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Stalling when hot

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sparkydave

sparkydave

Jedi Knight
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The one quirk my car has that is starting to become irritating is when it can't seem to idle when it's hot and I've started it after sitting for a few minutes. I'm guessing this is because the air intake is under the hood, so it's drawing in hot air that's been collecting around the hot engine until things cool off a bit. Maybe not such a good design, but does anyone else's do this? It runs okay after it's been running for a few minutes, but I'm having to keep giving it gas to keep it from dying before then. The temperature gauge reads 180 when it's running, although it does creep up around 212 after it's been off for a few minutes.
 
It sounds like your gas may be vaporizing. Couple of things I would suggest. First, make sure your heat shield is in place under the carb. Second, on the 1500's the gas line runs on the right side of the tunnel, crosses over the transmission housing and then to the fuel pump. Make sure the gas line portion over the transmission is not in contact with the housing as heat will radiate to the line. You may want to consider purchasing some insulation for the fuel line similar to what race cars use and install that.

Creeping up to 212 after a few minutes is normal.
 
Thanks Mike, but I've already insulated the fuel line when I was troubleshooting what I thought was vapor locking. The original heat shield under the carburetor was present until earlier this year, but I made a new one out of aluminum. I also got rid of the catalytic converter and wrapped the section of exhaust pipe below the carburetor in heat tape, but this problem has been the same for as long as I've had it.
 
Dave,
My 1500 does the same thing as you are describing. I haven't found a fix for it either. Sorry I can't help but at least I can commiserate. I thought it might be something to do with engine compartment temps too but if you open the hood it doesn't smooth out the idle any. I think it has to be a quirk of the carb in some manner.
JC
 
You say you made a new heat shield out of aluminumum. Is it just metal or did you use some insulation on it? The OEM ones, if I remember, had asbestos matting ont them. A sheet of metal would not do the job.
 
It will shield the heat somewhat, but will basically serve to reflect heat if it is not insulated. Actual insulation is superior to a simple sheet of metal.
 
Did SU spridget heat shields have insulation.
Answer, No.
They worked didn't they. Yes, some form of insulation will make a heat shield work better, but a heat shield where none exists will be an improvement.
 
i just bolted a heat shield to my canon manifold using the coolant cup stud, it does seem to help, but not as much as i thought it would. I will see if i can find some insulation.
i also upgraded my alternator, and WOW!! the car idles a lot more steadily . There was a huge difference there. i am still running on the stock ignition. it seemed like it was always right on the edge of stalling at a 7-8oo idle. with the new alt. it idles rock steady. i also have squeezed in an air intake on the right side and i am thinking about cutting another hole in the rad support to match the one for the heater intake, and use that to get some fresh air up to my carb. or mabe just a nice little low profile ram air intake on the hood. This would also help (ithink) to get the warm air out when sitting.

back to the heat shield insulation again..which side would be better for the insulation to mount on?


mark
 
Heat shields with insulation had it on the engine side. I had a heat problem with my Weber on a short Lynx intake mainifold where the center branch of the exhaust header was only about an inch below the bottom of the fuel bowl. A small heat shield made of polished stainless steel was enough to solve my problem. But my problem was minor and only occurred when stoping after cruising at high speed for over an hour. The header would heat the fuel bowl enough to boil the gas. As long as I was moving it was never a problem.
 
I actually had this problem even when the old heat shield was present, so I'm not convinced that that was why I'm having problems now. Thanks for the info though. Maybe someday I'll see if rerouting the air intake will have any effect, but for now I'll chalk it up to one of those endearing qualties unique to LBCs.
 
Here's a thought ... what kind of fuel pump do you have, and how well does it work?

On a related note, yesterday after the last autocross run of the day, when I was about to load the car on the trailer, it stalled (as it had been doing a lot during the day, while I was waiting in grid). We were loading the trunk full of folding chairs and the engine stopped. I tried to immediately restart, but it would not. Then smoke started coming from under the dash. I immediately popped the hood and discovered that the power wire for the DPO installed electric fuel pump was a crispy black line running toward the back of the car. I believe, although I haven't yet climbed underneath to confirm, that the pump was shot and it shorted out, drawing a large amount of current and frying the wire. I also think that the intermittent hammering (as if the tank was empty, even when it was not) was due to the failing fuel pump. It's very lucky that the wire lost continuity as it burned up, because I apparently had it on the unfused side of the fuse block (my mistake). I think a new fuel pump, better wiring, and careful fusing are now in order ...

At any rate, I thought that you might consider the fuel pressure as a possible problem, because my symptoms sound fairly similar to yours. I didn't detect any power loss as I was racing the car either. (I had the dual webers tuned this past week, so the throttle response was actually improved tremendously)
 
I have an electric fuel pump that is mounted on the passenger side inner fender. I see the same rough idle when the engine is hot. I've always considered it a vapor problem but it may not be. I think Dave still has the original mechanical pump.
JC
 
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