New Mexi 1600 longblock w/ SVDA dizzie, new 34 PICT/3 carb w/ choke connected. Stock oil bath air cleaner with air pre-heat hose connected, clean manifold with preheat tubes clean and connected.
Cold starts -- very easy. Hot starts (dash into 7-Eleven for curry Squishie) -- also very easy. Warm starts (sittin' for 30 minutes) gotta run the starter motor for 4-5 seconds before engine catches.
Maybe the choke does not quite track the engine's condition in between hot and cold?
...............That's right. It doesn't work effectively when the ignition has been off for more than a few minutes. You get too much choke with a hot engine and flood the engine. I used to adjust it back almost all the way 'lean' when driving in hot weather to lessen this problem. Another thing that could be working against you is the common problem of engine heat causing the gas to boil out of the carb's float chamber and causing flooding as well. I don't know of an easy fix for that one. Do you have one of those fiber whatever isolators between the carb and the manifold?
There's a composite gasket about 1/16'' between the carb and manifold, but I'm not sure how this boiling gas theory works. The engine starts fine when it's at operating temperature -- like only been off for a few minutes. And it starts fine when it is cold. It's the in-betweenly condition that it grumbles about, like having cooled down for 30 minutes or so from normal operating temp. Does that jibe with the boiling/flooding scenario?
Mind, it's not a problem, the engine starts after a few seconds; it's just something that I've been noticing and have been mentally worrying, like a dog a bone.
.............1/16" sounds too thin, try 2 or 3 instead. It takes a while for the heat to conduct into the carb float and boil out the gas through the vent tube. 30 minutes is probably what it takes to flood out the cylinders......I'm just guessing. I have a digital thermometer probe in the engine compartment of my '77 bug because I was worried last year that my tin wasn't properly isolating the the topside of the tin from the heated air exiting out the bottom. One thing that I've noticed is that the engine compartment is never much more than maybe 10 deg. higher than the outside ambient temp while I'm driving but when I turn the engine off, the compartment starts heating up to well over the 160 deg. limit of the temp probe/gauge within a minute or two. I don't remember what the boiling point of gasoline is but it's not very high. So it could be more than just heat conducting from the manifold into the carb that causes this. Of course, since I'm running an L-Jetronic EFI system, I don't ever have these problems anymore........BWAAAHAHA !!!!
Why don't you open the engine compartment lid the next time you park it for
30 minutes and see whether that makes any difference in how it starts?
Another idea: Since you're in a warm climate, put a block off plate in the joint where the manifold heat tube is attached to the muffler. Drive around and see whether it starts better and whether you even need manifold heat in Sandyeggo. I wouldn't try it up here in damp and cold NY but maybe it would be OK for you.
Me neither. The problem is that the manifold is HOT... if the engine has been properly assembled (ie, cross-over pipe is not clogged). During warm weather the siamesed portion of the intake manifold -- the part having the aluminum jacket -- contains a significant quanta of heat that gets dissipated into the engine compartment when you shut down the engine. A lot of that heat gets absorbed by the carburetor even WITH a gasket that provides good thermal isolation between the carb and the manifold... the carb has a lot of surface area and the air around it is HOT and things roll downhill from there.
I've used two techniques that help the situation. The first is to ALWAYS idle the engine for at least a minute before shutting down. I've got a clock right in front of me (where I usta have a sun visor) and you wouldn't belive how long a minute can be, just sitting there watching the gauges. How much does it help? Frankly, not a bunch... depends on the weather. Seriously hot day, it helps. Cold day, you won't see any change. Middling-warm, like we usually have here in sudden California... sorta iffy. But I've made it a habit, don't really notice it any more.
The second technique was hi-tek kewl. 12vdc computer fan that comes ON when the ignition goes OFF via a thermostatically controlled relay. When the temp at the sensor drops below 140, the thing shuts itself off. So you get to where you're going, climb out, walk away, the fan keeps humming away back there, eventually shuts itself off (you hope). Nothing very tricky about the set-up; ripped the parts out of a Ford 'Tempo' (? - I lose track) Radiator fan temp sensor. All I did was add a couple of relays to include a fail-safe.
So howz that work with the hard-starting? ONE fan, blowing on the carb, I didn't see any change. TWO fans, both blowing air OUT of the engine compartment, I saw a definte improvement.
But a couple of additional points need to be mentioned. The first is that damn PICT-34. It appears to be a LOT more sensitive to engine compartment heat than the older round-bowl carbs. Since I stopped using 34's I haven't had any problem with hot starts. Keep in mind, I drove a '65 whereas Rocky flies a 'loaf. My engine compartment is vented directly out the sides of the van whereas he's got that l-o-n-g upward column to those high-placed vents up behind his rear windows. I suspect his engine compartment stays hotter, longer, than mine does and is a contributing factor.
Bottom line: You really gotta love fuel injection :-)
Thanks Tim and Bob! This explanation makes sense. I'll prop the engine compartment door open when I expect to be needing the car within 30 minutes or so, and see how that affects this hot carb effect. Since I have taken everything back to stock (except the SDVA dizzie) I know that I don't have anything attractive in there for covetous kids looking for swell performance engine parts. Just a boring old baywindow.
The use of turbo tape or other insulation, in conjunction with a thermal barrier gasket, was the originally recommended fix for this problem but VW stopped recommending it when they found it promoted rusting of the manifold. The rust would progress under the cast aluminum of the siamesed section and cause the aluminum to crack. This sounds pretty extreme and I suspect the problem was linked to the use of salt on the roads but since the dealer did the install they were also responsible for the required repair.
This technique (ie, insulating the manifold) might be worth a try here in sunny sudden California using some of the more modern insulations such as Fiber-Frax. (Home boys used ironing board pads with pretty good results :-)
............That would help if there was vapor lock in the line caused by a hot engine compartment. It wouldn't do anything for the more common problem of gas boiling out of the carb's float chamber.
.............The gas in the line doesn't boil as easily as in the carb's float chamber. The float chamber is vented so that pressure can't build up like it does in the line where there's a float activated valve leading into the float chamber. When pressure rises, the boiling point rises. Vapor lock is a relatively uncommon problem compared to the typical flooded out situation involving the carb's float chamber vent spewing gas down the throat of the carb.
I've had that problem as well time ago. Sure enough it was the metal fuel line that comes from under the car that goes to the gas tank, it was touching the manifold causing vapor lock. One easy way to find out: Next time it locks up, pour some cold water on the fuel pump to cool it down. If it starts right back up... You know what your problem is.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.