Backfire through carb 5.7 mercruiser

[swampfx914]

Re: Backfire through carb 5.7 mercruiser

Is it possible for a shift interruptor switch to cause a problem like this?? Just grasping at straws!!

 

[akriverrat]

Re: Backfire through carb 5.7 mercruiser

time for a compression test.

 

[magster65]

Re: Backfire through carb 5.7 mercruiser

The shift interrupter causing this isn't likely. Did you check the fuel pressure under load? It still sounds to me like it's leaning out. If it's being starved for fuel it would do exactly as you described. After your compression test comes back good (fingers crossed), check your fuel delivery system again. Good luck!

 

[swampfx914]

Re: Backfire through carb 5.7 mercruiser

Ok compression test was good allcylinders were the same. I removed the rocker arms and performed a leak down test to see if maybe there was a cracked valve. all cylinder held air equally so I have pretty much eliminated the engine. I will test the fuel pressure under a load when i can get a tester. Does anyone have a part number or price for the ignition module on the distributor? I am totally baffled by this thing! I bet the fix is simple though but I sure think i am running out of simple things to check.

 

[magster65]

Re: Backfire through carb 5.7 mercruiser

Hey, did you read this? Something your fuel pressure test would show.<br /> post

 

[swampfx914]

Re: Backfire through carb 5.7 mercruiser

Hey Mag, do you know where that anitsiphon valve would be? I still have not been able to check the fuel pressure yet but i hope to today.

 

[magster65]

Re: Backfire through carb 5.7 mercruiser

I'm not absolutely sure but I think it's on the top of your fuel tank. Maybe someone else could help here?

 

[loadnet]

Re: Backfire through carb 5.7 mercruiser

Did you check the fuel tank VENT?<br /><br />Make sure it isn't clogged with spider webs.<br /><br />Clogged vent will cause a shortage of fuel to the carb under a load, thus causing a serious lean out and possible backfire.<br /><br />just a hunch.<br /><br />Pat

 

[pecothern]

Re: Backfire through carb 5.7 mercruiser

Mine did intermitent backfiring when the ignition coil was bad. I Had a very weak spark . Turned out Someone had put a coil on my boat that required a resistor but I had no resistor so running full twelve volts all the time burned up the coil. Replaced with a 12 volt accell coil and problem solved !!!

 

[luisito]

Re: Backfire through carb 5.7 mercruiser

look like you have a valve that is not seat right and stay open (bend).