1966 monza takes many tries to start up

[Scia13]

My 1966 four door takes anywhere from 2 to 12 tries to start depending on the day. I always pump the gas pedal multiple times before each crank. The car has an electric fuel pump and electronic ignition and relatively new battery. It runs completely fine once it gets started but it is slightly annoying to sit there cranking it a couple times to get it started. How could I resolve this?

Any help would be much appreciated,

-Simeon

[bbodie52]

A proper tune-up and system analysis will go a long way toward an easier, more-reliable startup. Follow all of the tuning, throttle synchronization and choke adjustment procedures as covered in the shop manual. A weak coil output or degraded ignition points/faulty condenser can contribute to the problem. The connecting wire between the points and the coil can degrade and break down. Clark's offers a replacement wire, if you think yours has deteriorated. A good ground connection within the distributor is important. Faulty plug wires, a faulty cap, or faulty rotor can also add to the problem. Check the operation of the accelerator pump in each primary carburetor. Check for vacuum leaks. Points begin to degrade on the day they are installed. Consider upgrading your distributor to utilize a breakerless ignition system, such as those made by FAST or Pertronix. A properly installed ignition system upgrade coupled with a tune-up may help a lot. If your carburetors have not been overhauled, adjusted, or cleaned in a long time, and if a normal range of tune-up adjustments does not clear thins up, a carburetor overhaul and rebuild maybe considered. Also check the condition of the metal contacts within the main engine compartment multiconnector for loose connections or signs of corrosion.

If you have a Corvair mechanical fuel pump, check its output pressure and fuel volume delivery, as outlined in the shop manual. A cracked rubber hose in the fuel line path between the furl tank and the fuel pump could conceivably result in fuel starvation, as the pump struggle to draw fuel all the way from the tank to the engine compartment. Also, if stale fuel is a possibility due to infrequent use of the Corvair, take steps to cycle fresh fuel into the vehicle periodically. Also, keep the battery fully charged.

There is no simple, or compressed method to tune and troubleshoot a Corvair engine. A certain amount of knowledge or understanding is essential for the person doing the tune-up to interpret the results and then to be able to make logical adjustments accordingly. I would encourage you to do your homework, ask questions for clarification when needed. and follow the guidance below and in the shop manual to ultimately get the desired results with your Corvair.

Here is a fair amount of tune-up info, but if you can work your way through it the explanations may help with your understanding of how the various subsystems interact with each other, and why the proper sequence should be followed so you don't end up adjusting one area improperly to compensate for another area that isn't functioning properly.

The dwell tachometer and timing light are the most common items thought of when working with an older engine in a classic car. As previously mentioned, however, there are ways to work around the lack of these tools. Adjusting the ignition points gap with a flat feeler gauge is a substitute for having a dwell tachometer. Setting the dwell with an electronic instrument is more accurate, however. The tachometer portion is needed to measure idle speeds and possibly to perform other tests where engine speed measurement is needed. It is possible to static-time your ignition system with a strip of paper placed between the ignition points. The engine timing mark can be manually positioned to the desired setting on the crankshaft pulley, and the distributor can be slowly rotated until the points just start to open and release the strip of paper. The distributor is then tightened and the mechanic has established an initial static timing setting. Of course, having a timing light makes things much easier, improves accuracy, and permits visual confirmation that the centrifugal advance is functioning. A vacuum gauge can be used for carburetor synchronization and other carburetor tests, and most vacuum gauges also double as a pressure gauge for measuring fuel pump output pressure. A UniSyn gauge, as shown below, measures airflow through each carburetor throat, and is an accurate way for synchronizing multiple carburetors at idle speeds and at partial throttle. A multimeter is a useful tool for troubleshooting and diagnosing electrical and charging system problems.

Many ignition systems in Corvairs have been upgraded by fitting an electronic ignition system to the distributor. These electronic ignition systems eliminate ignition points and condenser, which makes engine tuning somewhat easier and eliminates the need to periodically replace worn ignition points. The breakerless ignition system utilizes an optical or magnetic trigger to control the ignition coil. The system eliminates the need for a dwell meter or flat feeler gauge for ignition points adjustments. (A wire-type feeler gauge is needed for adjusting spark plug gaps). The tachometer portion of a dwell-tachometer, however, is still useful.

