Fuel dumping?

RaceDeck · #1 (**permalink**) 04-05-2002, 10:17 PM

I am having some trouble with my Holley 750.....Under hard accelleration, it starts to cut out and there is a heavy smell of fuel. we replaced the floats and seats and still a problem. I am only running a mechanical pump and it is at around 9psi. When I take the side screws out ot see where the fuel is at , it is right at screw level when at idle. The motor runs at around 170 to 200 degrees max and the carb is not very hot to the touch ( just warm) ....??? we had a problem earlier with the the floats....the floats were not operating and fuel was comming out the vent tubes....
Any thoughts. I do have a turkey pan on it if that changes anything????

THanks

RaceDeck

Mike I · #2 (**permalink**) 04-06-2002, 05:40 AM

RD,

Just a suggestion, but fuel pressure should be kept under 7.5 PSI on a Holley. If you don't have an adjustable regulator installed already you probably should get one and bring down that pressure.

Mike

Cobra20646 · #3 (**permalink**) 04-06-2002, 06:57 AM

Race,

9 psi sound a bit high, like stated above in Mikes post. I'm guessing your reading the pressure gauge under the hood and at idle too. I would like to see what happens to it when it under load/acceleration. Gauge accuracy is something to consider too.

At any rate, see if you can get that pressure down to 6 or 7 psi before you start tearing into that carb.

- Jim -

Bob Putnam · #4 (**permalink**) 04-06-2002, 07:36 AM

I'd also check your ignition system. The symptoms are also mimicking high speed/load breakdown.

RaceDeck · #5 (**permalink**) 04-06-2002, 08:24 AM

I am going to check it out today... Also, I should note that in all cases, the car runs ok when I first take it out.....then when I shut it down and let it sit a while, It is hard to start ( seems flooded) and it has al of the above symptoms? What I can not figure out though is that the bowls are not over filled????
Can this be vapor-lock? or could it also be the metering block? this holley has only maybe 20-40 hours on it???
thanks

Mike I · #6 (**permalink**) 04-06-2002, 08:46 AM

RD,

I experience a similar condition to what you indicate you have been going through, i.e. when I initially start my engine from a completely cold condition, it fires instantly and without any hiccups, and it will hold idle and run well until I shut it down. Upon restart (even if it's been shut down for several hours), I have to crank the engine for several seconds without giving it any fuel as though the plugs are loaded with fuel from a flooded condition. After it starts and I try to accelerate, it seems to stumble for a few seconds (if not stall altogether) and will eventually clear up as I continue to drive away. I suspect that I have a heat soak & vapor lock problem as well as not having a hot enough spark at start up. You may have a similar problem. I'm switching over to an MSD 6AL ignition that should cure the re-start problem and my Holley is coming off the car soon to be replaced by a 4x2 Weber IDF system, that should cause new problems to worry about...

Mike

Hotfingrs · #7 (**permalink**) 04-06-2002, 09:24 AM

RaceDeck,

You're describing a couple of different problems....in your first post, then answers you got were right on the money...fuel pressure or electrical...now you're saying that after you shut it down it's hard to start...smells like gas...etc. This sounds like the fuel is percolating out of the fuel bowls. This happens after you shut an engine down and underhodd temperatures build to the point where the gas boils out of the carb and into the intake runners. Upon restarting 2 things happen. All the gas in the bowls is now in the runners and on your plugs. Secondly, the fuel bowls are empty and take time to fill back up. Look at reducing underhood temps when you shut down...and also a phenolic spacer under the carb to keep heat away from it...and yes these things will happen even if your car runs cool...it all happens after shutdown

Coloradocobra · #8 (**permalink**) 04-06-2002, 10:01 AM

RaceDeck,

Not sure if your problem was the same as mine but I was confounded with flooding problems. Part of it is very much related to altitude and in SLC, that may be a concern. After trying several different combinations, the one that seems to have solved my flooding problem was a set of Holley off-road needles and seats.

I would definately get a pressure regulator to knock it down to 6 psi or so. As an experiment, set your float level down 1/4 below the sight and try it out. It may stumble a bit during transition but it will help identify floats as your problem. If it stops the flooding, try the off-road setup. There is another guy here in Denver that is having the same problem. I ran an old carb for the first year and it never hiccuped. The new carb had problems right out of the box - but now it runs great, so I am not sure if Holley has changed something in the float or bowl setup.

Gary

RaceDeck · #9 (**permalink**) 04-06-2002, 12:11 PM

I have an MSD 6AL on it now, so I think I am ok there. I am going to put a regulator on it today and turn down the pressure....We are aslo goign through the carb again.....
Here is exactly what happened last night.

I started on a cold motor and I took it out , all things seemed ok , even under accelleration...I drove for about 5 miles. then I shut down for 5 minutes to check for any fuel leaks, etc.. and all looked good. I went to restart and it took a couple of try's (not normal)...I took off and I accellerated hard in 1 thru 2nd and into 3rd and while in 3rd it started to cut out? ....kept driving and it startedt o do it more frequently....drove home, checked the floats at idle andthey were right at screw level. shut down for about 20 minutes and then tried to start it.....Would not start...Held throttle open for a minute....waited and then tried again...it started....reved high and then shut down....lot's of gas smell....

Note: Prior to completely rebuilding my car, we had a return fuel line to the tank ( it had FI at one time) and we took it out.....should I have left it in? Plus the carb is the only part in the motor that I did not get from Southern....since I only bought it last spring...should I go with a DeMon or new Holey....
RaceDeck

Coloradocobra · #10 (**permalink**) 04-06-2002, 07:33 PM

Get the car good and warm and while it is idling, open the hood and take off your air cleaner. Grab the roll bar and shake the car as hard as you can and watch for fuel coming out of the vent holes. If it sprays all over the place like mine did, set the floats down 1/4" first and try it again. If this cures it, then you may want to look at the needles and seats as I suggested above.

Also, right when it acts up, shut it down and check fuel levels in both bowls. When mine would get upset, fuel would pour out but if I let it sit and cool down, it would all evaporate and would not show the flooding condition. Just make sure you have an extinguisher handy!

Gary

Double Venom · #11 (**permalink**) 04-06-2002, 07:45 PM

Ok,
I take a hit everytime these blankety, blank Holley problems come up. Going to take my Edelbrock and go sit in the corner now.

DV = who has not had ONE single carb problem since we switched!

300 Cobras is NOT enough!

P.s. I know, I know it can be fixed, trouble shot, trouble shoot, trouble shoot, replace, replace replace.