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.

Holley mechanical fuel pump question

T

Truckin13

Registered Member
Joined
Dec 13, 2013
Posts
42
Reaction score
0
Location
Edmond, Ok
I was given a brand new Holley mechanical fuel pump today, I want to install it on my blazer with a 350. when I looked closer I noticed that my stock pump has 3 lines, I'm guessing an inlet an outlet to the carb and a return line to the fuel tank. They Holley only has an inlet and outlet. can I block off the return line to my tank and call it a day or is there more I need to do to run this pump?
 
Yes, the 3rd line is a vent and really isn't needed as the charcoal cannister has a vent back to the tank.
 
I've blocked off the return line on quite a few mechanical fuel pumps with no issues..but you also could get an inline fuel filter with a third nipple and retain the return line if desired,it might help prevent vapor lock..probably not needed unless your in a real hot climate..
 
Would you consider 100+ degree weather in the summer here in Oklahoma extremely hot climate? J drive this truck every day so I want to do it right the first time. I'm not a fan of electric fuel pumps. To me the least amount of wires on a vehicle the better, I always seam to have electrical problems with trucks.
 
Well,the electric fuel pumps do help prevent vapor lock better and only need one keyed ,fused 12V hot wire and a good ground to work,so its not a big deal to wire one up...and they are pretty reliable..


Personally I have not had any vapor locking issues with the return line nipple blocked off on a mechanical fuel pump on my vehicles,and it gets pretty hot here at times,though maybe not as hot as your area,or for a long duration..


I'd have to look up the hose routing for a return line equipped carbed vehicle to give you the right answer as far as hooking up that third nipple on the pump to the gas tank's return line right--I'm not sure if you would need to run a hose back to the gas tank for fuel return,or if you can use an existing one from the charcoal canister (which I assume is not hooked up to the holley carb since it has no provision for it)..might be a good idea to use new ethanol rated fuel hose anyway,the old stuff might not hold up to it..having the return line will help prevent vapor lock better than without it--whether you will "need"it though,only one way to find out..
 
I had planned on replacing the rubber portions of the fuel lines with (blue core) fuel lines. if someone had given me an electric fuel pump I would be using that but I was given a mechanical one that I feel is far superior to the worn out stock one. if I were to run a return line where would be the best place to incorporate it into the system?
 
Your gas tank or sending unit probably has a nipple for a return line ,depending on the year of the vehicle and where it was sold--I would say the best way would be to run a new hose (or steel line with short rubber sections to connect it) ,right back to the tank from the third nipple on the fuel pump--that way you wont have to worry about any original fuel hose or steel lines failing and leaking...and you'll gain the benifits of having a return line..

I'd check the fuel pump specs and make sure its the stock pressure rating,some Holley's are high pressure and high output,that might overwhelm the needle and seat and cause flooding--some require a fuel pressure regulator..a friend had me rebuild his carb 3 times years ago,before I found out his Holley fuel pump was putting out almost 18 PSI!...:doah:..turned out to be some hot rod racing version and his Q-jet couldn't handle the pressure..
 
diesel4me said:
Your gas tank or sending unit probably has a nipple for a return line ,depending on the year of the vehicle and where it was sold--I would say the best way would be to run a new hose (or steel line with short rubber sections to connect it) ,right back to the tank from the third nipple on the fuel pump--that way you wont have to worry about any original fuel hose or steel lines failing and leaking...and you'll gain the benifits of having a return line..
Click to expand...

The stock pump has a 3rd nipple, The new holly pump does not. If it did I would just hook the return line into the new pump. should I put a "T" fitting on the outlet of the new pump and run one back to the tank and one to the carb?
 
I have a Holley pump and I ran the no return line for a bit. It would drive ok, but would fall on its face on a hot day under heavy throttle as it would vapor lock from fuel getting too hot stuck in the line.

An old mopar guy was over and said he had just the thing. Ran home and came back with a fuel filter that had a 3rd nipple on it as a return. Hooked the return line up to it and all issues resolved.

This one. http://www.wixfilters.com/Lookup/PartDetails.aspx?Part=33054



I will never run one without a return after that. I wrapped my lines in heat reflector stuff and made heat shields, and all it did was make it take a little while longer to start acting up.
 
Deuling said:
I have a Holley pump and I ran the no return line for a bit. It would drive ok, but would fall on its face on a hot day under heavy throttle as it would vapor lock from fuel getting too hot stuck in the line.

An old mopar guy was over and said he had just the thing. Ran home and came back with a fuel filter that had a 3rd nipple on it as a return. Hooked the return line up to it and all issues resolved.

This one. http://www.wixfilters.com/Lookup/PartDetails.aspx?Part=33054



I will never run one without a return after that. I wrapped my lines in heat reflector stuff and made heat shields, and all it did was make it take a little while longer to start acting up.
Click to expand...

Thank you, ill have my little brother bring one of those home with him when he leaves work (Oreilly's auto parts) and as soon as it quits snowing here ill install the new pump.
 
Good deal.



I know it worked wonders for mine. I should prolly pick up a few spares.
 
That's good info Dueling, been dealing with the falling on it face problem for a while now. Only happens when it's hot out.

I don't have the return set up on mine but think I will add it when I swap out my 25 gal for 31 gal tank and a sender with the return.

Going to try the filter trick using the charcoal vent line when it warms up outside.

This has actually been going on for a few years and sure it's ethanol related.
 
I had a clear fuel filter right before the carb, and you could watch as it got hot, go from straight fuel, to bubbly ugliness when it got hot. It would let enough through for light throttle and idling. But as soon as I got on it, there just wasn't enough left.


Soon as I put that on, it was solid fuel in that clear filter all day long. So I actually took it off.
 
I never had the problem until a few years ago, rerouted fuel lines, fuel pump, tried diff carbs I had .replaced all rubber lines from tank with ethanol rating.

Was getting ready to check the tank sock for blockage when I replace my body mounts.

Ethanol fuels vaporizes and evaporates quicker causing these problems I'm sure.
 
Yah I wouldn't know. Haven't been around long enough to not have ethanol in my gas I'm sure lol.
 
You must log in or register to reply here.

Latest Posts

Top Bottom