Learning to work with the two Rochester primary carburetors on the Corvair really isn't all that difficult. But you should take the time to review the shop manuals and other attached manuals to get a better feel for what you are trying to accomplish. It is important to perform tuning steps in the right sequence, as outlined in the shop manuals and in the video below. Many of the tuning steps can impact the results found in other steps. There is a logical progression in tuning a Corvair engine, and skipping around or tuning components in a random order can only serve to confuse the outcome. The Delco Rochester service manual that I have attached is a good supplement to the Corvair shop manual. About half of the manual is dedicated to explaining the various subsystems and components of the Rochester HV carburetor. To some extent these carburetors perform as you would expect a computer-controlled fuel injection system and ignition system to operate — but they were designed at a time when computer-controlled systems that were designed to respond to sensor input throughout the car would only have been a dream. The various carburetor and ignition subsystems respond to engine temperature, engine speed, airflow and vacuum changes, etc. much like a modern engine — but without all of the sophisticated electronics and sensors. Engineers were attempting to accomplish the things we do now, but with much less sophistication — but still making changes as engine speed, throttle position, engine vacuum, and fluid and air flow characteristics varied. If you take the time to read through the Delco Rochester manual, you might come to understand how the choke system functions, what an accelerator pump does and why it exists, and how the distributor is designed to adjust timing at low engine speeds and at higher engine speeds using both a vacuum advance and a centrifugal advance to provide the correct timing at various engine speeds and load settings. A good understanding of how these systems work and what they are supposed to do can be a great help when tuning and troubleshooting your engine.

The links, videos, and attachments below should help you to understand how to work with a dual carburetor engine. Try not to be intimidated by two physically separated carburetors. They really function very much like a single two-barrel carburetor, but are physically separated from each other out of necessity due to the layout of the flat air cooled engine with cylinders opposed to each other. The Corvair engine layout is in many ways similar to many motorcycle engine configurations. It usually takes an experienced automobile mechanic a little adjustment time to get used to the way things are done on a motorcycle. The aluminum, air cooled flat six Corvair engine often is seen as a challenge to an automobile mechanic, who is not used to the "strange configuration" found in a Corvair.

http://www.corvairforum.com/forum/viewt ... 875#p90875


The entire shop manual and many other Corvair technical references can be downloaded at no cost using the following link...

Common and Useful Corvair Websites
http://www.corvairforum.com/forum/viewt ... 225&t=6007

Watching the video presentations below helps to provide insight and understanding about proper sequencing of the tuneup steps and procedures. Skipping around can insert obstacles and problems with getting the engine properly tuned.

The portion of the first video segment toward the end (Part 1, 5:10) and at the beginning of the second segment discusses throttle linkage adjustments and carburetor synchronization.

Tuning the Corvair Engine — Part 1



Tuning The Corvair Engine — Part 2

The Uni-Syn Carburetor Balancing Instrument is a tool that I remember as far back as the 1950s and 1960s. It was designed for use in multi-carburetor automobiles, motorcycles, etc. that were initially common in European vehicles, but were later found in American vehicles like the Corvair.

The Uni-Syn is an airflow gauge that must be calibrated to match the specific engine airflow moving through the carburetor throat. The flow control in the center of the Uni-Syn is mounted on a threaded pin. Rotating the flow control raises or lowers it, which increases/decreases the air gap, which impacts the air velocity passing the oriface that allows some airflow to pass through the gauge. With the Uni-Syn held firmly on the carburetor intake with the engine idling, the flow control is adjusted so that the plastic float is approximately centered in the glass sight tube. Once calibrated, the Uni-Syn can be moved back and forth between the two primary carburetors to compare airflow at idle. The goal is to play with the idle speed screws to get an even airflow level that matches between both carburetors, and at the same time produces the desired idle speed. Before fine-tuning this idle balance with a Uni-Syn, the ignition system, idle speed and idle mixture should have been adjusted following the standard procedures as described in the factory shop manual. The balancing step with the Uni-Syn gauge is added at the end of the tuning procedure to measure actual airflow though both carburetors at idle, and balancing that airflow using the airflow meter as a measuring tool, rather than simply relying on a physical balanced "calibration" using a strip of paper to detect initial contact between the idle speed adjustment screws and the carburetor linkage, followed by counting the screw turns needed to obtain the desired idle speed (and ensuring that the same number of screw turns are applied to each screw). That procedure achieves a fairly close initial setup. The use of the Uni-Syn airflow gauge as a final step ensures balance between the two carburetors by measuring actual airflow.

