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View Full Version : Vapor lock!!!



biggiefl
05-20-2013, 03:03 PM
For the SEADOGS who attended the ditch run a few weekends ago I did find out what happened. Ironically we were talking about vapor lock the night before. I would have put my money on the fuel pump being the way she bucked and spit for so long but would clear out with a good dose of throttle. Next day I hit the key and it fired right up....now thinking coil? Vapor lock? Checked fuel pressure and it was I think 5.5 or so, not the pump. Looked at the coil and no leaks or anything weird. Removed the fuel seperator and I could barely get a wrench on it as it was too long. I changed it the day of our St Pete run and I put one about 1 inch longer on it. Did not realize it being you screw the new one on, no wrench needed. Well the filter is now an inch lower towards the hot end of my exhaust manifolds and holds more fuel. Changed the filter and made up an aluminum heat shield that went between the manifold and the filter. Ran it 3 times so far and she is flawless.

Anyone else have this problem? My last I/O I had the filter on the transom, not the engine.

pipnit
05-21-2013, 10:05 AM
I've never had this problem with my Donzi but I've had it happen with other toys, most recently a 61 Tbird with a 390. The fuel like ran along the front of the block (stock routing) and it would boil. I changed the route and no more problems. It'll have you scratching your head for sure.

BUIZILLA
05-21-2013, 10:13 AM
back in 1970 I had a '70 340 Plymouth Duster (yeah, i'm old, get over it:spongebob:)... with the stock AVS carb in the summer it would get vapor lock from time to time, my grandfather had a '68 Town and Country wagon with a 440 Magnum and my dad and mom had 440's in both of their Chrysler product's, we ALL used to put a wooden clothes pin or two on the metal fuel line before the fuel pump, and it cured the problem, it was my grandfather's idea since he had an early 50's Caddy 20 years prior that did the same thing....

pipnit
05-21-2013, 11:47 AM
back in 1970 I had a '70 340 Plymouth Duster (yeah, i'm old, get over it:spongebob:)... with the stock AVS carb in the summer it would get vapor lock from time to time, my grandfather had a '68 Town and Country wagon with a 440 Magnum and my dad and mom had 440's in both of their Chrysler product's, we ALL used to put a wooden clothes pin or two on the metal fuel line before the fuel pump, and it cured the problem, it was my grandfather's idea since he had an early 50's Caddy 20 years prior that did the same thing....

LoL, I've heard of this and I've seen it on some hotrods just as a period piece. Sounds crazy but I guess it works. Originally, I thought they were put there to try to act as a heat sink (wood? lol) but then another older hotrodder said it simply insulates the line.

roadtrip se
05-21-2013, 11:49 AM
I had vaporlock issues all the time with 500HP carbed motors in my last Fountain. Could have been the 100+ degree temps we dealt with on a regular basis. I ended up having to install bigger fuel coolers to keep cool go juice cycling to the beasts. The 500EFI in the Classic never had the same issue, because it had better fuel cooling from the start. Then I moved to a cooler part of the Earth, which took care of it permanently...

pipnit
05-21-2013, 11:53 AM
Now this truly is OLD SCHOOL
76104


here is a solution I'd never seen before!
http://www.mgexp.com/phile/3/160024/cork%20002.jpg

MOP
05-21-2013, 12:39 PM
Cloths pins have worked fine but are kind of ugly, a neat job of wrapping the line with silver foil does a good job looks a bit better.

Phil

Conquistador_del_mar
05-21-2013, 02:20 PM
I have only experienced vapor lock once in all my years. It was a 1969 Chrysler New Yorker with a 440 in a record heat wave in Arkansas after idling too long. Living in Texas for 42 years with our extreme heat, I have never had a vapor lock problem. I find it strange that a boat engine manifold can produce so much heat.
The clothes pin insulating the fuel line from heat is a new one on me. I wonder how hot the fuel has to get to boil? Bill

biggiefl
05-21-2013, 03:00 PM
Bottom of manifolds get very hot like a car, the rest is water cooled. i think my problem stemmed from the filter being too long and giving the fuel a good time to get hot as it holds almost a quart. A fuel line can be burned up quickly a filter will retain the hot fuel. Who knows....might be coincidental but I have not had a hiccup since and it usually happened at least once a run, usually when I came off plane after a long cruise. Notice the warning sticker....4.75" might do the trick. you can also see the crude alum heat shield we made, there is not much more than an inch between the filter and manifold.

BUIZILLA
05-21-2013, 03:52 PM
my '95 454 MPI Merc had an exact shield like you made

Conquistador_del_mar
05-21-2013, 04:13 PM
Apparently there is enough heat to warrant the shields. Good job figuring it out biggiefl.

gcarter
05-21-2013, 04:49 PM
I had a '78 Datsun 280Z w/Bosch L-Jetronic injection. After racking up well over 200K miles, the injectors started leaking down between times it ran, and would eventually vapor lock. It would take awhile to get gas flowing through the system again (turning the key on and off to get the pump to run). As long as the pressure was correct (45-50 PSI, or so) it wouldn't vapor lock.
I eventually bought a set of used injectors w/only 60K miles on them and it fixed the problem.

Jeremy E
05-22-2013, 01:56 PM
76133 sorry I could not resist

biggiefl
05-22-2013, 02:32 PM
Yeah....look at the pot calling the kettle black. At least I did'nt run out of gas....oh wait......theorhetically......:screwy:

gcarter
05-22-2013, 03:14 PM
I got towed by a toon boat once, I was really glad he was there!:frown: