I've got a DT doosy for you.

[mcgryger]

Re: I've got a DT doosy for you.

Hey Cousinabe,
It is inside the pump, however,
I don't think it's the disc anymore. I fabricated an identical disc out of some high-tech fuel resistant membrane material from my fabrication shop at work and gave it a shot and took the boat out today. The engine still has the same problem. However, the last couple times i took it out, the timing retarding problem was pretty much the whole time even during fast idle in gear but not so much in neutral. Since it's no longer intermittent at high speeds like before i think it's going to be easier to troubleshoot. I'm still going to replace the pump but i just don't think it's a fuel problem. I'm going to continue troubleshooting the ignition system. Something is screwing up the timing in the two bottom cylinders.

 

[cousinabe]

Re: I've got a DT doosy for you.

did you ever figure out your issue??

 

[mcgryger]

Re: I've got a DT doosy for you.

Not yet.
I checked the coils with a peak volt meter. According to the factory manual, every reading was too low. I just figured it was because the readings the manual gives are with a specific meter. Not all the parts with incorrect readings can be that off.
So, I'm basically at a dead end with the ignition system. I'm going to check the carbs and fuel pumps again this weekend. I have a feeling that little disc with the hole in it made its way into the lower carb and i'm hoping to find that little piece lodged in a jet.

 

[99yam40]

Re: I've got a DT doosy for you.

you stated in one of your posts that the bottom cylinders timing was being retarded.
Have you seen this with a timing light?
How far has it been retarded and is it only on the two cylinders or all of them?
That could give you some idea of which parts to concentrate on.

I my self do not see how a fuel issue can change the timing on a motor or a couple of cylinders but I am not familiar with your motor and all the sensors.

 

[99yam40]

Re: I've got a DT doosy for you.

I just read your first post and it said

"Also, when the engine drops HP the timing drops from full WOT at 20 degrees full advance down to around 5 degrees--don't ask how we figured that out, probably broke half dozen laws doing it. Anyway, based on that, we knew it wasn't a fuel problem but had to be a simple glitch in the ignition system that's controlling the timing."

See if anyone can tell you how the timing is effected by fuel if you are still seeing the timing retard like that.

 

[mcgryger]

Re: I've got a DT doosy for you.

I agree--I don't see how fuel restriction can create a timing drop that much but it does make sense to make sure the engine is getting adequate fuel. In addition, from some of the other threads i've read here, there seems to be somewhat similar symptoms with fuel supply issues.

 

[ALWAYS SUMTHIN]

Re: I've got a DT doosy for you.

Any updates? Im having a similar problem.

 

[mcgryger]

Re: I've got a DT doosy for you.

Ok, I think I found the problem.
Above I described the little discs in the fuel pump and how one had a hole with a little piece that had broken off and was missing. I finally had a chance to pull the carbs off and do another once-over and this is when I found the broken off piece. It had made its way out of the fuel pump, through the fuel lines and ended up in the bottom carb. It was blocking fuel flow through the needle valve. This broken off piece is a paper thin, clear piece about a 1/8" x 1/4"--perfect size to intermittently block fuel flow. These little discs aren't listed in the parts catalog and can only be replaced by replacing the entire pump assembly. When i checked the needle valve awhile back, i only blew through the orifice in the needle seat--didn't actually remove it for inspection. Once i pulled the needle valve seat out, only then was i able to see the broken off piece. Anyway, i'm waiting for some parts to come in before i put everything back together. I plan to test next weekend and will post the results.
Thanks again for everyone's help.
Greg

 

[mswalter2009]

Epic

Epic

tale of troubleshooting. It's like a novelette. Can't wait for the final chapter. Great job!

 

[mcgryger]

Re: I've got a DT doosy for you.

Problem solved!
Took it out this morning for a test run with no problems. That little piece from the disc in the pump that was lodged in the needle valve seat was the culprit.
Thanks again to everyone that pointed me down paths.
Greg

 

[cousinabe]

Re: I've got a DT doosy for you.

Glad you got it sorted out!

 

[ALWAYS SUMTHIN]

Re: I've got a DT doosy for you.

Hey mcgryger,
I just wanted to thank you for your posts. I have a 93 dt200. I was originally having a problem with my primary ball collapsing. I would have to squeeze the ball to keep the motor going. I removed the screen in the tank pick up tube which seem to eliminate the ball collapsing problem, but now the motor will not go above 4100 rpms. Runs and idle's fine. In neutral it will get above 4100 rpm's but it just wont get above 4100 under load. There is no change when squeezing the ball and all plugs are firing at (4100 rpm's) full throttle. After eliminating the problem up to the fuel pumps, I took them apart to install the diaphragm rebuild kits that I had already purchased and found that one of the plastic disks you spoke of were ruptured. (Is it possible I ruptured it by pumping the ball so much???? ) It doesn't look like any peices are missing (I hope). It sucks that you cant buy those little plastic disks separate, they look like they should cost about 2 cents. I already bought 2 pump rebuild kits now I had to order a $90 pump assembly in order to replace that little plastic disk. Well anyway thanks for updating your posts. My pump assembly should be here tomorrow. I will install and run the boat this weekend. Hopefully thats the problem. I will update.

 

[mcgryger]

Re: I've got a DT doosy for you.

No, you shouldn't be able to break those one-way valves by pumping the bulb.
Bummer about the disc after you already ordered. I wish I would have known; I have three that are still good that I would have given you.
Anyway, you're still having a fuel restriction problem. double check the needle valve seat. This is very important when you have any debris in the fuel lines. Any crud that the filters don't catch or piece of that disc is going to end up against the needle valve seat and slow fuel flow to the carbs. It will start fine, idle fine but won't deliver enough fuel to keep the carbs happy under load. When you get the seat out you need to check the hole where you unscrewed the seat; that's where my blockage was. You should be able to isolate which carb is blocked by looking at the spark plugs. The problem carb will create wet plugs that don't look like their getting any spark. It's getting spark; it's just not igniting the fuel because it's not atomized, the fuel is basically being delivered to the combustion chamber via large drops; this is what's limiting your rpm's without audible or visual alarms; the lack of properly atomized fuel vapor.
If the needle valve seat is clear, then there is a fuel restriction somewhere else; could be air getting in the fuel line. Check for cracks and old hard lines.