Vapor lock issues.

[kevmic28]

350 with stock intake and rochester 4bbl carb.
Temps outside 100 plus Im getting vapor lock. New glass fuel filter between mechanical pump and carb, so I can see that when it stumbles and dies in the driveway the filter is empty.
Carb has started stumbling on accel. Like its cold or fuel starvation.
I put a new coil and plugs on this weekend and also a new water pump because I noticed temps a little high and some seepage. Cap and rotor seem like the are good.
The problem I am having have been going on for a while but getting worse with the heat. I think the plugs and coil helped to keep it from dying at stop lights because it stopped. It idles fine now but seems like it is still fuel starvation on accel.
Saturday after a 180 mile drive it stumbled and died as I pulled into the drive way. Normally I can floor the gas pedal and start it back up. But this day I could not. Got out and the filter was empty and I could hear the gas boiling in the carb.

I have been reading a lot on here about phenolic spacers for carbs helping with the gas boiling issues but none that I have seen delt with a rochester carb boiling. I have the stock spacer that is about 1/4 inches thick on it now. So I am stumped..... Thinking maybe the fuel line was getting to hot by the block and the water hoses I temporarily re routed the line away from them to see if that stopped the problem. It may have helped but not sure. Fuel pump is about 9 months old, mechanical and I was thinking maybe its bad and causing the fuel starvation and vapor lock but I am leaning towards the spacer needing to be thicker to solve this.
I am kinda rambling here to think out loud so I would appreciate any ideas yall have.

Cause this is driving me nuts.

[kevmic28]

Ok based on the overwhelming support I am going to change out the fuel pump first. Because I can get it today and order the spacer if I can ever find the right one for my carb.

[Notrodder]

Keep us posted. I'd like to know what the fix is. Since it is a stock intake and (I assume) the fuel lines are in reasonable condition, I would change out the pump first, also.

['72customdeluxe]

You might want to just use the clear filter for fuel system testing and not driving around, see signature for reasoning.. My stock style spacer with stock replacement pump and lmc repop lmc fuel line doesn't boil with headers and a/c in houston heat and traffic. Maybe revert to an in-carb filter with a steel fuel line

[cdowns]

did you check to see if the in carb fuel filter is clogged? you remove the large fitting on the carb that the fuelline goes into carb to find that filter// to check fuelpump capacity remove fuelline from carb put in jar turn engine over for 30seconds factory spec is about one pint pumped in 30seconds

if you aint pumping that much use lopressure to blow back into tank(less than 20lbs) with gascap removed\

try pump capacity test again if theres a good increase it means CRAP IN DA TANK SYNDROME

those lazyman rubber fuel lines start good fires

[kevmic28]

I actually have a new tank, new fuel lines. Been dealing with this issue for a while. But seems to have gotten worse since the heat has risen. When I had the new engine installed I handed then a brand new fuel pump to put on it but I have no idea if they or if they just reused the old 40 year old pump.
New filter. I didnt think to check the in carb filter. Ill do that tonight when it cools off. Its 105 in the shade right now.
This morning I checked the filter and it was full of gas, I started the truck for a minute then left it for a few hours. When I came home from school I checked the filter again and it was bone dry. So I am thinking the fuel pump is not holding pressure. If thats the case then its not keeping enough pressure when I am driving it to feed the carb.
I do have headers on it but stock intake.

[kevmic28]

Well decided to brave the heat and pulled the small filter on the carb. I found the remants of the material from the last little universal silver filter I had in between the carb and the pump. I pulled all that crap out of the middle of the filter and it runs better now and doesnt heasitate on accel any more. But it still feels like the engine is holding back, or not getting enough fuel. If I floor it its fine but if I slowly go up to speed it feels like it is dragging.
Could be fuel pump or could be tranny or could be brakes draggin or could be my imagination. I know when I pulled out of the driveway I lit the tires up. Which usually doesnt happen.

['72customdeluxe]

Or it's just slower than what you're used to? Try secondary flap settings. It will burn out on just primaries but then will run out of steam

[kevmic28]

Here is a pic of the old filter. The crap I pulled out of the in carb filter was the rubber glue they used to glue the filter together. I cut the silver part open and the filter just fell apart. It wasnt but maybe 3 or 4 months old.

[kevmic28]

ok went back out and the filter was dry as a bone again. So I am thinking it is the fuel pump. Cant hurt to change it. Its only like 20 bucks.

[grs]

I don't know who makes fuel pumps, but I put a carter on my truck.

[vectorit]

Are you sure your tank is properly vented?

[LONGHAIR]

If you are thinking about changiong fuel pumps anyway, why not switch to electric? That is an almost guarantee to solve your problem. You mount it as close to the tank as possible and then it "pushes" the fuel rather than sucking it. When it is pushed, the entire line is pressurized which cuts down on the bubbling/boiling. As long as you route your lines away from other heat sources, you should be good to go.

[kevmic28]

I dont believe I have a venting problem with the tank because I dont get any kind of suction problems when I take the cap off.
Yeah I am thinking about just putting an electric one on. Just need to decide which kind to put on.
Right now I will just go with the mechanical because its under waranty.
Im going to pick up a new in carb filter. Even though I cleaned the crap out of the inside I feel like it is still all clogged up.

