Should there be fuel in the cylinder?

[crabbie]

After being sidelined doing some renovations, I'm back to working on my '75 1500, which still won't start.

I think I've isolated it to being a fuel issue, so here's my question: if I disconnect the green wire from the switch (thus disabling the distributor and the plugs), should the plugs become wet with fuel when I turn the engine over?

Currently, the plugs are dry dry dry.

I just rebuilt the fuel pump for the sake of doing it, and fuel *is* reaching the carbs. The primer bulb becomes very firm when it's pumped up, and I can find no trace of any fuel leaks. If I cover the air intake of the top or middle carb with my hand, then fuel collects in the chamber when I turn the key. But after that?

What frustrates me is that I'd never had a problem starting this motor. Then one of the carb floats stuck, and since I didn't know to just tap the bowl, I took the top carb off, rebuilt it (along with replacing the fuel hoses between the pump and the carbs) and... now it doesn't start at all.

So I think I did something fundamental to the motor: perhaps disconnected a vacuum hose, or broken a seal or...? My (limited) understanding is that when the piston goes out, a vacuum should suck fuel into the carb end of the cylinder, then when the piston comes back the fuel is then pushed through a channel in the head to the plug side of the cylinder?

I was excited last week to find a cracked hose, but that turned out to be something else. I have fairly even compression on all cylinders. When the distributor is connected I get good spark, and I don't what I could have done to screw up the timing by fixing a carb, so I can't see it being a link-n-sync issue.

Any ideas or suggestions of things to check would be greatly appreciated.

Thanks.

rodney

 

[Chris1956]

Re: Should there be fuel in the cylinder?

Rodney, Looking for wet plugs is not a real good way to troubleshoot. Spray some 50::1 fuel mix into each carb throat and crank the motor. If it fires, your spark is good, and you probably have fuel issues. If it doesn't fire, either your spark is bad or the timing is off.

Are you choking the daylights out of the motor when trying to start? Do the choke plates close?

 

[crabbie]

Re: Should there be fuel in the cylinder?

I've tried this three times over the intervening weeks with the same result: the motor turns over (yes, with the choke covers engaged) but does not fire.

Then I would spray some fuel through the top carbs (with valve held open) and then the motor starts up right away.

So that would mean a fuel problem... any suggestions for what to check, next? I had just rebuilt the fuel pump, so presumably that's okay?

Thanks!

rodney

 

[Chris1956]

Re: Should there be fuel in the cylinder?

If the motor runs for 5 minutes, the fuel pump is working. It may not be 100% working, however that will only show up at high RPM.

Those motors are hard to start. if the starter is spinning too slow, they are even harder to start. Check the battery cables for corrosion and do a voltage drop test between the battery and the starter. The starter should have at least 9+Volts while cranking. Over pump the primer bulb to partially flood the motor. Also, check the compression. A motor with low compression will be hard to start.

 

[crabbie]

Re: Should there be fuel in the cylinder?

Okay, I'll annoy the neighbours for awhile this weekend and see how it runs.

As for the electrical system, nothing changes between not starting and starting, other than squirting some fuel into the chamber, so intuitively it would seem the spark is okay.

Definitely need a good charge on the battery though, just to keep it all turning over. Good thing I already have a good charger.

Thanks!

rodney

 

[Yepblaze]

Re: Should there be fuel in the cylinder?

Perhaps you, and your motor are used to starting with a flooding carb.

But now that you have repaired that issue, the rich flow of fuels at startup have gone.

These motors are notorious for needing a lot of choking and cranking to get going in the morning.

 

[MercFan]

Re: Should there be fuel in the cylinder?

If it helps, I have to force my carbs to flood before I even attempt a start.
check out these vids
http://forums.iboats.com/showthread.php?t=224757

 

[Texasmark]

Re: Should there be fuel in the cylinder?

Just a side note. Back in the '60's or so, Merc built a small engine industry around the concept that at trolling speeds fuel will puddle in the cylinders. So they develop their slanted fishing motors so that people who used their engines for trolling would have fewer excess fuel related problems.

Must be something to it.....having fuel in the cylinders.

I remember when I trolled a lot, I would tilt my larger, non slanted designed, engine up slightly and noticed that, after the trolling period was over, upon punching out, there was much less "cloud of smoke" indicating to me that the idea had merit.

Mark