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#1 |
Registered User
Join Date: Jul 2014
Location: indianapolis, indiana
Posts: 15
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vapor lock/electric fuel pump
I have a 1962 chevy 4x4 pu on a 72 blazer frame, I just bought it and it's sweet,, except, I drove it 50 miles one night and no problem, it has a 327ci, and sounds like it might have a moderate cam, it has a edelbrock 4 barrel and a edelbrock intake manafold. The second time I drove it, it ran great for 25 miles then puttered out like it was out of gas, I let it sit for an hour and drove home but after another 25 miles it did the same thing, I poured a little gas in the carb and it would drive a mile or so, that is how I got it home. I figured it was vapor lock, so I changeed the fuel filter to a see through one, and replaced the fuel pump, started and ran fine for the firs 20 miles or so and it started doing the same thing, and the fuel filter was dry, I would "prime" the thing with some gas in the carb and it would again go a few miles and then stall for lack of gas, let it sit for 1/2 hour or so and it would go till it heated up again. vapor lock right? Oh yes, when I put the new mechanical fuel pump on I also added a fuel pressure gauge, and when I first started it up it was about 3 lbs. pressure, then when it would die, and no fuel in filter, ther was no pressure. I just finished switching to a edelbrock red electric fuel pump, and removed and blocked off the hole where the mechanical pump was, while I was working on it, I noticed some of the intake manifold bolts were lose and oil was around them, I could see the oil that was around some of the bolts bubbling when it was running, that is how I found out they were lose so I tightened the bolts, finished the fuel pump conversition, and now it doesn't hardly run, won't idle, backfires through carb and stalls out when you drive it. The fuel pressure now is between 4/12 and 5 pounds at the carb with the electric pump. Could the increase in fuel pressure make it not run (too much gas getting to carb,) or would tightening up the intake manifold, make it so out of tune it wont run? And here is the kicker, when I started it up yesterday with the mechanical pump, my fender cover, and old quilt got caught in the fan and threw the belt, and got all wrapped around the fan,, oop's!! Could that somehow caused the timing chain to jump a gear or something and throw it way out of time?
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#2 |
Senior Member
![]() Join Date: Sep 2007
Location: Albuquerque NM
Posts: 7,848
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Re: vapor lock/electric fuel pump
Suscribed. My blazer does the same thing. New mech pump dies out after 10 miles.
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1967custom |
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#3 |
Registered User
Join Date: Jul 2014
Location: indianapolis, indiana
Posts: 15
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Re: vapor lock/electric fuel pump
Does it start up again after letting it set? Or start right up when you prime the carb with gas? That are the classic vapor lock symptoms. Electric pump is supposed to fix vapor lock because it pushes the gas, where a mech. pump sucks the gas from the tank. Hey, try putting some wooden clothes pins on your gas line where it might be getting hot, like by the headders, or exhaust manifold, sometimes that will fix vapor lock.
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#4 |
Registered User
Join Date: Dec 1999
Location: Mid NE USA
Posts: 2,212
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Re: vapor lock/electric fuel pump
When it does it next time take clamp at filter and loosen, If just air escapes then it should restart without waiting. Also if just air comes out then it could be vapor locking. Otherwise you may have a crack in fuel line somewhere when it gets fuel level below crack or hole in line. Just a couple thoughts. I am no expert.
Rom
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Member #111 68 C-10 ![]() 70 ![]() 76 Jeep CJ-5 Help Support the Board: http://67-72chevytrucks.com/vboard/payments.php He who knows nothing is closer to the truth than he whose mind is filled with falsehoods and errors. Thomas Jefferson |
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#5 |
Registered User
Join Date: Jul 2014
Location: indianapolis, indiana
Posts: 15
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Re: vapor lock/electric fuel pump
Thanks Husker, but it is getting lots of fuel now with the electric pump, I took the line off at the carb and turned pump on and it bled the air out, and then got lots of gas. I'm thinking somehow I fu#&%* up the timing when I got the quilt all entangeled in the fan, maybe for a second it put stress on the timing chain, and it jumped a gear because it is backfiring through the carb when it starts, and won't idle and barely runs, WOE IS ME!! I wonder how you can tell if it has jumped a gear?
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#6 |
Senior Member
![]() Join Date: Sep 2007
Location: Albuquerque NM
Posts: 7,848
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Re: vapor lock/electric fuel pump
Is gas spitting out the carb when you crank it?
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1967custom |
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#7 |
Senior Member
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
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Re: vapor lock/electric fuel pump
whern it happens try takin the gascap off
why an electric pump your just askin for problems?put a reliable mechanical pump in that will last you 40-50years usually
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#8 |
Registered User
Join Date: Jul 2014
Location: indianapolis, indiana
Posts: 15
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Re: vapor lock/electric fuel pump
no gas spitting out the carb when I crank it, and cd downs, if you have vapor lock problems, a mechanical pump doesn't fix that problem, vapor lock happens when gas vaporizes in the line before it gets to the pump, usually due to the line close to a heat sorce like exhaust or exhaust manifold, or a non vented gas cap can do it, but usually it's not that easy. Most times a electric pump will not vapor lock because it pushes the gas instad of sucking it like a mechanical pump does. That is why almost 100% of newer cars have electric pumps.
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#9 |
Registered User
Join Date: Sep 2013
Location: Gonzales, La
Posts: 1,441
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Re: vapor lock/electric fuel pump
Where did you mount the pump? I have the same issue and recently ordered a holley red electric pump. Interested in if your problem is timing or fuel related. Keep us posted on what you find.