[caboutin]

Find a gasoline station in your area that sells fuel without the eth additive. Start using that station to fill up and see what happens. :}

[kevmic28]

Originally Posted by caboutin

Find a gasoline station in your area that sells fuel without the eth additive. Start using that station to fill up and see what happens. :}

I filled up at 3 diffferent places in the past weekend. So who knows.
Seems like the boiling of the gas has stopped and the vapor lock has stopped for now. I put in a new carb filter and the clear glass filter filled up faster than before with the old carb filter.
But still stalls out while driving it. If I floor it it runs great but if I drive normal then it stalls like its not getting enough gas. Had to order a fuel pump so I will pick it up in the morning and put it on tomorrow.

[kevmic28]

Could a bad cap or rotor on my HEI Distibutor be causing it?

[kevmic28]

Ok here we go.
I put the new fuel pump on. man was it a pain in the ass. The rubber hose from the hard line to the pump had a big loop in it. Put new pump on. Put new line on and got rid of loop. New line form the pump up to the filter. So now other than the existing hard line all the lines are new. Blew out the line from the pump to the tank.
Started it up. filter filled up. idles fine. rev the engine fine. Put it in gear and give it the gas and it dies everytime. So now I cant even drive my truck at all.

So give me some more ideas cause I am out of them.
New fuel lines,
pump,
filters, inline and in carb,
new plugs.
Inspected the cap and rotor they look fine no vissible cracks or corrrosion.
Also it seems like when I rev it up in park its a little slow to respond.

Choke sticking?
I dont know. I am so tired of dealing with this. Everytime I work on it it seems to run a little worse. WTH????

[Notrodder]

My thoughts: Do the test that cdowns suggested with the new pump. If it's getting gas to the carb, check that the screws and mounting bolts on the carb are tight. Turn the throttle linkage and see that everything is opening as it should so you're getting air to match the gas. Now try turning your fuel metering screws on the base of the carb in a quarter turn and see if there's any improvement, if not try one half turn out and check again. This may or may not solve your problem, but it is easy to do and worth a try.

Another thing, it was a long time ago that this happened to me so I can't remember the symptoms, but the float in my carb sank and caused some kind of aggravating problem that a new float cured. Does anybody here think that this could be kev's problem?

[kevmic28]

Ok I was out messing with the carb just now and I noticed something.
Now bear with me cause I am not a carb guy but the secondary butterflies, I think that what they are called, dont move when the throttle is opened. The air flaps on the back half of the carb dont move at all.
Could it be that I am flooding the engine whenever I hit the gas because its not getting any air into it. If so how do I fix this. Carb is a rebuilt rochester 4bbl and less than a year old.
It starts and idles fine. When I put it in gear and just barely touch the gas it will move but if I get into the pedal it stalls out, but if I let off it goes back to idle. Fuel pressure check is good.

[68gmsee]

kev, I've been driving in the Texas heat since 1958 when I was 15yrs old and have never had a vapor lock issue. Maybe I've been lucky, but most of the problems that I've ever had with fuel issues or stalling, not starting, etc. have always been for other reasons. I'd look real carefully at gas supply and/or carb problems first.

The secondaries on the rochester carb should open with vacuum from the intake when you depress the pedal. On some, they will open on wide open throttle by a link. Not sure how yours is set up but there could be a small link that allows the rear butterflies to open only when the choke is fully open.

[68gmsee]

Let me rephrase that last paragraph... The flaps you're referring to should open with vacuum on wot. The bottom valves should be open on wot unless the choke link prevents them from opening. In other words the choke had to be fully opened. Hope this makes sense...

[kevmic28]

yeah I figured out that my choke is always on keeping tight on the butterfly linkage. Then I figured out that the vacuum line that controls the butterflies was closed off. The guy that rebuilt and installed my motor just plugged it up. So it has never been functioning right. Now might be because of the heat lately that I am finally noticing all of this.
I took it for a run after I removed the plug. It is running better but still bogging down and the fuel filter has air in it again. The line is pressurized before the fuel filter and not after to the carb.
Now on to the bad gas thing. Might be.. Some times the gas in the fuel filter looks clean as can be and sometimes its a yellowish brown color. But its a new tank and new lines and this is something I was dealing with off and on before I changed the tanks. But could be water in the tank maybe???? I may not be getting a good seal on the gas cap and with all the rain we got last week, I may have water in the gas??? The tank is just about empty. So I may just pull it tomorrow and remove all the gas and wipe it down and refill with fresh gas.

[oldgold70c10]

What your describing sounds like the accelerator pump in the carb has gone bad. This would starve the engine if you press on the pedal and cause it to stumble & stall.

You can check with the engine off by taking the air cleaner off, and with the choke open, look down the carb. Move the throttle and you should see it squirt gas down the carb. If it doesn't, you need to replace the little rubber cup on the accelerator pump in the carb.

[kevmic28]

Ok checked it. It squirts gas like it should. But interestingly I found a plastic plug cap from my air cleaner stuck next to the where the gas squirts out and removed it. Runs a little better but still bogging down and sometimes stalling on accel under load, but as soon as I let off the pedal it goes right back to idle speed. Fuel filter stayed full this time and clean colored gas.
I can floor it and run down the road but once I let off to stay at speed if feels like its struggling to stay running and it takes almost the full pedal to stay up to speed.
This is really driving me nuts.