New'n72

Ok...you will have to forgive me, I have had this car many years but I am not a mechanic by any stretch of the imagination and I could use some troubleshooting advise.

I recently had this '72 Cutlass tuned up. New plugs, ignition wires, condenser, rotor, distributor cap. Since then, it runs great but if I drive it a few miles, until the engine is up to temp, and then shut it off, I have a heck of a time getting it restarted. If I let it sit for 45 minutes to an hour or so, it will start up fine.

Discussion at work by the resident car people suggests that the coil may be the problem. That it changes or breaks down with increase in temperature.

What say you? Does this sound right? Any other ideas?

Thanks

dar83501

It sounds like a camshaft position sensor or crank angle sensor that's getting heat soaked and shutting the car off to me, but that car is probably too old for either of those sensors to be on it in the first place. I would suggest running a fuel pressure test to determine if it has anything to do with your fuel pump.

I have a '91 that started doing the exact same thing, it would run till it heated up, then it won't turn over for an hour or two until it cools. It wasn't the fuel pump, I changed the alternator, fuel filter, battery, coil, electronic ignition module, the camshaft position sensor, and the only things left are the computer and crank angle sensor..I'm going to replace the sensor soon as there's room in the shop so I can sell the car.

If the fuel pressure test comes up okay (be sure to test while the car is running, when you turn the key off, and start the car again), then I would think it's most likely electrical.

Also, when it refuses to start, does it try to turn over but there is no spark, or is it just a dead click?

New'n72

I should have given you more details in my first post. Sorry......The car runs great and the starter works fine, hot or cold. If I get the engine up to temp and then shut it off myself, it is hard to restart. The starter sounds good and turns the engine but it just doesn't fire.

This is a 350 with a 4 bbl.

The fuel pump is new this year, as is the line from pump to carburator and the filter.

It is not a question of power to turn over the engine but rather a question of possible weak spark, thus the 'coil' as a possible cause.

Once running it idols smooth and if I punch it, it does not hesitate or choke up, it moves out smartly. That would suggest, to me at least, that it not a carburator problem.

My only other novice thoughts would question what part vacumn might play in this. I know there is a vacumn line to the carb., I think that is the vacumn advance? Then too there is a vacumn line to the air cleaner which in turn has a temperature sensitive mechinism in it, of some sort.

Any advise is appreciated.

J-(Chicago)

My thoughts:
1. Does the new fuel line from the pump to the carb have a section of rubber in it? If so it may become pliable from engine heat and collapse on itself. Once the fuel is flowing again it will stiffen back up and be fine, but the initial start up will be bothersome.
2. The vacuum baffle in the air cleaner intake pipe. May be stuck closed and not getting enough vacuum to open until engine rpms are raised.
3. Carb choke. sticking closed when metal expands from heat, the rod may not move freely in the guide hole.
4. Hot air choke tube?
5. Timing too advanced? I'd check it just in case.

Try taking off the air cleaner lid, propping the choke open with a screwdriver,and pumping the gas pedal 10 times. It should start on 1 crank.

J-(Chicago)

I'm starting with air/fuel mixture problems here because if it was just running it obviously has spark.



here's some basics on an easy carb.
http://images.google.com/imgres?imgu...%3Den%26sa%3DG



http://images.google.com/imgres?imgu...%3Den%26sa%3DG

New'n72

No rubber in the fuil line. Its SS from the fuel pump to the carb.

Vacumn or choke might be a cancern. Vacumn is an enigma to me.

I have never been in a place or at a time of day that popping the air cleaner and dribbling some gas in the carb, was easy to do. I will try that this week end though.

I guess since no one even touched the 'coil' comment, that is not a very logical choice?

The more I think about it, the more I think you're on to something with the choke sticking. As I recall the last time this happened, I drove about 10 miles, went into a store and then came out a tried to start it. It coughed and sputtered initially when I turned the key. In other words it tried and almost started but then died and would not start again accept with a little time and much effort on my part.

The initial sputtering was very brief and weak but a definate attempt to do the right thing.

Thanks for the help....I will let you know what happens.

Oldsguy

conduct a physical inspection of the parts changed during the tune-up. Look for a loose A+ wire on the coil, make sure it is tightly attached to the stud on the coil. Make sure all your plug wires and coil wires are inserted fully into their respective tower locations. Make sure the distributor hold down is tight. Make sure the points are secured to the backing plate well. Inspect the A+ wire from it's point of origin to the coil (actually back track as far as you can go from the coil backwards) look for a place where it might be touching something hot or have cracks or nicks on it. The only reason I am mentioning these is that I really don't have a singular item to identify and what I recommended you do is what I would do first. It might take up a half hour of your time and you might find the culprit.

