the engine looks pretty bad (see below). Do not have a Suzuki service manual, so i did not test the gear counting coil, nor the TPS , which requires a special jumper/ patch cord to test.

Was also thinking about cleaning out the Vapor separator?

Could this be the culprit?

regulator.jpg