Slow to start after sitting

Guys,

This is essentially what I have been trying to say since my first post. There are no cures for long term fuel avaporation, as the carb, regardless of the ramifications, must be vented to the outside air. In my expiereince with my Qjet, the engine starts inmmediately when it stands for about 10 days. Any more time than that requires that the bowl fill part way before it lights. I hesitate to offer hard and fast time lines, as there are too many factors affecting it. The q-jet has its share of issues, including leaking plugs. In my experience, these issues were quite easily resolved, excepting the evaporation issue. This issue depends on the float level, underhood temps, and fuel quality, which at best, is "variable." Some of these cold start issues involve the operation of the choke, which, in many cases, is incorrectly adjusted, causing lean cold start mixtures, flooding due to inconsistent choke pull-off adjustments, or defective units, and "attempts" to address these issues with "let's try this."
I have expressed concerns regarding the CAUSE of a problem, and carefully determining the real CAUSE of a problem before attempting the repair. It is the determination of the cause before attempting the repair that separates the men from the boys. Most of us already understand that a thorough understanding of the involved systems. There are many books on these subjects, and a few that I trust, including Cliff's book. This book, I have found, is the most thoroughly researched treatise on this carb. I have worked with this carb for 35+ years, working with GM, on various applications during that time. It reflects a thorough understanding of the Q-jet, which, even now is considered a "black art."
I hope that those reading and considering the suggestions listed in this forum are intended to be suggestions for the resolution of the described issue. Though unfortunate, none of us can open a man's hood, and make the requisite checks before resolving a problem.I know I wish I could, and I can almost guarantee that Cliff wishes he could as well. This desire comes from two things: a genuine desire to be a part of the solution, and a thorough understanding of the involved systems, and how to address them. "This happened to me once" is a phrase I have heard ad nauseum, and has, on almost every occasion, led to the pursuit of an untamed ornithoid, or to a wild goose chase. Focus, guys, focus. Ray

 

Thanks guys for the kind words.

One item I forgot to mention, which relates to hard starting is the accellerator pump.

The new fuels contain enough ethanol and other additives these days that I'm suprised we can even get away with using a carburetor. Nothing made of rubber will fair well in contact with any of the currently available fuel blends.

This fuel is extemely hard on the soft tip of the fuel inlet valve needle. Good new here is that most kits will contain a Viton tipped needle, but there is still PLENTY of old stock in circulation that will NOT have the Viton parts, and most kits these days do NOT contain the correct OEM fuel inlet seat, it's pretty much a "one size fits all" deal. The new fuel is tough on the plastic end of the accellerator pump. We are seeing a few pump failures here and there, despite our best efforts to get our suppliers to upgrade the basic components that the pumps are made of.

The good hard blue plastic pumps with retainer are just about all gone. The softer plastic pumps and pumps w/o retainer started showing up about a year ago, phasing out the last of the good pumps. For some reason I will never figure out, they also eliminated the metal retainer to keep the plastic from opening up and allowing the shaft to pull back thru it. We're working on that problem currently, and hope to have a new pump available any day now.

The seal on the pump is another item that will fail. Don't think that you are in good shape because your pump has a blue seal on it. There are at least 5 grades of blue seals in circulation. Several have proved to not hold up all that well to the new fuels. They still swell up some in long term contact with fuel, and will stick in the pump bore, sometimes tight enough that it pulls the pump apart. We have upgraded this part several times, and currently have a seal that is holding up fine.

Beleive it or not, over the counter kits will still show up with buna rubber seals on the pumps, and the soft white plastic pump bodies with no retainer. The kits for early carburetors, prior to 1975 still come with a pump that does NOT have a garter spring under the seal. I would NOT use one of these pumps for any reason, as the life expectancy of these pumps can be about as long as it took me to type this!

We have been watching the spread of the new fuel across the country, and it has finally made it just about everywhere. 2 years ago we wouldn't get a call every other month for a Marine kit. Now, not a day goes buy we don't get an inquiry about one. It appears that the Marina's were the last to get ethanol fuels dumped on them.

If you are reading this and wondering why the new fuel didn't kill your accellerator pump or fuel inlet needle tip by now, keep in mind that the rubber parts in your carburetor had already been in contact with fuel for many years, and were no longer new and "soft". Rubber seems to harden up some as part of it's life cycle. This brings me to the point of the thread. Even if the pump has not completely failed, it may not be doing a perfect job of delivering the fuel that is trapped under it. This leads to hard starts, and poor engine performance with quick throttle openings.

Poor accl pump shot can/will cause a stumble/hesitation/bog when going onto the secondaries as well, as some of the fuel continues to flow after all the throttle blades are at 90 degrees to help avoid a lean condition as the airflaps open.......Cliff