New'n72

A+ wire is new and looks great. It's not touching the engine blockor anything hot.

The distributor cap is tight.

The car runs great!

Its a starting problem.

J-(Chicago)

Haha It's an Illinois air problem.
My choke was stuck closed this morning... go figure.

Also, A lot of water in my exhaust pipes this morning as well. Must have sprayed out 6 ounces of water by the time she was warmed up.


Sometimes It really sucks when 10 people are checking out your car. Especially when it starts like crap.

Olds64

That item could be a THERMAC door and heat stove. I know cars in the late 70s had them, I am not sure when they started using them. You can identify it by looking for a heat stove on the passenger side exhaust manifold that has a tube leading up to the air cleaner. If you have a THERMAC door that is malfunctioning it could cause poor idle or harsh starting conditions. The THERMAC door is in the air cleaner and channels outside air to the carb during normal operation and air off of the heat stove to the carb during start up. Just an idea.

J-(Chicago)

good idea olds64. I actually have a 72 455 block on a stand right now. I'll take a look and see if they had them.
I know for a fact that the air cleaner housings had the 3 inch circle vacuum diaphragm motor canister on the fresh air inlet though. (the one that dampers the air)

J-(Chicago)

Yep. there's an air bleed thermac inside. The only other thing on it is the rubber elbow for the valve cover crankcase.

The problem with the thermostatic theory is:
It opens and closes to help the car warm up faster for cold starts.

The thermac is closed off when the motor is hot, which is when he is having trouble.

If it doesn't ever close however it WOULD kinda be like putting a runner in a sauna after a marathon.

New'n72

As I recall the last time this happened, I drove about 10 miles, went into a store and then came out a tried to start it. It coughed and sputtered initially when I turned the key. In other words it tried and almost started but then died.

I went ahead and put a new coil on it last night. I had 4 different guys at work tell me it was a coil problem. I took it out this morning and ran it to the next town and back. I let it sit for about 20 minutes and then tried to start it. It sputterd and tried to start but acted like it just could quite get it. I turned the key off, pumped the gas peddel about 6 times and tried again. It gound for a couple seconds and then roared like a lion! Idol was good, rev it a little and it did not choke up and it sounded great.

I turned it off and let it sit another 30 minutes or so and tried it again. Same symptom. Try to start and sputter a few times then nothing. Pump the gas peddel a half dozen times and then try and after 5 seconds of grinding it caught and fired up.

It seems as though the coil may have made a slight difference but it is still kind'a iffy.

FYI: I do have the air cleaner set up that was talked about a couple posts back.

Sometimes It really sucks when 10 people are checking out your car. Especially when it starts like crap.
__________________
Man, you sure got that right!

New'n72

It has been sitting for about 2 hours now and cooled down. I just went out a tried it. I bearly touched the key and it fired up.

It definately starts better cold than when its hot.

Dapapadon

I tried to post this yesterday & the site was down. Hope it helps.

If the problem started with the tune up, I'd double check the timing. Get the timing advanced a little too much & you get hard starting when the engine is warm. The engine would run a little hot too, but if you don't have a gauge you woudn't see that.

Remember to disconnect the distributor vacuum advance and plug the vacuum line before setting the timming.

Don

J-(Chicago)

Mmhmm.
Looks like 4 guys at your work owe us beer haha.



If it can breathe, and the choke doesn't stick then
we're down to my #4 and 5 on the list and I think I'm gonna stick with Da Papa on this one.

New'n72

I will check the timing one day this week. Need to borrow a timing light.

Jim's rare 80

To find out if it's a choke issue, next time it doesn't start, warm. Instead of pumping the pedal 40 million times, just hold it right to the floor, and turn the key. Depressing the pedal to the floor manually opens the choke, regardless of temp. If it starts, choke adjustment is definitely the issue. Let us know how it goes.

LBF

Sounds like vapor lock to me. Does the fuel line run near the exhaust?

New'n72

I have tried holding the gas pedal down and letting it crank. No go.

I took the air clear off and watched the choke. When it was hot it was wide open and as it cooled it slowly closed.

The gas line runs from the fuel pump which is mounted on the right front of the engine, down and back. I have duals on it and it is possible, since I don't recall actually looking at the gas line, that it may come close to an exhaust?

The car runs great otherwise. Idols great, doesn't balk when I goose it.

