What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

quadrajet: the fuel pump, fuel bowl, and accelerator pump

I agree with you on the divorced style choke. I had that on my '72gmc and never had a problem.


The electric choke is annoying, like you said, if you turn onthe key and dont start right up for some reason it opens the choke making it difficult to start. I like the oil pressure guage idea, I will put that on the list.
 
Well a good rule of thumb baseline for idle, is bottomed out, then go 1/4 turn. That is your starting point. Afterwards is fine tuned with a vacuum gauge to try and achieve the highest HG. Once the engine is at operating temp of course.
 
I checked the volts at the distributor, it is ~14v. The small voltmeter is missing so I only had one significant digit. It is probaby 13.7v

Also, I read that these '74 and earlier K5s that had points, the power is reduced to 10v for the distributor. My grandpa had ran a full voltage wire to the dash, a flip switch, and back to the HEI distributor. I guess he ran into and figured out the 10v versus 12v problem.

EDIT: MrSchaeferPant was correct there - 1/4 turn from bottom just seemed to tight but later I have removed the dummy air hose and I am right there at a 1/4 turn.
 
Last edited:
I checked the volts at the distributor, it is ~14v. The small voltmeter is missing so I only had one significant digit. It is probaby 13.7v

Also, I read that these '74 and earlier K5s that had points, the power is reduced to 10v for the distributor. My grandpa had ran a full voltage wire to the dash, a flip switch, and back to the HEI distributor. I guess he ran into the 10v vs 12v issue and figured that out.
 
Last edited:
forest_peterson said:
I agree with you on the divorced style choke. I had that on my '72gmc and never had a problem.


The electric choke is annoying, like you said, if you turn onthe key and dont start right up for some reason it opens the choke making it difficult to start. I like the oil pressure guage idea, I will put that on the list.
Click to expand...

The reason it does that, is the electric choke is nothing but time. If you turn the ignition on the 'on' position, the spring heats up, regardless if the engine is running; which is fine if you immediately start it up. But with the wire running to the oil pressure switch, it only sends power/heat to the spring if the engine is running.

That's why I like the divorced choke intake manifold setup better. Purely mechanical. Stone cold, its at position A, operating temp its at position B. Anything in between, the spring is also in between. I don't know why GM switched to electrical when the best set up is that style. Maybe later model EGRs were in the way :dunno:
 
that's what the second small post on the starters are for... sends 12v to the ign while cranking on points systems....
 
ryoken said:
that's what the second small post on the starters are for... sends 12v to the ign while cranking on points systems....
Click to expand...

Always wondered what the 2nd post was for. But even then, what happens when you stop cranking? And even then again, if you're talking a points system. By the time points were gone and it was HEI, they were still on non-electric chokes? I don't know 'when' the electric chokes came about.
 
Yup, vacuum guage is what I used. Found the highest hg, 20 in-hg, not bad. The idle screws were basically bottomed out, there was no adjustment and the hg was still rising. Adding air and leaning it out gave a better adjustment band. It makes sense that if all the ports are plugged and some of these are controlled leaks then it will be rich and outside the idle adustment band.
 
once it lights off and you stop cranking, it runs on the reduced voltage thru whichever ballast resistor it runs, wire for GM, ceramic for Mopars, etc..
 
20 in-hg isn't bad at all. I was happy with 15-17 with my old tired out rigs :D IIRC, 22 is perfect.

But nothing else makes sense. If that was achieved bottomed out, then I dunno. So let me understand this right. You're lean while idle screws are bottomed out? What's your float set at?

EDIT: Wait, I'm backwards. If you're bottomed out, that IS lean.
 
ryoken said:
once it lights off and you stop cranking, it runs on the reduced voltage thru whichever ballast resistor it runs, wire for GM, ceramic for Mopars, etc..
Click to expand...

Ok. so much like ignition, AFTER cranking/start up, it reduces to 9v or whatever points were? So that 2nd post somehow sends no voltage to the electric choke until it begins cranking. Then after cranking, what moves that electricity from being applied "WHILE" cranking, to running. Interesting.

I'm mildly past my limit to understand as I'm 3-4 Buschs' in :whistle:

This applies to the OP as well :D
 
MrSchaeferPants said:
Ok. so much like ignition, AFTER cranking/start up, it reduces to 9v or whatever points were? So that 2nd post somehow sends no voltage to the electric choke until it begins cranking. Then after cranking, what moves that electricity from being applied "WHILE" cranking, to running. Interesting.

I'm mildly past my limit to understand as I'm 3-4 Buschs' in :whistle:

This applies to the OP as well :D
Click to expand...


the second small post on the starter is only energized while cranking.. technically, both ign feeds are hot going to the coil when cranking, but obviously the 12 coming from the starter is what it's at till the starter disengages..

not sure where the old GM's pick up choke power.. I know on all the marine carb set up's I play with, it comes off a small output stud on the alternator.. same as that start ign wire, it doesn't have output unless the alt is spinning..
 
ryoken said:
the second small post on the starter is only energized while cranking.. technically, both ign feeds are hot going to the coil when cranking, but obviously the 12 coming from the starter is what it's at till the starter disengages..

not sure where the old GM's pick up choke power.. I know on all the marine carb set up's I play with, it comes off a small output stud on the alternator.. same as that start ign wire, it doesn't have output unless the alt is spinning..
Click to expand...

Small stud on alt, I will take a look at that
 
yeah, I have no idea if the CS, etc alts used on these have that, but it's obvious.. dead when off, hot when running..
 
It is Sunday, I last started on Thursday, and the float bowl is almost empty. The pencil line on that chop-stick is the mark I made on rebuild when the fuel bowl was dry.

20150222_111218.jpg
 
Last edited:
Lots of posts, well plugs are sealed? Still, sitting that long and still has fuel, does it start?
 
@dyeager535 on page 5 there is a video of the well plug test with compressed air and soap - they look tight. On startup there is never the puff of black smoke associated with leaking well plugs.

It started right up.

I assume the accelerator pump takes longer to dry out since it is sealed. Awhile back while the carb was open, I followed Cliff's advice and removed the clip from the float, since then I don't see fuel and air bubbling back through the filter - the filter stays full of fuel. (EDIT: later found in Cliff's q-jet book that the accel pump only has an outlet check valve not inlet like I thought - means that as fuel bowl dries the accelerator pump shot does too.)
 
Last edited:
You must log in or register to reply here.

Latest Posts

Top Bottom