no start issue to a flooding issue 3.7 165

[johnzonh]

Ok I am at wits end. I have the black sheep of mercs but after getting rid of a coolant leak with a riser gasket (and subsequent new head, intake, and exhaust gaskets..) couldn't get my engine to start.

did quite a few things...

rebuilt the carb during the winter (mercarb 2bbl)
had a bad starter...replaced that.
had a bad starter assist solenoid...replaced that.
needed to rule out compression issues... no problem there.
needed to rule out ignition issues...replaced coil (it failed the resistance primary test) replaced plugs, wires, condenser, etc.
wanted to make sure the coil was getting enough juice at the start..replaced the solenoid wire to coil, replaced ignition wire to rule out voltage issues to the coil.

when i realized the engine had a coolant leak, it still fired right up even with all the garbage in the oil. I didn't let it run more than a few seconds. no hydro lock. mechanically sound

ok..so after all that... this morning...the engine finally popped a few...but quit.

Could not get it to start again, added no gas.

smelled gas... which has been strong nonetheless. took off the carb... intake manifold was swimming in gas.

emptied the gas... tried again..same issue.

pulled the carb... intake full of gas... went back to my carb kit and replaced the float needle with the spring set (per instructions in many places that identified this issue)

cleaned out the carb... re set the float for the the new needle set up.

carb back on ... added NO gas, primed NONE. intake flooded again..

the carb see through tube is clear. the fuel pump is the stock mechanical, it IS pumping fine. even by hand crank of the engine. there is a filter under the pump. no separator before it. The fuel lines were inspected along with the anti siphon valve. the tank vent is clear.

I give up. I am at the end of my expertise with this thing and I just don't know where to go from here. Every thing I have done so far is to spec.

 

[stonyloam]

The line from the pump is clear, but could it be FULL of gas? just a wild guess. Do you have the needle with the little spring in it? You could try putting the old needle ans seat back in, if you still have it. I ran into similar problems with an old tractor, wound up reusing the old needle and seat.

 

[johnzonh]

I was thinking of doing that. I saved all the old stuff. Each time i have pulled that line off the carb it has been bone dry. I just don't get it. I guess I can try the old needle and seat. sighhhhhhhh. frustrating. what was even more discouraging was for the couple of times it turned and popped it didn't backfire. i didn't even touch the distributor when I did the gaskets. i wanted to try to have the same conditions before and after the gasket change. I know the fuel pump has been known to rupture and is infamous in the 3.7. but it has been pumping quite nicely. excessively annoying because all the fuel is going in my intake!

 

[stonyloam]

I can't think of anything else, unless the float has a hole in it and filled with gas, but that seems pretty unlikely. It sure sounds like something is wrong with the needle and seat, hanging up or just not sealing. Maybe setting the float a little deeper might put a little more pressure on the seat. Could be the new needle is a little short or the spring is a little soft.

 

[NHGuy]

Is there spark at the plug wires? Lay a spark plug against ground and crank it.
Is the safety lanyard in the run position?
Are the plug wires in the right positions?
Good idea to retry the previous needle & seat.
My carb book says, remove the carburetor, empty it of fuel. Test the needle & seat seal by tipping it upside down and apply vacuum to the fuel feed. If the needle seals well, plumb in a low pressure gauge in the fuel feed line to see if the pump is sending too much pressure. Most carbs want 4 to 7 pounds. Too much pressure will over come the float force on the needle.
If you first want to be sure the motor runs, disconnect the fuel feed and put a tbspn of gas in the throat to see if she fires. It will obviously not run with a bunch of fuel in the intake. Also before you do that remove the spark plugs and spin it over a bit to get the combustion chambers empty of raw fuel too.
You also say you did the head gasket, are the valves lashed right?

 

[johnzonh]

ok so here is another update. I went back and installed the original needle and seat. also went with the spring loaded setup and original float... set to specs. still didn't start but this time I found out that it wasn't spitting out fuel all over the place for a change. For once... didn't smell like gas all over.

However, after several hours of frustration and thinking what is happening NOW... for kicks tonight I plugged in my timing light...and while cranking ( since I am a one man show I couldn't test a live spark plug and crank at the same time) I got no spark from any plug. only things that have not been changed out are the cap and rotor and points...all of which seemed fine but I will have to change them out to rule out any other ignition issues. I left them alone because the engine started fine with all sorts of water in the oil.

I am limited on $$ and time... so this will have to wait for another week. the summer is wasting away and I am still here with a dead engine. I certainly don't want to drag this over to a marina and spend a fortune.

FYI for the questions about what was done...valve lash is in specs... rockers torqued to spec (closed valves) i cleaned out the intake, cleaned the plugs. This baby should be starting.

 

[boltonranger]

Check your points that could be the entire problem you don't have to replace them to rule them out. -br

 

[stonyloam]

+1 on the points. Try this, remove the cap and rotor, pull the center wire from the cap and lay it near bare block metal, put a piece of insulating material between the points, turn on the ignition and with a piece of insulated wire jumper across the points. If you get a spark every time you remove the wire, your points are bad.