vapor lock/electric fuel pump

[runamuck]

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?

[michael bustamante]

Suscribed. My blazer does the same thing. New mech pump dies out after 10 miles.

[runamuck]

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.

[Husker]

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

[runamuck]

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?

[michael bustamante]

Is gas spitting out the carb when you crank it?

[cdowns]

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

[runamuck]

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.

[CST10]

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.

[cdowns]

Originally Posted by runamuck

no gas spitting out the carb when I crank it, and cd downs, if you have vapo. That is why almost 100% of newer cars have electric pumps.

really i thought they needed electric pump because of fuel ionjection??

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

[runamuck]

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 Geech!!! What a freak thing to happen, to get that blanket sucked into the fan, it was wrapped around it a good one and it caused the belt to come off, so I'm thinking maybe for a second it put a strain on the timing chain assembly and broke off a tooth from the nylon gear, or it just jumped a few teeth. or it sucked some of the quilts stuffing into the motor when it shreadded around the fan. I'm off to work now, but I'll keep you posted on what I find out next week.
Thanks for the reply, and I'll keep ya posted.

[Zeke's Garage]

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.

[runamuck]

Originally Posted by Zeke's Garage

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.

Thanks for thew great insight. Today when I got home I hooked up the timing light, but couldn't get it started, it would sputter, and backfire, even lite the carb on fire once, so I got my wife to try to start it @ the ignition, and I loosened the distributor and turned it while she was cranking it, at one point it started right up and idled fine after turning the distrubutor clockwise. I marked where the distrubutor was at befor I turned it, and I ended turning it about 1/2 inch clockwise. I then checked the timing with the light, and it's now set, according to the marks @ it is now a little bit past the 12 degrees btdc, and it seemed to run o.k, at least sitting at idle at 10 degrees btdc, so I guess apparantly it did jump time. Do you think I need to remove timing chain cover now and see if maybe there is a chiped tooth, or just run it like it is? Tomarrow I'm going to test drive it and see if my vapor lock problem is gome with the new pump, @ 4 1/2 lbs fuel pressure. My reason I believe it jumped time is it ran great before, except it seemed to vapor lock,and all I did was install a electric "red" holly pump, tighten the intake manafold bolts, and after that started it and sucked the quilt into the fan, so I guess it might vave gave the crank damper a shock as the quilt wrapped around it all and caused the timing chain to jump, I can't explain the timing getting off so much any other way. What do you guys think?

[runamuck]

Originally Posted by runamuck

Thanks for thew great insight. Today when I got home I hooked up the timing light, but couldn't get it started, it would sputter, and backfire, even lite the carb on fire once, so I got my wife to try to start it @ the ignition, and I loosened the distributor and turned it while she was cranking it, at one point it started right up and idled fine after turning the distrubutor clockwise. I marked where the distrubutor was at befor I turned it, and I ended turning it about 1/2 inch clockwise. I then checked the timing with the light, and it's now set, according to the marks @ it is now a little bit past the 12 degrees btdc, and it seemed to run o.k, at least sitting at idle at 10 degrees btdc, so I guess apparantly it did jump time. Do you think I need to remove timing chain cover now and see if maybe there is a chiped tooth, or just run it like it is? Tomarrow I'm going to test drive it and see if my vapor lock problem is gome with the new pump, @ 4 1/2 lbs fuel pressure. My reason I believe it jumped time is it ran great before, except it seemed to vapor lock,and all I did was install a electric "red" holly pump, tighten the intake manafold bolts, and after that started it and sucked the quilt into the fan, so I guess it might vave gave the crank damper a shock as the quilt wrapped around it all and caused the timing chain to jump, I can't explain the timing getting off so much any other way. What do you guys think?

oop's, i meant I turned the distrubutor counter clockwise to get it to run

[alsriv2]

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.

[Eddie H.]

Originally Posted by cdowns

really i thought they needed electric pump because of fuel ionjection??

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

Actually, GM produced several thousand vehicles with carburetors and electric fuel pumps in the tank, beginning in the early 70's and for several model years thereafter including the Vega, Citation, Celebrity, etc.

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.

[runamuck]

Originally Posted by Eddie H.

Actually, GM produced several thousand vehicles with carburetors and electric fuel pumps in the tank, beginning in the early 70's and for several model years thereafter including the Vega, Citation, Celebrity, etc.

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.

Thanks for clearing that up Eddie, I didn't want to argue with the guy, but you set the record streight.

[runamuck]

Originally Posted by alsriv2

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.

Thanks alsirv, that is the only explanation i can figure too, is either the chain was streached enough to jump a gear, or a tooth is missing, because it defeanitly was way out of time after the incident with the quilt getting caught in the fan. The timing seems to be right now, with moving the distributor about 3/4 inch counter clockwise, moving it while my wife cranked it was the only way to get it started to put the timing light on it. Weird huh! Yes, when I get time I'm gonna take the manifold off and replace the gasket, as well I should take the cover off the timing chain and inspect what's going on in there. I wanted a project, and I guess I got one, but first I need to figure out the vapor lock symptoms. I ordered a new gas tank sending unit with a new pickup screen, and I'm gonna replace the whole gas line and move it away from inside the frame close to the headers, to outside the frame away from the heat source, boy if that doesn't fix the what seems to be vapor lock, I will be at a loss for why it's starving for gas after driving it 20 miles or so, I'll keep all you fine people that have gave me usful advise posted on what I find.

[runamuck]

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.