Once engine dies from low idle, it will crank no start 99 speedster 787

[Toyextuh]

Hi guys, I have a 99 speedster. Both carbs on both motors have been rebuilt with OEM mikuni rebuild kits and raves have been done by last owner due to the same issue I'm stating now. I then proceeded to redo the left side carb rebuild again with OEM mikuni kits. Once in a blue moon, I'll fire up the boat at home and it will run great on trailer, I then can take it to the water same day and drive it perfectly hitting 40+ mph. Problem is, if I ever idle too low on the left side engine, it will shut off, from there it wont start again, it will just crank no start. If I go days of crank no starting at home, or once in a blue moon if I remove the plugs and crank it without it and reinstall, it will start up then I can take it to the water again and repeat the whole process. Thing is, removing plugs and cranking doesnt always do the trick. I also have a new fuel pump on the driver side. I'm running out of ideas. As of now, its crank no start on driver side engine. I have spark and I have fuel (I assume so because my plugs are wet). Even if I spray carb cleaner, it wont start up EVEN though I have spark. Sometimes, the right side engine will produce the same concern as I'm having on the left side engine. Again, the previous owner had this problem too, therefore led him to replace both rave valves, carb rebuild, and fuel pump rebuild. It was only when I took ownership. I redid the left side carb rebuild with pop off pressures at 38 psi mag and pto, and installed a new fuel pump. Both engines have new fuel lines and oil injection lines, idle 3k out of water, about 1500 rmps in water. I have to keep the idle up on left engine to prevent dying and running into this issue.

 

[POPPS]

load test the battery,,,on a fully charged battery,,,then,,,check compression to rule out simply faulty top end,,,this is not a rav problem,,,and we assume new plugs,,,I may have missed that in my reading,

 

[Toyextuh]

Compression is 145 each cylinder, new plugs gapped to .020 NGK BR8ES. When before cranking I have 12.5 V. When cranking it drops to around 11.4V on the non starting engine. Also, want to point out. Sometimes the other engine will do this too, I guess you can say that they start up intermittently and when they do, thats the time I can take it to the water and enjoy it, If I ever let it die at low idle or shut it off, it may just act up again. Meant to say these are new rotary valves not rave valves.

 

[wernerml]

Quote: "if I ever idle too low on the left side engine, it will shut off" Do you mean it stalls?

Does it seem to be because the engine is idling too slow and it stalls?

If it is idling at a reasonable RPM then maybe the low speed mixture is too rich and you are fouling the plugs. You may need to tweak both the idle speed screw (throttle stop) and the low speed mixture needle until you get an even idle at the desired speed.

Spark plugs that foul out at low speed due to too much fuel need to be removed, cleaned and dried. Sometimes a small propane torch can be used to burn off the extra fuel on the business end of the spark plugs then try to restart. (Don't cook the plugs, just flash burn the excess fuel)

The low speed fuel needle should be adjusted to just the rich side of max rpm with the throttles closed. If that's too slow adjust the speed screw and verify the mixture is still good.

It can be difficult to get the plugs clean and dry for a restart. I kind of think that from you comment about cranking the engine with the plugs out.

 

[Toyextuh]

Quote: "if I ever idle too low on the left side engine, it will shut off" Do you mean it stalls?

Does it seem to be because the engine is idling too slow and it stalls?

If it is idling at a reasonable RPM then maybe the low speed mixture is too rich and you are fouling the plugs. You may need to tweak both the idle speed screw (throttle stop) and the low speed mixture needle until you get an even idle at the desired speed.

Spark plugs that foul out at low speed due to too much fuel need to be removed, cleaned and dried. Sometimes a small propane torch can be used to burn off the extra fuel on the business end of the spark plugs then try to restart. (Don't cook the plugs, just flash burn the excess fuel)

The low speed fuel needle should be adjusted to just the rich side of max rpm with the throttles closed. If that's too slow adjust the speed screw and verify the mixture is still good.

It can be difficult to get the plugs clean and dry for a restart. I kind of think that from you comment about cranking the engine with the plugs out.

Yes it stalls and thats great advice! However, When I did the rebuild, I did 1.5 turns out low speed and 0 on high, I can tweak it as mentioned. However I do want to point out that today, I took the working engine plugs out and put it in the non working engine and it didn't start. I then reinstalled those plugs back into the good engine and fired up. I also verified that when cranking the bad engine with plugs out, I do have spark, and I even spray carb cleaner into the cylinders and tried cranking but still no go. One thing I did notice that could be correct on your end is that when I remove the plugs and crank them and reinstall and crank, it does TRY to fire up for milliseconds but never catches. I'll recheck compression and spark again this week. Whats the best way to check for fuel?