1987 3.7 165 flooding intake ...why why why???

[johnzonh]

i have put up several posts about my non-start issues with this and figured I would update again. I need help figuring out this one.

I was trying to diagnose a non start situation over the last two months after a new head gasket...new starter...carb rebuild...(Mercarb 2bbl) new coil , points, cap, condenser, plug wires. Got the engine to fire but it only lasted a few seconds... (added no gas) and then it would not start again.

I am frustrated to no end..but these are the facts...

The engine started two months ago with the existing mechanical fuel pump...no flooding...no issues ..other than water in the oil from a leaking riser gasket..so to rule out any other leaks..replaced all the gaskets. Now..no leaks... engine didn't hydro lock...mechanically sound.

-each time I have attempted to restart this motor..without adding throttle...the intake floods. I have replaced the needle and seat with the originals, have also gone to the spring loaded needle and seat. Mixed and matched needles and seats. Still...floods the intake. Each time I have pulled the carb apart..the float bowl is about HALF full. Each time I have inspected the carb...the sight tube is CLEAN..no fuel..nor does is smell like fuel. the fuel pump...works, and it seems like the carb is doing its job of halting fuel flow at the top end of the float travel.

-the needle and seats all have not stuck..and seem to close correctly.

-good compression test...

-coil voltage in "ON" is right at 5 volts

-coil voltage in "START" oscillates my multimeter...all wires appear in good working order. Just for grins I ran jumpers from ignition and solenoid connections to the coil..to ensure proper voltage was getting to the col.

-plugs..all 4 are fuel soaked. I am getting tired of cleaning them.

I know for a fact this thing is drowning in fuel... and I know it will start....it just won't stay running. (when it ran for a few bumps...it sounded good) So...let's just say the fuel pump is putting out too much pressure ( have yet to check) would it flood the carb....(the bowl is only half full at each check) or the manifold like I am constantly experiencing??? It is getting rediculous to keep having to soak up a 1/4 inch of gas out of that @#$@$ manifold every night..and I really want to get on the water.. summer is wasting away. I just give up ..and I don't know what to do next.

john

 

[glenn property of pam]

coil voltage should be higher with key on 6v seems rather low. Is that reading the voltage with the points open or shut?.
Choke is on at start up (engine cold) so it may seem fuel rich if you have to crank and crank to try starting.

 

[nola mike]

Did you say you replaced the fuel pump? A lot of reports about not having the proper gasket thickness on a new fuel pump leading to increased fuel pressure...

 

[alldodge]

i have put up several posts about my non-start issues with this and figured I would update again. I need help figuring out this one.

I was trying to diagnose a non start situation over the last two months after a new head gasket...new starter...carb rebuild...(Mercarb 2bbl) new coil , points, cap, condenser, plug wires. Got the engine to fire but it only lasted a few seconds... (added no gas) and then it would not start again.

I am frustrated to no end..but these are the facts...

The engine started two months ago with the existing mechanical fuel pump...no flooding...no issues ..other than water in the oil from a leaking riser gasket..so to rule out any other leaks..replaced all the gaskets. Now..no leaks... engine didn't hydro lock...mechanically sound.

-each time I have attempted to restart this motor..without adding throttle...the intake floods. I have replaced the needle and seat with the originals, have also gone to the spring loaded needle and seat. Mixed and matched needles and seats. Still...floods the intake. Each time I have pulled the carb apart..the float bowl is about HALF full. Each time I have inspected the carb...the sight tube is CLEAN..no fuel..nor does is smell like fuel. the fuel pump...works, and it seems like the carb is doing its job of halting fuel flow at the top end of the float travel.

-the needle and seats all have not stuck..and seem to close correctly.

-good compression test...

-coil voltage in "ON" is right at 5 volts

-coil voltage in "START" oscillates my multimeter...all wires appear in good working order. Just for grins I ran jumpers from ignition and solenoid connections to the coil..to ensure proper voltage was getting to the col.

-plugs..all 4 are fuel soaked. I am getting tired of cleaning them.

I know for a fact this thing is drowning in fuel... and I know it will start....it just won't stay running. (when it ran for a few bumps...it sounded good) So...let's just say the fuel pump is putting out too much pressure ( have yet to check) would it flood the carb....(the bowl is only half full at each check) or the manifold like I am constantly experiencing??? It is getting rediculous to keep having to soak up a 1/4 inch of gas out of that @#$@$ manifold every night..and I really want to get on the water.. summer is wasting away. I just give up ..and I don't know what to do next.

john

Howdy John
Sorry to hear about your continuing issue. If the engine is flooding it is either a bad carb setup, the carb has a crack and is leaking fuel, or a fuel pump with to much pressure. With a mechanical fuel pump I don't think your fuel pump is putting out to much pressure. Since you pulled the carb apart and rebuilt it a few times and keep readjusting and nothing has changed. I would suggest either take the carb to another shop/person (known to be good with carbs) and let them rebuild it, or buy another and try it.

