hard start to start
 

'72 GMC P/U with 350 A/T Headers and Qudrajet 4bbl

Choke is working fine. But...I have to pump accelerator pedal 7-8 times in the morning, then it might start. If not, I pump it about 1 and a half times more then it starts.

The original 'cold start' instructions on the back of driver's side sunvisor says to press pedal all the way to the floor, and slowly release. Then start engine. If engine does not start, repeat procedure.

How do I get this to work right? I don't remember truck ever starting that easy, but would be great if it would.

Thanks,
Keith

Re: hard start to start
 

I have to ask, how do you know the choke is working? Can you describe how your is working? Does it start to run, then die? Or does it not catch at all?

The choke is supposed to be almost completely closed when cranking, once the engine starts and vacuum is produce the "choke unloader" is supposed to open the choke a bit more to allow enough air for the fast idle to run.

Maybe the choke appears to be operating properly but is incorrectly adjusted?

Re: hard start to start
 

After you check the choke, you may have to also take the carb off and give a good cleaning, get a carb kit and replace the needle valve and base. It may be that the needle valve is gummed up and/or has debris allowing the gas to leak back out. The kit also has the accelerator pump and some other parts in it like ball bearings, gaskets, that you can replace also.

Another thing that can happen on these quadrajets is leaking jet plugs under the top half. In other words you have to remove the base to see the plugs. Check to see if they've been epoxied up to prevent leaking. If not, you will have to do it.

Caution: they're not the easiest things to work on, so if you're not experienced or this is a daily driver, I'd have someone else do it.

Re: hard start to start
 

I push the gas pedal 'once' and choke closes...but, I have to pump gas pedal 7-8 times before engine starts...when engine does start, choke opens about 1/8th of an inch or so and fast idle starts...as engine warms up, choke plate opens completely up...seems to me choke is doing what it is suppose to do...my problem is there is no gas pumping into carb from fuel line to start engine...I'm 54 yrs old, and all carbs I have ever seen, when you pump gas pedal, they would shoot a stream of gas into carb to start engine...
even if choke was tied open, you could still press gas pedal, shoot gas into carb, and start engine...when I pump gas pedal, it doesn't shoot gas into carb...once engine does start, it runs fine

Re: hard start to start
 

Sounds like the fuel is leaking down back to the tank. How old is the fuel pump? If you cant answer that then, go ahead and buy a new one. Also would really check the accelerator pump to see if its worn out. Would also check the condition of the rubber lines all the way back to the tank.

Choke sounds like its doing its job, just sounds like the fuel delivery is having issues getting to the carb.

Smitty

Re: hard start to start
 

fuel pump is about 15 yrs old, at least...put new one on there at least that long ago...
also, bought this Quad 3 or 4 months ago from Auto Supply... [remanufactured/rebuilt]...
just cranked truck this morning, pumped gas pedal 4 or 5 times, and it fired right up...
could accelerator pump be worn out, and still look new...
took it out a couple weeks ago and it looked good...

just took fuel line to carb loose...turned motor over...shot stream of gas out hose the size of hose's inside diamater [1/4"]...I'd say fuel pump is ok...?

Re: hard start to start
 

Yup. Accelerator pump. Plugged discharge port or checkball stuck. Try this link.
Sean does good things to your carb. Or rebuild it yourself or find a good mechanic.
http://www.smicarburetor.com/

Re: hard start to start
 

is there a way to check discharge port to be sure it isn't stopped up and clear it, if it is stopped up before I have to take carb apart...

uh...I was thinking discharge port was where gas shot into carb from fuel line...is this correct, or is discharge port under check ball...

Re: hard start to start
 

have you changed out the fuel filter inside the carb inlet recently?

Re: hard start to start
 

Sometimes mentioning what parts have been replaced at the beginning helps so we won't give a lengthy, boring answer... ;)

After you run it for a few minutes, remove the breather and manually move the throttle. If it squirts gas than you know the pump is working.

Also, after about half hour, have someone start the engine while you look at the exhaust to see if you see black smoke which would indicate fuel leakage.

Even with a new carb, you could still have a problem. I've had to return a few in the past.

Re: hard start to start
 

no filter inside carb inlet...inline filter on fuel line before carb...

Re: hard start to start
 

took fuel line to carb loose...turned motor over...shot stream of gas out hose the size of hose's inside diamater [1/4"] ...I'd say fuel pump is ok...
seems to me if fuel pump wasn't working, I would have problems trying to drive truck ...ie [no gas to carb]...truck runs fine once started...

ps...my truck don't smoke any at all

Re: hard start to start
 

just got through driving truck for 2 hours...no problem

Re: hard start to start
 

Sorry. I was referring to the accelerator pump not the fuel pump.

Re: hard start to start
 

15 years???? I would replace it.....Hard to tell about the volume without measuring it.

The accelerator pump has a rubber gasket that usually cracks and fails.

Smitty