Carter fuel pump wiring

[BullDoozer]

Hey all I got me a ‘81 720 with the z22 and a manual fuel pump, running a Weber with the transdapt one piece spacer. I’m having intermittent idle issues and, after plugging up every vacuum leak I could find, she’s still a little off. Been reading the Weber likes a high flow pump with low pressure so I opted for the Carter 4070 (I think that’s the part number). Was just curious if any of you have done away with the mechanical pump and if you’ve any tips for the safest and most reliable way to get the carter wired to the ignition and whatnot. Should I try to find a 720 fuel pump relay at the junk yard and make that work?? Any and all input is appreciated! 

[bottomwatcher]

I believe 82 was the first year z22 and I don't think they came with a manual pump. The is an unmachined space for one. My 82 came with a z22. I ran a Weber on the stock electric zero issues.

[BullDoozer]

It’s definitely an 81 with a z22 and manual pump so maybe I got a unicorn but none the less trying to get an electric pump wired in for less “pulsating” fuel delivery 

[datzenmike]

Z22 is '81 and '82.

 

Use the mechanical pump they are regulated for 3-3.5 PSI, just right. Electric pumps pulse also and would matter more if this was a EFI set up. Carburetors don't care.  When the mechanical pulp gets up to pressure fuel is bypassed back to the inlet. Don't over think this... the mechanical delivers all the fuel a Z22 will need no matter the carburetor on it.

[Crashtd420]

16 hours ago, BullDoozer said:

Hey all I got me a ‘81 720 with the z22 and a manual fuel pump, running a Weber with the transdapt one piece spacer. I’m having intermittent idle issues and, after plugging up every vacuum leak I could find, she’s still a little off. Been reading the Weber likes a high flow pump with low pressure so I opted for the Carter 4070 (I think that’s the part number). Was just curious if any of you have done away with the mechanical pump and if you’ve any tips for the safest and most reliable way to get the carter wired to the ignition and whatnot. Should I try to find a 720 fuel pump relay at the junk yard and make that work?? Any and all input is appreciated! 

I have that same pump on my side draft weber .... it actually put out the higher end of its psi... about 6.5.... you'll probably need to add a regulator too,  but you may have a return line to help with that, at bare minimum I would verify psi at the carburetor...

 

For wiring if you can do the oem fuel pump relay that would work, no idea if the wiring would be in the truck but it might be tucked away.. with my 521 I opted to use a oil pressure switch and relay...

It Sends power while cranking and then as long as there is oil pressure the pump will run..... 

[Stinky]

Generally speaking...you can't have high flow w.low pressure....especially w.a 5/16" line.  The reason is that if you put a lot of gas in that line (flow), then it has to go somewhere (pressure).

 

You cant have pressure w.o flow....and when you have flow, you have pressure, unless it is regulated.

 

At what pressure is your carb supposed to operate?   Try "redlineweber.com" and look up their customer service #.  This is important.  To much pressure and you will foul plugs.

 

Did it ever run good w.this set-up.  Not sure that fuel flow is ur problem

[datzenmike]

Webers like around 3 the stock mechanical is 3-3.5.

 

 

Stock mechanical pump...

 

If the line is closed the pump will reach it's regulated maximum pressure and that's it. You could say maximum pressure and zero flow. If there is a return line there will be a very small flow recirculating back to the tank.

 

If the line has an opening either through the needle valve into the float chamber and or a restriction for the return line the pump should easily be capable of supplying maximum pressure and still produce some flow. Certainly the float chamber will fill in about a second and even at full throttle the pump will easily keep it topped up. I think that if you put a pressure gauge on it and drove down the highway at full throttle the gauge would still read maximum regulated pressure.

 

If the line is open enough, like the hose off, the pump will never reach maximum pressure but will reach maximum flow about 1.4 liters per minute. (what engine uses 1.4 liters a minute????)

 

 

If you have a mechanical pump I don't know why you are messing around with an unknown electric pump.