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Holley 650 cfm 4V double pump
#1
After 6 months repairing my Stang, first start done.
The carburetor have been completly dissasembled (Holley 4150 650 cfm manual choke), new kit in, but unfortunatly the primary pump is not sending gas.

I used the SMP 661A, maybe a seal on the metering block stop the gas?

Anyway, it's like a game, and I will find out where is the problem.
(no H pipe yet installed).

Any advice would be helpfull.
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#2
I found the problem, was a seal on the metering block, primary one, that was not sealing at one point, so couldn't send fuel from the fuel bowl to the pump discharge nozzle.
Now the engine start ok, with a perfect idle.
But the mixture is too rich, spark plugs are black, and smokes at the exaust, very stinky.
I screwed clock wise the 2 idle mixture screws, then back 1 and half turn, the same.
Question: is the level of fuel in the bowls can affect the mixture at idle?
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#3
it can if the floats are very high.

try this with the engine running. turn the idle bleed screws clockwise to close them off, the engine should stall out. instantly.

if the idle bleeds are closed and the engine keeps running then the butterflies are open too far at idle, or you could have a vacuum leak somewhere.

basically this tests the function of the idle bleeds.

Now you have to look at the float level and also the position of the secondaries butterfly, many times during rebuild the adjustment of the secondaries has opened them too far, this means you have to close down the primary butterfly to maintain low idle rpms, but the secondaries will be overriding the idle bleed adjustments and pouring fuel into the intake.

so you do the idle bleed screw shutdown test to see if the secondaries need adjustments. if the idle bleeds closing shuts the engine down then you can go to look at the fuel bowl.
but first i would run the engine let it warm up. you have a manual choke so make sure it is turning off correctly. then shut down the motor and don't touch the throttle linkage.
shine a flashlight down the barrels of the carb and look at the position of the butterflies for primary and secondary they should look even and open about the same amount.

adjusting the fuel bowls on the holley can get dangerous. holley requires you to make adjustments to the fuel bowls with the engine running normally at idle with the idle bleeds reset to 1.5 turns.
you have to open up the fuel bowl inspection plugs and the fuel is suppose to be licking the bottom of the inspection plug hole.

that is great but what happens when the float is stuck or too high, gas comes shooting out of the inspection hole, you the engine everything is covered in gas and one spark and boom.

so holey makes clear plastic fuel bowl inspection caps. you take out the brass plugs, use a little oil on the plastic threads of the clear plugs and they have a little oring on them for a seal.
install them run the car and view the fuel level height in both bowls. then you can shutdown the car and make adjustments to the float level restart and view the change. much less dangerous.
once done, remove the plastic caps and reinstall the brass caps with the metal ring seals. the plastic caps are only meant for adjusting the bowls do not leave them on all the time.
and remember to lube the threads on the plastic caps and just install them finger tight so they do not leak, the thread on the plastic caps can snap off inside the inspection hole. that will be a VERY bad thing.

So to recap.
first test operation of the idle bleeds by closing them and making sure the engine stalls out and shuts-down.
take a look at how open the primary and secondary butterflies are you want them to look evenly opened. if not they should be adjusted into a more balanced state.
next get the inspection plugs for the fuel bowls and view float level. make adjustments as needed.
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#4
I saw the video from Holley, and definitly I don't want to open anything on the carb while the engine running, too dangerous.
Well, I come back from the garage and did the first step you told me, I start the engine, then close the 2 idle screws, and then the engine don't stop, no change at all.
The carb was running well before I decide to open it to change all seals, including the power valve. I didn't touch any set up on the butterflies.
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#5
you may have linkage hanging up somewhere, did you look at the position of the butterflies to make sure the primary and secondaries were opened about the same?

try this... start the engine let it run for a minute till stable.

cup hands over the carburetor intake, and choke it of air, the engine should slow down and should stall out, if it keeps going, you have a vacuum leak and that may be the source of problems.
the manual choke can be the source of a vac leak on the 4150. but you could have something wrong with the base of the carb, also make sure you capped off any vacuum sources you are not using like the pcv/brake booster on the carb base if not being used.

on the front of the 4150 base is a small 1/8" vacuum source some people forget to cap it because it is very hard to see when the carb is installed on the intake.

what is happening is extra air is coming from somewhere and overriding the mixture, that air can be an uncapped line, a vac leak, incorrectly adjusted butterflies.

when the butterflies are open too far you expose too much of the transition slot which overrides the idle circuit and renders the idle bleed screws null.


for a problem with linkage many people when they rebuild the carb get the fast idle cam on the passenger side stuck or in the wrong position.
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#6
So, all vacuum sources are plugged.
I noticed that the secondary butterfly don't open as much as the primary.

I will check all what you wrote. I'm leaving tomorrow for my job for more or less a week. Then I will come back to this post and continue to check my carb untill it works perfectly.

And of course thanks for your help Smile

I was thinking about the screws which hold the body throttle assembly with the body. I have 6 screws and there are 8 holes.
And I changed the base gasket, which is different as the one I use from the kit, which is only a square, the old one has 4 holes for the 4 butterflies, and maybe was plugging the two holes where 2 screws are missing?
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#7
Don't worry if the secondaries look closed compared to the primaries it would be nice if they are even but if that is the case. You may have a vacuum leak at the carb base or internally on the carb. You could have an incorrect gasket in the metering block causing a problem too it happens the holly gaskets are a true pain in the butt. You can use the wrong one or install it backwards. And clog up a fuel or air circuit. Right now I think you have a small vacuum leak somewhere.
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#8
I watch this movie, look at minute 18.
http://www.youtube.com/watch?v=ie74DaaDYa4
8 screws he put, I only have 6, the leak can comme from there? one of the holes or both?
The screws which are missing are from middle and back middle
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#9
I remember I asked this questions before on this thread.
http://www.7173mustangs.com/thread-holley-4160-carb
  Reply
#10
Yes you can have a leak from there with missing hardware, the gasket might be bowing causing a leak at the carb base.
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