Vapor Lock Issues??? Help

ALCON: Moved to PA for the next 18 months to attend school... dragged my 53 with me here to have a little touch of home. Recently she has been shutting down after running for 25-30 minutes when I get into stop and go traffic. The weather here has been hot and humid and until I arrived here I had not had this problem. I replaced my fuel pump today as the old one needed work and I had a fresh one that I wanted to put in. Lots of pressure when I turned it over to pump up fuel and the hand primmer worked very nicely. I ran the beast and after 15 minutes it shut down and would not start until it cooled off!

I'm thinking vapor lock at this point .. the fuel line running from the pump to the carb was hot to the touch and the pump itself was hot to the touch too. I have my heat shield in place over the fuel pump and my beast has all the original filters (Tank and the one on the firewall) in addition to one inline filter between the pump and the carb. I'm going to wrap my fuel lines tomorrow between the pump and carb, and check to make sure that the adjustable heat riser is in the correct position. I'm tempted to insulate the carb bowl on the bottom as it gets a lot of heat from the manifolds

Any other comments regards things I might do to alleviate this issue would be appreciated .. would prefer not to have to resort to an electric fuel pump ... I drove this thing from WI to OH and back last AUG and never had an issue with Vapor lock so I'm a bit mystified why it would be an issue now ..

Yup they will do that when it gets hot. Try a rubber fuel line from the pump to the carb, routed well away from the manifolds. Looks like crap I know, but helps with this issue.

By your avitar pic, you with a AVN unit perhaps?? I have the same set up in my M-37 as you do. I had cut the stock metal line and put a replaceable civie filter in (Killed me to do it) but after a bad tank of gas...........not taking any more chances. Anyways I am a aircraft mechanic and I have known about the vapor lock issue from the start so I installed on my fuel line a "Fire Sleeve". All aircraft fluid lines are covered with it so in the event of a fire behind the engine, the lines will not burn through as fast and feeding a fire to make it burn faster.
Mine was put to the test this July 4th parade as we were at 88 degrees in a very long parade and she pulled through without a hicup.

For the rest of us flat landers, What is a "Fire Sleeve"? Anyone with an M-37 might benifit. Thanks

Summit Racing sells the heat barrier in tube form. They also have it in sheets that I put on the heat shield for extra protection. I have it on my M37 and I have never had heat related issues .

ALCON: Thanks for the replies ... VTDD, sorry not aviation .. those birds were supporting one of my missions on the "Dark Continent" (Africa).

Ordered heat/fire tube and reflective heat barrier goodies today from summit racing .. will try that out to see what happens .. in the mean time going to try an old school remedy and use a few clothes pins on my fuel lines ... supposed to draw heat off the lines .. will provide updates as goodies come in and clothes pins go on!

//R//
Mark

1943ht said:

Ordered heat/fire tube and reflective heat barrier goodies today from summit racing .. will try that out to see what happens .. in the mean time going to try an old school remedy and use a few clothes pins on my fuel lines ... supposed to draw heat off the lines .. will provide updates as goodies come in and clothes pins go on!

//R//
Mark

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I was told the same thing by a old collector I knew, he said it was the stupidist thing he ever heard of till he tried it and it WORKED FOR HIM on his old jeep... Go figure!


I had a backup elec fuel pump/ filter on my 37 that was mounted back by the fuel tank and when my 37 started bucking into vapor lock I would just turn it on and problem solved

Bill W said:

I was told the same thing by a old collector I knew, he said it was the stupidist thing he ever heard of till he tried it and it WORKED FOR HIM on his old jeep... Go figure!


I had a backup elec fuel pump/ filter on my 37 that was mounted back by the fuel tank and when my 37 started bucking into vapor lock I would just turn it on and problem solved

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Bill I will forget that I ever seen this picture!!!! As you know Ive seen your truck and I will remember it always as pure and original as the sun on that note, I probably also know where you got that pump as I have two on the shelf from possibly the same person

1943ht said:

Ordered heat/fire tube and reflective heat barrier goodies today from summit racing .. will try that out to see what happens .. in the mean time going to try an old school remedy and use a few clothes pins on my fuel lines ... supposed to draw heat off the lines .. will provide updates as goodies come in and clothes pins go on!

//R//
Mark

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This will work, put it on and you should be ok.

rosco said:

For the rest of us flat landers, What is a "Fire Sleeve"? Anyone with an M-37 might benifit. Thanks

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I thought I explained it pretty well in what it is in my reply.............so for the flat landers.
http://www.aircraftspruce.com/catalog/appages/aqfiresleeve.php

Not to mention, since its aircraft and the military flies airplanes and helicopters with this...........well if your being judged in a motor pool class, you should not get whacked on it as it very well can be a GI fix!!!

vtdeucedriver said:

Bill I will forget that I ever seen this picture!!!! As you know Ive seen your truck and I will remember it always as pure and original as the sun on that note, I probably also know where you got that pump as I have two on the shelf from possibly the same person

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Lets see, the person I bought mine from owned a Sherman tank and also once owned a Grumman Duck

Got my goodies from summit racing today (Fire Tube, shield ) .. drove the truck the last two days in 91+ degree heat without any issues .. and I did the clothespin thing .. may hold off on the summit install and just see how things go ... she is running great again and I can tell he difference with the new rebuilt fuel pump ..

My experience with M and WC series Dodges:
The first thing to look at when "vapor lock" is suspected is the fuel pressure at the carb (inexpensive in-line pressure gage is the ticket!).
Most problems are related to tiny air leak (pin holes in gas line, loose fittings or cracked line flares) or weak fuel pump.

True vapor lock usually occurs AHEAD of the fuel pump. A fuel pump will move liquid but not vapor. If the fuel boils after the pump it should push it on thru.Thats why you put the electrict.pumps back at the tank. Sometimes vapor lock will manifest its self more when the tank gets lower on fuel. Just some general observations based on 50 years of problem solving.

Thanks for all the input, ideas and personal experience with this issue. Installed my firetube insulation on my fuel line from pump to carb and from my AC filter On the firewall (I have all the original filters on my truck) to the fuel pump .. I did not cover the original fuel lines lines along the frame from the tank but did cover the line from the frame up to the filter on the firewall. I also covered the top of the fuel-pump shield with a heat reflective material that keeps heat from transferring thue the shield from the "E" manifold to the pump and that has been more of a piece of mind thing. The pump does stay cooler to the touch. I'll snap a couple of pics and post.

I have driven the truck for the last three days in 98-100+ degree (102Today) weather without a single problem!! I have driven in stop and go traffic and shut it down repeatedly while running errands and it has started each time. My confidence in my baby has returned and we are planning on taking her out on a camping trip next weekend. I drove it to Gettysburg PA for lunch yesterday and back and she ran like a fine watch.. I have put 285 miles on her in the last three days and believe that the vapor-lock issue is resolved.

Thank you for all the help!!!