rhodyrocket2

Hi
I have a 1972 cutlass convertible 350 4 bbl original points ignition with an irritating hot start problem. I have spent quite a bit of time trying to figure this out and now I am asking for ideas.
First, the car ALWAYS starts up great when cold. Spark plug wires are pretty new. The car runs fine, no bucking or stalling when driven. When the car is shut off and started within a few minutes, it starts fine. But if the car is let to sit for a half hour after driving It has to crank over for at least 30 seconds before starting. No smoke or fumes after starting. The starter is fine, it cranks over great.
So here is what I have done, nothing has helped.

The original Qjet was replaced with edlebrock, but it did this before I changed the carb. Choke works fine and is off when engine is warm.

I sprayed starting fluid after it would not start. thinking the carb was empty

I changed plugs and checked spark plug gap and replaced point, checked dwell.
Checked voltage at coil 7V running 12 volts when starting
I backed off the timing to 2 degrees.
Switched the coil
Changed the coil wire
I still wanted to eliminate the carb leaking/flooding issue for the new carb so after I drove it I pulled carb and put a pice of paper under it and put it back on the manifold and let it sit for 30 min, no fuel leaked from the carb. So no flooding. I don't think its a float issue as it starts cold fine and runs great.

I loosened the gas cap thinking a vent issue
I have heard of a leaking fuel pump siphoning gas from carb when off(but why would it start cold fine?) but I pulled the external filter right after I shut it off to stop siphoning.

NONE of these things changed the problem. Car starts fine cold, runs fine, if you shut it off and restart within a minute it starts fine, But if you leave it warm and try restarting after a half hour, it cranks and cranks then starts a bit rough then runs fine. I pump the carb when this is happening and it doesn't help.

I am leaning towards an electrical problem that occurs when the engine is hot.

I am considering replacing the distributor with an HEI type. But since all the small items addressed I will start spending money now.

The charcoal cannister is not hooked up, but I don't think that is the issue.

So, what would you do?

Thanks!

M

lshlsh2

Check the positive wire that runs from the battery to the starter. I was having a similar problem and my battery cable was bad near the starter. Replaced and didn't have that problem any more.

Larry

hookem horns

Symptoms sounds like a fuel boil-off, so maybe a phenolic carb spacer to insulate it from the intake manifold. Only odd thing is you said starting fluid did not help, but suppose that could also evaporate before trying to start again.

Have you checked to see if you are getting a spark when the problem occurs?

oldcutlass

Do you have the original manifold on the engine? If not, is Edelbrock carb mounted with a spreadbore adapter?

rhodyrocket2

I don't think it boil off, that was my first thought. When it would not start I checked down the carb and I could see gas when I pumped it.

Its stock manifold with a square bore adapter. But again, remember it starts great cold.

I am going to check for spark when it doesnot start using an old spark plug.

I will also jump the resistor wire to the coil going straight from the battery to the coil.

Octania

flooded?
You have pretty well ruled out LACK of fuel...

Ign coil might fail first when hot, so verify spark when hot. Use the adjustable gap tester if possible, and compare to cold spark strength.

Or, just replace the coil or swap to HEI and see if that helps.

oldcutlass

Is your dwell set at 30? What happens if you hold your accelerator 1/2 way to the floor while you crank.

cutlassjoe

Mine does that too. 350 4bbl with a holley 600. If I hold the gas all the way to the floor when starting it fires right up. Have you tried anything like that?

adis

I'm with Larry. Had similar hot start problems. Replaced my battery cable to the starter, replaced my neg batt cable with a 2 gauge cable, checked my grounds. Solved the problem but just to be sure I put a repo starter heat shield on from Fusick and I wrapped my coil in heat shielding. I think in my case the heat in the thick gauge wires and stArter armature windings was causing more resistance making for hard starts. I'm no mechanic tho...good luck with the trouble shooting.

oldcutlass

Do you even read any of the prior posts? He clearly states it cranks fine.

