The Stovebolt Site Forums The Shop Area Engine Shop Hard warm starting

Advice needed.
I am experiencing hard starting with the 1956 235ci engine in my 1952 Chevy 1/2 ton pickup. It starts quickly cold and runs excellent but when I've driven it to normal operating temperature (180) and shut it off for 5 to 15 minutes it starts hard. When I shut it off and try to start it immediately it starts right up. The starter turns over the engine properly but it just takes much longer to start then it does when it is cold or cooled down. It has always started, but it is worrisome when I must stop away from home. It has an automatic choke that seems to be operating properly. I have replaced the in line fuel filter (before the fuel pump) put in new AC R43 spark plugs, points and condenser, checked timing and dwell. I only use no alcohol or no ethanol 90 octane rec. fuel. Any suggestions would be appreciated. Thank you in advance. Chuck 52

You're having typical "hot soak" starting problems. The fuel in the float bowl is expanding and spilling over into the intake manifold, creating a flooded condition after 5-15 minutes of being stopped with the engine hot. Is there an insulator block between the intake manifold and the carburetor? If not, install one. Lowering the float level slightly might also help, but that can create a lean surge during normal driving.

A work-around would be to crank the engine with the throttle held wide open after a hot stop, which will help clear the flood quickly. Just back off to a fast idle soon after the engine starts to avoid over-revving it. It's going to run rough for a few seconds, so don't go back to idle immediately.

These situations used to be commonplace and drivers knew how to deal with them instinctively before computer dumbed down everybody's driving skills. Now if an engine doesn't start in 5 seconds or less, hot of cold, most people panic.
Jerry

Thanks jerry. Clears it up for me and my 250 that does the same on warm days

What HotRod said^^^^^
Plus
Winter grade fuel will make the problem worse in early spring when the weather warms quickly.

Winter grade fuel boils or vaporizes at a lower temp, so that hot carb becomes a "tea pot".

Thank you for your quick response, Jerry.
You make good sense. I do have an insulator block (about a 1/2 inch) below the carburetor but I will follow your other advice. Thank you.
Dan

Lincoln, Would a phenolic or a wood spacer under the carb help?

The regular spacer the factory installed was Bakelite, a primitive form of phenolic. I've seen home-brewed ones made from various kinds of plastic, wood, and other non-heat-conducting materials. Whatever you choose, I doubt if it would be more effective than the OEM reproduction spacer most of the restoration places have to offer. Be sure not to block any vacuum passages if you choose to make your own.
Jerry

I think they were a phenolic material.

http://www.classicparts.com/1954-62-Carburetor-Insulator-L-6-235/productinfo/81%2D212/#.WR0Couv3arU

http://www.classicparts.com/1937-54-Carburetor-Insulator-L-6-216/productinfo/81%2D211/#.WR0Cyuv3arU

I have the exact same issued you described. If I shut if off it will crank right back up, but if it got up to 180 and is shut off for more than 5 minutes, it is much harder to crank. After about 20-30 minutes of cooling, it will fire right back up. Mine is a 1953 235 in a 1946 truck.

When you say hard to crank..... does it just have to crank a while before starting, or does it grunt and kick back?

Roy, we're up against an age-old problem in describing what's going on. The way I taught 30-something years' worth of students was this:

"Cranking" is the act of the starter turning the engine over. It's either slow, normal, too fast, or not at all.

"Starting" is when the engine actually begins to run under its own power. Far too many people blur the distinction between cranking and starting because they've never been taught the difference, A "slow crank" or "no crank" situation needs a completely different diagnostic procedure than a "cranks but doesn't start" condition.

What the original symptom being described seems to be is a "cranks normal speed but won't start" situation, caused by a temporary flooding condition from overheated fuel in the float chamber. At least that's what I understand from the description we've been given. Holding the throttle wide open during cranking does two things- - - -it provides plenty of air to dilute the flooded mixture in the intake, and it avoids adding more gasoline to the mix by pumping the gas pedal and making the accelerator pump put more gas into the manifold.
Jerry

From Chuck 52.
I appreciate all of your comments and suggestions. When warmed up the starter turns over the engine properly, not slow at all. As I stated earlier, I have the original plastic type insulator between the carburetor and manifold. Also, it was suggested that my heat riser may be stuck. I checked and it is not stuck and the spring is working properly.
Again, thanks to all of you for your concern.
Dan

Agreed Hotrod. My old 235 and 261 both sometimes would require me to open the throttle a bit wile starting it once hot. I got so used to doing that it was second nature to hold the throttle open with the same foot I was pressing the starter button with.

Especially since it had the old Rochester carb on it.

Once running they both ran fine.

