Very hard to start when cold (DT75)

Hello everyone,

Sorry my first post has to be a request-for-help, but I'm kind of at a loss here as I don't know too much about outboards. Some background info before I start, the engine in question is a Suzuki DT75. I bought the boat as a project (which I won't ever do again!) and I had the carbs rebuilt last month since the engine had been sitting for a year prior to me getting it.

The engine's compression is 120 on each cylinder. I have new fuel lines, a new primer bulb and a new water separator installed.

When I prime it, the primer bulb does get hard. But when you crank it, it cranks and cranks, and finally sputters, but won't run. When I crank it I am making sure the choke is activated; the choke does work and closes the butterflies when the key is pushed in. (Which, by the way, is a pretty annoying way of choking the engine if you ask me)

Now I know it isn't necessarily a good idea, but I sprayed some 2-stroke starting fluid I got at a marina directly into the carbs. Choked it and cranked it, and it fired right up and ran great - provided I kept the choke closed. It ran for probably a minute or two, so it was obviously using its own gasoline supply, but as soon as I let up on the choke it died.

So, I have basically two questions:

1) What would cause the engine to be so cold blooded? Like I said the carbs were cleaned out, fuel lines replaced, and fresh gas used to run it. Spark plugs are new. Perhaps a weak fuel pump?

2) If I am going to have to keep the engine choked for a long time to warm it up, is there any reason I couldn't wire the choke up to a switch on the dash - I am not sure I have the patience to sit there pushing that key in for 10 minutes.

Any insight or info is appreciated. If you need more info, don't hesitate to ask! Thanks!

Obviously something is wrong here.--------------Check to make sure you have spark that will jump a gap of 3/8" or better while cranking with the sparkplugs in. A weak battery / starter motor may not crank the motor fast enough for the ignition to work.-------------No way should it take 10 minutes to start this motor.---------Best to trouble shoot and fix the problem.

racerone,

Thanks for the reply. I am not sure how much the spark plugs will arc, I will try and have someone help me with that this weekend. (I can't crank and look at the spark tester at the same time...my arms aren't that long).

The battery is new and the starter was replaced recently; it turns over well.

Some updates; I messed with it some more yesterday.

I fired it up again using the starting fluid, and just let it run for a bit (keeping the choke closed). It probably ran for about a solid minute at idle before it sputtered and died.

This time, I cranked it without spraying starting fluid into the carbs, but kept the choke closed, and it fired up and ran, but only for about 10 seconds before dying off again.

I tried several more times - sometimes it required starting fluid, sometimes it didn't, sometimes it wanted the choke closed, sometimes it didn't. But the end result was always the same - it would fire, run for about 10-20 seconds, and then lose power and die. During the 10-20 seconds, it seemed to run strong. I tried once to "feather" the throttle to keep it running, but that didn't work.

I am beginning to think I may have a fuel pump issue. I did notice that my primer bulb does get hard, but I can always still squeeze it somewhat, even after its supposedly hard. I am not sure if this is the way it is supposed to be, or if this means fuel is getting pushed past a bad diaphragm.

The primer bulb issue combined with the running only for 10 seconds issue makes me think I may need to replace my fuel pump diaphragm.

But, since I am new at this, opinions from more experienced people are much appreciated. I never really feel like I am certain of what my next step should be.

If you need to keep choke " on " while running it indicates a problem in the carburetors ( dirt / blockage )-----------If you can continue to squeeze the bulb ( manual fuel pump ) , the fuel is going somewhere. Check for a hole in the pump diapragm.--------------Get a helper to check the strength of the spark and that you have spark at each cylinder,as that is important.

I'll think I am going to go ahead and replace the diaphragm, its cheap enough and it will eliminate that problem. I am nearly certain at least one of my problems is there.

I'll have my younger brother help me with the spark issue tomorrow. I did check the spark awhile back and had it at all 3 cylinders, but since I was doing the cranking I don't know how far it was arcing since I couldn't see it and I just had my helper verify it was sparking.

Thanks for the help so far!

Ok, here is the latest:

Today, I replaced the fuel pump diaphragms, the fuel filter and the little rubber seal that goes with the fuel filter.

