I drive my vette to work twice a week and use it once on weekends.
I cover it in a 'breethable' cover the rest of the time.
ok, now to the problem, It is a '77 with a fairly new engine (1 year
old GM 350)
It doesn't start up right away sometimes.
I usually pump the accelerator pedal once before starting and twist the
It usually catches 3 out of 5 times. Other times I either get a petrol
smell or the godawful cranking from the starter. I let it sit sometimes
10 mins before starting her up again.
But sometimes, I just floor the accelerator and turn the ignition till
it catches. Then of course the engine springs to life and the car
shakes and a ton of smoke comes out the exhaust.
It runs perfectly after that. I guess it's the cold engine or
something, but I need to know.
What am I doing wrong ? Or am I just not pumping enough before start ?
or flooding it ?
Just a guess but pump it once and then hold it about 3/4 open for a
bit and let the mechanical linkage and choke set. Then crank it over
at an idle throttle position. Remember your engine temperature and if
that don't work pump it twice the next time. What works on a cold
engine doesn't always work on a hot engine when it's naturally
aspirated so adjust the procedure with the engine temperature.
Nope, nothing happens unless you keep pumping it, note the term
"pumping". That's why I said pump it once, if that is not sufficient
pump it twice the next time. There is about a 1/2 diameter piston like
pump in the carburetor the squirts 2 jets of raw fuel into the cold
manifold, one on each side. The way to flood it is to just keep
pumping or if the choke sticks. As you hold the throttle open the
linkage is free to set its self to fast idle speed and sets the choke.
Now you can crank it and when it starts it should be on fast idle if
you let off on the pedal as I said before you started it. Until the
choke stove warms up and a bimetal spring warms up and pulls the
linkage back to a normal run speed the fast idle will be maintained
until you kick it off by blipping the pedal.
Oh in addition, when the car does start, when I put it into gear i can
hear a thud and the car jolts a bit, then i reverse and when I put it
into forward gear, it jolts and thuds again.. This is not an engine
noise, it is transmission.. Do I need to replace anything ?
If it's normal then i'm just being paranoid.
I guess the reason I haven't put a stereo in yet is so I can monitor
the engine noise at all times for something out of the ordinary.. I
guess I get carried away sometimes.
keep adding to my vette page by the way, check it sometime.
it's a carborator, if it is cold, pump it at least 3 times then try starting
the car. It is not fuel injected, when cold there is no fuel in the system
it has evaporated, so the intake and carborator will be dry inside until you
press on the peddle.
On my 72 Vette (350/4 spd) and 54 Pontiac with a 400 cid sbc t350 tranny,
all you do is pump it once and it fires up right away. After sitting for
The problem is that the choke is not set properly. You should have a
quadrajet carb on the 350. You need to pump it once to set the choke closed
and to put a squirt of gas in the line. As you crank, the vacuum should
open the choke a little bit (usually set with a drill bit) to the first
fast idle knotch which also has a fast idle rpm adjuster screw.
After the car warms up, the electric choke coil or intake manifold choke
coil oven will heat up and then you have to kick it down to release the
fast idle and get to the slow idle setting.
Most garages don't like to spend the time to set up a quadrajet because to
do it properly can take a couple of days. You have to have the engine cold
for the cold engine settings and hot for the normal idle. It takes me a
couple of days to get everything right. Most is waiting for the engine to
cool down so that I can test it again.
There are 3 functions of the choke:
1. Initial startup where it is closed completely so you can suck in as much
fuel as possible.
2. Once its fired, the choke opens a little bit to let the engine run at a
richer mixture than normal.
3. Once its warmed up, the choke opens all the way for a normal mixture.
Excuse my barging into the discussion which is usually spent just
lurking,reading,learning, admiring posts,questions,problems solutions and
such things posted after a long day at the office.
Being an avid chevy owner, a fool at times with my spending, one
knowledgeable ex mechanic turned firefighter friend to guide me with his
knowledge,the calm to guide me to think and with a dogged detrimination to
do it myself, I beg forgiveness in mudding the waters to what appears to be
a simple question with some already knowledgable answers and solutions.
Now before I begin, alittle about me.While not really of interest to many, I
have welding as my fortay,the welding makes me the bucks to do the car
This means I've funded a small education with lots of car magazine tech
articals and owned a lot of cars over the years,all GM's for the most part.
Most had Q-jets 4 bbls..and mostly I've kept them running. Part of my fleet
includes a 95 and 85 C4 hence my vette fetish.
