unable to start Yamaha 70TLRP engine

[abeza]

Hi all,

I am unable to start the engine, have a good spark, suspected a bad fuel pump, replaced the fuel pump, same problem. After a few presses of the primer bulb, the bulb becomes hard to squeeze. Opened the line going to the top Carb,
squeezed the primer bulb, fuel comes out of the opened fuel line at a good rate. The engine runs when I squirt a small amount of fuel into the carb, stops after a few seconds. When I turn over the engine, very little or no fuel comes out of the open fuel line. I removed the fuel pump from the engine, put my finger on the hole that applies pressure to the fuel pump and I only feel pressure from the port when I slightly put my finger on the pressure port. The lines to the three carb's are ok. Any help would be highly appreciated.

August Beza

 

[JB]

Re: unable to start Yamaha 70TLRP engine

Ahoy, August.

Werlcome to iboats.

I would look for restriction in the fuel supply, August. The primer bulb is much stronger than the fuel pump.

You might have a restricted vent on your tank, restricted fuel pickup, stuck anti-siphon valve or even a kinked or pinched fuel line.

There is a small possibility that you have carb trouble, too. If you hand prime until the bulb firms up there should be plenty of fuel in the carbs to run the engine for 10 or 15 seconds. . .unless the carbs are clogged up, too.

 

[Yamajoe]

Re: unable to start Yamaha 70TLRP engine

Agree with what JB said; when was the last time the carbs were cleaned? tear down the carbs if it has been awhile since they have been done; hook up a portable tank, if the motor runs for more than 15 - 30 sec, your problem is anywhere from tank to motor fuel connector; and do the link and sinc.

 

[abeza]

Re: unable to start Yamaha 70TLRP engine

Thanks JB and Yamajoe for your quick reply,
I have a question to ask, if the bulb firms up, is that an indication that
the fuel is getting to the carb's but there is a restriction in the carb's to the fuel flow? Is there some sort of valve stuck in the carbs preventing the fuel from
entering?. I don't have a maintenance manual and have never worked on
outboard motor carb's, I have to do some research before I delve into a carb
tear down. I will do the other checks as suggested and post my results.

Thanks again, August Beza

 

[abeza]

Re: unable to start Yamaha 70TLRP engine

Resolved my problem, removed the three carb's and found all valves
associated with the floats, stuck in closed position. Disassembled,
cleaned, reassembled carb's, installed carb's, engine now starts
and runs perfect. Thanks again JB & Yamajoe for all your help.

August Beza