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Carbed 454 not running right!! please help!!!

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Carbed 454 not running right!! please help!!!

Joshw_7 Joshw_7
I love my Chevy Chevette! | Posts: 2 | Joined: 01/13
Posted: 01/25/13
09:24 PM

i swapped a carbed 454 into my 94 yukon... i am using the factory in tank pump with a regulator i currently have it set to 8 psi... i tryed everything from 4 up and under WOT it cuts out and doesn't want to accelerate... it stutters i guess you can call it.. i don't know what is going on... please help!! Frown  

waynep71222 waynep71222
My first time was in a Chevy | Posts: 218 | Joined: 04/12
Posted: 01/25/13
10:30 PM

these are verification tests.... only take a small amount of time to follow and VERIFY your systems are operating properly... without hands on... this is where to start... when i fix cars hands on.. they are the first things i dig into...  

can you perform a FULL FLOW FUEL SYSTEM TEST.. by disconnecting the fuel line right at the carb... extending that line with a hose into a clean clear plastic bottle...    cycle the fuel pump on... either by cranking or jumping the fuel pump relay...

make sure that the fuel pump is able to supply enough fuel through the regulator to feed the carb...

you need almost a PINT in 10 to 15 seconds to keep up with the usage needs of a big block;

thats half a quart..

you could have a dirty ground connection on the frame rail next to the intank fuel pump connections.. or a dirty ground connection between the cab and the frame near the right front cab mount...   or from the engine to the body connection.. yep... its a long way to supply electrons from the battery to the fuel pump ground connection...

since the engine is sitting on rubber mounts.. you have to have proper ground connections...

80S Chevy Truck Battery Cables

if you run this test... and include battery negative to the frame as test 5 on the lower half..

post some results..  it will point you toward any bad grounds in just a few minutes ... saves A lot of hair pulling... screaming in your mind.. why won't this work...

VOLTAGE Drop Testing

there could also be issues with the adjustments of your quadrajet...
incorrect APT adjustment.. or incorrect secondary air door spring tension adjustment..

so you only have issues at WOT???  or do you have issues anytime except WOT..

so... do the primaries work OK///

is it possible that the if its only acting up on the secondary... that the 4 brass tubes have fallen out of the upper cover..   i have found a LOT of quadrajets that the secondary tubes are loose and have fallen into the main body..  preventing the proper dispensing of fuel to the secondaries...  

Joshw_7 Joshw_7
I love my Chevy Chevette! | Posts: 2 | Joined: 01/13
Posted: 01/26/13
09:58 AM

oh I am running a carter comp 625... (edelbrock)  i would try my quad but i fabbed my tps to the edelbrock and don't have a bracket for the quad.. it only happens at WOT. if i take of from a light or already cruising at 40 if i punch it its falls on its face... so yeah the primaries seem to be ok...oh and only under a load.. if i free rev it in park it doesn't do it. but a bad ground!?!? ill have to check all the grounds then..  

pepsi1 pepsi1
Big Block power for the win | Posts: 940 | Joined: 03/11
Posted: 01/28/13
03:29 AM

Welcome to Super Chevy:

First (3) things come to mind....

1.Was there a Big Block, or Small Block in your Yukon.

2.Did you check the condition of the 454 before you installed it...

3.Replace the o.E. fuel pump with an aftermarket Hi-Performance Fuel Pump.

What I would do. If the known condition of the carb and engine are okay!

1.First thing Replace Fuel Filter first.

2.The 454 with a carb will drink alot more fuel them the metered TBI.

3.Replace the Fuel Pump with a Hi-Performance pump. Set the pressure at 7 PSI then try it. I would replace the fuel filter with an external pump. Make sure the Fuel Filter is before the Fuel Pump.
  The OE systems have a sock on the Fuel Pump in the tank....Any questions or problems. Let us know...


zman123 zman123
I love my Chevy Chevette! | Posts: 3 | Joined: 05/12
Posted: 02/01/13
07:07 PM

When is the last time you changed the fuel filter? A dirty filter will let fuel through at a low demand but not enough when you open up the secondaries under load. simple to check. One of the first things I do.  

Ravoll Ravoll
V-6 Camaros rule! | Posts: 85 | Joined: 02/12
Posted: 02/20/13
05:42 PM

Could it be that your stock fuel lines are to small? Maybe I'm wrong but it seems to me that 8 psi in a skinny line would be less "volume" than say,8 psi in a stove pipe.

And another thing is mechanical fuel pumps will pump faster at higher engine speeds and your electric probably only runs 1 single speed,no matter how high the engine revs are.

I ask this cause I had this problem after taking a 64 Impala, that started life as a 283/one barrel, and planted a 454 in it.Tried stronger fuel pumps and filter bypasses.Nothing helped until we changed to larger I.D. fuel lines(12mm copper tubing if I remember correctly).
After that no more starving at WOT. Tongue

I would do what Wayne suggests,and see if your fuel pump delivers the correct volume, and if not, find out why.  
The older I get,the faster I was.

Bobs427 Bobs427
I love my Chevy Chevette! | Posts: 2 | Joined: 02/13
Posted: 02/21/13
03:15 PM

Hi Rav:

I suggested to a poster that if he was redoing his fuel lines to go with a minimum of a 1/2" fuel line. Some other clown posted in why does he need such a big fuel line. I posted back. If he listens to you he will have the same problem forever.
  Some guys just don't understand the fuel system is only going to use whats the demand is.
  The original poster had a 5/16th fuel line. He wrote in because the engine was surging under WOT. He went to the 1/2" fuel line and put a return line back to the tank. He PM'd me and said the problem was gone. for about $25.00 US.

How are you doing? I have been having login problems, I spent $150.00 someone suggested I had a Virus. I didn't there is a security breach somewhere in the system, and its affected my computer. All the other websites I go to I don't have a problem.

Bob aka-pepsi1  

Ravoll Ravoll
V-6 Camaros rule! | Posts: 85 | Joined: 02/12
Posted: 02/22/13
04:53 PM

Hi Bob,
Yeah I was thinking.Does'nt the electronic controlling the pump on a fuel injection system,command the pump to run at variable speeds depending on RPM and engine load.One could think it would have to,in order to maintain a pressure constant on the rails/injectors.Driving fast increases fuel demand,and more demand means it has to be delivered faster.Stomping on it drops the line pressure,so the pump is run faster to compensate.

If some one drops a carbed engine into a vehicle that is set up for fuel injection,
the pump may only run at one speed,depending on what wiring was no longer hooked up,
and may not be recieving feedback on line pressure.

Just a thought.  
The older I get,the faster I was.