What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Fuel pump rod

Wes Harden

Wes Harden

1 ton status
Staff member
Moderator
GMOTM Winner
Joined
May 28, 2005
Posts
18,702
Solutions
2
Reaction score
24,689
Location
Lake Havasu City AZ
Anyone know how much travel a sbc fuel pump rod is supposed to have.
This is the concussion I am coming to, 3 mechanical pumps that can't keep a mild 350 with stock qjet happy.
The rod on my engine moves 3/8 to 7 /16ths total travel , eyeballed.
Not sure gm ever published the spec, only volume over time iirc.
 
That seems about right. Have you tried a pressure test?
Maybe a bad pickup at the tank?
 
Looking on google I found a thread on a Camaro forum and one member measured a new Crane cam's fuel pump lobe and determined the "stroke" for the push rod was .395,which is a bit over 3/8" so I would say your lobe isn't worn..the thread was started asking about a BBC ,but I see no reason a SBC would be any different as far as the stroke for a mechanical fuel pump..
I would agree with 76Zimmer,there might be an air leak in the fuel line or sending unit intake tube ,letting it suck air instead of fuel,and it wont always leak fuel if a steel line has a pinhole on the top of a bend or on an uphill plane..

Are you using a pump with the large "can" and 3 fittings,or just the shallow "can" with 2 fuel hose connections ?...the larger can ones have a return line and are usually used on vehicles with A/C and 4 barrel carbs..
 
1st, 2nd pumps had the return this latest is a performance "80 gph free flow" 2 chamber, all new hoses and pick up. runs fine on an electric pump. no leaks
 
Float set too low?
I still say try a pressure test after the pump(s) electric and mechanical
 
I will, going to change the line from pump to carb new Performance pump has output port in higher location so factory pipe got tweaked. the truck runs on either the mechanical is acts up in 4th @42ish at 1500, no power, bucks and hesitates, add the electric and runs fine. Issue is electric failed 1 year and 2k miles. Now I have trust issues
 
Pump push rod worn to a shorter length ? :dunno:
 
Could be, I didn't actually measure it. I did have it out, I should have. I wonder if the correct length is published somewhere.
 
Fuel is probably boiling in the line from the pump to the carb.
I’ve done quite a bit of testing with similar trouble.
Putting a return to the tank up near the carb was the only solution for me. Completely eliminated any hesitation at any time.
Tried an edelbrock high volume pump, didn’t care.
Replaced the pump pushrod, didn’t care.
3 line pump didn’t work either.
Never bothered with an electric pump, don’t want one.
Use a Delco or Carter pump with the correct pressure.
Many aftermarket pumps put out too much pressure and cause other issues.
You can plumb a Wix 33041 filter 3/8 in and out with a 1/4 vapor return up near the carb. If you don’t have a return system use the tank vent line that goes to the canister as your return. Leave the gas cap loose and see what happens.
 
Last edited:
I doubt the pump push rod would wear down,and not ruin the cam lobe at the same time...Dorman has new push rods available for cheap money,and I think on Rock Auto they list the length specs on them.

Wix makes a few different filters with the return line port used on some Mopars and AMC's that have the return line nipple on the side of the can,rather than in line with the others on one end like the 33041 above,if that will make routing the return hose easier-- WIX 33054..Wix 33054 filter.jpg
 
well I think wix no longer makes that 33041, Having a hard time finding in stock. I have 1 coming from Napa a 3041 but the young lady asked me if it was an oil filter, and then some stuff I didn't hear. We will see what they have for me tomorrow. I'll check out the others, Bob, I was thinking that mopar did use the return filter back in the day.
 
They should still make them,probably have to order one from a warehouse though--the counterperson is probably too young to know what a old style gas filter is!...far as I remember all Wix fuel filters had a "33" prefix and all the oil filters had a "51" prefix,and NAPA just dropped the first digit and calls it a "Balkamp" instead..

I have a 1993 Wix catalog with nice illustrations of their fuel filters and I'm sure there are more with return line fittings,these two are the ones most often used (or were,back when!)..
 
I tried looking it up on Wix's web site, by number then by type and size doesn't show. The cross reference still list it, but not sure they are making it. RockAuto doesn't even show it, Summit amazon Oreilly's all show it as not available/not in stock. if you see them and use them nab them up.
 
I'm still thinking you may want to have a look at the inside of the tank for cracks in the lines or something out of whack.
 
blazer74 said:
Fuel is probably boiling in the line from the pump to the carb.
I’ve done quite a bit of testing with similar trouble.
Putting a return to the tank up near the carb was the only solution for me. Completely eliminated any hesitation at any time.
Tried an edelbrock high volume pump, didn’t care.
Replaced the pump pushrod, didn’t care.
3 line pump didn’t work either.
Never bothered with an electric pump, don’t want one.
Use a Delco or Carter pump with the correct pressure.
Many aftermarket pumps put out too much pressure and cause other issues.
You can plumb a Wix 33041 filter 3/8 in and out with a 1/4 vapor return up near the carb. If you don’t have a return system use the tank vent line that goes to the canister as your return. Leave the gas cap loose and see what happens.
Click to expand...
I will be trying the filter idea. Mine has been giving me fits. I think I even have a mopar one lying around the shop. Can’t beat free!
 
I also have this now https://www.summitracing.com/parts/hly-12-887, Holley say out as close to carb as possible. I think I would prefer it down on the frame where the metal to original fuel pump is, also convenient for the 1/4 return line. I also have another pump otw. larger more amps will provide 14 psi max so need the regulator. Some one here is running one posted up in my other thread last year. I think they have tbi tank & pump
 
You must log in or register to reply here.

Latest Posts

Top Bottom