MDchanic

Which would imply minor flooding, which would be consistent with all of the things we have been told so far:

• Cranks fine
• Carb had fuel in it (accel pump squirts well)
• No running problems when hot, other than starting (electrical components going bad when hot would also produce weak acceleration when hot).

If it's a little bit flooded, 30 seconds of cranking is not actually that bad.
If you can reduce that to 5 seconds by holding the pedal to the floor, that's probably as good as you'll get.

- Eric

adis

Yes I did read the prior posts. I'll try again:

I had exactly the same problem as you are having, I repaced my battery, the positive battery cable, the pos lead from the starter up to a relay on the fire wall, replaced my neg batt cable with a 2 gauge cable, replaced my coil with an accel coil that i wrapped in heat shielding, chacked the leads from the coil to the distributor, all the distributor wear parts, my spark plugs and wires, i checked all my grounds to the block/frame, and my problem was solved. i no longer had hard hot starts with good cranking, and good fuel delivery. i think the heat in the heaver gauge cables and coil windings causes higher resistance making for hard hot starts. i'm no mechanic tho...good luck with the troubleshooting.

MDchanic

Adis, changing the starter wires would help if the starter were cranking slowly, which it is not in rhody's case. He says it is cranking just fine.

While it is true, according to electrical theory, that increasing heat increases resistance, in the case of copper starter wires, the amount of heat we're talking about should not cause any noticeable change in resistance. There may be other areas, such as dirty armatures or carbon brushes, where heat may increase resistance enough to matter, and increased heat may also break down thin insulating layers in starter windings, allowing current leakage

Finally, you describe replacing numerous components all at the same time - this does not help rhody to troubleshoot, as it does not tell him which of those replaced components it was that fixed your problem.

- Eric

Lady72nRob71

Out of curiosity, does your fuel pump have 2 lines or 3?
Mine has 2 and I can hear it percolating shortly after shutting the engine off. I have a similar hot-start issue and I am wondering if its related to the boiling fuel.

mydadscutlass

Had same problem got rid of points and put in hei much better and also put in a msd spark box car never ever gave me trouble again

bkeese

When you turn an engine off it continues to get hotter for a while before it starts to cool. How hot is it getting? Does it boil over? How hot is the carb? I had a Jeep that did this, ran great, but would spew 15-30 minutes after it was shut down.

Highwayman

Never say never.

I've got a Buick in my fleet with an HEI. The constant twisting of the plate by the vacuum advance flexed and eventually broke the wires inside the distributor. As the advance worked it would make and break the connection causing an intermittent problem. Anyone that has ever tried to shoot an intermittent electrical problem knows how much fun that is.

Seriousfun

Jx2

Sugar Bear

Have you been able to confirm that there is no spark during the no-start condition? Was the 12 volts at cranking confirmed during the no-start condition or a during a start condition? If there is no spark it would help diagnose the problem if we know if there is voltage or not to the primary side of the coil during the actual no start.

When the points were changed was the condenser changed? Does it have separate points and condenser or the combined uni-points? If there is primary voltage to the coil during the no-start condition and no spark it could be a condenser opening up when the engine goes into heat soak.

On Q-jets the float level can be monitored through the vent in the top between the primaries and the secondaries to see if the fuel is leaking or evaporating. I don't know if this can be done with the Edelbrock, anyone???

oldcutlass

If you pump the accelerator and fuel comes out, its all good. You can also remove the top and check float level, but he states its not going into the manifold when its sitting in the prior posts and when he pumps the gas it squirts.

I'm curious of the voltage/ spark test when it does not start also.

rhodyrocket2

Hey guys!

Wow, been away and amazed at your discussion! Its been raining up here so I haven't driven the convertible much. Drove it today and got cusght in another shower!

I will be doing the following.

Change the batt cables and the wires from the solenoid (except the resistor one), cheap and why not. Check and clean engine grounds.

If it still is a problem I will check for spark when cranking.

and then depress accelerator when cranking but I think I have done that.

And then report back.