I also wrote down exactly what I did and what happened:

Attempt #1
-Used starting fluid and the choke was closed
-It started easily and ran smoothly for 15 seconds with the choke still closed.
-After 15 seconds, I opened the choke. The engine sped up, ran for another 5 seconds or so and died.

Attempt #2
-No starting fluid
-Choke closed
-It started easily and ran smoothly for 5 seconds with the choke still closed.
-After 5 seconds, I opened the choke. The engine sped up, ran for another 5 seconds or so and died.

Attempt #3
-No starting fluid
-Choke open
-Started easily and ran for 2-3 seconds and died

Attempt #4
-Used starting fluid.
-Choke closed
-Started easily and ran smoothly for a full minute with the choke closed.
-After 1 minute, I opened the choke. The engine sped up, ran for another 5 seconds or so and died.

Attempt #5
-No starting fluid
-Choke closed
-Started easily and ran smoothly for AT LEAST 3 minutes with the choke closed.
-Sometime between the 3 and 4 minute mark, I opened the choke. The engine sped up, ran for another 5 seconds or so and died.


The pattern, which is easy to see, is that when I open the choke the engine ultimately dies. When it was running with the choke closed, it was idling fast and strong - I should also note that I had the idle speed switch set to Fast Idle.

So what would cause this? Should I just let it idle for 10 minutes or so with the choke closed to let it warm up? I was told that I should be able to let up on the choke right after the engine starts.

Or is there something else wrong, that when the engine starts sucking in more air, it can't deliver enough fuel to compensate? Like I said, the fuel pump diaphragm and filter are both brand new.

Anyway, I appreciate your helping me with this wordy posts. Thanks so much.

there is a blockage in the carburetors-------------------They need to be cleaned / inspected again.-------------------Or the low speed idle needles ( if equipped ) need to be opened up.

Fairly thourough testing,----------------Each test indicates a LACK OF FUEL.-----------------After it quits and stalls, drain the carburetors to see if they are full of fuel or not !!!!!.

I apologize for such a basic question, but how do I drain the carburetors?

Also, someone suggested that I run some fresh gas with Sea Foam in it to help try and clean out the carbs. Any chance this would help, or would it just make a smokey mess?

Carburetors can only be " properly cleaned " by taking them apart.------------There are just too many small jets and parts that " mechanic in a can " will not clean.Cleaning the carburetors is not really that hard to do. If you own an outboard it is a good skill to learn.----------------Before a boat is taken out of the water the best thing to do is disconnect fuel and run it till it stops.

The prospect of rebuilding the carbs isn't that scary to me, however I was reading in the Clymers manual that the carbs on this particular engine have to be "balanced", and it requires some sort of Suzuki gizmo.....that part is what scares me!

If you take them apart carefully and note the linkages ( digital pictures ) it is easy.----------------Do one at a time.--------------Note that carburetors must be fully closed at idle.-------------------I am sure that after you are done you will be proud and and say " that was easy "----I think this balancing is a bit overstated.

Sounds good! I'll take the carbs apart! (one at at time)

Looking at the ---------brown's point ----------website---------------On the parts pictures I do not see any pitfalls.Linkages snap into place and main jet is in the nozzle. Thus the main jet sits in the bottom of the bowl , where all the dirt/ water would be.Not sure which year/ model you have but drain screws also appear to be on the float bowls.

Well, the mechanic I used the first time said he'd rebuild the carbs again; should have it back next Sunday. I will post the results!

And I'll probably start a new post - why isn't my engine charging - but I will wait to get it back to do that.

Thanks for all the help!

any luck with it

Sorry for the delay.

I got it back from the mechanic's on Sunday. I wanted to fire it up and see how it ran there, but the weather was kind of nasty outside so I just took it home. The mechanic said that the carbs had a bunch of junk inside them; so I am fairly confident that was the main problem.

Tomorrow I am going to see how she runs, and if I can I'm going to test it on the water.

I will post the results! Thanks for all the help.

thats good i was wondering what he found

Well, there has been no change. It still does the exact same *$^#* thing.

I am VERY close to swearing off this hobby for good.

But, what else could it be? The carbs were JUST rebuilt, the fuel pump has been replaced, the fuel lines have been replaced, and I was running fresh gas.

I even tried to rev it up to keep it running, and it would run strong for a few seconds and die. It has to be a fuel delivery problem, but for the life if me I can't think of anything that would be restricting the fuel flow at this point.

