Exhaust manifold heat flap position if no spring

[squidtone]

I have encountered a vexing problem with hot starting on my CJ. If I drive it and get it fully heated up, then stop someplace, it is difficult to re-start. I found that if I hold the pedal down and crank for 10 or 15 seconds it will start but it coughs and sputters, smokes black, then clears up and runs fine. I noticed steady bubbles in the fuel filter....the carb is too hot? Then I remembered the lowly exhaust flap for preheating the cold carb....I checked and sheepishly admit I never paid attention to it, and sure enough I notice the bimetallic coil spring does not have a "stop", so it is not doing anything. The weighted arm hangs straight down. Which way should I manually rotate/move the counterweight arm in order to close the flap (i.e. prevent exhaust from heating intake manifold? I'd like to try another run to see if this solves my problem (and then put fixing this on my list of things to do)
Thanks,
Dave

[1955CJ-5]

The picture shows the "cold" (open flap) position of the weighted arm...so "up" would close the internal flap.

Also sounds like some vapor lock may be causing problems.� Are you using ethanol gas? Someone had a problem before but I don't remember the fix...maybe as easy as bending the fuel line away from the exhaust manifold. Basically you need to insulate or protect the fuel feed line pump to carb� from the residual manifold heat...

[squidtone]

Thanks for the picture '55.
Hmmm, my weighted arm hangs straight down...perhaps someone adjusted it to do so. I can move the arm counterclockwise and hear a clank...I'll assume that's the plate closing off the intake...so I'll try wiring it up to see if this helps. Then soak that little nut and bolt and see if I can adjust it (and make a stop for the spring)
Is that a sheet metal tab on the right side of the pivot? to serve as a stop?

[1955CJ-5]

The tab is sheet metal. I got mine from Walcks as I needed to order the entire heat riser kit...

https://walcks4wd.com/manifold-heat-riser-stop-bracket-1941-1953-l-head-4-cylinder-only.html

It would probably be easy enough to make...I could try and get a few dimensions for you....

That link doesn't work for me unless I copy and paste it..or search Walck's for "Heat Riser"

[1955CJ-5]

Here is what i measured....

16 ga steel, 3/4" wide

3/4" on the flat with the hole.

1/2" drop

1/2" where the coil rests.

I had to saw my old one out, and replace it with new. The shaft was broken and the flap damaged. The flap is welded to the shaft.

[1955CJ-5]

Hmmm, my weighted arm hangs straight down...perhaps someone adjusted it to do so.

There is a slot in the shaft for a short metal key that extends into the slot in the weighted arm.

Maybe yours is gone or sheared off?

[squidtone]

Ohhh, that's good info...I can see from your picture the thin piece of strip metal that goes from the slot in the arm into the slot of the shaft. I will definitely have to take mine apart. The "key" must have sheared. It seems tight enough though, and I was able to wire the arm up and hold the flap.
And the good news is I then took a drive, got it hot, shut down, and five minutes later it started back up with no sputtering. (maybe 4 seconds cranking).
Then when I got home I turned off the Jeep, let it sit for a half a minute, then opened the hood and felt the carburetor....it was warm but not hot; I could leave my hand on it. Not terribly scientific since I didn't try this before I wired up the arm, but I think this may have been my problem.
Thanks  1955CJ-5!
P.S. I love the picture of the hacksaw assembled in-situ to get the flap and shaft out!

[1955CJ-5]

P.S. I love the picture of the hacksaw assembled in-situ to get the flap and shaft out!

That sawing of the riser shaft started out with the blade only....and a pair of leather gloves....then an ah-ha! moment and I realized I could use the handle....

Glad you have improved your hot-start problem. 4 seconds, maybe 4 revolutions, is standard I think!

Randy

[BillT]

Note that all rebuild kits do not include the key that indexes the arm to the shaft. You want to confirm that the kit you order includes the part if needed.

[1955CJ-5]

Note that all rebuild kits do not include the key that indexes the arm to the shaft. You want to confirm that the kit you order includes the part if needed

I'm pretty sure I got mine from one of the military vehicle vendors. Ron Fitzpatrick maybe...but it was about 5 years ago...

Also, though the arm and the bi-metallic coil are keyed to the shaft, there is no mark or index for the flapper that needs to be welded in place on the shaft.

I remember a lot of messing around with a heat gun on the coil, watching the movement of the shaft and adjusting the flapper on the shaft before welding it in place.

There may be a better reference in setting the heat riser up, but I never found it....there is a description of it's operation on page 113 of the manual..the exhaust section....

I guess if your old one is partially intact you could check the relationship between the flapper and the slot in the shaft....I'll remember to do that next time!

Randy

[squidtone]

Well it's been so busy this summer I haven't had time to follow up on my hot start/flooded engine problem.
Tying off the exhaust flap didn't solve my problem after all. It may have helped a bit, but I had some more episodes of flooding after sitting for a few minutes after a hot shut off.

I think I know what it is though....
I installed a pressure regulator after my fuel pump so I could set the pressure to a SOLEX friendly 1.5 psi. I put a pressure gauge on there to do the adjustment and it's still on there.
The lower pressure made my SOLEX very happy, and it runs fantastic. The pressure stays at 1.5 psi very steadily when running. However, after some patient observation, I realized that the pressure goes UP very slowly after a hot shut off. In fact after about 10 minutes I found the pressure to be over 5 psi just sitting there. I'm sure the poor little SOLEX cannot handle this pressure, and the needle/seat allows fuel to flow past and gas pours down the throat. Flooding. Hard to restart.
I did some research and it seems the Willys engine fuel supply is a "dead headed" system...the fuel has only one place to go after it gets pressurized...into the carburetor. The Holley regulator I use can't get rid of excess pressure unless the engine is running and allows excess pressure to bleed off. If the engine is shut off, and conditions such as excess heat expand the fuel pump, lines, filter, etc, the pressure climbs and has nowhere to go resulting in over 5 psi to the carb. Apparently this is/was a very common problem in the old days for many cars and trucks. Manufacturers addressed the problem by incorporating a fuel bypass system. Essentially putting in a return line with an oriface to bleed off excess pressure back to the tank. It also can prevent vapor lock among other things. I remember now my CJ-8 had a fuel filter with a bypass return line; it was an extra output on the filter and it indeed had a small oriface...ah ha. So, I will fabricate up a return line and report back when I install and test it! I think it will solve my problem of excess pressure.

[SteveKfl]

Wouldn't a vented fuel cap release the pressure when off?

[squidtone]

It does have a vented fuel cap, so the tank at ambient atmosphere pressure. I kind of thought that fuel pressure would bleed down back through the fuel pump after shut off, but now I'm not so sure.
So either the fuel pump or Holley fuel pressure regulator act like a one way check valve.

[mtnman37879]

In order for a pump to work it has to have a one way valve. So your fuel pump does have a one way valve.

[scoutpilot]

What is happening is this. After a hot shutdown, with a bad heat riser, the heat is transferred to the carburetor bowl. The fuel inside begins to boil. There's your excess pressure. This excess pressure has to go somewhere. That somewhere is through the metering device and straight into the intake manifold.