Once the balanced idle airflow and desired idle speed have been achieved, a similar procedure can be used to synchronize the airflow when the carburetors are held open at a faster engine speed by the throttle linkage. Again, the shop manual procedure can be used to set the initial mechanical balance between the two sides of the throttle linkage. The linkage segment connecting the accelerator pedal to the cross-linkage between the two carburetors is temporarily disconnected, and a turnbuckle is temporarily attached to hold the throttle opened against the pull of the throttle return spring.

The turnbuckle can be adjusted to hold the throttle open at approximately 1500 RPM. The Uni-Syn center flow control is readjusted to re-calibrate the float to a position somewhere in the center travel of the sight tube, based on the increased airflow through the carburetors at the higher steady RPM maintained by the turnbuckle arrangement. As with the idle synchronization procedure, the re-calibrated Uni-Syn is used to measure the airflow moving through the two carburetors. The goal is to fine-tune the threaded portion of the carburetor actuation linkage so that the same airflow reading is attained on each carburetor, but this time with the throttles held open by a pull on the throttle linkage, instead of by the setting of the idle speed screws. When the airflow has been balanced using the throttle linkage adjustment, the balancing procedure has been completed and the normal accelerator pedal throttle linkage can be reconnected.

TIPS & CLARIFICATION...

With the engine at idle, you want to open the Uni-Syn flow control as much as possible, but still keep the float in the sight glass at about mid-level. Then check the other carburetor, which you want to read the same flow rate. You may have to adjust the flow control a few times as you adjust the carburetor settings. Just remember to check each carburetor with the flow control set at the same point, and to keep the sight glass in the vertical to prevent the float from hanging up in the tube.

The wheel in the Uni-Syn venturi controls the flow through the tube, or in other words how high the bead is in the cylinder for a given engine speed. You need enough flow to not strangle the engine, and the bead works just as well in the lower third (which still lets good air flow through). Make sure the idle speed doesn't drop when you place the tool on the carb: if it does, open it up.

Before setting the carbs, make sure that the ignition is right: points and timing set, good wires and plugs. Poor running is often blamed on carbs when in fact it's a weak, retarded spark. Check the throttle shafts: loose ones let in air and lean the mixture, raising idle speed, as well as throw off the linkage action. Check the linkage that connects the carburetors. if it's loose, one will open before the other. Make sure there are no vacuum leaks.



With a twin carburetor set up, disconnect the linkage that connects one carburetor to the other. Set the idle speed with the linkage screws first. Use the Uni-Syn to check that each carburetor is drawing equally at idle. This may take a few tries until you get both drawing equally at the speed you want. Blip the throttle to see if they come back to those settings (worn throttle shafts can fool you). Set the idle mixture screws in accordance with the shop manual instructions. Check the balance again. Hook the linkage back up. If one carburetor now draws more, adjust the linkage until it's back to roughly equal.

Once the carburetors are drawing equally at idle, hold an engine speed: at about 1500 RPM. This checks that the mechanical linkage is pulling equally. You'll need to open up the Uni-Syn center wheel to draw more air and bring the bead down in the tube. If both carburetors are within a bead's thickness of each other, that's good. If one is definitely off from the other, the higher flow carburetor's linkage is being pulled more than the other. You'll need to figure out why that's happening mechanically to rectify it.

You need to backtrack a little...

The goal is normally to try to match the left and right carburetors as closely as possible. Rebuilding or replacing one carburetor while neglecting to do the same on the other side encourages something of a mismatch.

After checking for vacuum leaks (don't forget the Powerglide transmission vacuum modulator as a possibility), disconnect and plug the vacuum advance line that is coming from the right carburetor. (Make sure that the rubber hose is connected to the vertical vacuum tube on the right carburetor, and NOT the horizontal vacuum tube, which should be connected to the choke mechanism vacuum break unit on each carburetor). Temporarily readjust the carburetor idle speed screws to get the engine idle slowed down to about 700 rpm in NEUTRAL. This will ensure that the centrifugal advance mechanism in the distributor is not affecting the timing. Then recheck the points (dwell) with a dwell-tachometer and then the base timing setting with a timing light, and set them correctly for your engine, using the specs in the shop manual.




See Vacuum gauge viewtopic.php?f=225&t=10563

At this point, you will have confirmed that there are no vacuum leaks, and that the ignition system settings (dwell and timing) are correct. Reconnect the vacuum advance tube between the right carburetor and the distributor vacuum advance mechanism.

