USArmyZ28

iTrader: (3)

Sup guys, this is a non LSX vehicle but it still has a old school carbed chevy 350 in a 93 silverado. The problem is sometimes when ever I drive it a lil hard apparently the "float bowl" dries up and the engine acts like its starving for gas and sometimes completely dies. Sometimes when I turn it on after priming it itll fire right up and then die, then you have to prime it up again and turn it on. I have to drive this thing from GA to KY in a few weeks and I dont want to get stranded, its got a holley carb and the engine looks really really clean. Do you think its the carb or fuel pump or what? Im sorry I asked on here but alot of you guys know a whole lot more then I do.

02BLACKTAWS6

My immediate thought was fuel pump.

USArmyZ28

iTrader: (3)

Im starting to lean to the fuel pump, Im taking it to a mechanic tomorrow who is very familiar with these engines. How hard is it to replace a fuel pump in something like this? Its got an Electric fuel pump running at 7.5-8 psi is that low? The previous owner said the float bowl has to be adjusted to .015, I have no idea wtf that is lol. He said it should be fine to drive as long as you dont go to fast but Im not doing 60 mph for 800 ******* miles lol

gc302047

iTrader: (4)

i dont know much about carbs but the problem could possibly be your float bowl dryin up. My brother has a 350 sb in his impala and he said his float bowls were malfuctioning and he went and bought a carb rebuild kit at autozone for 50 bucks and it fixed the problem.

Daredevil_TA

iTrader: (6)

....dude your signature ******* kills me LOL-but anyway-did you try posting in the SBC forum? I dont know much about carbs either, ive never had to mess with one.

USArmyZ28

iTrader: (3)

I posted it at chevy highperformance boards too, the problem is so ******* weird. Let me explain this.

This morning when the weather is nice and cool the truck fires right up and has a real nice idle at about 950 RPM, the truck ran awesome all the way to post and I had gotten on it from about 60-90ish to pass this 18 wheeler. Truck kept going real strong with no bucking or anything, I come back out to go to lunch the truck fires up bogs and dies. Start it again and its hunting for idle bogging from 800 all the way to almost 300 rpm's. Im starting to think it may be having vapor lock issues as well cause it only gives me problems when the day is really hot. Its about 95 degrees average here so that cant help lol

angel71rs

Yup, sounds like vapor lock. Is your fuel line near any high heat sources like a header pipe? If so, move/bend it, maybe wrap it with insulation. And you can also put a heat shield under the carb:

http://summitracing.com/search/?keyw...20shield&dds=1

1 FMF

iTrader: (1)

it sounds like a combination of vapor lock and the fuel in the bowls of the carb boiling from the heat of the engine below especially after you shut the engine off hot then restart, plus the average 95F temperature outside. If the carb is mounted on the engine with just a thin gasket between the metal parts, then the fix for this would be installing a phenolic spacer, or other spacer of some thickness being a material other than metal so heat doesn't transfer as easily from the intake manifold into the metal of the carb.

from your description i would not say fuel pump because (a) it runs hard and continues hard and doesn't stumble so it's getting fuel, and (b) it starts when cold, and (c) it's an electric pump so when you turn the key to start it's pumping and is supplying fuel.
Carbs should get on average 4-6 psi of fuel, and can tolerate up to around 10psi before the fuel pressure overwhelms the needle and floods the carb. If you're getting 7-8 psi at the inlet of the carb then that's great.

other than the carb spacer, you're problem seems mostly heat related. solution is to lower or get rid of the heat- maybe run a cooler thermostat, if you have a 190-200F thermostat in there then swap it out for a 160F or 180F, although if the ambient temp outside is 95F then that plus the lack of ventilation of the engine compartment is probably the biggest cause, find a way to get airflow through the engine compartment either new hood with vents or something. one thing you can do to diagnose it is next time it's hot out and you run it hard, as soon as you stop open the hood and find shade, idle for few minutes then shut down. If the problem goes away then it's a heat/vapor lock and/or fuel boiling out of carb problem. Also, when conditions are such that the problem will most likely happen then before you restart it have someone watch down the throat of the carb as you pump the gas pedal, the carb's accelerator pump should squirt fuel, if it doesn't or obviously doesn't do the same amount when engine is cold then the fuel is boiling out of the carb after shutdown.

