Hello all, I find the 455 slow to start after sitting in the garage a couple weeks or so... I have a John Osborne tweeked Rochester. I am wondering if the fuel pump should be replaced? I need to pump as I crank it over for a good 5 seconds (sometimes longer) to fire up. If I drop a little gas down the carb it will fire up right away. It will start right up after running for any amount of time. Any thoughts?
I to have one of johns carbs Loeve the performance and responsiveness if it . My car has never run so good. My car also starts hard after sitting for 3 or more days . I beleive the fuel pump is alowing the fuel to drain down and any thing in the bowl evaporates after a few days i am useing a oil can with gas 2 or 3 squirts down the carb and she fires right up. ,I am thinking of going to a electric pump to get the fuel there faster
Something to consider here guys is the chemistry we presently call gasoline. Very frequently, the Reid vapor pressure, which has risen over the last few years due to fuel injection's ability to pressurize the system. This results in the fuel's vaporizing prematurely, emptying the bowl. Though there are other ways the fuel might disappear from the bowl, you might try another brand. I have a 1985 GMC Safari, one of the last to be carbureted. After a couple of days, the bowl has lost half of its volume. After four days, the engine cranks noticably longer before starting, and frequently, after two weeks, the engine must be cranked twice before firing. After carefully observing its behavior, I have concluded that it is the crap we call fuel, as it it now more chemicals than gasoline. It does not even smell like gasoline anymore. We can thank the enviro-wackos for that. It is also possible that the choke on your carb does not close all the way, causing an increased cranking time cold. That is easy to check. With the engine overnight cold, set the choke, and try to open it with your finger. There should be a noticable resistance to your finger, and the choke should be COMPLETELY closed. Let me know. Ray
Just some food for thought. I have a Holley 750 on mine with the choke airhorn milled off and currently using an AC mechanical pump and an Autometer fuel pressure gauge that will hold the pressure for hours, if not all day after the car is shut off. When I turn the key the car starts immediately, it doesn't matter if it is cold or warm or if it sits for a day or a week, and I can get out, walk away, and it'll idle at 700rpm. If you are using a Q-jet, the first thing I would look at is the well plugs in the bottom of the fuel bowl. They typically leak the fuel out of the bowls and the common fix is to expoxy them. Bill
the fuel is evaporating from the carb bowl. the correct inline gas filter stops the fuel from draining back out of the carb. if my car sits from a week or longer, i dump a little fuel down the airhorn tube. car fires right up. there has been a lot of discussion on this site on this subject, in the past.
FYI, Reid Vapor Pressure (RVP) of gasoline blends has been consistently becoming lower since the '80's thanks to the EPA's push to reduce evaporative emissions. If anything, the fuel is less volatile than it used to be; we've gone from RVP's > 11 down to 7.0 to 9.0 depending on the season and state. Devon
The quick fix is an electric fuel pump.... but that is a band aid..... but all the guys are right... heat soak, cat pee gas,,,, leakage,,,, ect.... pesky....
OK Fine, here is what I am trying... New stage 1 pump from from TA, replacement line from just right(eliminating the inline filter) and putting a inline filter back in the factory location. I always use atleast 92 non oxygenated fuel(no Ethanol). snow flying yesterday so test window is short! Hmmm... I guess I can try to start it anytime! :3gears: :3gears:
With the advent of fuel injection, the need for correct RVP for carbs is gone. It now becomes an issue of evaporation from the tanks, which are now completely sealed as well, leaving very little for a standard. These carbs had issues with the plugs leaking, and I would check that, but don't be surprised if the issue is one of evaporation, especially if the vehicle reeks of fuel a couple of hours after shut down. The underhood temps exceed 250 deg at that point, and the bowl could empty itself completely after three or four hours, if the conditions are right, and the fuel is not. You might try a different brand of fuel, but after several days, I think they will have all evaporated. Welcome to the wonderful world of the future. Ray