Following the procedures in the shop manual, the base (starting point) idle settings on each carburetor are to be established. With the throttle linkage at both carburetors disconnected from the cross linkage between the two carburetors, a narrow strip of paper is used like a feeler gauge by placing it between the idle speed adjusting screw and the carburetor throttle linkage. With the throttle closed, the idle speed screw is slowly backed away until it just releases its grip on the strip of paper. This establishes its point of contact with the throttle linkage. Then carefully turn the screw clockwise an a additional 1-1/2 turns to establish the idle speed preset. Perform this same procedure on the other carburetor. Then perform the idle mixture preset on both carburetors by gently turning the idle mixture screws all the way in so they just bottom-out in the carburetor. Then back each screw out counterclockwise 1-1/2 turns.



With the engine running, the correct idle speed for your engine must be established. With a manual transmission-based engine, the idle speed is set to the speed designated in the shop manual. This can be a starting point with the automatic transmission-based engine as well. Any adjustment made to increase or decrease the idle speed must be duplicated at both carburetors, so that the carburetor settings remain in sync on both sides. (A uni-syn gauge, or a vacuum gauge, if available, can be used to more-accurately synchronize the two carburetors so that they are each contributing an equal amount of airflow to the engine idle). With a Powerglide-based engine, the final idle speed must be set with the transmission in DRIVE, to load the engine with the resistance provided by the fluid coupling (torque converter). The goal is to achieve a slow, smooth and steady idle speed in DRIVE.

With the carburetor idle settings in sync, and the correct idle speed established in DRIVE, the last step is to reconnect the main throttle linkage between the two carburetors, and then the throttle linkage connection to the accelerator pedal. These procedures are described in the shop manual. There is an adjustment point in the linkage on the left side. The goal is to have both carburetors connected to the cross-linkage, without the linkage binding or holding either carburetor throttle open or impacting the idle speed. The link on the left carburetor is adjusted so that bot the right and left carburetor connections slip into the cross linkage. Finally, the adjustable link and throttle return spring is adjusted to slip into the cross link without changing the idle speed, so that the gas pedal permits opening the throttle fully but also allows the throttle to return fully to the idle setting.

[irfgt]

When you say 2-12 tries how long is a try? Some people let it try for about 2 seconds and consider this a try, Almost any Corvair will be harder to start after a hot soak and holding the accelerator about 1/4 the way down and not pumping while attempting for at least 15 seconds should result in a start.

[Frank DuVal]

Have you taken the air cleaner off to see if there is fuel squirting into the carburetor throat when you move the accelerator pedal/linkage? Easy to do and will answer many questions.

Also, just one push of the accelerator pedal to set the chokes on a cold start.

NO pushes of the accelerator pedal on a hot start. Crank with foot off pedal, then step slowly on pedal if no start, going all the way to the floor if necessary, and hold it there (clears a flooded engine).

Best to correct starting procedure before going into a full tune up!

[Dennis66]

A little more info on the "2-12 tries". Cold only? Hot only? Cranking for how long? Backfiring, coughing, nothing? If it's cold, I agree with Frank, check for the carb accelerator pumps squirting a good strong stream. Do this by removing the air cleaner and working the throttle before any cranking. Dennis

[manvair]

I suspect your chokes are not closing properly, and you are having to add lots of gas to make up for it.

[jimbrandberg]

I tend to open the throttle a little when I turn the key.
Jim Brandberg

[Lane66Monza]

Engine cold or hot issue.

You have an lectric fuel pump - do you have a prime switch to fill the carb bowls when car has sat a few days. Ethanol fuel evaporates when sitting unused for a couple days after a run.

Dies it start right up after run or the next day?

[Scia13]

Engine cold or hot issue.

You have an lectric fuel pump - do you have a prime switch to fill the carb bowls when car has sat a few days. Ethanol fuel evaporates when sitting unused for a couple days after a run.

Dies it start right up after run or the next day?

No I do not have a prime switch. It started first time one day but otherwise it always takes multiple tries even if I drove it the day before. However, It starts right up if I just drove it.

I will try starting it with just pumping the pedal once to set the chokes and then letting onto the throttle slowly.

[Scia13]

Engine cold or hot issue.

You have an lectric fuel pump - do you have a prime switch to fill the carb bowls when car has sat a few days. Ethanol fuel evaporates when sitting unused for a couple days after a run.

Dies it start right up after run or the next day?

Actually there is a switch mounted at the very bottom of the dash right above the parking brake. Could that be the prime switch?

[Lane66Monza]

Turn the ignition switch on and select switch on. See if you hear the pump. If you do hear it, use the switch for a few seconds prior to every start if engine is cold.

Hopefully you got an electrical schematic of how the electric pump was wired into your car by the previous owner. That way you will know what functions control the pump, when the ignition is on.