Also make sure your radiator fans or radiator clutch fan is working, if they are electric fans then rig up a manual switch to turn them on, that'll get airflow moving through engine compartment on hot days to push out the heat.

redbird555

iTrader: (14)

I'd go with vapor lock and or a bad fuel pump also my mustang has the same problem down here in the fl summer (hell on earth). Fuel boils out of the bowl especially after I've been stopped or sitting in traffic for a long time. Starts to run a tad rough then when I go it just dies. Everybody's fix is different wrap the fuel lines or try to keep the carb cooler. The ethanol in the gas doesnt make it any better I've noticed that if I get pure gas it barely ever happens.
Dan

USArmyZ28

iTrader: (3)

Wow really good info, but its DEFINATELY heat related. I finally had a day off yesterday and I attempted to go to the movies and the truck ran maybe 10 minutes in the afternoon heat before it died completely, then I pulled over it wouldnt start right up. I had to prime quite a few times before it would start, it would run maybe 3 minutes and then die. Very frustrating. According to the temp gauge the engine its self is running pretty cool, I forgot what temp its actually reading but the needle isnt even a 1/4 of the way up and stays there even if its idling for a long time. Im pretty sure its vapor lock and the previous owner told me him self the float bowl needs to get the right adjustment.

1FMF; the fans run the entire time the engine is on, would that help it some? I cant get the hood or anything like that, Im just really worried about driving this thing for 700 miles straight from GA to KY.

USArmyZ28

iTrader: (3)

Ok so I took it to the shop, the owner recognized the truck from the previous owner and said that they never took out the old in tank fuel pump and added an external electric fuel pump and this is whats causing the problems. The previous owner said he by passed the old fuel pump how ever, can this be the problem? Why is it running so shitty in hot weather?

1 FMF

iTrader: (1)

the fans on can be good or bad, if it's blowing heat into the engine bay you can actually make it hotter underneath the hood on top of the engine. And if you're float is not set correctly well then that's a problem, don't bother doing anything else to you set the float level and have the idle mixture screws adjusted, along with verifying the timing.

are you saying that you can be driving down the road and the engine will just die? Or you can be idling stopped and the engine will die?

i was under the impression the problem was only after you shut the engine off hot that it would not restart. If the engine is running and it just dies, it is not vapor lock since you say you have two electric pumps which aren't on the engine, vapor lock only happens when the fuel pump is mounted on the engine. http://en.wikipedia.org/wiki/Vapor_lock

after it dies when it's hot, as quick as possible pull the coil wire off the cap and have someone else turn the engine over and see if you have spark. It may not be a fuel issue, it may be the ignition coil getting hot and failing. When it cools off after a while, can be as fast as 30 seconds, it'll provide spark and engine will run. other than that, only other thing i can think off is carb problem, pull it off and clean it out. Also inspect some spark plugs, if they are real black- dry fouled. What kind of ignition system you have? What are you using for a coil?

USArmyZ28

iTrader: (3)

Ill check out the ignition stuff, the mechanic recognized the truck and said when they swapped out the V6 for the 350 thats in it now that they never removed the intank fuel pump. The mechanic said that the fuel pump has to come out, Im honestly not sure what kind of ignition its using. I can see all the spark plug wires plugging into the big coil like thing behind the air filter but this is getting before my time lol. he also said that its running bad in the heat because one of the pumps is over heating. Im lookin at a 400$ estimate to remove the tank and take the fuel pump out.

The shop ran all the diagnostics and came to the conclusion that the pump definately has to come out of the fuel tank.