If the engine still doesn't start using the traditional advice offered by Jerry:

http://www.thecarburetorshop.com/Troubleshooting.htm#Hardstarthot

Often, the method in the link above must be employed when trying to restart a large V-8; but I have also occasionally used it with inline engines as well.

Jon.

My question is, why doesn't every single stock 216/235/261 suffer from hard warm starting?
I had a well worn in (not out) 216 which did it, but my 10,000 mile-since-rebuild '53 full pressure 235 does not.
Would worn rings cause it due to less vacuum action from the piston going down failing to quickly pull the puddle out of the intake?
Carl

Everyone I have owned liked an open throttle during hot restart ( two foot technique left foot on the gas)

The easy answer is there are many variables like:

Fuel quality and kind
Under hood temperature ( Air movement)
Engine running temperature ( thermostat)
Manifold temperature ( heat riser)
Carb temperature ( insulator)
Fuel temperature
Float level. ( tweak the level lower helps)
Needle and seat condition
Fuel pressure and fuel pump type
Driving style. (City vs highway)
Ambient temperature
Altitude
Engine condition ( worn vs fresh rebuild)
Battery condition and cranking speed
Hot start........Starting technique


Even the last years of carbs before FI became the standard they used solenoids to block the jets with key off. This was to stop flooding and engine run on during hot operation. Even the Briggs on the lawn tractor had these solenoids.

The newly rebuilt 1954 235 with W-1 in my 41 does this once in a while. I learned to employ the hot start method Jon referenced pressing the accelerator just very slightly while starting and it solved the issue. I think I do it automatically now as I don't think about it any longer. It was an intermittent issue that had much to do with the engine temperature, air temperature, and humidity. You will figure out what technique your particular engine/carburetor needs.

After a little practice a one foot technique is easy. Part of the right foot on the throttle, part on the starter.

Keeps left foot free if needed due to cranking on a hill.

I'd say compression has alot to do with it. My 216 is so worn I can easily turn it by hand with the plugs in.
Cold start needs max choke and the throttle held at mid position (around 1100 rpm).
Warm start requires the one foot boogie i.e trans in neutral, parking brake set and the right toe hitting the stomp starter with the right heel holding the throttle at WOT. If it doesn't catch I slowly allow the throttle to start closing while hitting the starter. So far it's the ticket to get started.

My brand new rebuilt 235, still on the run stand, fires right off cold, warm or hot. Single or dual carbs.

I call this scenario "The saga of my 37 Buick". Same problem that I was NOT going to let whip me. I knew it was fuel percolation as Jerry said because when it finally started it rolled out a big cloud of black smoke. First I re-routed the fuel line from pump to carb completely away from any heat source. Next I milled out a custom finned heat shield/heat dispenser that not only insulated but had a lot of surface area to dispel heat. I then put a ball valve at the float bowl inlet so I could cut the fuel off and let engine run to use up fuel in the bowl. Had a friend with a starter/generator shop build me a custom starter that had the case seam welded to cut down on fields pulling away from armature and 6 volt guts to really spin the engine. Opened hood after a long run to let heat out of engine bay (this helped) and even rigged up an old windshield defroster fan to blow across the carb while hood was open. Never cured the problem but come up with a band aid that lets it start; a real GM HEI distributor with plugs gapped at 0.060 for a hot fat spark. I guess I used a sledge hammer to kill an ant but it DOES start. Pic is of an Olds V8 dizzy modified to fit the straight 8 Buick which is like a 235 with two more cylinders.

http://s32.photobucket.com/user/coilover/media/Dar%20Dog%20HEI%20003_3.jpg.html

Sometimes after a long run on a hot day I'll restart my truck after it's set for 10 or 15 minutes. I let it run for about 5 or 10 seconds, just enough to clear out the excess gas, but not long enough to create any heat. I don't do it often except on extremely hot days partly to cycle the coolant to avoid hot spots in the otherwise uncirculated coolant.

Hi All,
Again, greatly appreciate all the advice and suggestions that each of you have offered. I had our pickup out yesterday and it started up quickly throughout the day. Temp. gauge did get up to 180 several different times with quick start ups even when I allowed a 5 to 15 minuted wait. It was a very cool day though with a high of only low 60s. I will consider and try the suggestions offered when needed in the future on warmer days and report back.
Dan

The technique I use is to sit there with my left foot on the accelerator, keeping it wide open. I wait for a minute or two. Then without releasing it I hit the starter and very shortly it will fire up.

This was a problem on my 235 until I abandoned the mechanical fuel pump and went with an electric one. After that it started much easier when hot. Put the electric pump back by the gas tank. They're meant to push better than they pull.
Jon