Whats the wire to the choke do?

Hi,

I had the wire melt while trying to start my car yesterday, I was glad I had a quick disconnect on the battery.

I removed the wire, it went between the starter solenoid terminal and the choke control on the manifold, well, I found that wire has been a problem for a while causing the engine to crank slow when starting.

As soon as I removed the wire the engine turns over like 3 times faster now when starting it.

Anyway, I live in SoCal were the weather is warm pretty much year round. Do I need the wire connected to the choke system? or can I live without it.

I searched and cannot find anything that tells me exactly what it does.

Thanks

It activates the choke. It closes the choke while cranking.

Sounds like you should leave it unhooked.

You must have a bad choke, or a bad wire. Check the wire, it could be frayed or the insulation falling right off. If the wire is good, try a new choke. They are called a Sisson choke, they turn up on Ebay and at vintage Chrysler parts dealers.

They also need an asbestos insulating gasket underneath to work right.

Thanks for the info, I am going to go backward on this and install a manual cable to control the choke with. I have a brand new one hanging on the wall.

Just a FYI for some members. Some electric auto chokes work by energizing the choke coil to open the choke. If you remove the wire to the choke, the choke will stay on or closed all the time. Cars with carburetors like Solex (VW) Hitachi (Datsun-Nissan) work this way.

The Sisson choke is better, and easier to install.

update, I printed the adjustment instructions and adjusted the choke. I started the car cold with the air cleaner off so I could watch. The choke closes enough to keep the engine running and as it warmed up the choke opened until it was fully open when the temp was reading 180. So it is working, I thought it might be the source of a constant miss I have but it was not, I tried adjusting the timing and it does not matter if I advance or retard it the miss is still there. I put plugs and wires in it a while back but the wires were the modern type with the carbon core not real wire. I filed the points and had them set exact. The cap and rotor are new. Soooo I will pull the plugs, check the points and probably go ahead and invest in a good set of wires.

My wife does not understand but this is how I spell fun!

Oh and is tthe timing mark suppose to be on the part of the crank pulley that is flat? or is on the round part?

Instead of pulling all the plugs, first why not try pulling each spark plug wire one at a time while the engine is running to find where the cylinder misfire is.

i hate getting shocked!

Anyway I found part of the problem, my point gap was worn down to less than .010. I put a little lube on the shaft and reset it to .018 and it is running much smoother but if I listen at the tail pipe I can still hear a miss. So I may have to try your suggestion and see If I can find which wire it is. The plugs all looked good. The cap and rotor is fine. When I turn the mixture screw all the way in on the carb the engine quits like it is suppose to.

You won't get a shock if you pull the wires out of the distributor cap, or buy a pair of insulated pliers made for pulling plug wires. Or wear a rubber glove, or use one of those plastic gadgets they make for removing fuses.

Find which one is misfiring, take out the plug, connect it up and see if it is firing. Could be a bad wire, bad plug, or worn distributor cap. But, could also be low compression on one cylinder due to a burned valve.

And check plug gap. I go 3 to 5 over specs on 50 year plus motors.

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Shorting the plug terminal to ground,with a screw driver is simple an safe,,,

If the plug is firing it will change the sound,,

If it is missing,,there will be no change,,,it still misses,,

I pulled each wire at the distributor one at a time, i am getting bright snappy spark at each wire as I pull it and the engine sounds the same each time, so it's not the wires or the plugs, I wish it would have been.

I did this at night and turned off all the lights, started the engine and I did not see any spark straying to ground or jumping from wire to wire.

So I took it for a ride. When I am accelerating it is smooth. It is missing at idle and when I hold the gas in a steady position. I have done a rebuild kit in this carb. I cleaned it in a Ultrasonic cleaner using simple green and water. I used compressed air to clear the passages and dry everything out. I then sat it in the sun for a while to make sure it was dry before assembling it with new parts.

I think I will take it to dyno test if I can find a shop in RIverside that has one and see what they say.

I am open to suggestions on this...

Is the miss a steady miss,,,or sort of a wandering miss,???

Next step i think is compresson test

A valve just starting,,,,,,just starting to burn will sometimes act this way,,

That is,,,a steady miss at quiet idle,,and will show up with screwdriver test,,

Cheers,,Ben

Try putting a vacuum gauge on the inlet manifold on the underside of the carburetor at a suitable tapping point, and watch the needle - if it pulsates ( not steady ) when the engine is idling , then you have an internal issue somewhere, maybe valves or springs for as start.....

