Hesitation problem under load 454 Magnum, I need some idea's
#11
fuel filter on inlet has been removed and inspected, was clean. still...no luck
#12
mine is stock which i think is a rochester, would it a similar design?
#13
stock, i thick rochester, can the jets be checked without taking the carb off?
#14
Registered
Make sure the choke isnt stuck closed. I'd make sure secondary butterflies on the carbs are opening.
Not exactly sure on the marine rochestors, but on automotive ones, if the choke is closed, the secondaries will not open.
Not exactly sure on the marine rochestors, but on automotive ones, if the choke is closed, the secondaries will not open.
#15
Registered
Join Date: Jul 2004
Location: Hobe Sound, FL
Posts: 121
Likes: 0
Received 0 Likes
on
0 Posts
Might consider pulling the valve covers if it is not a fuel problem. Let the motor idle (do not rev it or oil will go everywhere). Then check to see all your rockers are moving the same while idling. If one or more don't, you ate a cam lobe. This happened to me a few years ago and the engine behavior was just as you described. You won't necessarily find play in the pushrods since a wiped off lobe can be down to the base circle.
#16
RIPSTA Racing Team
VIP Member
+1 on check the timing advance rate. Use a fuel pressure gauge to check pressure while under a load. Doesn't sound like anything mechanical to me but what do I know? I'm always learning. My guess is the timing isn't advancing quick enough under a load or it's not getting enough fuel. Drain your fuel filters into a clear glass container and see what settles. One crappy load of fuel will take forever to work it's way thru. Just my 2cts.
#17
+1 on check the timing advance rate. Use a fuel pressure gauge to check pressure while under a load. Doesn't sound like anything mechanical to me but what do I know? I'm always learning. My guess is the timing isn't advancing quick enough under a load or it's not getting enough fuel. Drain your fuel filters into a clear glass container and see what settles. One crappy load of fuel will take forever to work it's way thru. Just my 2cts.
Carbs are off now, and dropping them by the carb place for a quick check (it was rebuilt 2 years ago)
I have two tanks, feeding into one Y (no valve) drained the filters about 3 times now, looks perfect, nothing in it, nothing floating, nothing at the bottom.
Have freinds that use the same gas station, and they have no problems (so doubt it would be bad gas)
#18
This is a reply from Scream and Fly:
Sounds like a fuel restriction or air leak into the fuel system or a bad fuel pump. Put a vacxuum gauge and clear hose on the fuel line where it ataches to the motor and a pressure gauge at the carb. Rub the boay under load and observe the gauges. Vacuum should read 3 - 5 inches, any less and air bubbles in the clear hose indicate an air leak such as a broken pickup, cut or loose hose. High vacuum will indicate a restriction such as a clogged pickup, clogged anti-siphon valve, collapsed hose or clogged fuel tank vent. Fuel pressure should be 6 - 9 psi. Normal vacuum and low pressure indicates a bad fuel pump. High pressure indicates a clogged filter in the carb..
Sounds like a fuel restriction or air leak into the fuel system or a bad fuel pump. Put a vacxuum gauge and clear hose on the fuel line where it ataches to the motor and a pressure gauge at the carb. Rub the boay under load and observe the gauges. Vacuum should read 3 - 5 inches, any less and air bubbles in the clear hose indicate an air leak such as a broken pickup, cut or loose hose. High vacuum will indicate a restriction such as a clogged pickup, clogged anti-siphon valve, collapsed hose or clogged fuel tank vent. Fuel pressure should be 6 - 9 psi. Normal vacuum and low pressure indicates a bad fuel pump. High pressure indicates a clogged filter in the carb..
#19
That makes no sence to me, (or does it??)
I plan to open it up and take a peak. (after I buy the torx to open it up)
Do I need a new top gasket for a Rochester Quadra jet? (was rebuilt 2 years ago, with very few running hours on it)
#20
fixed! very strange a little spring that keeps the secondary flap closed had a littlw worn notch in it.
and that was stopping the secondary carb to open.
lubed the spring up, and reduced the spring tension
works great now. now that i know that caused the problem, i'll dremal the spring notch or get replace the spring.
i think the carb rebuilder who rebuilt it 2 years ago should have noticed the wear and replaced it (probaly a $2.00 part, and i spent 3 weekends and about $300 in parts....frustrating
but its working now
thank you to everyone that helped out with idea and suggestions greatly appreciated
and that was stopping the secondary carb to open.
lubed the spring up, and reduced the spring tension
works great now. now that i know that caused the problem, i'll dremal the spring notch or get replace the spring.
i think the carb rebuilder who rebuilt it 2 years ago should have noticed the wear and replaced it (probaly a $2.00 part, and i spent 3 weekends and about $300 in parts....frustrating
but its working now
thank you to everyone that helped out with idea and suggestions greatly appreciated