# CIS-E: Carter GP4070 external pump to replace the Transfer pump? Concerns?



## TheRealEddie (May 8, 2006)

Greetings,
I'm doing some research on removing the transfer pump from the tank on my CIS-E 16v GTI and replacing it with an external pump. The car is used for stage rally and I've been experiencing issues with the transfer pump and the float mechanism so I am investigating removing the pump from the tank. 
A friend did direct me to a Carter pump that he has experience with CIS-E but I'm looking for more info on potential issues from the gurus in here. The pump of interest if the GP4070 which is popular with the carb guys and does 72gph at 4-6psi. Link: http://store.summitracing.com/...w=sku
Any out front, potential issues here? I have been given scheme for plumbing the system up but I just want to flush out any potential problems.
thanks,
eddie


----------



## tolusina (Oct 19, 2004)

*Re: CIS-E: Carter GP4070 external pump to replace the Transfer pump? Concerns? (TheRealEddie)*

Response to your IM, pasted here so others can follow......

_Quote, originally posted by *TheRealEddie via IM* »_I stage rally a 16v GTI CIS-E and one of the weak points for the car is the in-tank transfer pump which can separate from the float mechanism (caused me a DNF last event). I'm researching pulling the transfer pump out of the tank and thought you might have some answers for me. In a thread you said that the transfer pump needs to pump a quart in 30 seconds to the accumulator. I'm looking at a particular pump that pumps at 6 psi and does 72gph which is roughly 2.4 quarts in 30 seconds. Do you know of potential problems if the flow rate is too high? I'm not certain what happens if the low pressure pump pumps more fuel to the accumulator than the high pressure pump can deal with. Furthermore, do you have a feel for what pressure the stock transfer pump does? 6 psi intuitively looks like a good candidate but thats just a gut feeling and nothing based on experience.


---
All I've got for you are thoughts, theories and conjecture.
Ryan, WackyWabbitRacer, has the real experience you want to tap into,
http://forums.vwvortex.com/zer...25503
He's sometimes here on the CIS forum, often in the Golf I & Jetta I forum.

Anyway, approximately a quart in 30 seconds is the stock in-tank pump's specs, what it is expected to pump. If a stock pump can't pump that quart, it's due for a dirt nap.
I doubt that a stock CIS main pump needs that full quart for input, I'm just about sure it doesn't.
You know that while plastic accumulator/reservoir in-line between the in-tank and main pumps? All the in-tank pump has to do is keep that accumulator/reservoir full so that the main pump can draw from that accumulator/reservoir.
That accumulator/reservoir has four hoses, the output of the in-tank pump, the inlet for the main pump, return flow from the fuel loop/pressure regulator and return flow into the tank. There are no valves or anything else inside except for a slight restriction in the return line to the tank.

The in-tank pump pumps rather freely with little restriction into the accumulator/reservoir, excess in-tank pump flow goes to the back tank, in-tank pump pressure build up is avoided (or relieved) via the return line to the tank.

Stock, all the in-tank pump and the accumulator/reservoir is to keep fuel available to the main pump especially during hard cornering with less than 1/4 tank when the in-tank pump starves, there being no baffles inside an A1 (or I think A2) tank.

I verified the function of the in-tank pump and accumulator/reservoir set up on my '92 Cabriolet (A1 chassis) DigiFant car. Both pumps quit, replacing both was an expensive proposition I figured a work around for. I installed a single Chevy pump in the tank, did away with the accumulator/reservoir and main pump, mounted a Dodge Pickup fuel filter under the hood. All is fine with this system aside from hard cornering with 1/4 tank or less when the pump starves. The starvation is self correcting, the cornering speed simply drops until fuel gets back to the pump. I don't corner hard often enough to care.
---
I'm guessing your car is an A2 chassis, I've head rumor that A3 tanks can retrofit into A2 chassis cars.
The A3 tank has a huge access hole in the top for the pump-level sender assembly WITH integral baffles and no cornering starvation issues. You might want to consider an A3 tank though I don't know what pump to recommend as a single in-tank unit capable of CIS pressures.

WWR has posted a schematic of his race car set up, maybe he's bookmarked the thread.


----------



## TheRealEddie (May 8, 2006)

*Re: CIS-E: Carter GP4070 external pump to replace the Transfer pump? Concerns? (tolusina)*


_Quote, originally posted by *tolusina* »_
I verified the function of the in-tank pump and accumulator/reservoir set up on my '92 Cabriolet (A1 chassis) DigiFant car. Both pumps quit, replacing both was an expensive proposition I figured a work around for. I installed a single Chevy pump in the tank, did away with the accumulator/reservoir and main pump, mounted a Dodge Pickup fuel filter under the hood. All is fine with this system aside from hard cornering with 1/4 tank or less when the pump starves. The starvation is self correcting, the cornering speed simply drops until fuel gets back to the pump. I don't corner hard often enough to care.


Well the good thing about stage rally as opposed to a track car is that I generally more fuel than I need since it could be 60 miles, many of which are flat out, to the next service so fuel slosh isn't likely an issue.








Thanks for the description of your experiences with the operation of the transfer pump and accumulator. It sounds like it indeed should be no problem to use that Carter pump as the excess fuel to the accumulator will just loop back to the tank via the return line.
Heh, the dream would be to ditch the transfer pump/high pressure pump rig and go to a single external pump with an inline filter. Similar to what you describe except with an external pump. Not sure of the CIS requirements, I take it CIS is higher pressure than Digi...now where'd that bentley go?


----------



## tolusina (Oct 19, 2004)

*FV-QR*

CIS system pressures are around 70 to 80 PSI, Digi runs 35 to 45 PSI.
I've never deadheaded an EFI pump since way back in the D-Jetronic days, those pegged a 100 PSI gauge, no idea what a more modern pump can do. Maybe I'll deadhead my DigiChevy pump and find out one of these days.


----------



## TheRealEddie (May 8, 2006)

*Re: FV-QR (tolusina)*


_Quote, originally posted by *tolusina* »_CIS system pressures are around 70 to 80 PSI, .. 


Hmmm....
http://store.summitracing.com/...w=sku








But I suppose the question on my mind is how is this pump different than the stock one? How is it primed?




_Modified by TheRealEddie at 12:25 PM 8-27-2008_


----------