A cylinder leak down test may well be the better diagnostic test to identify which cylinder is the culprit ............it will pick up an issue well before a compression test does and doesn't rely on even continuos cranking speed to give an accurate result across all the cylinders... Keep us posted

Ok, New info,

I finally put the vacuum gauge on the line the distributor uses for vacuum advance...it connects on the intake by the carb.

The needle on the gauge is rock solid, but it is sitting on the number 9...nowhere near the green part of the dial. Moving the timing has no effect on the needle.

When I blip the throttle the needle jumps to the green and then goes back to #9 (in the red) immediately.

One other thing I noticed was when I disconnected the vacuum line so I could hook up the gauge with the eng running. There was only a slight difference in rpm with the line disconnected.

Here is a pic of my gauge, the needle should be in the green around 20 but it is in the red around 9 to 10.

I sprayed WD40 around the intake before and got no change in rpm so I crossed off intake leak. but according to the dial it is a leak somewhere.

What say the pro's?

Thanks

This simple engine is teaching me how much I really do not know...:eek::confused:

Ok, New info,

I finally put the vacuum gauge on the line the distributor uses for vacuum advance...it connects on the intake by the carb.

The needle on the gauge is rock solid, but it is sitting on the number 9...nowhere near the green part of the dial. Moving the timing has no effect on the needle.

When I blip the throttle the needle jumps to the green and then goes back to #9 (in the red) immediately.

One other thing I noticed was when I disconnected the vacuum line so I could hook up the gauge with the eng running. There was only a slight difference in rpm with the line disconnected.

Here is a pic of my gauge, the needle should be in the green around 20 but it is in the red around 9 to 10.[ATTACH=CONFIG]260606[/ATTACH]

I sprayed WD40 around the intake before and got no change in rpm so I crossed off intake leak. but according to the dial it is a leak somewhere.

What say the pro's?

Thanks

This simple engine is teaching me how much I really do not know...:eek::confused:

Hello

Based on your description , you are seeing whats termed as "Ported Vacuum" from the Carb throttle body base.

This take off point is used specifically for the vacuum advance on the dizzy and will not give a true indication of the engine manifold vacuum. In my expereince the ported vacuum drilling / tapping point is different for auto and mans trans vechicles, hence the different part number in many spares catalogues for the carb throttle bodies.

In manual transmissions there is generally no vacuum at idle, whereas in Autos there is. Thats why when you disconenct the line at idle, its actually retarding the spark timing hence the drop in engine rpms. You can check that with a strobe timing light to confirm what Im surmising here.

If the engine is idling smoothly, you are correct in that there is no vacuum leak present.

So to get a true manifold vacuum reading you need to locate a tapping point under the throttle body of the carb, such as a vacuum pump, vacuum wiper motor, brake booster connection if fitted etc.

My Chieftain has a combination vacuum / fuel pump which interconnects to the wiper vacuum motor and so its simple to tie the Hg gauge into.

At the wiper motor i see true manifold vacuum and time the engine accordingly and check that using the strobe light.

Its a sure fire way to get your spark timing correct, but you still may have to retard it slightly if you suffer from detonation if advanced too far.

You should check your total spark advance at say 3000 rpms for this is the critical setting, timing at idle is only the starting point and depending on many parameters ( vacuum and mechanical advance being only 2 parameters to start ) the Total advance may be excessive at highway speed, and you cant hear the detonation then........... generally the higher the compression the less the total spark advance...........

Generally these old girls run approx 28-32 deg Total spark advance.

There will be no marks to measure that amount of degree's of spark timing. To mark the front pulley is quite simple using the formula : Pulley diameter * 3.1416 divided by 36 or 72 - this gives the linear distance on the pulley diameter for 10 or 5 degree increments.........

Hope this helps.

Wrong place to put the guage.

The vacuum advance line draws vacuum from above the throttle plate-cause of very low reading.

You need to plug the guage into the intake manifold for full true engine vacuum readings!

You will find a intake manifold plug at the rear firewall side of the manifold right under the carb...

Bob

To find the miss, crank up cold and begin feeling of the exhaust ports, the offending cylinder will remain cold or be very slow to warm up with the others.