Slight update: i was messing with it some more, and I noticed gas leaks out of the carburetors after it dies.

Perhaps the floats aren't set right?

Who / what qualifications does the party who is working for you have.-----------------Fuel leaking out of the carburetors when squeezing the primer bulb ( manual fuel pump ) or when motor is running, indicates float valves are not sealing.--------------This really should be a simple problem to solve.

At this point, I think its safe to say the guy who was working for me won't be anymore.

I took my Clymers manual back to the library (didn't want a fine ). How would I stop the float valves from leaking? I'm willing to yank the carbs off one by one myself if needed.

Most carburetors when held upside down need the float level / parallel with carburetor body.--------------Post a picture if you like.-----------------Time to learn this simple job for yourself to save money and frustration.

I think you're right. I'll take the first carb off either today or tomorrow and let you know what I find. I'll even post pics.

first buy a factory manual
second only use oem arts on carbs, the aftermarket ones suck

When I bought the boat, the seller gave me a DT75 shop manual. Has an exploded diagram of the carb.

Well, I took the top carb off and took the float bowl off. The carb looks to be pretty clean inside, and the float didn't look obviously out of adjustment. Here are some pics:

This is the float bowl removed. Its actually pretty clean inside, and the gasket is new, so I guess the mechanic actually did take this apart and clean it:



This one is the how the float was sitting without any adjustment. The shop manual says the float height should be 0.69-0.77" measured from the top of the "nozzle" as they are calling it. However, to achieve this measurement, the float definitely wouldn't be sitting level when it was upside down (I thought I remembered reading somewhere that it was)


The only thing that seemed out of the ordinary was the pilot jet. Its broken on the outside of the carb. I tried to get a pic, but my camera doesn't do well with close up shots. Looks like it was meant to have a slotted screwdriver turn it for adjustment, however the slotted area has broken away on one side.



I haven't done anything at this point other than remove the float bowl, all the adjustments are as they were when the carb was removed. I haven't taken out any nozzles, valves, or jets. This shop manual is surprisingly sparse on carburetor rebuild information, so I don't know where the idle jets are or anything else I am supposed to clean out is. I'm going to get the Clymers manual back from the library tomorrow.

Any ideas so far? If you need additional pictures let me know.

that aint clean!!!

Ok, here is the latest.

One at time, I pulled each carb off. I cleaned the heck out of it, and sprayed carb cleaner down each jet and passage. Each one was free and clear, and the carb cleaner sprayed through nicely. I cleaned off the needle valves on each one, and I set the floats for the proper height per the Clymers manual. Put the carbs back together, and reinstalled them. (Carb #2 had the float setting way off; the other two were within spec)

I also took off each fuel line and blew a bunch of carb cleaner through them.

Went to start it, and nothing has changed. At first, it would fire up, and run if I had the choke closed. When I opened the choke, it would speed up and die. One one occasion, I was able to close the choke and it stayed running. Opened it again, and it sped up and nearly died, but I was able to close the choke again and it stayed running. I did that twice; the third time it died anyway.

I should also mention that it actually ran worse now than it did before. After several attempts to start it, I couldn't even get it to sputter - just cranking with nothing happening. I had my brother check the spark at the spark plugs while I was cranking it; I had spark.

I also attempted to start it using a cheap clear fuel filter, made no difference. (To eliminate the small pinhole leak in the OEM fuel filter housing from the equation)

The reed valves didn't appear to have anything obviously wrong with them. My camera is too crappy to get a pic of them.

At this point, I am baffled. I've worked on all kinds of engines, from flatheads, to Edsels, to SBC's, to LS1 Vette engines......never had one that completely baffled me; I always had an idea of where to turn next.

I'm basically looking for what I should look for next. Its got to be a fuel related problem since I have spark, but I don't know what else to check for. I was using fuel from the same portable tank on my brother's boat; his boat ran perfectly this morning on that very same gas.

i would se all new parts on carbs

then you will need to sync them to the motor
you have to clean carbs in an ultrasonic cleaner is the best way to clean them

Found out I have access to an ultrasonic cleaner at work - never knew we had one! So I am going to try to borrow it this weekend and put the disassembled carbs in it. (One at a time; its not very big).

Any suggestions on a cleaning fluid? Is there any reason not to use carb cleaner?