Hot Starting Issues

[Jeff Balazs]

Just had an experience I was hoping I was avoid. Had the truck up to operating temp shut it off and then 10 minutes later it gave me fits trying to get it restarted. It was around 75 degrees today. This is the first time this has happened but I have been aware that it was a potential issue with these trucks.

 

I have eliminated the mechanical pump and the fuel line has been rerouted over to the fender well. Fuel supply is nice and cool. I have considered making a spacer to go between the manifold and the carb. That chore is now going to the top of my list. These manifolds get way too warm IMO.

 

As luck would have it a friend and neighbor of mine was present when this occurred. He is brilliant guy......two engineering Phds......and designs machines that make components for the medical field. We discussed it for a few minutes and he made a phone call to a supplier. He is getting me a piece of a special composite material that is used to insulate dies from heat in presses, etc...

It is less than 1/4" thick and is easily cut and shaped. The plan is to use this to make a combination insulator/heat shield to fit between the manifold and the carb. I will test this out and if it works as I hope it does I will keep any of you that might be interested posted.

 

Jeff

[austinsailor]

Oh, No! Here it comes again, the "vapor lock isn't real" discussion! :<)

Gene

[DJ194950]

Heat wise-

can you touch the fuel line at the pump, carb, the carb and keep your fingers there for a few seconds? If not, possible vaporization.

Chase that.

If you can touch those- get out the voltmeter and check voltage at the coil.

Go from there.

 

Got to keep driving!

 

Hope to catch up with you at the BBQ!

 

Doug

[T120]

...Phenolic is a material commonly used as a carb spacer.If you do a search on the forum "phenolic spacer" will come

up with some results.Also I recall Hudson used heat shields at the base of their carburetors on their "Twin H manifolds".

And I gather some have experienced coil problems as well under some conditions as mentioned...

[TodFitch]

I guess my question is, didn't your truck have that insulating spacer already on it? I thought it was standard on all the Mopar L-6 engines from the early '30s on up. . .

[55 Fargo]

post deleted

Edited March 7, 2014 by Fargos-Go-Far

[T120]

"Vapor lock" as it was termed was mentioned in the "Manual for Plymouth Owners" published by Popular Mechanics  in 1950.Blended fuels at that time were listed as a contributing factor.Today's ethanol blends may aggravate the problem.The importance of the metal shield over the fuel pump was also mentioned.

[Desotodav]

Try the old solution Jeff... it's said to work well!

 

[wallytoo]

jeff,

no idea about your situation. i did read your post, though, and see that you have an electric pump (at the tank/in the tank?), so it would be pretty damn difficult to touch the lines near the pump, and they shouldn't be warm at all that far away from the block.

as far as starting, even though the truck was warm, did you engage the choke a little? i've found that sometimes they need it to start, even when hot. not full choke, but maybe 1/3 to 1/4.

wally

[JBNeal]

Vapor lock or faulty batt.cables or maybe it's time for Coke bottle of H2O down the carb 

 

BTW watch your spacer thickness as it may affect your carb linkage

Edited February 23, 2014 by JBNeal

[TodFitch]

Based on the description, it sounds like heat soaking of the carburetor leading to gas percolating and getting into the manifold. Prevention: Assure phenolic insulating spacer is under the carburetor, lower the float settings slightly below factory recommendations. I'd add find some place that sells less volatile gasoline except I don't think that is possible though some people swear by adding a little diesel to the tank.

 

If percolation due to a heat soaked carburetor is the issue, using the choke probably is the wrong thing. Better would be to hold the throttle wide open to move the gas on out of the manifold.

 

To me "vapor lock" can only occur when the fuel pump stops pumping because it has vapor in it. Immediate fix is to cool the fuel pump down, I find pouring some water on the pump works very well. But having the fuel pump heat shield installed will greatly reduce the issue.