I haven't driven it much lately with the weather turning colder.

kevinkpk

How fast does it crank? If the advance is too far it might start when cold. I had the same (and am still to some extent) with a distributor advance, cold no problem, hot it would barley start at times. If it sounds like (during crank, hot) like a low battery it is probably timming too far advanced. I ended up replacing my distributor because of it being worn out.

kevinkpk

Vapor lock dosen't mean that the fuel line is near a hot spot, or exhaust, but yes heat AND usually a fuel line that has alot of bends and particularily around a hot section of the engine.

I had a 69 Caprice that vapor locked ALOT, that problem was a result of a crooked fuel line in the front of the engine feeding the carb.

LBF

My vapor lock problems were solved years ago with the addition of an electric fuel pump.

New'n72

To recap: Fuel line has had the rubber sections replaced, fuel pump is new, line from fuel pump to carb (stainless) is new, as is fuel filter, points, rotor, cap, condenser, plug wires and plugs are all new, coil is also new.

Carburator is original (110K miles) and has not been rebuilt.

Engine has not been pulled and/or rebuilt. Except for parts mentioned, it is all original.

Choke seems to step through its' stages as it should.

I have NOT checked the timing yet. Meant to a few weeks back but couldn't borrow a timimg light at that time and since then I have had other things to do, not car related.

Gas tank was not dropped and steamed but as I said before, it runs great and gives no other indication of crud in the fuel line or clogging the filter.

Since I am not a mechanic and have not ever really been interested in the mechanical operations of automobiles other than driving them, I can ask some very basic questions and they may have nothing to do with the problem so bear with me, please.

For instance: Isn't there a reservoir in the fuel system someplace? The fuel pump or the carb? Something that holds a small amount of gas for initial ignition? Could this be draining and causing the line to be syphoned dry so that the pump has to fill the line to the carb and the reservoir before it gets any fuel through the carburator to the cylinders? That is what is acts like. Its like it has no gas to the heads and after cranking and/or using the gas pedal for several minutes it finally fires up. It acts the same as when I let the car sit for several days and then start it. The first time, I have to crank quite a bit and hold the gas peddal to the floor, to get it started.

Once it starts, everthing is fine and it runs without fault.

kevinkpk

For instance: Isn't there a reservoir in the fuel system someplace? The fuel pump or the carb? Something that holds a small amount of gas for initial ignition?

That is in the carburetor, there is a float that opens a valve when the float is low and allows gas from the fuel pump, and shutsoff when it is full.

Does the starter crank the engine over the same when hot or cold (same speed)? If, when "hot" trying to crank, does it act like the battery is not charged? If thats not the case it's most likley fuel related.

New'n72

Yes it cranks at the same speed and it is NOT sluggish or slow. It does not have the indications of a low or weak battery.

As I said everything is the same as if I let it set for a week and then tried to start it. I would have to crank for quite a while and floor the gas pedal. Same thing when hot.

kevinkpk

My guess is vapor lock, make sure you don't have any tight bends in the fuel line, especially comming from the fuel pump, and not routed close to exhaust or anything that creates heat. Fuel pump is new, which dosen't mean it is functioning properly, but probably so. It could be float setting in the carb is not allowing enough fuel in the bowl, but you'd have a problem with it cutting out when (especially) hard acceleration. As I said, this is just my guess, I am sure someone else will other a suggestion.
Also with vapor loack, your car could just quit, so hmm.

New'n72

I have had a vapor lock problem on another car I had years ago. Not a problem that I am all that familiar with but wouldn't the engine (or part that is causing the vapor lock) have to cool down significantly for the lock to clear?

My problem happens when I leave it for 15 or 20 minutes. This was in the summer time, too. Not a lot of "cooling down" going on there, I would think?

It has never just "stopped" on me when driving, either.

I'm not disputing your advise. just trying to understand.

Olds64

Troubleshooting is difficult. You mentioned that the carburetor has never been rebuilt. This could be a problem. Whenever I do a tune up on a car that I purchase I always rebuild the carburetor. You also mentioned the points were replaced. Did the mechanic set your dwell when he tuned it up? Just thinking that might be something to check since nobody has mentioned it yet.

kevinkpk

Could be trash in the carburetor, when it's hot, it is restricting fuel to the jets or so? I'd think if the point dwell was way off, might not start when cold or hot. Dwell tach meters are reasonably cheap $25 or so. Point dwell should be 28-30 degrees. Also is it a 2 or 4 barrell? Could also be the accelerator pump in the carb.

New'n72

It is a 4 BBL/350.

Timing and dwell were set up by the local shop I take my contemporary vehicles to. I say contemporary because the mechanics are younger than my 1972 Olds (and me) by a long shot and if they can't hook it up to a computer and have the computer do the troubleshooting, its a crap shoot as to wether they can get it fixed.

