Holley carb flows too much fuel

madvette74 · 11-18-05, 01:30 AM

I have a 750 DP... my secondary bowl, holds pressure at times, and sometimes it just dumps all the fuel in my engine, I changed the needle but still seems to do this, what would cause this? just to add. I set it up where it would just barely dribble out of the site plug, it was fine for a while, today I noticed the engine started to putter. I shut it off looked down the carb and I could hear the fuel spilling onto the butterflys.

motorman · 11-18-05, 02:14 AM

Quote:

Originally Posted by madvette74

I have a 750 DP... my secondary bowl, holds pressure at times, and sometimes it just dumps all the fuel in my engine, I changed the needle but still seems to do this, what would cause this? just to add. I set it up where it would just barely dribble out of the site plug, it was fine for a while, today I noticed the engine started to putter. I shut it off looked down the carb and I could hear the fuel spilling onto the butterflys.

check for a warped main body where the metering sets and check the metering body for flatness. make sure the float doe not have any fuel in it.

Vettehead Mikey · 11-18-05, 07:39 AM

What are you using for a fuel pump?

madvette74 · 11-18-05, 09:51 PM

I been using the same hollley blue pump for 5 years. I have an autometer fuel gauge I can read from within the car.. I noticed there been times where the pressure jumps up to 9psi sometimes, even though I changed the regulater to another new one, it seldom does this. if the secondaries weren't working would I notice a difference in indle quality? I noticed also recently that when I drive the car it feels like it's running on 7 cylinders. this has to be carb related.. this started at the same time as the flooding of the secondaries.. I took apart the carb and cleaned it. looked clean inside but still runs rough..
so as of now I have the float level needle turn in, so they fuel supply is off. this carb is not old maybe 3 years 2500 miles on it.. I want to add, that when the heard the car start sounding like it was going to die by flooding i looked at the fuel pressure gauge and it was 6-1/2 psi.. thats the pressure it was at when it was dumping the fuel into the secondaries could I need to change the float? and needle again?

Vettehead Mikey · 11-19-05, 12:09 PM

Quote:

Originally Posted by madvette74

I noticed there been times where the pressure jumps up to 9psi sometimes,

This is just my peculiar stick in the mud thinking, but to me adding a pump that requires a regulator to reduce pressure is almost asking for problems. The stock pump puts out more than enough flow and pressure to handle almost any street driven engine.

Most carbs cannot handle more than 5-7 psi and will flood accordingly if this pressure is exceeded. Since engine power output is in no way tied to fuel pump pressure (remember this not a fuel injected car) then raising inlet pressure beyond the stock setting is futile and can lead to the flooding you are seeing.

I would try reducing pressure to as low as you can go and see if your probelm goes away. If it still floods, then you need to what Clem (motorman) suggests as well as look at your float and needle.

madvette74 · 11-20-05, 02:08 AM

i'll try it again, ok so i'll need to check into that. but now I am wondering why my car sounds like crap? wondering if the wires can do this, the wires are about 4 years old. low milage.. I unplugged a spark plug wire and it still fely like it ran the same, should I check to see how many ohms are in the wires?
could it possibly be a msd ignition.. I may need to restart a new thread, after I check evey angle.

11-20-05, 10:48 PM

maybe fouled some plugs with that flooding

rgtrough · 11-21-05, 09:38 AM

Hey Madvette, your carb needs 7psi of fuel pressure. This can drop off abit at wot. Make sure your float level needle does not have debris in it holding it open. Adjust your float level to where they are level with the opening. There is a fine line with this adjustment. If your fuel pressure is to high the gas will blow right by the needle valves filling the bowls and blow fuel out of the vent tubes into the carb. I agree that you probably have fouled some of your plugs because of this condition. peace Bud

norvalwilhelm · 11-21-05, 03:02 PM

I agree with a possible fowled plug or two. Your needle and seat seem to be leaking, could be dirt related. It is simple to pull the needle and seat out and blow it out.
Adjust like you have been doing with just a slight trickle on the secondaries when idleing.
To check for carb leaks shut the motor down then let the carb sit over night. Check in the morning by pulling the slight plugs in the bowls and see if the level is anywhere near the sight plug. A leaker will be down.

madvette74 · 11-21-05, 03:14 PM

ok, I reset the float level, again.. I changed the plugs even though it runs better, when on the hiway it still feels like it's missing a cylinder.. I also have a feeling that the fuel will pour out the bowl again. it will be the 3rd time if it happens again.. I was wondering if it could be my msd box.. I dont even know how to check this.. but worst comes to worse with the flooding, i'll buy a new float and another needle.

rgtrough · 11-21-05, 05:49 PM

Hey Mad, When you pulled your plugs were the ends carboned? If not they probably weren't fouled. I went through this same thing once and I found out that my fuel pressure gauge was faulty. It read 6 lb. when it really was producing 9 to 11 lbs. resulting in the blow through problem I described earlier. The carb was being flooded through the vent tubes. Check your plug wires, they have been known to fail. And yes your MSD box can fail. Keep us posted.
peace Bud

Kid_Again · 11-21-05, 06:02 PM

Sounds just like the problem I had on the big block where the carb o-rings had failed. It sounds to me like you are over-pressurizing the system. I would, as advised, turn the pressure 'way down and see if you can hold it between 5 and 7 psi. It should run fine at that pressure but you may want to change the o-rings AGAIN to make sure. Maybe just one change at a time.

Regardless, if you've been driving it that way for a while, you have washed the cylinders down with gas. I would immediately change the oil and not put it back on the road till it's correct. BTDT

madvette74 · 11-21-05, 09:43 PM

yup, I'll change the fliud again.. I checked the plugs after 150 miles today, should I say I pulled one plug and broke it.. but it looked real good no carbon.
the pic does not do justice because it appears dark but it really looked good..
I may have found the problem with the figh pressure reading.. I changed my inline fuel filter, it was bad.. should of changed this a long time ago.. I am thinking that I probaly got the high pressure reading because the filter would clog up. I would shut the pump of and turn it back on and the pressure would be fine..the filter is located in one of those summit chrome dp lines with a fuel pressure gauge, and my auto meter gauge (fuel) is located just before this, . so far no high pressure readings.. this is a bummer, well I will first replace the wires, remove all plugs to check to see if there is one bad one. maybe it is a wire hopefully.. if not replace the msd box. it's been in my car since 1990
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rgtrough · 11-22-05, 09:52 PM

Hey Mad, This stuff will drive you mad. Don't change the plug wires without checking the resistence first. If you don't have a digital multi meter go to Radio Shack and pick up an inexpensive one. You will be able to use this tool for many projects plus if your wires are ok you will save a few bucks. Not knowing what the resistence of your wires are suppose to be, just check each one and see how close the readings are to matching. If your plug boots are bad the problem may not show up until the exhaust manifold gets hot. There are many resons for a miss. peace Bud

madvette74 · 11-23-05, 02:28 PM

got a multi meter not sure how this thing works, where to plug the red one and where the black one goe's, and what resistance should accell 8.8 wires should have...
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