She's got compression, spark and she cranks ... but won't start

[zul]

Tested compression and spark today, check. Popped on the ear muffs and the motor cranks and cranks. No start.

I've had several looks into the fuel filter over the last few weeks and found clear fuel at times, greenish/yellow fuel other times. I think that the oil pump is working sometimes and not sending oil at other times (yikes!). Had a good day on the lake 4-5 days ago. Everything went well all day. Throughout the day I had blue smoke and was burning oil with sea foam in the gas tank. Lots of idling, plenty of low rpm running and some WOT. Later in the day, when I hit the throttle it bogged down, lost power. Start, Idle, hit the throttle ... bogged down (twice). Idled to the dock and she wouldn't start again. Cleared the filter and could only get clear gas again.

All was good until ... the ... end of the day. Sputtered out and won't start. Help?! Ideas!>?

 

[ibrw1]

Wow, 1st, never spray that ether crap down the carburetor to get engine running. My neighbor did that and destroyed his engine! Turns out only issue he has was a loose hose clamp between the gas tank and the bottom of his fuel pump. Can you connect a CLEAN SOURCE of gas? Did you change filter? Can you dump all the gas out of the tank? What engine is it? What year? What is engine serial number?

 

[Chris1956]

Yes, tell us the year and HP of your motor. If you have oil injection, I would recommend premixing your fuel, until you get the motor sorted out.

If you have compression, fuel and spark, either the choke is not functioning correctly, or the timing is off. Does she crank fast enough to start. Most need 300RPM or so to start.

 

[zul]

1996 75 hp Merc. It cranks plenty fast and normal. I can hear the choke engage at turn key. The gas tank is internal, so I can't dump the gas all that easy.

I wanted to pre-mix one gallon of gas but my neighbor was worried about 'too much oil' or 'double oil' screwing up the motor.
For testing purposes I got a 1-gallon tank that I intended to pre-mix. I was planning to disconnect the regular fuel line (drain it) and set it into my 1-gal with 50:1 gas. Is it OK to do that? Does the hose need special fastener? Will air or possible spill factor be a safety problem? I can make sure that the hose/tank doesn't spill in the control of my garage... but... if I can do it up safe, I'll do it the right way. I spent hours online trying to figure the proper way to get a small separate fuel can set up ??

With clear gas in the fuel filter, I think the oil pump isn't working. And that leads to the worst of things, me thinks. Other troubleshooting ideas are welcome!

 

[Chris1956]

Double oil will not harm the motor. It will simply smoke more.

The way I understand Merc oil injection, is that oil in the engine-mounted reservoir is gravity fed to a pump. The pump pumps the oil into a line that is tee'd to the gasoline line. The gas and oil mix at the tee. So, depending on where you look at the fuel, it may be mixed or not.

Well, the first test I would do is put my hand over the carb throats and crank the motor to see if it will start. If not, you have eliminated the choke as an issue. Next is to advance the throttle in neutral (if you can) until the carbs are just ready to open. Now put a timing light on the top cylinder and crank her. Note the timing. That timing number should match the idle pickup timing. 0-9* ATDC is a usual idle pickup timing spec. See what you have.

 

[zul]

I'll try the covering up the air intake and see if it starts. The timing light might go above my skill level and tool set. Maybe get er to a mechanic this week?

There is approx 8 gallons of fresh gas and (sea foam) in the tank from 5 days ago. Should I add some oil to the tank? If I can get a working motor I'm going to cap the oil pump and mix my own.

Overall, the web searching leads me to believe that I may have 'spun a bearing' ... which is expensive and possible game ender.

 

[zul]

No luck. Hmmm. Any other ideas? If not, it's off the find an OB mechanic in the desert ...

 

[Chris1956]

Not sure what you mean by "spun a bearing". I would add some oil to the tank to premix the fuel.

As you know, motors need fuel, spark and compression and correct timing to run. You say it has compression and spark and choking didn't help. So either the carbs are completely clogged, you really don't have spark or the timing is off.

 

[scamp12]

Can you drain any of the carbs . see what comes out . maybe some water got in there that will settle to the bottom and it will kill the motor .

 

[zul]

OK - After reading all the posts I'm beginning to think that it may be a fuel line/pump problem. I've read the FAQ on checking the fuel line but here's the deal ...

When I squeeze the bulb, fuel goes into the clear fuel filter. It fills up about 70% of the filter and the bulb gets firm. Then, most of this fuel drains back out. Is that normal?

Two weeks ago, I replaced the fuel filter. When I did that, I noticed the original fuel line that connects to the filter was only 2 inches long and makes a 90 deg bend. The fuel line that I installed has a small kink at that bend. I was careful to keep this kink in the line to a minimum but there is just no way to make that bend smooth/clean in 2 inches. After I installed this fuel line, I ran the boat for 2-3 hours. That's when it bogged down (loss of power when getting on the throttle), I was able to idle to shore and it hasn't started since.

So - Is it possible that the kink in the fuel line is preventing fuel from getting to the engine? Could the kink put stress on the fuel pump? Or damage the fuel pump??
Is there a simple way to test that the fuel pump is working and the fuel is actually reaching the motor??!!

Since, I've cut a new line to try to get rid of that kink but with the available space, it's just wanting to kink. If it is important, I can remove 1-2 inches from the NEXT fuel line but it looks like this would cause a pinch in THAT line. Again, I'll cut 2 new lines and reposition the filter if it is important to have zero pinch or kink.