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Discussion Starter · #1 ·
Quick rundown of what I have going on before my question:
I am converting my mk3 aba to r1 bike carbs. Ive acquired just about all I need component wise, and started getting my lines routed and all that jazz. Since I’m using carbs ill be running a carter low PSI pump and FPR. As such, I wont be needing the in tank pump considering the PSI range it users. It will need removed. Ive replaced many mk3 pumps so I’m already half dove in...

My question is, what is everyone doing once the pumps removed? Just run a bit of line down to the bottom of the tank? If that’s the case, is there an aftermarket fuel sock you’ve placed over the fuel line inlet? I’m honestly sorta stumped about what to do here...
 

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Discussion Starter · #5 ·
I have just left the in tank pump. As long as you are running a lpfp and a regulator I don’t think you’d have any issues.


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So you’ve just left your original pump as is and just “cut the power” to the pump so to speak? I mean....**** yeah I guess I could just do that and leave everything alone with the stock pump.....maybe I am overthinking all this:banghead::facepalm:
 

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So you’ve just left your original pump as is and just “cut the power” to the pump so to speak? I mean....**** yeah I guess I could just do that and leave everything alone with the stock pump.....maybe I am overthinking all this:banghead::facepalm:
I left power running to the in tank pump.
I removed the undercar fuel pump and replaced it with a low pressure motorcycle pump. Also running a Holley fuel pressure regulator in the bay.
Definitely less complicated than it seems.


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Discussion Starter · #7 ·
[HR][/HR]
I left power running to the in tank pump.
I removed the undercar fuel pump and replaced it with a low pressure motorcycle pump. Also running a Holley fuel pressure regulator in the bay.
Definitely less complicated than it seems.


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Thanks for the heads up I appreciate it. OEM pump is inop in this tank and I’ve already got my new pump, FPR, and gauge installed in the bay. Maybe ill just put some power to the pump tomorrow night and see what sort of pressure I am getting.
 

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Been down this road before. Leave both high pressure and low pressure pump as-is and get a bypass fuel pressure regulator. This way the proper pressure goes to the carb and the excess fuel goes back to the return lines. This is literally what the muscle-car owners are doing nowadays to avoid electric pump failure and to avoid vaporlock
 

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^ Bypass fuel pressure regulator is a good way to go.

If you want to be cheap (I was) you can get a fuel filter that has a second offset outlet. That second outlet is typically oriented higher and plumbed to the tank to allow any vapor (or in your case) excess fuel to return to the tank.

I did this on my prior Mk2 and had a gauge before the carbs. With the in-tank pump only, it would put about 3-4 PSI at the carb fuel line. IIRC, it was an off the shelf 5/16" fuel filter with a 1/4" second outlet which probably helped create some of the back pressure.

Here's a photo. I was using a Holley pressure regulator before (sitting on strut tower) but it was accomplishing the same thing and the fittings were clunky.

 

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I've been converting my daughter's 87 cabby with the redline kit. I've removed all the CIS parts.

My question is this: is there a relay in the CIS system that would prevent the fuel pumps from pumping if the CIS is disconected?

I hear and feel the pump relay click, but I'm not getting fuel to the engine bay and do not hear the pump and transfer pump turn on.
 

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I figured it out.

I've been used to newer cars where the fuel pump(s) prime when the ignition is turned to the run position or when the driver's door is opened.

Apparently, the fuel pumps in this car fire up when the starter is engaged. I heard the pump power down after I stopped engaging the starter.
 
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