[Jeff Balazs]

There is no insulating spacer on my truck currently. Just a gasket between the manifold and the carb. The fuel line to the carb is a flex line routed over from the filter which I have mounted on the inner fender. The fuel supply is cool and well filtered right up to the point it enters the carb in this current arrangement.

 

In the original arrangement there was a glass bowl type filter mounted directly ahead of the carb. When warm I often observed the fuel in it percolating after shut down. This is not surprising as it was directly above the manifold which get's too hot to touch when the engine is up to operating temperature. Based on this I think the same thing is happening inside the float bowl. Yesterday when this event occurred I could really smell raw gas as I tried to get it started. Honestly I have never smelled it like this before. I tried using the choke, wide open throttle, etc but it took quite a while before I could get it to start. Once it did it ran just fine. I would add that the engine is in a very good state of tune.......excellent compression....timing and vacuum readings are perfect. It is not prone to stalling either.

 

I don't really think it has anything to do with the coil in this instance. It is a new item and has never given any cause for concern. I have a 6 volt alternator on the truck and it does a great job keeping the system charged up.

 

Here in Southern California our fuel supply is regulated by the State and the Air Quality Management Districts. We actually have different formulations for winter and summer. I have spoken with several friends who own garages and are professional mechanics and it is a consensus opinion the the winter formulations are rubbish. This may have quite a lot to do with this incident as we are in the middle of the warmest and driest winter on record here.

 

My plan now is to make a spacer from this composite material I mentioned. My friend Carlos assures me that it is a much better material than phenolic for this application. I am going to shape it to extend out over the manifold some to act as a heat shield under the carb body as well as act as an actual insulator. Once I have had a chance to road test it for a period I will update this posting with pictures and particulars.

 

Jeff

[wallytoo]

J

I have eliminated the mechanical pump and the fuel line has been rerouted over to the fender well.

Immediate fix is to cool the fuel pump down, I find pouring some water on the pump works very well. But having the fuel pump heat shield installed will greatly reduce the issue.

you find that often with electric pumps remotely mounted? or in the tank? because i don't.

[HanksB3B]

Based on the description, it sounds like heat soaking of the carburetor leading to gas percolating and getting into the manifold. Prevention: Assure phenolic insulating spacer is under the carburetor, lower the float settings slightly below factory recommendations. I'd add find some place that sells less volatile gasoline except I don't think that is possible though some people swear by adding a little diesel to the tank.

 

If percolation due to a heat soaked carburetor is the issue, using the choke probably is the wrong thing. Better would be to hold the throttle wide open to move the gas on out of the manifold.

 

To me "vapor lock" can only occur when the fuel pump stops pumping because it has vapor in it. Immediate fix is to cool the fuel pump down, I find pouring some water on the pump works very well. But having the fuel pump heat shield installed will greatly reduce the issue.

Tod has pretty much nailed it here. Set the float level lower to prevent the percolating/overflow. Another trick I have learned is to remove the air filter give it a shot of WD40 and fire it up. Has worked for me every time.

 

The special heat. insulting gasket sounds like a good idea to me as well

 

Hank

[Merle Coggins]

I don't think the trucks used a spacer under the carb. I know my truck doesn't have one and I don't recap ever seeing one on a truck.

When I experience fuel perculation, hard starting, after sitting for a few minutes hot, I just give it about 1/4 to 1/2 throttle while cranking. It starts every time that way. Just need more air to account for the added fuel in the manifold.

Merle

[Jeff Balazs]

Hank;

What I am shooting for is a permanent solution or fix. Hopefully the material my friend is getting me will do the trick. If it doesn't I will look for something else.

 

In my opinion these manifolds seem to get much hotter than they actually need to. A few of the aftermarket manifolds I have seen have some provision to be tied into the cooling system. That might do wonders to keep things from getting too hot. Either way I am going to keep at it until I find a way to eliminate this condition. This type of issue may be tolerable in a truck that see's only limited use but it ain't going to fly in my daily driver. I have nothing at all against keeping a can of WD40 at hand ...... but having to rely on it as starting fluid is a band-aide and not a solution.