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#10 | |
Senior Member
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
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Re: vapor lock/electric fuel pump
Quote:
carbs have no need for electric pumps and vapor lock is mostly a myth GENERAL MOTORS NEVER PRODUCED A VEHICLE WITH A CARB THAT HAD AN ELECTRIC PUMP
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71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY Last edited by cdowns; 08-03-2014 at 09:51 PM. |
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#11 |
Registered User
Join Date: Jul 2014
Location: indianapolis, indiana
Posts: 15
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Re: vapor lock/electric fuel pump
Hi cst 10, I mounted the pump just below the gas tank on the frame, and have it wired thru a relay switch and into the egnition switch so it can only pump with the key on, I have an oil pressure safty switch but haven't wired it yet. The more I ponder my problem, the more I'm leaning tword the timing gear, because when it's running, i'm getting 4 1/2 pounds to 5 pounds fuel pressure at the carb, so that should be good, and I tried loosening the manifold bolts like it was before I made the conversition with no change, I really don't know what that would have to do with it backfiring thru the carb anyway, and I tried running it with the pump turnid off and just off the gas in the float bowls, and no change, and it was running great before this happened, well, except for the mythical vapor lock
![]() Thanks for the reply, and I'll keep ya posted. |
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#12 |
Senior Member
![]() Join Date: Feb 2010
Location: Kennesaw, GA
Posts: 288
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Re: vapor lock/electric fuel pump
It's unlikely that the fan/quilting incident caused any internal damage to your engine.
It sounds to me like you fixed a vacuum leak at your manifold, which will require you to reset your idle mixture screws on the carb. The best way to do this (without a sideband O2 sensor) is to hook up a vacuum gauge to a manifold vacuum port (one that is not controlled by the carb), and adjust your idle mixture screws until you reach the highest vacuum reading the engine will provide. You may also need to adjust your idle speed as you do this to keep the engine running. Once that's done, verify your timing settings with a timing light connected to #1 spark plug. Disconnect and plug the vacuum hose going to the distributor, and check to see what the initial timing is set to. Should be about 12 - 17 degrees BTDC on an SBC depending on your cam. If you're seeing those timing settings then you can be assured that your cam/timing chain hasn't jumped, but if you're still seeing drivability issues, you'll need to look further. From what I know vapor lock can be a real thing.. but it's not as common as is reported. Mostly it's the floats set too low in the carb or a plugged filter sock in the tank or an inline filter, or crap in the carb. In my experience, unless you're running a return line with your electric fuel pump (where the fuel is constantly being circulated back to the tank, you're not getting any better heat dissipation with the electric pump than you would with a mechanical pump. Go ahead and verify your hard lines aren't running close to the manifolds, but I would have a look at your fuel lines and tank sender. Seeing you had ~3psi with the manual pump and about 5-6 with your electric, I'm guessing a blocked pickup sock or plugged inline filter starving a float bowl that may have floats set too low. Anyway, enough of the novel.. good luck with it and let us know what you find.
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#13 | |
Registered User
Join Date: Jul 2014
Location: indianapolis, indiana
Posts: 15
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Re: vapor lock/electric fuel pump
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#14 | |
Registered User
Join Date: Jul 2014
Location: indianapolis, indiana
Posts: 15
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Re: vapor lock/electric fuel pump
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#15 |
Registered User
![]() Join Date: Sep 2010
Location: Formerly MD and San Diego, now loving life in Arizona
Posts: 1,636
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Re: vapor lock/electric fuel pump
In my humble opinion, if your timing chain jumped, you have some serious wear and tear inside that engine. Unless the timing chain is seriously stretched and loose or there is badly worn teeth on one of the timing gears, it would be impossible for a SBC engine to jump a tooth. (there is no idler gear in a Sbc engine)
You indicated that the intake manifold was loose and you had to tighten it down. That could very well be an sign of a tired engine that needs to be investigated for overall condition. At the very least the intake gasket should probably be replaced due to deterioration from being loose. The last thing you would want to have is water start mixing with engine oil due to a worn gasket. You have a very nice looking truck and I wish you the very best with your new adventure.
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#16 | |
Registered User
Join Date: Mar 2001
Location: Paradise TX USA
Posts: 1,200
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Re: vapor lock/electric fuel pump
Quote:
Vapor lock is very real, which is why Chrysler had a recall in the early 80's that involved installing electric fuel pumps on several models with carburetors and mechanical pumps in order to cure their vapor lock problems.
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"Negative people always seem to have a problem for every solution" |
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#17 | |
Registered User
Join Date: Jul 2014
Location: indianapolis, indiana
Posts: 15
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Re: vapor lock/electric fuel pump
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#18 | |
Registered User
Join Date: Jul 2014
Location: indianapolis, indiana
Posts: 15
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Re: vapor lock/electric fuel pump
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#19 |
Registered User
Join Date: Jul 2014
Location: indianapolis, indiana
Posts: 15
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Re: vapor lock/electric fuel pump
ok, seems my vapor lock problem was just that, or maybe not. Today I replaced and moved away from any heat source the fuel line from the holly red pump, to the carb with a temp. rubber fuel line (didn't want to replace with all new metal tube line until I knew it was my problem) and I also removed the fuel tank sending unit and replaced the screen at the fuel pickup with a sending unit sock. One of those two fix's fixed the problem. I drove it today 50 miles or so in hot weather and no fuel starvation, yipeeeee!! So I ordered a new fuel sending unit with the right filter screen, and will now remove old fuel line, and replace it with new metal tubing away from any heat source. Thanks for all the input guys. I'm just "shadetree" so I do appreciate feedback.
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