Ray, are you saying again that RVP is higher now than it used to be??? Confused with that, I have seen and tested the opposite trend. SHED testing tells us the lower the RVP, the lower the emissions, which is what has had the EPA all fired up to reduce it. There is no such thing as "sealed" when it comes to fuel system emissions...every joint in the system, every rubber hose and even the low permeation materials themselves still permeate gasoline molecules. Trust me, I have endured plenty of headaches from high temp SHED testing and the amount of money we spent to lower these emissions, and lower RVP was part of it. My company was the first to patent a method of bonding Tefzel to the ID of a nylon fuel line without an adhesive to help even more. In Michigan we see the RVP increase around October, goes from around 7.5 or so to 9.0 because of the cold weather. The Winter gas wreaks havoc on the poor assembly plants who are trying to fill with winter fuel in 72 degree temps...the vapor generation is so bad they call us every year about their premature shut-offs at their filling stations. Some have had to spend big bucks on fuel chillers. Most of the guys who call don't even know that there is a difference in formulation due to climate change. God forbid they tried to fill with the old stuff from the '70's! Devon
I THINK WHAT IS HAPPENING IS THE FUEL IS LEAKING OUT OF THE BOTTOM OF THE BOWL,THERE IS SOME SOFT PLUGS THAT LEAK ON THE QUADRAJETS.IT CAN BE FIXED BY SEALING UP THE PLUGS. RANDY
Ray, I just dug up some info that will surprise us both, I think. Typical RVP of gasoline in the US: Summer fuel 1960 8.7 1965 9.0 1970 9.2 1975 9.2 1980 9.8 1985 10.3 Winter fuel 1960 11.2 1965 11.5 1970 12.1 1975 12.1 1980 12.5 1985 13.5 It's only in the last two decades that the RVP has drastically dropped again. But in the end, our RVP now is still lower than in the '70's and '80's. The big spike in the 1980's was an interesting find. Devon
Bill is correct. I have the same problem and I know for sure the well plugs leak on mine. If I start the car the next day its fine, but wait a few days it takes a few cranks then pump the foot feed a couple and to life she comes.
I have been out of touch with these requirements the last few years, but I was well aware of the rise in the '80's, as I was with GM in their engine performance dept during that time. I guess I should not be too suprised at the drop, as vapor emissions have gotten the stink eye from the EPA lately. The advent of fuel injection is probably the reason the drop was less noticed. I mention this phenomena since, after rebuilding a carb, noting all of the possibilities, it is still possible for the fuel to evaporate from the bowl, emptying it quickly. That does not mean that the overhaul was in vain, just that it has limitations. Something to consider here is that RVP will likely continue to fall, as fuel handling science improves, and the injection system become almost exclusively direct, using very high pressure pumps, and smaller orifices in the injectors. Ray
Not saying you guys are wrong about all this RVP stuff, but can someone explain why the fuel isn't evaporating out of my carburetor? And no, I no longer have the electric pump hooked up. Couldn't stand the noise anymore. I hit the key and the car starts, hot or cold, no matter how long it sits. Bill
Same for me, Bill. After a month of sitting mine will fire immediately, even with the electric pump off. Still plenty of fuel in the front & rear bowls. Devon
My Qjet has the same problem. Rebuilt by John Osborneand runs very well, but after a month it would loose fuel if sitting for more than 2-3- days. A second rebuild to seal the plugs in the bottom, and still needs 5-6 seconds of cranking before the fuel returns and it will start. I my try another carb to see if there is a difference
Just a note on sealing up bottom plugs. By this time, almost 100 percent of the carburetors we get in here for rebuilding have some sort of glue over the factory plugs. In most cases it is JB Weld. I pressure test every casting and they leak right thru any sort of expoxy dabbed over the plugs to seal them up. Even if the bond looks good, they still leak. We use and recomend to remove the factory plugs, and tap the casting for screw in plugs. We use Marine Tex on the threads, and use a tapered tap for the casting so they seal at interference in the threads. Trapping the epoxy in the threads of the screw in plugs is a permanent repair. Any sort of expoxy dabbed over leaking plugs is about as effective as cutting your arm off and putting a bandaide over it! The FIRST course of action when you have a q-jet with an empty bowl after 1-2 days of sitting is to pressure test and effectively seal up the bottom plugs. I've done static tests recently after hot shut-down, and still have fuel in the carb bowl after a week, with enough trapped pump shot to effectively start up my engine. Nothing can be done about long term evaporation, and not much helps for draining back other than to install a solid fuel inlet seat instead of a "windowed" one to increase the height of the fuel level where it could leak down to. They do make filters with check valves in them, but there are very restrictive, and not recomended for high HP applications. If you are making apprx 450 or more HP, you should be using an electric pump anyhow, which quickly solves any and all issues related to this topic. Sure, some folks get away with mechanical pumps running into the 10's. For every guy doing so, there are at least 30 guys who can't get out of the 13's' trying to do the same thing....FWIW.....Cliff
Excellent post!!! They say you learn something new everyday, so now that I've done that already this morning I can ignore any other lessons for the remainder of the day :laugh: Bill
