backfire on start 1977 Chysler 135

seattle scott

Petty Officer 2nd Class
Joined
Nov 1, 2011
Messages
113
Engine was running fine for a few days, now on start up the first attempt always leads to an exhaust backfire then on the second attempt starts right up. This happens when engine is cold and when hot. Read something that maybe I need to back out the low speed jets some more, think they are about 1 turn out from seated now. Any thoughts?

Additional, I forgot since I wasn't there, the engine is bogging down when going to WOT, which I recollect can be related to idle needle adjustment. Correct?
 

foodfisher

Captain
Joined
Feb 18, 2009
Messages
3,756
Re: backfire on start 1977 Chysler 135

Can be a fuel pump diaphram also. One backfire can tear it.
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Re: backfire on start 1977 Chysler 135

If carb needles are set too lean, the engine will not bog at WOT, but rather will melt a piston or two and slow down--radically. Your needles do not appear to be set too lean but---Check compression on all cylinders anyway.

Bogging at full throttle is always a function of poor fuel delivery. You need to check float levels, all hoses and connections and the fuel pump. Check the screen and any quick-connects for partial clogs. Check that the tank pick-up is clear. Also remove the pump and check that the impulse hole in the bypass cover is not clogged with carbon. Do the same for the second stage impulse hose and fittings.
 

seattle scott

Petty Officer 2nd Class
Joined
Nov 1, 2011
Messages
113
Re: backfire on start 1977 Chysler 135

I will run through the fuel supply items, thanks. Is backfire a timing issue?
 
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