My caveat with buying another is even a new rebuilt could have issues.

 

[stonyloam]

need to check the fuel pressure.

 

[johnzonh]

well that's another chunk of change I just don't have. the thing is before I changed out all the gaskets...the very same carb that was rebuilt worked just fine. It started with all that crap in the oil from the riser gasket failure. I will check the fuel pressure this week. other than tapping the accel pump should ANYTHING be dripping into the intake if I am just cranking the engine?

 

[johnzonh]

the voltage is low from a low battery... points closed. so I wasn't worried about that. I just wanted to make sure the resistor wire was functioning. The fuel pump I left alone...since it seemed to be working properly. The choke was on (closed) at startup. I will double check the clearance on the choke cold..closed position. I have the numbers at home that I am looking for but everything has been to spec.

 

[Eric 3.7LX Alpha 1]

There have been a lot of recent fuel pump issues with new 470 pumps putting out over 7 psi. It may just be one model in particular I am not sure.

An line pressure gauge will tell you what you are dealing with, and at least you can eliminate the carb if that's the case. Too much psi can push the needle valve open and flood you out.

 

[stonyloam]

Could the power valve gasket be shot and leaking? That would leak fuel from the bottom of the bowl, I think. Did a little more research, yeah it could be a problem with the power valve, I think.

 

[NHGuy]

You can also pinch off the rubber fuel line before the pump, then put a bit of gas in the top of the carb to see how it fires off. It will probably run for a few seconds and then die. Sure does sound like a carb problem. Does the choke plate feel like it is free to open once the motor is running? You could also try propping the choke open with a pen or something while you crank, midsummer doesn't take much to start a well tuned ignition.

 

[500dollar744ti]

^^^ that's what I would do.

 

[alldodge]

well that's another chunk of change I just don't have. the thing is before I changed out all the gaskets...the very same carb that was rebuilt worked just fine. It started with all that crap in the oil from the riser gasket failure. I will check the fuel pressure this week. other than tapping the accel pump should ANYTHING be dripping into the intake if I am just cranking the engine?

For the most part no, there could be a drip every so many revs, but there should not be enough to really see unless looking real close. Fuel pressure should be between 3 to 7 psi

 

[Walt T]

Float aint floating

 

[johnzonh]

the float is fine. both old and new floats are fine. I talked to some guys at my local garage and it isn't the pump. needle and seat are operating fine. something got stuck in the carb and its siphoning the fuel into the intake. confirmed by a few carburetor guys I have talked to. I will let everyone know what I find out. looks like I am going to be doing an all-nighter again on my boat..here we go!

 

[johnzonh]

NHguy thanks...everyone else thanks the power valve was replaced...I also have the old one. I keep all the old stuff for this reason. I do notice that the power piston very loose in its socket (if I just open the top of the carb..it falls out) would it be beneficial to peen it in place? it operates up and down on the spring just fine. I am leaning toward crap in the carb...and something is staying open that shouldn't be. again..the bowl isn't flooding (it stays about half full when I open it) and when I pull off the fuel inlet line...a small amount of fuel will come out under pressure ..but it isn't excessive. tells me the needle is closing properly and so far the diaphram in the pump is ok (I do want to convert to a marine elec pump next year)

Alldodge..under cranking...it just plain floods the intake. depressing... i think i gave it one hit on the accel pump thats it... still ended up with about 1/4 inch of gas in the intake.

it is a real mystery to me. I am not the brightest bulb out there but this should just start.

the boat was run previously in salt water from the other owner...and the fuel filter under the pump was disintegrating. sighhh time to clean clean clean.

 

[1977 SILVERLINE]

Have you tried pressurizing your carb on the bench?Go to an auto parts store and buy a cheap electric fuel pump,stick the suction side into a can of gas and the outlet side into the carb and see if the bowl fills up and overflows. And I'm not for sure on the two barrels but on the four barrels I believe there are some plugs on the bottom of the carb that tend to leak directly into the intake. I believe you can epoxy them to prevent them from leaking.

 

[johnzonh]

got an update for everyone...figured it out. As I was saying the carb never flooded..but the intake did... had an AHAAAAAAAAA moment the other night....and what was happening was that the power piston was never fully seated in its recess...so each time I took apart the carb.... and it fell out...and then put it back together...didn't realize that each time it was resting on the power valve!!!! so.... cranking engine vacuum never pulled the piston up.... and guess what??? a whooooooooooooooole bunch of fuel went right into the intake! fixed the piston last night...peened it in place...engine started. GO FIGURE!

 

[nola mike]

Could the power valve gasket be shot and leaking? That would leak fuel from the bottom of the bowl, I think. Did a little more research, yeah it could be a problem with the power valve, I think.

Hmmm... Terry knows 470's! Glad it's working!

 

[SDSeville]

Hmmm... Terry knows 470's! Glad it's working!

^^+1