carburetor cleaned, but trouble starting car

R

rustychevy

New member
Here is my situation: I had the carburetor cleaned and it seems to be a good job as far as the cleaning is concerned. But now I have trouble starting the car. I pump the gas, turn the engine, and although it tries it doesn't start. I hold it for under 10 seconds then shut it down. It takes 2 or 3 more tries to get it going. What is the problem? I am guessing the problem won't go away so I will have to take it back to the garage. Will I have to pay for service or will it be a continuation of the original job and no fee will be involved?
 
When it does start how does it run ?. What vehicle, type of carb. First thought is the accelerator pump. If it runs rich when it does start the floats could be hanging up. Another thought could be a massive vacuum leak.

Dave
 
A carburetor? OMG.. What's that??? Lemme think...

Ok. Well, I haven't touched a carburetor in like 15 years, but back in the day I did rebuild, set the mixture, and R&R more than a few. A couple of thoughts:

1. Was the problem there before the garage touched it? If not, I'm guessing there could be a vacuum leak from something that didn't get hooked up correctly. Does it idle smooth?

2. Does it idle rough cold and smooth warm - or vice versa? That would likely be a problem with the choke or the choke pull off valve.

3. Do you have good fuel pressure going into the carb after the filter? You can check this with a cheap low pressure fuel pump gauge. It's been so long, but if I recall it should be between 9-16 lbs or so of pressure.

4. Did the dude at the shop monkey with floats or try to "set" the air fuel mixture? This could be bad. I've seen people "monkey" with carburetors that were fine. Depending on the monkey, sometimes the only option is replacement.

What's wrong for sure - nobody knows until they look at it. It could really be anything. But, first - you have to figure out if the problem was there prior to the cleaning?
 
There is going to be a lot of assuming in my response. When someone tells me a carb had been cleaned, I assume it has been rebuilt. I also assume you are talking about a cold/first start up. Assuming this problem didn't exist before the carb was rebuilt and the car actually runs reasonably well once it lights off. I would look to see if the choke was properly adjusted? Because you said it eventually fires I assume there is fuel in the bowl.

Fuel supply (pump, filters, etc.) problems are often noticed on high demand rather than at start up, again this assumes there is fuel in the bowl. You can remove the air filter, open the choke, look down the carb throat and open the throttle and visually see if fuel squirts into the carb. If there is fuel in the bowl but you don't see it squirt there could be an issue with the accelerator pump. You would notice this when it is running as well, it would fall flat when you hit the pedal.

If the carb has fuel in the bowl, the engine will fire even if there is no fuel supply. It will run out of fuel quickly but it will start. If the float level is set to high, the carb could be dumping at shut down and you could have puddling in the manifold. This problem usually manifests itself on warm restarts, the engine is flooded. The longer it sits the more time it has for puddling to evaporate and usually isn't a problem when cold but would run rough if the carb is dumping.

This all said, you could also have ignition or compression problems that mimic the description you have given. Gotta have three things all properly timed, compression, ignition and fuel to light her off. I've probably done nothing more than give you way too many if, ands or buts.
 
I am trying to find the answers about the type of carburetor and the fuel pump. The other questions I can answer now.
The car is an 84 chevy caprice classic.
Q: When it does start how does it run?
A: So far once the engine starts there are no problems. The farthest I take the car is a 20 mile round trip. There are no problems starting the car after being in park 3 times in one day.
Q: Was the problem there before the garage touched it?
A: On occasion I would have to turn the engine a second time, but the engine never struggled as it does now.
Q: Does it idle smooth?
A: No problems that I am aware of.
Q: Do you have good fuel pressure going into the carb after the filter?
A: If I understand the question, the car runs better since it has been cleaned.
Q: When someone tells me a carb had been cleaned, I assume it has been rebuilt.
A: Carb was "cleaned" some new/used parts were needed. The bills states: "rebuilt carburetor" and "choke pulloff".
Also a new filter.
Q: I also assume you are talking about a cold/first start up.
A: First start, no problem so far otherwise.
 
If I had to guess, it sounds like the accelerator pump may not be working correctly. That "primes" the engine with fuel for a cold start.

You should be able to check this by looking down the barrel(s) and having someone pump the pedal a few times. You should see liquid fuel squirting into the barrel.

