I replaced the fuel pump on my LG4 this weekend and the car runs fine with everything hooked up except for the vacuum line to the air cleaner. When I plug that in, it dies immediately. Not sure why. Too much fuel from the new pump? Fuel pump is a Carter M6626.




Could it be timing related? I was tinkering with timing(adjusting by ear) before replacing the fuel pump.

 

Not if the timing is back to where it was before. OTOH if it's now retarded from there, then possibly yes.

Otherwise, needs the idle speed bumped up a bit.

Not sure why every time every car stops running right the first thing everybody seems to want to do is mess with the "timing". It NEVER changes on its own unless the dist hold-down bolt is loose or the dist itself is seriously BROKEN somehow, therefore it CANNOT change the way the car runs. Put it back and leave it alone until whatever was causing the car to run wrong (fuel pump in this case) is repaired. Once the car WORKS RIGHT, then of course there's nothing wrong with trying to tune it; butt messing with ANY "tuning" kind of settings when a car is defective, leads to nothing but tail-chasing and MORE messes to clean up once the REAL problem is resolved. Let this be a lesson to you for the future.

 

I was playing with timing because I had dieseling at shutoff after the car was warmed up. I ruled out a vacuum leak so timing was next on my list. This is when I discovered that the original fuel pump was leaking.

 

Well, put it back where it was when the car ran right, and go from there.

 

Test your fuel pressure. A new pump may require a regulator... If the fuel pressure is too high it will blow the needle off the seat and overwhelm the fuel bowl with supply. I have an aftermarket pump and I run a regulator to achieve roughly 6 psi.

 

I'm fairly certain the pressure from the new Carter fuel pump is too high. I got timing all set and it just wreaks of gas. If you try to give it throttle with the breather vacuum port capped, it just wants to bog and die. I've got a NOS fuel pump arriving any day now I'm going to throw that on and see if it solves my issue.

To summarize, it ran well on the original carb and fuel pump.
-pulled the original carb off when it started leaking, sent if off for rebuild and replaced it with an E4ME from a 1985 LG4 auto and it ran alright with that carb installed.
-adjusted the timing by ear after the carb was installed and it ran great.
-original fuel pump started leaking so I replaced it with a Carter M6626 and that's when the bog/vacuum breather issues started.
-got a new timing light and made sure timing was good and the bog/vacuum issue is still there.

My original carb is supposed to be back from rebuild tomorrow as well so I'll be putting that back on the car.

 

Update: NOS fuel pump and rebuilt carb(courtesy of mountain man fuel systems) installed. Runs much better. Still a slight miss that I can hear at idle so I think I'll tackle plugs and wires next.