One redeeming feature to the shop is that they do have a old guy, like me, that used to work on cars before there were computers to hook them to. He ususally keeps them on the straight and narrow.

As for crud in the carburator; wouldn't that also show up during acceleration and idle, after the engine heated up?

kevinkpk

You know what, I wonder if it isn't the accelerator pump, in the carb???????

kevinkpk

I posted this once, can't see it, so here goes again, I am wondering if the accelerator pump in the carb is the problem?

J-(Chicago)

[QUOTE=New'n72;19872]It is a 4 BBL/350. Timing and dwell were set up by the local shop I take my contemporary vehicles to.QUOTE]








Let me know if that fixed the problem.



Another thing I was thinking.....
That new stainless line .
Does it arch up above the carb before it connects to the front?
Mine is arched way up so the fuel doesn't drain back down, there's even a little fuel line impression in my hood insulation.

Also out of curiosity, what heat rate spark plug are you using?

We will get to the bottom of this. Eventually.
We have reached the end of my list, so I will have to re think a new one

J-(Chicago)

Did you ever vacuum pump test the thermac and air intake flue?
I don't remember if you did or not.

Hot air choke tube is ok?

J-(Chicago)

Ok...
List 2

1. Stainless fuel line arch
2. EgR valve stuck open
3. Carburetor flooding..... check your float with a float gauge. engine must be warm, idling,and have the choke wide open

New'n72

Since the weather has changed here in the last week or so and gotten a lot colder I don't know the status of my problem. I have not driven it in a couple weeks. I will try and take a little drive later today and see if the outside temp has affected the symptoms.

I have not 'tested' the thermac. I'll have to read up on how to do that.

My fuel line does not have a pronounced arch to it but it does angle up slightly after the first bend and before it drops down to connect to the fuel pump.

I purchased an original Service Manual, recently, and was reading up about starting problems. The carburator section says the following:

No Hot Start: correct starting proceedure used but still no start, check 1 & 2 under "No Cold Start".
No Cold start: 1) Engine Flooded? No
2)No Fuel in Carburetor? That is what it acts like

Defective Fuel Pump?

Check float needle for sticking in seat or binding float.

That would be number 3 on J-(Chicago)'s list.

Egr valve? No reference to Egr in the service manual....pre Egr?????

I have an "emission canister".

This is a "Controlled Combustion System" CCS for short, per the Service Manual. Seems like all emission concerns revolve around that Thermac and the air-cleaner mechanism.

Hope I am not causing more confusion with my lack of experience comments here. Sure wish I had played with cars and engines 40 years ago but my head was in other plcaes back then.

kevinkpk

This is a "Controlled Combustion System" CCS for short, per the Service Manual. Seems like all emission concerns revolve around that Thermac and the air-cleaner mechanism.

Hope I am not causing more confusion with my lack of experience comments here. Sure wish I had played with cars and engines 40 years ago but my head was in other plcaes back then

Was this car built in California, with emmissions for such? If so, unhook the line marked air cleaner at the cannister, and reroute from the air cleaner the vacuum line, give that a try. Not a problem with posting, thats what this forum is for.

New'n72

Was this car built in California, with emmissions for such?

No not that I know of. I bought it new in St. Louis, MO. in August of '72.

The Carb. is not flooding or at least I don't smell any gas like I would expect to smell if it was flooded.

Since I can't find a reference in the service manula for "Egr valve" maybe you could tell me what exactly it is and where I might look for it.

Does it go by another name depending on year or model?


As a point of interest: I fired the old girl up and let it warm up in the garage, then took it out on the road for about 20 minutes, mostly highway driving at 55-60.

I came back home and pulled into the garage and shut off the ignition. Went in the house and waited about 10 minutes then tried to start it. It cranked for maybe 3-4 seconds and fired up. Not my usual scenario. I immediately turned it off. I tried again after 30 minutes had passed and it started immediately. It is now an hour past and I tried and it and it started within 1 or 2 seconds of cranking.

The temp here today is around 35F. When this occured and I started this thread it was 90F. Now I am not sure if the temp had an effect on the symptoms or if something else changed and the problem has disappeared.

J-(Chicago)

Well....
That's the best kind of thing to appreciate on thanksgiving

It was a good day for cruising around here despite the cold temperatures.

The last 2 days of rain cleaned the streets off real nice.

Too bad traffic was kinda ridiculous with all of the travelers and shopping centers around here.

I'll get you some pics of the egr on my 72 motor.