I have a 78 Chevy 1/2 ton 4X4 with a 350. The engine has about 78K
miles on it. The transmission is brand new. The truck will start
fine, idles good, and you can rev it up (while in park) with no
problem...runs nice and smooth. When I drive it, after a couple
seconds of accelerating, it starts to hesitate, surge and, if I don't
back off the gas, it will eventually stall. It feels as if it is
running out of gas. I have replaced cap, rotor, wires, ignition
module, coil, carburetor, fuel filter and fuel pump and there is no
improvement whatsoever. I checked the timing and it looks good. What
if you have a quad4mv carburetor on it, they have an internal filter in the
inlet to the carburetor.
This will plug up and then a spring in front ot it pushes it back to allow
some fuel to enter, then closes again.
Results, a surging engine when power is called for.
runs like you said.
throw the filter and spring away and use an external filter.
BETTER YET!!! Replace the filter in the carb with a new one! If you are
running an in-line filter AND the in garb filter, throw away the in-line
filter. The in carb filter is MORE than adequate!
If all the fuel filtering is new, check any soft-lines that are on the
truck for deterioration and or kinks. Also check all the hard-lines for
kinks. If all is good so far, drop the tank(s) and check for a strainer IN
the tank on the inlet line on the sending unit.
You may have a cracked valve. Check your cylinder compression. If one's
lower than the rest, you have a problem.
If a valve is just slightly chipped on a edge, I've seen that exact
symptom before, it would only miss under load, unfortunatly for me it
was my truck that time. A compression check easily pinpointed the
problem, and sure enough when the head was pulled, a chipped valve. Only
after I replaced all of the parts you mentioned as well.
somewhat related question...the 355 (heated right up) in my summer toy will
behave as if its starving for fuel when really hot, on high speed runs.
When its cold, the car goes like a bat outta hell...I can do several
foot-to-the-floor-till-it-runs-outta-power runs with no problems...do it
when its hot outside and the engine is hot, forget it!! it'll make power
till about halfway thru 2nd gear and then stumble and fall down till you let
off....feather the throttle and it comes back!!
any thoughts? the car runs too strong to have any broken parts inside, and
this problem is temperature related...and very intermittent.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.