We actually drove our bird this weekend! yea! Drove to the emissions testing and it passed (what a sigh of relief). Tomorrow I can get the plates! One thing we noticed that hasnt happend before, was after parking it in the garage for the night, the next morning it took about 8-10 seconds or cranking before it would start. Drove it again yesterday for a few miles to get it warmed up then parked it for a few hours, same thing happened. It seems when the car is hot from driving and then parked for a while, the gas dissapears from the fuel filter (we have a glass one). We dont have any problems turning it on and off when it's hot, just after it's been parked for a few hours after being putting away hot. Does this sound like fuel percolation? Couldnt find anything doing a search so thought I would ask. What can we do to fix this? Thanks!
one of the reasons I got rid of my "see thru" filter...it bugged me seeing no gas in it after the car got hot, it was running , but filter was empty...gas never showed up....lol plus I was worried about a glass or plastic filter cracking, and spill fuel....went to a metal filter...
what about your filter location? is it in a very hot place? close to a exhaust or such? I tied mine up with a tie strap right behind the fan shroud so the fan blows on it all the time...
I think the new gas blends are more volatile than in the past. Modern cars have the pump in the tank and the whole fuel line is highly pressurized (~40 psi?), which would tend to reduce the boiling. Our cars have neg pressure on the suction side of the pump and then only about 6-8 psi between the pump and carb. I noticed the same thing in my clear filter and, like Bjorn, solved it by removing the glass filter and adding a filter next to the tank. But I'm sure the fuel is still boiling in the fuel line and carb but my car runs OK. I figure while the car is running, the fuel pump just keeps pumping gas into the fuel bowls to keep them filled with liquid gas and the excess fuel vapor just gets burned. After the car sits hot, like you said, it may take some cranking to get enough fuel back into the carb.
Could be a couple of things, when you shut down the motor the fuel will siphon back down through the pump. You could also have some slightly leaky bowl plugs if you're running a Q-jet. The Q-jets also had different types of primary jets, some had a small hole in the side allowing fuel levels to drop when shut off, others did'nt have that hole and the fuel level was maintained longer. In any event the bowl is vented to the atomosphere and all will evaporate over time. Some longer than others, mine is good for 3 days max without any starting problems. After that she cranks for about 8-10 seconds.
For starters, we'll change out that fuel filter. We dont to take any chances on a break and a fire... good recommendation Bjorn.
We're running a new Holley 4150 600cfm. Up until a few days ago, the car was only started to drive in and out of the garage, so it really never got warmed up. It hasnt been until now were the engine gets fully warmed up that we started experiencing this problem. So I'm assuming it has to do with the heat and not a carb adjustment or worn carb parts. Should we try a wood carb spacer? Does that really help keep the carb cooler?
Mine is the same, if it sits for more than a few days it cranks for about 5 seconds, then fires strong. All other times it fires as soon as I turn the key. Just one of those things...
One thing to consider is that it shouldn't really matter whether there is gas in the filter because the float bowl is where the gas will be to start the car. There is a check valve on the inlet that should stop the fuel in the bowl from siphoning back. If anything give it one or two pumps of the pedal before you start to crank and it should fire from the accelerator pump shot.
It could be needing to be tuned to your motor, i.e.jets, fuel mixture, etc. How warm is your car running? Maybe the fuel line is getting to warm & causing the fuel to boil?
I fixed my edelbrock with new jets & rods and proper adjustments with fuel mixture screws. It starts right up 90% of the time & occasionally taking a few cranks to start.
Ok, Took the carb off, rejetted from 64's to 61's and it ran worse (64's came installed from the factory for sea level and we are at 5,700 ft)so we put the 64's back in. Now we havent had a problem starting it. I did notice the fuel boiling a little in the glass filter though. We dont have a temp gauge but something we're seriously considering. We havent driven it further than 8 miles on one outing and havent gone over 50mph yet. Should we expect things to get hotter if we drive further, or would this amount of driving be sufficent to stabilize the heat we can expect?
It should stay cool as long as your moving. What's your temp gauge tell you? It should still also stay cool when idling. I did put the spacer between the carb and manifold and that seemed to help with the fuel boiling or percolating at the carb. I don't have a glass filter so I don't know if it's boiling at that part of the fuel line.
you can also buy a temp gun....I bought a small hand held unit ,about 1/2" x 1" and 3" long for about $20...great to check for hot spots...you can also use it to check your own temp (forehead) or temp of wines!
A temp gauge would be a very good idea. Even if only to leave it on until you're sure everything is working properly. I believe(not possitive) that 67s came from the factory with a heat sheild that went between the int man and the carb to help reflect some of the heat. The first thing I would do is throw that glass fuel filter in the garbage before the fire happens and then get the proper heat sheild for the carb(if qjet). With the fuel at the boiling point like that vapor lock will be your nemesis. You really shouldn't be running that hot. You need to find out how hot you're getting and go from there.
Ok, We hooked up a water temp gauge, drove it around between 25mph and 50 mph for 7 miles. Temp stayed between 170 - 185 while driving. The highest the temp got was 200 when we were idling in the driveway. When we parked it, I noticed the fuel still percolating in the glass fuel filter (havent changed that yet). Could it just be the glass is getting hot enought to boil just in the filter? Havent had any problems starting it. One pump of the pedal and it starts the first time when cold.
Is your fuel line that passes from the pump to the carburetor touching the water pump anywhere? If so bend it so that it doesn't. Keep it off of the water passage in the intake also.
Are there fuel stains on the carburetor indicating a slow leak from the float bowl? I guess it would actually leak into the intake if the well plugs were leaking.
I use a glass filter without any issues. I want to see debris if any should ever get in there.
John, No stains or leaks. The fuel line isnt touchng anything. We just have 3/8" fuel hose running from the pump to the filter then again from the filter to the carb. Could it that be the problem? Should we have hard lines run? We are running a vapor return line, I dont know if that makes a difference. We do feel a lot better knowing the water temp is right around 190 on average. Could it be our altitude? I know water boils at a lower temp here, wonder if that's what's happenng with the gas.
I had pretty much the same thing happening to me awhile back with a Q-jet. I spoke with a guy who occassionally posts on this board who goes by the name "carbking". He is very knowledgable about all things carburator--pontiacs in particular.
The way he explained it to me is that todays gas is more volitile than the gas available when these cars were built. The Q-jets float design is such that there is a relatively short distance between the float bulbs and the fulcrum where the weight of the floats rests. When that fuel gets warm, the pressure created in the bowl easily overpowers the weight of the floats, allowing fuel from the bowl to escape through the needle valves down into the IM--flooding the engine. He said the thing to do was to run the starter without pumping the accelerator for a bit when starting when conditions like this were likely to exist. This would have the effect of pumping the excess gas out of the engine until the car would start.
