vapor lock
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vapor lock
i have a 1977 f150 with a 400m and edelbrock manifold and carb. had a 79 bronco with same setup and problem but sold it before i figured out a cure. after you go down the highway on a warm day and you say, stop for any reason and get back in after five minutes and go to take off with any pedal pressure at all it falls flat. if you real feather it , it will finally take off again. hers what ive done so far. replaced all filters and rubber hoses including sock in tank. i have pu a new fuel pump, i have insulated the steel fuel line from the pump, up to the top of the engine. still doesnt help. my next thing i can think of is to put a thicker spacer between the carb and mainfold which i have on order. anyone else had this problem and able to correct it? thanks in advance for any advise you have.
Fleet Mechanic
Joined: Jul 2000
Posts: 1,493
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From: SE Iowa
vapor lock
The problem is the fuel line is running too close to the exhaust manifold. You'll have to cut the fuel line back by he firewall and run a new line to the outside of the frame rail. Then cross back into the engine bay right by the fuel pump. Either that or try insulating the fuel line in its present location.
Stryder
Stryder
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Joined: Aug 2000
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From: (near) Denver USA
vapor lock
Try an electric fuel pump. I know a few guys w/ vapor lock probs on M-blocks who solved the prob w/ an electric pump.
You can mount it inside the frame rail, under the cab. If you have dual tanks, put the pump right after the tank selector valve. I'd also use a filter both before and after the pump.
If you do an electric pump, make sure you wire in an oil pressure switch (tee the oil pressure sender line on the back of the block) so when the engine stops, the pump stops. You can also scavenge a fuel pump inertia switch from a later model car (shuts off fuel in case of hard impact, i.e., accident) and wire it in the pump power wire somewhere.
Also, insulating the line from the pump to the carb is a good idea.
Good luck.
You can mount it inside the frame rail, under the cab. If you have dual tanks, put the pump right after the tank selector valve. I'd also use a filter both before and after the pump.
If you do an electric pump, make sure you wire in an oil pressure switch (tee the oil pressure sender line on the back of the block) so when the engine stops, the pump stops. You can also scavenge a fuel pump inertia switch from a later model car (shuts off fuel in case of hard impact, i.e., accident) and wire it in the pump power wire somewhere.
Also, insulating the line from the pump to the carb is a good idea.
Good luck.
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vapor lock
i have know done everything you all have suggested and though it seems to be better it still will totally die after its hot and you go to take of, usually about at the 2-3 shift. will the pickup in the distributer do this? it is not isolated to one or two cylinders the whole motor will dye if you keep your foot in it. if you take your foot out of it and feather it , it will start running again. thanks for your suggestions any others? tracy
Posting Guru
Joined: Aug 2000
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From: (near) Denver USA
vapor lock
If you get the engine to run by feathering the throttle, that would indicate it's not the ignition.
What carb are you using? Has it been rebuilt recently? Have you checked float level. If float is too low, the bowl can empty when you nail the throttle before the pump catches up.
What fuel pump(s) are you using? What kind of filters?
Need more info to help you troubleshoot.
What carb are you using? Has it been rebuilt recently? Have you checked float level. If float is too low, the bowl can empty when you nail the throttle before the pump catches up.
What fuel pump(s) are you using? What kind of filters?
Need more info to help you troubleshoot.
Freshman User
Joined: Jul 1999
Posts: 25
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vapor lock
I've been experiencing the same problems with my '83 E-350 460 4bbl RV, except mine doesn't coincide with stopping - mine is mostly hot days and high altitudes (9000 feet or greater). I tried the new filters, new hoses, new pump(s), rerouted and insulated fuel lines, too. Nothing worked.
A posting to an RV group got me a number of replies about the fuel diverter valve (not sure if your year/model/engine has this, but mine does). The fuel diverter valve dumps fuel back to the tank when pressure and/or temp exceeds limits. When it opens to maximum, the electronic pump can't supply enough fuel to the carb for anything more than about 1/4 throttle, in my case. One poster had a fuel pressure gauge hooked up and observed pressure drop from around 8 psi down to around 2 psi, IIRC. His solution, which I've just completed as well, was to install a manual fuel pump from a '70something Lincoln 460(I can't remember the exact year, but he picked the last year that the fuel pump had just 2 lines... I'll look it up and post it) anyway; install this mechanical pump in-line with the electric pump. This will provide the volume capacity to supply the carb when the fuel diverter opens up. I've made one test run with no problems, however this is still non-conclusive, since my problem usually took 2-3 hours to show up and was pretty random.
Good luck!
