93anthracite Posted May 6, 2008 Share Posted May 6, 2008 I'm working through my development plans for my car and just have a few quick questions that I couldn't find the answers for and just wanted to be sure before I started buying parts. The car is a stock 73 L24 with early SU carbs. There will eventually be an L28ET under the hood. Car is being used strictly for autoX and road courses. To prevent fuel starving, I'll be using a surge tank, which requires the use of a low pressure pump to fill it, then the high pressure pump for the EFI motor. -can I use the Carter GP4070 (http://store.summitracing.com/partdetail.asp?autofilter=1&part=CRT%2DP4070&N=700+115&autoview=sku) to pump fuel to my carb'd engine for now and then use it to fill the surge tank once I switch over to EFI? My gut says it flows enough to keep it full at all times, but I just need some confirmation... -when using the Carter GP4070 on the L24+carbs, will the stock return line allow the fuel to flow fast enough that there isn't a flooding issue at the engine? I noticed it is a bit smaller than the feed line and I'm trying to avoid replacing the lines until I put in the turbo motor... -when wiring up the fuel pumps, is there a delay necessary for the EFI pump to ensure that the surge tank has fuel in it to go to the EFI pump?(i.e. will it hurt the EFI pump if it doesn't have fuel the instant it turns on?) -how big does the surge tank need to be? 1 pint, 1 quart, 1/2 gallon...?? Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 20, 2008 Share Posted May 20, 2008 -can I use the Carter GP4070 (http://store.summitracing.com/partdetail.asp?autofilter=1&part=CRT%2DP4070&N=700+115&autoview=sku) to pump fuel to my carb'd engine for now and then use it to fill the surge tank once I switch over to EFI? My gut says it flows enough to keep it full at all times, but I just need some confirmation... Yes it will work fine. Remember that the lift pump to the surge tank is not under pressure, and most all pumps flow more at 0psi than at their rated pressure. I have used cheap EFI pumps as lift pumps and they flow a lot more at 0psi than at 43psig. -when using the Carter GP4070 on the L24+carbs, will the stock return line allow the fuel to flow fast enough that there isn't a flooding issue at the engine? I noticed it is a bit smaller than the feed line and I'm trying to avoid replacing the lines until I put in the turbo motor... You need a low pressure inline FPR with that pump. It should be hooked up like: pump -> FPR -> Fuel rail -> return. Without an FPR, the pressure may go too high. You can hook up a gauge to test it before you go out and buy a regulator. -when wiring up the fuel pumps, is there a delay necessary for the EFI pump to ensure that the surge tank has fuel in it to go to the EFI pump?(i.e. will it hurt the EFI pump if it doesn't have fuel the instant it turns on?) Running pump for a long period dry is bad, but for a few seconds, it is not a problem. If you are concerned, the first time you prime the system run the lift pump first. Once the surge tank is full, then hook up the power to the EFI pump. After that the surge tank will always have fuel in it, no delay is required. -how big does the surge tank need to be? 1 pint, 1 quart, 1/2 gallon...?? 1-3 quarts is more than enough. Remember the return from the fuel rail should go to the surge tank, not the main tank. Quote Link to comment Share on other sites More sharing options...
drunkenmaster Posted June 23, 2008 Share Posted June 23, 2008 Running pump for a long period dry is bad, but for a few seconds, it is not a problem. If you are concerned, the first time you prime the system run the lift pump first. Once the surge tank is full, then hook up the power to the EFI pump. After that the surge tank will always have fuel in it, no delay is required. Did you run your lift pump from the same relay as the EFI pump (i.e. fuel pump relay)? Thanks Quote Link to comment Share on other sites More sharing options...
z-ya Posted June 23, 2008 Share Posted June 23, 2008 Yes, a 30A relay should handle both pumps. If you are running a pump that requires a lot of power, you can always add another relay. Quote Link to comment Share on other sites More sharing options...
drunkenmaster Posted June 23, 2008 Share Posted June 23, 2008 Great, thanks for the info. Quote Link to comment Share on other sites More sharing options...
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