Hard to start with a backfire out the carb.
 

Sorry this will take a few to explain, so bear with me.

If my truck sits a day or more, it is very hard to start. I basically have to keep pumping till is starts to fire. It will then backfire out the carb. and I will have to do it a couple more times before I get it to actually run ok.
I have been doing this the past few times thinking it just cold out and she don't want to go. Well tonight I did the task and got her running, but noticed a popping sound from the #8 cyl. So I pulled the spark plug and it was solid black. I cleaned it and she fired up and no noise.

So questions?
1. The carb. is an old Quadrajet. But it does fine when it is warm, does cold play a big part for the carb?

2. My fuel line drains back after shut down, is my fuel pump dying?

3. Since I can't figure out my wiring on my alternator, it is basically ran one wire style and does not excite until RPM's, is my HEI not getting enough power to spark the fuel during crank since the alt. is not charging?

Thanks,
Evil

Re: Hard to start with a backfire out the carb.
 

1. The choke and other settings can cause lots of what you describe.
2.? hummm
3.You should be getting whatever voltage the battery is putting out.It may be a bit low because of the drain from cranking the engine.

Re: Hard to start with a backfire out the carb.
 

1) Timing is everything. Set your base timing first, then mechanical and vacuum advance. Don't trust the timing tab, check TDC with a piston stop.

2) Check your plug wires, cap, rotor, etc., replace as neccessary.

3) Carb adjustment. I like to start by finding a manual and setting them to base settings, then following the procedures. A $15 vacuum guage will work miracles. Q jets are pretty easy to rebuild if you have to.

Re: Hard to start with a backfire out the carb.
 

My choke is disconected right now, I was told that I would just have to hold the throttle till it warms up. Is this a problem?
It has a hot air choke on it and I just capped it off.

Re: Hard to start with a backfire out the carb.
 

I am also trying to figure the vacuum lines out; I have the transmission line and distributor line to hook up.

Re: Hard to start with a backfire out the carb.
 

Caution: Long answer. ;)

Yes... In cold weather, this will definitely cause a problem. I'd find a way to hook up a manual choke if you can't hook up the automatic one.

Lots of easter-egging can cause you a lot of grief in the long run. Basically write yourself a plan of action depending on how well you know this engine and the condition it's in. If you don't know, then start with the very basics (some have already been mentioned) Also get a manual to help you out.

1. check all hoses for vacuum leaks

2. all your engine settings correct-timing, compression, carb floats.

3. all ignition equipment in good or new condition-wires, plugs, cap, rotor, battery, etc.

Other things to check.

If you suspect the fuel is being drained out of the carb, then you may have to go with a carb kit.

A weak output of the fuel pump. Can be caused by clogged fuel filters, clogged fuel lines or bad pump.

Are you burning oil?

This is just a start. Sounds like a lot, but once you know your engine and what you've done to it, it makes it easier to diagnose problems.

Re: Hard to start with a backfire out the carb.
 

Should I be using the intake port on the rear of the intake for the vacuum advance?
It is currently plugged.

Re: Hard to start with a backfire out the carb.
 

Regarding the "drain back" issue....I had what I thought was the same thing. I tightened up all of the hose clamps on the fuel lines and solved that issue.
It doesn't take much of a leaking clamp to allow air to enter the line and the fuel to be gone. The time it takes to start it after it sets is spent pumping fuel back to the carb. So, check all of your hose clamps. It could even be a hose that is allowing the air to enter.

The vacuum line to the power brakes connects at either the rear of the carb (large port) or on the intake. You need ported vacuum for the vacuum advance.

Re: Hard to start with a backfire out the carb.
 

I've used both ported and engine vacuum for vacuum advance. Seems to work ok on either.

Ported vacuum is a vacuum tube on the carburetor that's above the butterflies where engine vacuum is below the butterflies. You should have both on your carb. Just make sure you plug the ones you're not using.

Don't forget to plug all vacuum tubes on the carb when checking your timing, though.

If you want to learn more about pros and cons about ported vs non ported this guy has a good writeup. Gets a little complicated but its a good one to learn about how vacuum advance works.
http://www.hotrodders.com/forum/dist...1-a-59033.html

Re: Hard to start with a backfire out the carb.
 

Carb goes emty over night due to leaking well plugs. I installed an inline carter electric fuel pump. No more problems. Get an electric choke out of 80 and up Qjet.

Re: Hard to start with a backfire out the carb.
 

This is a little off topic but, get rid of that glass fuel filter.
Sure they look neat & all, but it ever bounces on something hard & breaks; you'll hate yourself forever as you watch your truck burn to the ground.

Re: Hard to start with a backfire out the carb.
 

Ok so I will use the ported vacuum on the front of the carb for the vacuum advance.

I am going to use the rear intake port for the trans. vacuum.

As far as the climate choke, I found Mr. Gasket makes a stove choke kit, is this all I need to make that darn choke work?

Re: Hard to start with a backfire out the carb.
 

Ok so I got a chance to replace wires and plugs. #7 & #8 wires had small heat cracks down to the core. All plugs are new and she started and ran fine. Now I need to get a timing light and set the proper timing and re adjust the carb. It is idling high, but smooth. Thank you all for your help.

Re: Hard to start with a backfire out the carb.
 

That's great! Thanks for feedback.