If I had followed the commercial for MCI, I would be still smarter,richer,
still married and have more of a social life...but I don't,so I have some
experiences working on cars instead.
But I'm no mechanic.I'm here to learn.And I like to share.
A properly set up carb, even a Q-Jet should be practically trouble fee if
all is working well. But anyone whoever took a carb apart learns 3 things,
maybe 4, and possible 5 from the experience.
1) To find the number off the Q Jet carb, you'll have to scrape through the
gunk hiding the stamped number location located on the dr. side back corner
of the carb,usually requiring an old tooth brush dipped in carb clearner for
scrubbing and a mirror and flash light to read the number.That number is
needed to purchase a carb kits loaded with gaskets, an accellerator
pump,needle and seat, maybe a small ball bearing, a couple of springs,some
misc this and that with a 4 to 10 page set of instructions. You will have
left overs...really. The carb kits are some what universal.
2) Did I mention you need to soak all parts in carb cleaner, buy a gal..
Rubber Gloves,keep the tooth brush handy. No open flames and lots of
ventilation for working, and especially a clean spacey work area to step by
painful step, lay out all the parts and pieces. Becareful, yes that ball
bearing does belong in the carb. Tools needed for re and re are rather
simple really. A socket,extention and wratchet, a tubing wrench or two,
maybe an open and box end wrenches,screw drivers,flat amd philips, pin
punch, pen and tape to mark any vacume line locations and you about good to
go. Oh yea,maybe a bandaid or two and a few profanities may be called for.
Newer Q Jets, usually have metric bolts, and torx screws. Screws located top
and bottom of the carb. Did I mention the need for a compressed air supply?
3) Once you read the instruction, you realize what a mistake you made in
thinking you could do this with just a few simple tools because it is more
complicated then that, and it really is to do it properly. Now I don't say
this to scare any guys like me from doing this. No guts no glory. You learn
nothing by your successes only by your failures, go for it. At the least you
can do a freshing up of the carb.Just becareful in taking it apart.Don't
bend any linkages, forget any parts, replace the float while your at it, and
take your time. Alot of time the accellerator pump is not doing it's job,
gaskets may be leaking, and let not forget the biggest area of Q Jet
complaints,vacume leaks from the wearing of the throttle shaft.The latter is
a pain to repair.
4) Was the carb really the problem?
5) Was paying someone to fix it really that much of an expense?
The original post mentions a few things, new/recent engine up grade being
one.Not driving the car much being the other.Happens 3 out of 5 times. Any
owner of a GM with a Q Jet usually has there own way of starting, regardless
of what the factory tells us. Why...? My guess,age of the carb,wear and
adjustment play a factor, and lets not forget the weather.
A lot of things could effect the operation of a properly set carb if the
rebuilt engine was upgraded, cam specs,compression ratios,ignition timing,
would all have an effect on operational performance.Including starting.
Maybe it was crap gas.A semi plugged fuel filter? Leaking carb plugs? Was
any work done to the carb since the up grade? Was this a problem recently or
before? How about the choke element if it's bi metallic,the linkage rod or
the adjustment if it electric? Lets not forget any temp/vac sensors for
polution control systems.
On that note, my skills at diagnostic work need work, but I'm a heck of a re
and re man.
Keep up the good work men. I perfer EFI.
Thanks for all the input, I am not sure I really want to touch the
carb, or even open it up myself. The thought of losing or messing up
any precision part in there would give me nightmares. Dad's idea worked
and the car starts up after pumping and then tapping it once once it
Just out of curiosity, how much does it cost to convet to EFI and what
needs to be removed ?
Actually it isn't all that hard to convert to EFI depending on the year of
engine, and of course the year of donor car.Your 77 should be almost a bolt
on using 85 to 87 Camero or corvette TPI parts with the exception being the
bung being welded in the exhaust for an oxygen sensor, and concideration for
the fuel pump and fuel lines.
Other wise a complete engine swap is the way to go due to cylinder head
design changes on sbc engines.
Ebay has lots of units being offered, however I went the route of buying a
complete running wreck to strip,and sell off the unused parts to off set the
cost , and to make sure I wasn't going to nickle and dime myself on misc
parts,sensors or cut wires.
Do a google search for Tuned Port Inject and the information to take the
fear out will be easly answered.
Best of all, no more pumping the gas to start,fuel ecomomy is up,throttle
response is excellent.
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