I don't think its fuel

I slipped a piece of paper under the carb right after shut down, let it sit and checked the paper. No fuel stain.

I wish I could check the edlebrock carb's float externally like a qjet related/flooding. let me know if its possible.

Plus the adage 90% of carb problems are really electrical is very true in my experience.

Now I did retrofit a newer alternator with an internal regulator many years ago. I have heard it can cause it car to keep running when you try and shut it off but not the opposite. Let me know.

Then I check back with you guys.


and hell got another problem! A mouse or squirrel chewed a fist sized hole in my top! Opening the door the first time was a bit wierd, thought I would get bit. But I gues it left or never entered the car!

mmurphy77

https://classicoldsmobile.com/forums...rcolation.html

Just to add, I have been running 93 octane Ethanol-free the last few tanks and have not had the problem so draw your own conclusions.

oldcutlass

You might also check to see if it's been under your hood! Squirrels can do alot of damage to car wiring. They nest in strange places! It can be under your dash, or seat.

BILL DEMMER

7 volts running sounds a little low, iirc, it's supposed to be 9 volts running.


bill

MDchanic

But his problem is while cranking, when he's got 12v, not while running.

- Eric

olds66

Interesting email string... my 66 cutlass has a similar problem. when i try to start it being parked for a while it takes a while but definitely developed a big cloud of smoke like it was flooded. it also has the phenomen when getting into stop and go traffic after normal driving in hot weather it starts to slightly smoke and finally stalls. takes 5 min cooling down before it starts again... any ideas?

oldcutlass

I would start my own thread on this, so it does not interfere with OP's project.

garys 68

No firing with ether means spark.
Get a no start condition.
Use a spark tester to determine if you have a working ignition. Check all cylinders.
If no spark, check for 12 volts at coil. If not, it's a wiring issue.
If you have 12 V, ground the - post of the coil and check for a spark.
If you get a spark at that test, your problem is in the distributor or an intermittant issue with any wiring off the - coil post (ie tach)

79MKII

Any updates on this issue? I'm having the exact same problem....starts great cold, runs perfectly at all times but cranks a long time before starting only when hot unless accelerator is pressed to the floor while cranking....have edelbrock carb and HEI. I'll be watching for more info and will let you know if I find anything with mine.

455man

I might have missed this but is it the stock intake manifold? Sounds like the heat soak that I had. Floor it and it finally starts. If its not electrical an insulating spacer solved it for me.

BILL DEMMER

at the age these vehicles are, i would verify proper operation of the exhaust crossover heat valve.


bill

Lady72nRob71

A 72 350 does not have a valve, it is a constant passage of exhaust gas under the carb. I hate it - discolored my engine paint big time.

highschoololds

Best upgrade I did to mine for cranking was install a Pertronix Ignitor.

Mochi

Hey I'm going to chime in here. First thanks to this forum I've probably fixed and learned more about my olds then ever.
I had the hot start/ heat soaking issue. So here's what I did and it seems to have fixed it. From cheapest to most expensive.
1. Re routed the fuel line to keep cool
2. Changed the thermostat to a 160
3. Phenolic spacer
4. Petronix ignition
Now let me say this, I started with the Petronix ignition and that solved problems I didn't even know I had and really made her motor very happy. What solved the hot start was the phenolic spacer. After I installed it I ran her pretty hard, parked her, waited about 20 minutes and went to start her and she started right up. Prior to this it took forever and she didn't want to keep running. Until I got her to cool down.

1965cutlassragtop

i guess i should stop complaining about my problems, lol. my head is spinning from this one!!!

best changes i made under the hood that helped cold & hot starting was an HEI distributor (points are a pain in the ***) & 160 thermostat (engine is much cooler all around).

MDchanic

Just to clarify, the valve doesn't stop the exhaust gasses from circulating under the carb, it makes them circulate more, by closing off one exhaust outlet and forcing all of that side's exhaust gasses to go through the manifold crossover in order to get to the other side.
When the valve is open, it's just like Rob's car is all the time.

- Eric