Discussing Heat & Fuel Related Issues

[Sam Buchanan]

13 minutes ago, keithb7 said:

Dug into my used parts today and took apart a set of manifolds to get a good look at the flapper valve. Grasp a better understanding.  Then I wired my ‘38 flapper valve closed. I Went for a drive. Warmish day here. Sun beating down.
 

I indeed suffered fuel starvation while pulling 2 different long hill climbs today. Back up electric pump saved me both times. When I got home I shut off the key and let heat soak take over. 15 mins later...No start.  I am comfortable now and have mastered the fuel boil start procedure.  Electric pump engaged. Mash the throttle and hold it down and crank. Then it’ll start.  I’m somewhat happy I can deal with this interim. 
 

I’ll proceed to get a phenolic spacer. All metal fuel lines. Maybe wrap them in  some type of heat wrap insulation too. We’ll see. Also will fix the exhaust flapper set up. 
We shall overcome!....Hopefully. 
 

 

 

 

I don't think you are dealing with vapor lock when the car struggles up a hill, that sounds more like a fuel delivery problem. When the car is underway under full throttle cool fuel from the tank is being pumped at relatively high volume to the carb.....if the pump is healthy. The fact the electric pump "fixes" the problem would convince me even more that there are issues with the mechanical pump. If the check valves in the pump are weak there will be all sorts of delivery problems, sometimes intermittent. A minute leak on the suction side can allow air to be sucked into the pump and reduce fuel flow. I've chased these problems with aircraft pumps (same design) and the fix is a new pump.

 

I think you are chasing the wrong problem until you put a good pump on your engine. 

Edited May 10, 2020 by Sam Buchanan

[keithb7]

Sam there could very well be a couple of compounding problems here. Most symptoms seem to have appeared as soon as the local weather got hot.
 

 This morning, cooler outside I pulled the hill no fuel starvation problems at all. At first start up in the morning, the engine is running before the crankshaft makes 1 full turn. I did not replace the long fuel line from the tank, along the frame. It too could be a contributor? No leaks though.  I did seal up any fitting connections. 
 

I just rebuilt my mechanical pump. With a pressure gauge on it in the garage its making good pressure. A pressure gauge hooked up to monitor pressure while pulling the hill would be nice. 
 

I’m pretty convinced heat is another contributing factor. I get the hard starts as soon as it is parked and heat soak sets in. I repeated this scenario multiple times. 

[Sam Buchanan]

1 hour ago, keithb7 said:

Sam there could very well be a couple of compounding problems here. Most symptoms seem to have appeared as soon as the local weather got hot.
 

 This morning, cooler outside I pulled the hill no fuel starvation problems at all. At first start up in the morning, the engine is running before the crankshaft makes 1 full turn. I did not replace the long fuel line from the tank, along the frame. It too could be a contributor? No leaks though.  I did seal up any fitting connections. 
 

I just rebuilt my mechanical pump. With a pressure gauge on it in the garage its making good pressure. A pressure gauge hooked up to monitor pressure while pulling the hill would be nice. 
 

I’m pretty convinced heat is another contributing factor. I get the hard starts as soon as it is parked and heat soak sets in. I repeated this scenario multiple times. 

 

Keith, my car (and it sounds like this is common due to carb percolation) is also hesitant to start after it has heat-soaked for 15 minutes, but it always fires up after cranking a few seconds. But even in the hottest temps, and we had some scorchers in Alabama last summer, the car never failed to run properly in stop and go or highway traffic (after going to an electric pump).  That is why I think you are dealing with more than just vapor lock...most likely faulty fuel flow. Mechanical fuel pumps can do devious things and fail intermittently, sometimes after they get hot (suction leak...weak check valve?). My original mechanical pump would work for a time then with no warning lose prime, I never could figure out how to predict when this would happen (I was awarded a flatbed tow one time....). That pump is now in a land fill...... I had no emotional ties to it.  ? 

 

I suspect our ethanol-contaminated gas aggravates any weakness in the fuel system due to vapor pressures the old pumps were never designed to handle. A strong pump is fine as evidenced by many forum members, but I wonder if a weak pump might flake out when faced with low pressure adversity.   

 

Stay with it.....but try to avoid tunnel vision, don't discount the most obvious possibility.   

Edited May 11, 2020 by Sam Buchanan

[DJK]

https://www.jegs.com/i/JEGS/555/32011/10002/-1

[keithb7]

A great friend indeed threw this together this morning. I’ll give it a shot. Won’t hurt. 
 

 

[soth122003]

If that spacer is made from wood, I'd seal it so that over time it will not soak up fuel and swell, distort or deteriorate. 

 

Joe Lee

[keithb7]

It's not made of wood. It appears to be some type of synthetic material. It was located in the "stash of crap pile out back" that we all have, but cannot throw out.  We heated it up considerably with a heat gun. No distortion or melting. So I figure it's worth a try.

Edited May 11, 2020 by keithb7

[Sam Buchanan]

36 minutes ago, keithb7 said:

It's not made of wood. It appears to be some type of synthetic material. It was located in the "stash of crap pile out back" that we all have, but cannot throw out.  We heated it up considerably with a heat gun. No distortion or melting. So I figure it's worth a try.

 

You might want to soak it in gasoline overnight to make sure the resin doesn't deteriorate or swell.