Re: Carbed 5.3 won’t start please help!
 

Is the secondaries adjustable on your carb?
Could be too far open.

Or high idle on choke needs adjusted.

Re: Carbed 5.3 won’t start please help!
 

Good to hear you have it running. Glad it was a simple fix. Now you can get into dialing in the timing and carburetor The fun stuff!

Re: Carbed 5.3 won’t start please help!
 

Isn't a 600cfm a bit small?

Re: Carbed 5.3 won’t start please help!
 

Yes, dialing it in will be challenging but fun. I tried to research a good bit on a carb. I hope the 600 is enough. It’s pretty tunable.

Re: Carbed 5.3 won’t start please help!
 

Try removing the accelerator cable from the carb lever, leave the return springs on...then start the engine...I have seen cables hold the throttle lever open...

Also look for vacuum leaks as these will cause high idle levels...

Cam sensor fault is most likely a bad sensor...

Great that you got it going...

:chevy::chevy::chevy:

Re: Carbed 5.3 won’t start please help!
 

I don’t have the cable hooked up, I’m reading up on the carb. I’ll have to mess with it some. I ran it about 15 minutes today and cranked it a few times. A couple times shutting it off it wanted to keep running with the key off, like it was running out of fuel. Never had a this happen before, another fault in the wiring somewhere? At least it’s running now thanks to everyone’s direction!

Re: Carbed 5.3 won’t start please help!
 

It’s not in your wiring.
Running on is known as dieseling.
If your primary throttle is open enough to allow a bit too much air into the motor, a hot spot in your intake will ignite the air and a bit of fuel to make it run without the ignition on. It continues to try to run because the air going into the intake draws a little fuel from the carb.
Cure is to close the throttle almost completely.

There’s a section in this link which deals with the transfer slot on a Holley. Your carb is the same. If you get your transfer slot set you’ll likely cure your high idle and your run on.

http://www.crankshaftcoalition.com/w...EI_distributor

Re: Carbed 5.3 won’t start please help!
 

Or the alternator is back feeding power thru the MSD box. Needs a diode in the charge wire.

Re: Carbed 5.3 won’t start please help!
 

You guys are very informative and I’m greatful for the help. I’ll look into the article and see what I can find out. Thank you and I’ll update soon.

Re: Carbed 5.3 won’t start please help!
 

OK, I went through a similar issue with mine. If you're getting a cam fault code, you will have starting issues. Make sure you have genuine cam and crank sensors!! I honestly believe my issue was using aftermarket cam sensors. I finally went to a front timing cover and timing gear setup from a GTO, with GM sensors. No more starting issues.

As for the 600 cfm carb, it'll be fine for that 5.3. I have a +.010 5.7 with AFR heads making 531hp and it only pulled 580cfm at 6000rpm on the dyno.

Re: Carbed 5.3 won’t start please help!
 

I've tried to look but it seems the primaries are not adjustable on the Summit 600 to mu knowledge. The secondaries appear to be adjustable. Summit tech line told me not to mess with any transfer slot adjustment but I may have too much fuel pressure? I have an inline gauge that reads 4 1/2 when running but it could be off. it is also dieseling on occasion when i shut the key off. You guys seem to know much more than the Summit tech. I'll adjust primary and secondary if possible. Anyone else ever adjust this on a Summit carb?

Re: Carbed 5.3 won’t start please help!
 

Here are a few pics. Seems my transfer slot is way out of spec.

Re: Carbed 5.3 won’t start please help!
 

http://67-72chevytrucks.com/vboard/a...1&d=1542058490

http://67-72chevytrucks.com/vboard/a...1&d=1542058493

http://67-72chevytrucks.com/vboard/a...1&d=1542058493

Re: Carbed 5.3 won’t start please help!
 

Of course you have a primary adjustment. It sets your idle speed.
Did you pull the carb off to find the secondary screw adjuster?

Give us a better pic of the complete bottom of the carb.

Re: Carbed 5.3 won’t start please help!
 

Re: Carbed 5.3 won’t start please help!
 

I know my main idle adjustment on the throttle linkage but it’s already all the way out, not even touching. See how much gap is in the primaries at idle? Has to be a way to close that gap some.

Re: Carbed 5.3 won’t start please help!
 

Check the high idle screw.
It’s on the passenger side. Under the choke.

Is your choke wide open?

Re: Carbed 5.3 won’t start please help!
 

I don’t think the choke is open but I’ll check. It look like it’s on the lowest notch. I see the 1/4 screw head under choke. That’s my high idle screw?

Re: Carbed 5.3 won’t start please help!
 

Yup!
That’s likely it.

Exactly what carb do you have?

Re: Carbed 5.3 won’t start please help!
 

Summit 600 electric choke with vacuum secondary.

Re: Carbed 5.3 won’t start please help!
 

Give us a link to it.
There are different styles.

Re: Carbed 5.3 won’t start please help!
 

Re: Carbed 5.3 won’t start please help!
 

It’s a 4010 style.
Your electric choke is adjustable by turning the black cap if you need to lean it out.

Re: Carbed 5.3 won’t start please help!
 

Roger that, I’ll try that and also adjust the gap on the primary. Thanks and I’ll update afterwards.

Re: Carbed 5.3 won’t start please help!
 

Adjusted the primaries and the choke a bit. I’ll hook up in a bit and update on how it runs. Does the transfer slot look correct now?

http://67-72chevytrucks.com/vboard/a...1&d=1542124593

http://67-72chevytrucks.com/vboard/a...1&d=1542124593