Is there anything else connected to the vacuum fitting you used to check intake vacuum? Very low intake vacuum readings like that may be due to extremely retarded valve timing (not ignition timing). Causes could be in front gear set or even an extremely worn keyway if the crank gear is not clamped to prevent movement. Retarded valve timing could significantly affect idle quality and speed and may require adjusting idle mixture and increasing the idle setting with idle adjustment screw. Retarded valve timing typically shows up as very low torque and power at low engine speeds but improves with engine rpm.

A steady reading of 9" is not likely worn rings or cylinders unless it fogs blue smoke and drinks oil.

EDIT: IF YOU ARE USING PORTED VACUUM, DISREGARD THIS POST AND CHECK MANIFOLD VACUUM. INFORMATION GIVEN MAY BE VALID BUT NOT APPLICABLE TO YOUR PROBLEM.....

You guys are absolutely correct< I thought that line went to the intake, it does not, it goes to the carb. The only port I see is the one for the brake booster. I will try to get a reducer tomorrow so i can plug the vacuum gauge into it and test again.

thanks for the pic,s. Boy that eng sure does look nice and clean...

Yes, Just tap into the brake booster supply line.

Thats my 1950 Chrysler 8 T&C .

:DHi ,

Back to "As the flathead turns"

I bought reducers, and new line and hooked up the vacuum gauge. I got the needle stationary with only very tiny movement in the green at 21. when I blip the gas the needle jumps to 8 and then down to 22 and then back to 21.

I do think I might have a small leak in the booster system because the engine did run a tiny bit smoother with the gauge on. It still has 3 distinct put put put at the exhaust pipe that is audible.

I am pretty sure my brake booster does not work but what I did try was creating a vacuum in the booster system to check for leaks when I first got the car and I did not notice any loss in vacuum.

Thanks for your help with this aggravating problem...what should I check next ?

update to the update:

I plugged the vacuum line to the booster at the intake and took it for a drive. In 1st and 2end gear with steady speed I felt no miss like before, in fact it was smooth even in the low gears. There is some kind of miss at idle but it is different from what was there before and liveable...

I also notice it stop like it has always stopped since I bought it (like semi truck) so the brake booster is kaput. I see in Hemmings there is a guy who repairs them, I'll probably buy one from him and give him my old core. If he has the model I need.

Thanks for your invaluable help...I'm going to drive the ole girl to work tonight!:p

A quick check for your brake booster (apart from what you have already determined in there is no vacuum assist with it connected or disconnected to the engine manifold vacuum , when trying to stop.)

Try this - With the engine stopped, push the brake pedal as far down as it will go at least 5-8 times to utilize any remaining vacuum within the booster.

Then holding the brake pedal down, start the engine. If the pedal stays at the same height, the booster is kaput. If the pedal drops down, then there is assistance occurring due to the Differential pressure across the booster to the brake hydraulics.

Also if you pump the pedal rapidly when the engine is idling, if the booster is functioning the engine should go off song until the vacuum is stabilized within the intake manifold again.......

Re the "put put put" in the exhaust at idle, suggest that the leak down test may well be the ideal test here to identify if you have a cylinder / engine valve slightly off song there...... I doubt if its spark as there is minimal engine fuel load then and a miss will usually occur in an under engine load.....

if you can locate someone to do the leak down test then its valuable information to be had.

I do it on a regular basis ( every oil change ) as its a great tool for condition based monitoring of engines. ....

Drag racers also do this after every pass to ensure the engine is still operating at max efficiency ..

If you want I can send you a procedure of how to do it if you are not familiar with it, you will need an air compressor and a Leak down tester with suitable spark plug threaded adaptors, send me a PM so I can email it across to you.<o:p></o:p>

cheers <o:p></o:p>

If your booster was working you would know it. The booster 1949-52 chryslers will throw you to the windshield when they are operating properly. I have several cars with them that work.

Booster Dewey in portland can fix your Vacu-Ease internal valve booster.

Yep the booster is definitely not working, so I'll pull it and send it to Portland. I'll probably do the leakdown test on Monday. The new rings are broke in so now would be a good time to check it. When I had the head off, the valves looked ok but that does not mean a couple aren't leaking.

I alos think I will check cold valve adjustment, that has probably not been done in 90,000 miles!

Getting back to the burned choke wire. The same issue occurred on my 36 Dodge and I unhooked the toasted wire and left it be. It started and ran alright most of the time. It wasn't until I sourced a new Sisson choke and a new gasket that I realized on installation the old gasket was as thin as toilet tissue. That must have been the reason for the burned wire because now the car starts and runs like a new car! So don't give up on the Sisson, it's a great unit.