The fact you say it idles smooth cold & hot leads me to believe its not a choke issue or a vacuum leak. But, the choke could not be set right or not closing enough - its hard to say without looking at it. I think those GM carbs had a temperature sensitive spring that could modify the choke position - can't recall for sure. The fact that you mentioned it doesn't happen after the car has been driven that day may indicate this could be the issue.
 
on the side of the carb is a big black plastic disc, see if there I a vacum hose attached to the housing of it, and make sure it's clear and not cracked etc.

on the disc it should have a flat blade screw driver spot, this is used to adjust the choke. do this with the air filter off and look down the carb
 
Rustychevy, having read your response, I would once again suggest you check or have checked the choke adjustment. This includes the vacuum brake/choke pull off. It isn't used to set the choke but rather open the choke once vacuum is present. One other thing to look for is: what's coming out the tail pipe when this car finally fires. If you see black smoke in quantity, the choke is likely adjusted too tight.

I believe you can rule out the accelerator pump simply because if this were the problem you would likely also be noticing a flat spot upon acceleration or simply revving the engine when the vehicle is running.

A choke that is set either too tight (rich) or to loose (lean) will cause the problem you have described and could have very easily been misadjusted during a rebuild. When there is a problem more often than not when these carbs are rebuilt a technician will set them on the tight side. As an engine gets older the opposite is usually preferred. This is particularly true with a Rochester Quadrajet carb. These were common four barrels during the era you describe. These carbs tend to have an issue with the well plugs leaking and often go unnoticed during a rebuild assuming they didn't use electronic metering rods. Other than affecting the mileage and start up they can go undetected. If you don't see smoke when started it could have easily been set too lean. The Rochester two barrels back in 84 were particularly sensitive to choke pull off adjustment. These problems are easily checked and easily adjusted regardless of whether you have a two or four barrel, the pull off has been replaced so their shouldn't be a need for common parts.

The choke plate should be just tight enough to close when the engine is dead cold. Once the engine fires the choke pull off should open just enough for the engine to run cleanly until the choke coil heats and fully opens the choke blade. The fact the you are saying this problem is new or at least different than before the rebuild leads me to believe that many other issues like the fuel pump or fuel filter could initially be ruled out. The fuel filters are internal in the Rochester carbs and are always replaced during a quality rebuild.

Hope this doesn't sound like I'm just blowing a bunch of smoke in typing this. Good luck in your pursuit.

P.S. I would assume that any business/technician worth their salt would look at this free of charge if it were a fresh rebuild. During my career I had a very small percentage of "come backs" (hated them, like a kick in the gut if I made a mistake) but I know I certainly would have jumped right on it if a customer had a complaint such as yours.
 
Take it back to where it was serviced. Give them a chance to rectify the situation. 84 Caprice is most likely a QuadraJet 4bbl. If they are no help re-post and can show you things to check. Just did a carb rebuild seminar for the local Firebird Club I belong to and went through about a half a dozen carbs with a old friend/employer that had a carb repair shop from 64 till about 2 years ago.
 
I started the car Friday morning after the third try. I took a four mile drive into town, I am glad I did not go any further. As I walked past the car I noticed a pool collecting on the ground. I looked under the hood and antifreeze was coming from the radiator. I also noticed that a tube of some sort under the engine was disconnected. The mechanic came by the next morning. The radiator was not his work. There was a crack in the year-old cap, he replaced it. Don't know how the tube was disconnected, but he put that back. It is for hot air from the engine if I remember. As far as the carburetor is concerned, the mechanic said the car was running "lean" after the cleaning and the adding of the replacement parts. He told me to apply two quick pumps to the floor, then a slow quarter pump. I tried it today and got it right the first try, so I expect no problems from now on. The car is running better since the carburetor was cleaned so if nothing else goes wrong I will be pleased with the results.
 
rustychevy said:
I started the car Friday morning after the third try. I took a four mile drive into town, I am glad I did not go any further. As I walked past the car I noticed a pool collecting on the ground. I looked under the hood and antifreeze was coming from the radiator. I also noticed that a tube of some sort under the engine was disconnected. The mechanic came by the next morning. The radiator was not his work. There was a crack in the year-old cap, he replaced it. Don't know how the tube was disconnected, but he put that back. It is for hot air from the engine if I remember. As far as the carburetor is concerned, the mechanic said the car was running "lean" after the cleaning and the adding of the replacement parts. He told me to apply two quick pumps to the floor, then a slow quarter pump. I tried it today and got it right the first try, so I expect no problems from now on. The car is running better since the carburetor was cleaned so if nothing else goes wrong I will be pleased with the results.
Click to expand...

The "tow quick pumps" engages the choke
 
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