M37 vapor lock?

[Old Fart]

Hope I’m in the rite place, first time in a forum, I have a 53 m37, all original, 98% rust free, got it runnin like a top. Iv been pulling palmettos out of the ground on my property, if I let the motor idle for about 20 mins or so it will die and it will not start for a few hrs or so, get a little whiff of funky exhaust , was thinking maybe vapor locked but not sure. Any input would be greatly appreciated. Thanks old fart

 

[NDT]

Yup sounds like classic M37 vapor lock. Heat from the exhaust manifold cooks the nearby fuel line.

 

[hndrsonj]

Do you have the little heat shield on the manifold?

 

[Old Fart]

No, on the heat shield, i will look for info on it, think i will reroute the fuel line as well n see what happins. Thanks for your swift replys

 

[TGP (IL)]

Need to have the heat shield as mentioned, above the pump.
Typical military and power wagon vendors have nice reproductions available.

Moving the fuel line from pump to carb. farther away from the manifold will help.

Biggest problem is the manifold preheat stove (butterfly) located between the
Intake and Exhaust manifold is usually stuck(froze) in the winter position or somewhere
In between.

You can try to move it but probably stuck.
If forced it will break.

Replacement shaft and butterfly are also available.
Requires R&R manifold and separating the two halves, another can of worms to open.

Tom

 

[Old Fart]

Need to have the heat shield as mentioned, above the pump.
Typical military and power wagon vendors have nice reproductions available.

Moving the fuel line from pump to carb. farther away from the manifold will help.

Biggest problem is the manifold preheat stove (butterfly) located between the
Intake and Exhaust manifold is usually stuck(froze) in the winter position or somewhere
In between.

You can try to move it but probably stuck.
If forced it will break.

Replacement shaft and butterfly are also available.
Requires R&R manifold and separating the two halves, another can of worms to open.

Tom

Thank you Tom for responding, the butterfly actually works on this truck and was the first thing i went thru, or shud i say functions anyway, went thru it when i replaced manifold gaskets n rebuilt the carb, i do understand the seperation of manifolds and was hoping to not go that direction but very good info, gunna try fuel line relocation n try to make or buy needed heat shield, gunna try to find pictures of shield. Truck runs perfect other than this issue and really shows up when i use the wench in the field, truck is so original that i would not attempt to modify manifolds unless it gets worse. Do you think that the type of fuel line mite make a differense like rubber or copper or steel from pump to carb? Thank you very mutch for your help. Old fart

 

[TGP (IL)]

Nice Truck.
Some like to use quality rubber line from pump to carb routed over to
Inner fender and back to the carb.

I used 5/16 steel brake line routed as mentioned on my WDX Power Wagon
And fuel hose on the M37 as a temporary fix one year at the rally.
Still planning on changing it, but haven't done so.
Both work.

Tom

 

[Old Fart]

Nice Truck.
Some like to use quality rubber line from pump to carb routed over to
Inner fender and back to the carb.

I used 5/16 steel brake line routed as mentioned on my WDX Power Wagon
And fuel hose on the M37 as a temporary fix one year at the rally.
Still planning on changing it, but haven't done so.
Both work.

Tom

I put a brake line on it rite after i got it ( ( 20 yrs ago ) and removed a mish mash of copper and rubber fuel line that looked

Nice Truck.
Some like to use quality rubber line from pump to carb routed over to
Inner fender and back to the carb.

I used 5/16 steel brake line routed as mentioned on my WDX Power Wagon
And fuel hose on the M37 as a temporary fix one year at the rally.
Still planning on changing it, but haven't done so.
Both work.

Tom

When i got the truck ( 20 yrs ago ) it had a mesh mash of copper and rubber fuel line and that looked
way outa place, i put in a brake line, and thinkin maybe now whoever did it knew sumthin i didnt, lol. In the picture i assume ther was a shield jus above the fuel pump

 

[Old Fart]

I put a brake line on it rite after i got it ( ( 20 yrs ago ) and removed a mish mash of copper and rubber fuel line that looked

When i got the truck ( 20 yrs ago ) it had a mesh mash of copper and rubber fuel line and that looked
way outa place, i put in a brake line, and thinkin maybe now whoever did it knew sumthin i didnt, lol. In the picture i assume ther was a shield jus above the fuel pump

think i will buy a longer brake line n route towards fender n around to carb n see if that does the trick, thanks for all the info

 

[Old Fart]

My sons and i a few years back at combat airsoft event, long ride but allotta fun

 

[OutpostM37]

I had vapor lock issues on the M37 flat head 6 in summer time here in Phx Az. Summer time easily hits 115*F. Finally went with an Aerospace 24 volt electric fuel pump. No issues now. I had the heat shield, but 115*F before you start, with oxygenated fuel was an issue.

 

[Old Fart]

very nice, if it works there it shud work anywere, iv been ta phx in summer and it was way hotter than here. Thank you for sharing

 

[zak]

This is the pump heat shield and line with a heat reflective wrap. Works great

 

[Old Fart]

This is the pump heat shield and line with a heat reflective wrap. Works greatView attachment 790768

Thank you Zak , i see now what im lookin for on heat shield, i also see that i am missing parts on the manifold preheat butterfly that Tgp was talkin about, gunna try and purchase those parts if i can figure out where n how, local auto parts guys are no help on this truck, is that a speshel high heat paint you used to paint those parts? Thank you all for all your help. old fart

 

[zak]

Thank you Zak , i see now what im lookin for on heat shield, i also see that i am missing parts on the manifold preheat butterfly that Tgp was talkin about, gunna try and purchase those parts if i can figure out where n how, local auto parts guys are no help on this truck, is that a speshel high heat paint you used to paint those parts? Thank you all for all your help. old fart

Paint is from Eastwood supposed to be high heat but needs touching up in places. There are a few vendors that have m37 parts shouldn't be too hard to find what you need.