Intake pop and loss of power ???

R

Rafi

New Member
Aug 29, 2018
3
Boat Info
1996 searay 215 express cruiser
Engines
350 mercruiser
So this is whats going on with my 96 EC215 ..... i bought it off my friend so i knew what was going on. I changed the fuel pump with the same holley one just new. Drained the fuel tank and put in all new fuel. After ripping it around for about 30-40 minutes its started happening again. Pops out the intake, chuggin along while popping out the intake and then it dies, wait a minute fires right up idles fine and then under load propelling forward it starts to pop again, power is way down and it occasionally dies, starts back up and idles fine until you give it throttle.. i have not done anything with the carb other than make sure the metal screen filters are clean. Possible relay somewhere, carb messed up??? Any input would be great im damn near going bonkers trying to figure it out
 
vent line to tank plugged up
 
atrick said:
vent line to tank plugged up
Click to expand...

to see if the vent line is clogged run the boat with the gas cap off....if the problem goes away the vent line is clogged...if not you have another problem....

cliff
 
So it would build pressure after running for awhile and pump wouldnt be able to suck the fuel??? That what you are tryin to get at??? Im goin to look at that today...... would the fuel pump relay cause this?
 
A pop like that is a sign of a lean condition. In addition to the fuel vent mentioned above, a couple of other things to check:

  • Make sure no leaks around carburetor base.
  • Fuel feed line - make sure it is tight, not sucking air. Also, if the fuel line is original it's time to replace it, they start deteriorating from the inside and will collapse under load. Engine appears to run out of fuel.

Sounds like you have a fuel delivery issue.
 
Rafi said:
So it would build pressure after running for awhile and pump wouldnt be able to suck the fuel??? That what you are tryin to get at??? Im goin to look at that today...... would the fuel pump relay cause this?
Click to expand...


actually the opposite is true....as the fuel pump sucks the gas out of the tank fresh air needs to enter the tank to replace the volume of air in the tank equal to the gas that was sucked out....if no fresh air can enter the tank and the fuel continues to be sucked out of the tank a vacuum is created....this vacuum can build as the fuel pump continues to suck out fuel to the point it is stronger than the suction of the fuel pump and the gas flow will be shut off....

by running the boat with the gas cap off you are creating a second path (other than the vent line) for fresh air to enter the tank....

cliff
 
this is what I did today i pulled the valve covers and put a hand on the rockers they all seemed the same no vertical movement minimal side to side which is fine. I did not do the full oem procedure to tighten them down cuz they seemed ok but I did disconnect the vent line put my finger over the tank hole and blew in the tube. Air went nowhere until I pulled away from the vent tube and whatever I blew in came right back out. Seems to me like it's going right back into the tank because when I blew in it without my finger on the tank hole it just ran right out that hole, like the vent system is closed and not open to atmosphere.... hell I could be doing dum things but that's all I could get done tonight since a storm is on it's way here
 
I had an issue last season with a “popping” noise and loss of power.

A new distributor cap and rotor cured the issue.


Stick to the basics first. When was the last tune-up?
 
Sounds like the fuel cap has a one-way valve. It's allowing "your air" to flow back into the tank via the fuel fill hose since the cap doesn't allow the vent hose to outwardly vent to the atmosphere. However, the cap should allow the vent hose to inwardly vent, so to say.

Try the same thing with the cap off. Or, try sucking on the vent hose instead of blowing into it (with the fuel fill cap closed).

How clean/dirty is the flame arrestor?
 
Lazy Daze said:
Try the same thing with the cap off. Or, try sucking on the vent hose instead of blowing into it (with the fuel fill cap closed)
Click to expand...

I would suggest that you do not do this with your mouth.

With the cap on, trying to draw air out of the vent will just create vacuum and no air flow.

Worse, with the cap off, drawing air out of the tank by mouth on the vent hose could introduce super concentrated gasoline vapor into your lungs.
 
Espos4 said:
I would suggest that you do not do this with your mouth.

With the cap on, trying to draw air out of the vent will just create vacuum and no air flow.

Worse, with the cap off, drawing air out of the tank by mouth on the vent hose could introduce super concentrated gasoline vapor into your lungs.
Click to expand...
If the cap vent is working properly, it should allow fresh air through the cap and through the vent hose. That is the exact function of the vent - to allow outside air to enter the tank to replace the gas volume as it is used up.

Obviously, common sense prevails here. But, how many of us have siphoned gas out of a tank by mouth? Yeah, it's not officially "recommended", but a whole bunch of us DIY'ers have done it... with the occasional mouthful of gas :)
 
I assumed (there’s that word again) that his vent was connected to a separate port and drawing air through it would get a lungful of vapors before the fresh air.
 
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