 

Jeff

[TodFitch]

Any chance the heat riser is stuck in the cold (heat directed toward carburetor) position?

[Jeff Balazs]

Tod;

It is not stuck and moves freely when the throttle is applied. It could however be contributing to the problem as I have a feeling it channels more heat than necessary to the manifold at slow engine speeds. I have thought about just eliminating it as it is certainly not needed in this climate.

 

Jeff

[55 Fargo]

post deleted

Edited March 7, 2014 by Fargos-Go-Far

[MBF]

Like others have said, I think this phenomenon is caused mostly by the newly formulated gasolines alcohol content and heat sink of the carb, pump and fuel line.  My truck would sit and idle after a long run but when I took off it would buck and cut out on a pull for a minute or so.  I installed the heat shield on the fuel pump, and insulated the line from the pump to the carb and the problem seems to have been cured.  I never had this problem when the vehicle was first started cold, and it would start fine when hot.  Just my 2 cents.  Mike

Edited February 24, 2014 by MBFowler

[Don Coatney]

I have never had this problem. I do not have a heat shield on my fuel pump but I did route my pump to carburetor line ahead of the exhaust manifold.

 

[Jeff Balazs]

Mike;

I feel it is almost certainly caused by these conditions. I had already eliminated the chance of heat effecting the fuel before it enters the carb by using an electric fuel pump and rerouting the fuel line. It was my hope that these changes would have been enough to prevent this from happening. Obviously that didn't quite work as planned.

I am going to see if I can eliminate this condition by the use of a composite spacer and heat shield. I do know I will have to make a modified arm for the throttle linkage to accommodate the thickness of the spacer. Other than that it should be fairly straightforward. It is looking like we are going to have a very warm summer and I want to do whatever I can to prevent this from being a regular occurrence.

Jeff

[HanksB3B]

Jeff,

 

All things being equal, My heat riser has never worked (broken spring) and I was told in this warm climate it would not really make much of a difference. During 2014 I've been busy improving and solving all kinds of stuff and have not yet really operated my truck for any length of time on a long trip with the correct fuel filter and hard line from the fuel pump to the carburetor I now have. I've also added a heat shield. There supposed to be a thick cardboard insulating gasket 14-34-2 between the carburetor and the manifold that is supposed to be there that I assume you also have installed Jeff. For now, I will carry that can of WD40 until yours goes into production and I can get one. 

 

 

Hank 

Edited February 24, 2014 by HanksB3B

[52b3b Joe]

Try the old solution Jeff... it's said to work well!

 

It does help. My dad tried this in our 41 Desoto this past summer. We took a 1500 mile trip with the car to the Desoto convention and the car had no problems in 90+ F degree weather. The car did over heat one due to it being a very hot day and we were stuck in traffic. Everyone kept asking about them all over the fuel line, and I think some of the people thought he was crazy. We did win the award for furthest driven pre-war car there. 

[MBF]

Before I did anything with my truck I noticed that the problem would resolve itself with a runtime of a few minutes.  I assumed that it was the fresh gas getting to the carb cooling it down and eliminating the suspected vapor issues.  That's why I think the heat shield, and insulating the gas line helped.  On my 1 ton, I have a manifold setup from a Chrysler I-6 that has a larger plenum under the carb than the original manifold that is about 2" taller than the original.  I've read articles on phase separation in the new gas blends, I'm wondering if something similar happens in the bowl of the carb with exposure to heat?   I've never had this problem with the slant 6 in my pickup, but if the truck sits for a week or more, the bowl is almost empty when I first try to start it.   That 2 bbl has a phonelic spacer under the carb.  I think where you've got a hot manifold sitting below the carb on anything that you're going to have a problem w heat sink especially with the new gas formulations.