Greg
A posting to an RV group got me a number of replies about the fuel diverter valve (not sure if your year/model/engine has this, but mine does). The fuel diverter valve dumps fuel back to the tank when pressure and/or temp exceeds limits. When it opens to maximum, the electronic pump can't supply enough fuel to the carb for anything more than about 1/4 throttle, in my case. One poster had a fuel pressure gauge hooked up and observed pressure drop from around 8 psi down to around 2 psi, IIRC. His solution, which I've just completed as well, was to install a manual fuel pump from a '70something Lincoln 460(I can't remember the exact year, but he picked the last year that the fuel pump had just 2 lines... I'll look it up and post it) anyway; install this mechanical pump in-line with the electric pump. This will provide the volume capacity to supply the carb when the fuel diverter opens up. I've made one test run with no problems, however this is still non-conclusive, since my problem usually took 2-3 hours to show up and was pretty random.
Good luck!
Greg
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Joined: Jul 1999
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vapor lock
uh, just re-read your original post... your 77 already has a mechanical pump, doesn't it? Duh, sorry! Anyway, maybe application of my solution to your problem is add an electric fuel pump as well, as suggested by a previous post. A guy at the speed shop recommends a birchwood spacer between the carb and manifold as the best heat insulator, for what it's worth...
Greg
Greg
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vapor lock
I had a 72 w/360 It was a crack in the base plate of the carb? It leaked gas to the manifold causing it to freeze up? Any help? Oh it was a holley carb? I did all the stuff to solve the prob but it was the carb? Hank< hmpalm at bellsouth.net>Vaper look only happens when their is to much heat to the fuel line .So if moving the fuel line doesn't do it check for leaks from the carb.Mine would ice up? The absense of heat from the gas on the hot manifold"Intake"Hey when you figure it out let me know what it was <hmpalm at bellsouth.net>
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vapor lock
I have a 1984 F150 that has a vapor lock problem. I was nearly stranded in the desert north of Phoenix this last weekend. I have installed an electric fuel pump, changed all flexible lines and I have the same problem. My truck will run, but at full throttle, the truck stalls. The nice thing is I can get home, but not as quick.
I am going to try some gas treatment and another brand of gas. I was using Chevron, but I had about 1/2 tank of mid grade ARCO. I wonder if the higher grade contributed to the problem. For those of you from cooler climes; my problem occured on a day when it was 109F. (But it was a dry heat.)
Marc
I am going to try some gas treatment and another brand of gas. I was using Chevron, but I had about 1/2 tank of mid grade ARCO. I wonder if the higher grade contributed to the problem. For those of you from cooler climes; my problem occured on a day when it was 109F. (But it was a dry heat.)
Marc
Lead Driver
Joined: Nov 2000
Posts: 6,637
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From: Albuquerque
vapor lock
I have solved this problem on a couple of vehicles. Here's what it took.
First be sure the cooling system is up to snuf. Anything over 195 degrees is problematical. Second, electric fuel pump. Last and possibly most effective is using a return style fuel regulator and a line back to the tank. These mods changed a non drivable vehicle into one that's a pleaure to drive in the summer, with the air on, with the camper on and with the boat on the back. It can be a little expensive but it took all of these to fix mine. Good luck and be carefull with fuel lines.
1977 Ford F-100
400m/c6
280,000 miles
Stock on the outside
modified/rebuilt everything
First be sure the cooling system is up to snuf. Anything over 195 degrees is problematical. Second, electric fuel pump. Last and possibly most effective is using a return style fuel regulator and a line back to the tank. These mods changed a non drivable vehicle into one that's a pleaure to drive in the summer, with the air on, with the camper on and with the boat on the back. It can be a little expensive but it took all of these to fix mine. Good luck and be carefull with fuel lines.
1977 Ford F-100
400m/c6
280,000 miles
Stock on the outside
modified/rebuilt everything
Thread Starter
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vapor lock
got my problem solved. after doing everthing that everyone suggested and a few other things i decided i was going to change the pickup inside the distributor for the duraspark ignition. well i took it out and noticed the wire was pretty much broken where the wire meets at the pickup. so what was happening was when you step on it , i.e. when entering the free way the vaccume would move the advance plate, therefour pull the wire apart where it was broken just far apart to make it seem like it was out of gas. would come back to life when you feathered or let off on it. that turned out to be an expensive lesson and project. might help someone else down the road though. thanks
Lead Driver
Joined: Nov 2000
Posts: 6,637
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From: Albuquerque
vapor lock
[font size="1" color="#FF0000"]LAST EDITED ON 06-Jun-01 AT 12:42 PM (EST)[/font][p]Dang! I hate it when it does that. You'll probably be miles ahead for the work you did tho.
1977 Ford F-100
400m/c6
280,000 miles
Stock on the outside
modified/rebuilt everything
1977 Ford F-100
400m/c6
280,000 miles
Stock on the outside
modified/rebuilt everything
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