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Post by cline48 on Aug 25, 2022 20:43:45 GMT -5
I have never had a vapor lock problem until this year. While in the Medicine Bow mountains the vapor lock problem showed up. This year I put a rebuilt engine in my Jeep. With 40 over pistons all new or New old stock parts (Cam tappets valves and springs) rebuilt carburetor, rebuilt AC fuel pump and the distributor rebuilt and recurved. My old engine had 60 over pistons and never had a vapor lock problem.
My fuel system is stock with hard pipe routed properly from the tank along the frame to the fuel pump. The only thing I changed was the rubber fuel line from the hard pipe to the pump because the rubber fuel line jacket was cracked. I changed it with Aeroquip push lock hose and fittings. Now I’m questioning that.
Record radiator running a 160 deg. Bellows type thermostat all was with my old engine before.
The first time the vapor lock happened it was in the morning and the air temperature was starting to warm up and we were starting to climb a grade. I stopped and poured water on the fuel pump and I was able to move again. The problem kept getting worse and I found the inlet fitting on the pump was loose and I fixed that on the trail.
The pump was sucking air and I could see bubbles on the inlet side of the pump. That night at camp I did some changes to the hose to the pump and that stopped the bubbles on the inlet side of the pump. But, there were small bubbles coming in around the glass bowl and the cork gasket. There were no chips in the glass bowl, so I tightened up the bail. The next day, I had the same problems with vapor locking. That night I changed out the fuel pump with the one that I was using on my old engine. Still had the same problem sucking air around the glass bowl. I cut out a new cork gasket, but that didn’t stop the bubbles. We did advance the timing up to about 9 deg tdc. also. The next morning, we changed out the fuel pump with a Car Quest Air Tech. 572 pump and didn’t have any problems the rest of the week there or while were were in Colorado at 12,800. Except one time when I let it idle for about 15 minutes I had a little vapor lock problem.
While in Colorado I put a rubber fuel line from the drain fitting on the fuel tank to the fuel pump for back up in case I had a problem getting fuel. We also checked the vacuum on the suction side of the pump and it read about one-inch pound of vacuum.
We also did some temperature reading on different parts of the fuel system and engine. We did this at 9,700 ft. I don’t remember the air temp.
Jeep inlet to pump out of pump Temp at block behind pump Temp sending unit
Shacks 113 148 163 180
Oilleaker 108 126 142 169
Muley 138 159 167 178
BW 110 113 119 182
Lee 117 126 130 166
Grumpy 124 129 147 164
I don’t understand why mine has the biggest temperature difference between the inlet and outlet from the fuel pump. There is 35 degrees difference. And BW’s is only 3 degrees difference. Oilleaker’s fuel pump was bubbling the whole time we there and never had any problem with vapor lock.
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Post by rickg on Aug 25, 2022 22:02:06 GMT -5
Watching an empty glass bowl fill with fuel after pouring a cup of cool water on it is "fasten 8"-ing to see for sure.
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Lee
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Vagabond Jeeper
Posts: 642
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Post by Lee on Aug 26, 2022 7:02:22 GMT -5
Much to add to this topic in given time 😬
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Post by Scoutpilot on Aug 26, 2022 11:04:51 GMT -5
The more data about engines, pumps, operating conditions, etc. we can tabulate the closer to a solution we could be.
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Post by brucew on Aug 26, 2022 12:21:01 GMT -5
"Well the other five of us aren’t having a problem.’"
I don’t reckon I’ll ever hear the end of that, will I? BW
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oilleaker1
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Post by oilleaker1 on Aug 27, 2022 5:09:51 GMT -5
While at mike's FCT my '51 M38 had fuel deliver issues that were not showing at 3700 feet. At 8-9000 feet they showed up. I could not go up a hill without starving out on fuel. The pump that helped Shack at 9-11000 feet fixed my M38 for the rest of the week. My 6 check valve military pump was rebuilt with all new internals in the original body. I solved the problem when I discovered that the replaceable check valves were leaking air under the check valves with gaskets. I had bead blasted the white corrosion clean which roughed up the pockets too much. A Dremel tool stone fit the pockets perfectly. I hand lapped the seats and shortened the steel hold down posts a bit so that when retained , the checks were held tight. it's worked perfect ever since. So another possible cause is the checks are leaking by internally and show themselves at elevation. Another condition mentioned is that by tightening the glass bowl hold down, it may be warping the pump body where the gasket surface is. Using ring gear clamps versus the band spring steel clamps was also mentioned. A clamp that doesn't hold evenly all the way around can squeeze one portion out of round giving a air leak, but not a fuel leak. Hard to believe that a barbed fitting will allow a air leak under suction, but I watched more bubbles appear by simply squeezing those connections while running?? Stock cooling fan and shroud blowing air on the pump or not? A replacement non stock radiator a possible cause for the heat? When the incoming fuel follows the frame and enters the front of the pump, it shouldn't be acted on (heated) until after it exits the pump up to the carburator. I don't understand why the same system from one Jeep to another has such fuel pump body different temperatures. Red Willy has a electric assist fuel pump at the tank, and it still had vapor lock. So, is the fuel waiting to enter the carburator being heated and expanding back down to the pump and emptying the pump locking things up? Vapor lock? When you look at the glass bowls, they are empty. As muley stated, pour cold water on the pump, it fills up and then fills the glass bowl at the filter on the carb also. Strange as heck. Jeep then starts and runs. Viton versus steel inlet valve???
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oilleaker1
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Post by oilleaker1 on Aug 27, 2022 5:11:04 GMT -5
Watching an empty glass bowl fill with fuel after pouring a cup of cool water on it is "fasten 8"-ing to see for sure. Especially with a 10 button blouse!
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Post by m38mike on Aug 27, 2022 6:07:46 GMT -5
What type of fuel was being used; ethanol or non-ethanol? Regular or premium? I'm interested in any conclusions you all reach in this analysis since I've got 50+ Jeeps about to ascend to TDR for some fall color touring, and I'm betting that more than one will be affected by this same problem.
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oilleaker1
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Post by oilleaker1 on Aug 27, 2022 6:11:04 GMT -5
I always use premium non ethanol.
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Post by muley on Aug 27, 2022 9:49:17 GMT -5
87 no corn.
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Post by cline48 on Aug 27, 2022 16:18:28 GMT -5
What type of fuel was being used; ethanol or non-ethanol? Regular or premium? I'm interested in any conclusions you all reach in this analysis since I've got 50+ Jeeps about to ascend to TDR for some fall color touring, and I'm betting that more than one will be affected by this same problem. I was burning Premium No Corn! That us what the gas pump said it was.
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Post by m38mike on Aug 28, 2022 3:36:50 GMT -5
Well, it sounds like ethanol was not part of the problem.
Shack, Does your exhaust pipe run close to the frame going back to the muffler? Just wondering if heat from the pipe is being contained within the frame and heating your gas in the line before it gets to the pump.
Did anyone look at what diameter everyone's fuel line is? Just wondering if smaller diameter might be more apt to vaporlock.
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Post by rickg on Aug 28, 2022 10:06:32 GMT -5
Did anyone look at what diameter everyone's fuel line is? . 1pc 1/4" steel tank to rubber line w/brass ferrules to F/P.
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Post by Scoutpilot on Aug 28, 2022 13:59:34 GMT -5
I recommend 5/16" steel. More volume equals a longer time to heat up.
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Post by cline48 on Aug 28, 2022 15:37:01 GMT -5
Well, it sounds like ethanol was not part of the problem. Shack, Does your exhaust pipe run close to the frame going back to the muffler? Just wondering if heat from the pipe is being contained within the frame and heating your gas in the line before it gets to the pump. Did anyone look at what diameter everyone's fuel line is? Just wondering if smaller diameter might be more apt to vaporlock. I believe that both the exhaust and fuel system is as close to stock as it can get. My Exhaust is what Walcks sells. From the manifold it drops down and runs up close to the drag link with space between the frame and pipe. Then the exhaust pipe extension runs between the transmission and crossmember. I believe this is the stock routing of the exhaust system. I do not have the heat shied that protects the master cylinder. I have one that I need to get put on. My fuel line is also from Walcks 1/4' steel line with rubber hose for the crossover to the pump. Held by a clip on the hat channel just forward of the tank outlet, goes forward & turns and goes thru the toe-board gusset, there's a clip there, then one on the inner fender near the fore end of the line. The rubber hose that I was using was not the brass crimped fitting that is stock. I was using a house made up from a Hose & Handling company here in Omaha. They make hose for all application's. That is all they do there is make hose for all industries. The hose that I had made was Eaton Aeroquip socketless fittings and hose. I know it not stock hose but that is all that I could get in town at the time. The application of the hose and fittings are rated for pressure and suction also. From the fuel pump to the carb is steel line also.
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