No start, and electrical strangeness

[Rivets]

Try removing the spark plug and seeing if it will spin easily. Also, make sure that you have a good 12V at the starter.

 

[mjavant]

wow, not to hijack your thread, but this same problem has been bothering me the past few days. I'm getting roughly the same voltages as you at the same locations. After getting roughly less than 5v on the starter side of the solenoid and same at the starter i was assuming it is the solenoid that was bad, and my motor spins freely once the spark plug is pulled and i checked my valve clearances and they were in spec, so idk either....:confused3:

 

[Rivets]

MJ, with the spark plug out rotate the engine by hand and watch carefully to see if one of the valves jumps slightly just before TDC. We need to check to see if the compression release is working.

 

[mudpie]

I'm pretty sure I've got it figured out. There were multiple problems.

First, the starter solenoid was definately bad. Also the starter. I put in a new solenoid and a good (though used) starter. It cranked, but slowly, which I couldn't figure out because the battery was new.

As it turns out though, the new battery my brother had bought was only a 200 amp, which didn't have enough juice to crank the 18hp motor.

I put a 285 amp battery in it and it cranks fine, but still wouldn't start. I pulled the fuel line and found no fuel flow when cranking, so I'm assuming a new fuel pump will finally make it run. Haven't got their yet though.

 

[Rivets]

Before you buy a new pump test it by removing the fuel line to the carb and turn the engine over. If no fuel comes out the line, either the pump is bad or the pulse line. Is bad. Pulse line should be checked for cracks and/or air leaks.

 

[mudpie]

I'll check the line. My mower shop guy is pretty good though...he's not out to just sell me parts. He also suggested checking for fuel flow. When I pulled the line off, there was no flow at all.

 

[Rivets]

If the pulse line looks good, you'll probably looking at a new pump.

 

[mudpie]

Well, I spoke too soon. It cranks great now, but still won't start.

I replaced the fuel pump....no start.
I bypassed the fuel filter....no start.

In the process of replacing the pump, fuel began flowing from the tank when I pulled the line off, so it's obviously getting fuel to the pump.

The line from the pump to the carburetor is new....came with the pump. The line from the pump to the oil fill tube seems good. I blew through it to check for blockage, and blew into it with my thumb on the other end to check for leaks. Nothing. Just in case, I swapped it with the old hose that went from the pump to the carb, and the mower still didn't run.

I'm so close that it's become even more frustrating. The electrical issues are worked out, and it starts right up and runs fine for a few seconds when I pour a little gas into the carb.

Any thoughts on why it's not drawing fuel on it's own would be much appreciated. I'm totally out of my element with mowers.
:mur:

Thanks

 

[Rivets]

Two things. Have you checked to see if you spark, I'm assuming yes. You said that the pulse line comes off the fill tube. Is the fill tube cracked? Also, does the dip stick fit tightly? Both of these could cause low crankcase pressure. I can't remember, have you sprayed some carb cleaner into the carb air horn to see if it will start that way? Some things to check.

 

[mudpie]

It's got spark, and does run with gas poured in the carb. I'm assuming, based on your suggestions that the fuel pump works off vacuum pressure from the oil fill tube. It is loose currently. I got tired of putting everything back together, then taking it apart again when it wouldn't start, so I've got the top shroud off while I'm working on it. The shroud is what holds the oil fill tube tight in place.

Could be as simple as just putting it all back together completely I suppose. I may end up feeling really dumb, but hey, if it runs, I can live with that.
:biggrin:

Thanks for the suggestions.