tory

I would say look for a pump that is good at creating suction from the tank. The Carter sucks very well from the tank, provides a ton of volume, but not much pressure. If your feeder pump is shaped the same as the walbro, I would say that it will not work as well. The two pumps perform entirely different functions. The carter will provide 72 GPM, or for higher output you could look into the Holley pumps (blue, red, black).

I thought I would post here and let you guys know that the feeder pump fix worked for me. I am copying it from my post in the Volkswagen forums, so a few things will sound funny. I finally got enough money to repair the issues the car has been having. I reworked the fuel system so that a Carter carburetor pump has taken the place of the Bosch 044. It has an upright configuration that made it hard to retrofit, but I made it work with a very funky fitting that I will get a picture of soon. Then I cut some lines up and spliced in another Walbro pump near the passenger rear shocktower. It is a smaller Walbro(GSL-393) than the one I had before(GSL-392), but still flows enough fuel at 70 psi to make 300 FWHP. I went with Walbro because I found it for cheap on ebay, I was assured that it was brand new and genuine, and I already had the AN fittings for it. There is an inline 35 micron filter between the two pumps, but other than that it is a direct feed. Electrically, I wired them up with seperate 4-pin relays. The walbro has a direct fused line from the battery, and grounds to the ground strap on the trans. The Carter accepts power from the main fuseboard in the trunk. I used the fuel pump output on the megasquirt relay board to trigger both relays so that the fuel pumps will turn off with no engine signal (so I have a relay triggering two relays, haha). Additionally, the Carter's power supply is interrupted with a Ford inertia switch. Brian at BoostEngineering.net gave me one free with my EDIS kit. It is mounted in the front apron and will disconnect power from the pump if there is a jolt (from a crash). I have scraped the swaybar several times and am happy to report that it hasn't prematurely cut off yet. It also makes for a really obscure killswitch when the car is parked somewhere. Other than a leak from one of the fittings that was easily repaired, the startup was perfect. Static fuel pressure is rock solid, with no noises coming from the Walbro. The Carter is a little loud but pretty indistinguishable once the engine's on. So to all the old heads on here ( Pile, raygreenwood) who kept wagging your fingers, you won. It works. I am a believer. Sorry for doubting the necessity; even now if I could get away without a feeder I would have, but here I am. Best of all, the two small pumps in combination use less peak amps than the big Bosch. Symptoms I had before that some relate to fuel temperature (cavitation, boiling) never occurred. It was 100 degrees out today, and the fuel never hiccupped once. Can't wait to do some real tuning on this thing. Took mom out to get lunch. I can tell how much I'm going to love this car by how much she hated it. EDIT: here's a picture of the Carter, with the crazy fitting I made from some NPT tubing and a -12 weld-on bung. Also, I was playing with the engine when I got home and the fan sucked in a spark plug wire. Woohoo! One step forward and two back. Need to figure out how to make another, and then secure them to the firewall properly. I'm so happy the fuel system works I'm not even that mad. EDIT # 2: For anyone that wants a good deal on this pump, here's the link: 75 bucks with free shipping and install kit. When the link goes bad, the seller's name is djd16. http://cgi.ebay.com/ebaymotors/BMW-E30-E12-E21-M10-M20-M30-New-Walbro-GSL393-Fuel-Pump_W0QQitemZ220440180907QQcmdZViewItemQQptZMotors_Car_Truck_Parts_Accessories?hash=item33534238ab&_trksid=p3911.c0.m14&_trkparms=65:12|66:2|39:1|72:1205|240:1318#ht_2877wt_1191

Yea, that's weird. Before I had routed my tank venting lines, I had the ports capped off... took it for a few test drives around the block and noticed the tank was swollen with air pressure, so I pulled off the cap too. Funny enough though, this was long before the pump started acting up and making noise. The only reason I noticed the tank being puffed up was because I was driving without a hood, and the fuel gauge sending unit on top of the tank was hissing. Hey Sean, you mentioned that you have 2 Walbro's that you tried. Which one is on the car now? I just got the Carter pump, and now I'm making all the fittings for it to work. I want to try out the old pump to see if the feeder solves the problem. If not, I can at least harvest the AN fittings from it and get a new one.

This is where mine was under the tank, and it started doing the screaming meemies after about 10 miles of test driving. So I think results can really be all over the place.

I figured the same thing with the direct feed. It's good to hear it works that way. I think I will hook it up the same way you have, when I get some more cash to spend. Now I have to go dig up that old Walbro and see how it works! If it's still crap I can still use the AN fittings with a new one. Thanks again Sean. -tory edit: BTW, awesome car. One of the guys at a dyno shop around here had a beautiful early Z with a built six from a later model, gnarly single turbo, massive front mount, and cheater slicks. I couldn't tell you all the specs, I'm not familiar with these cars. But they sure are sexy.

Cool. Thanks a lot for posting your progress Sean. As far as the routing goes, did you hook up the Walbro directly to the Carter? I read that the Carter pump has a built in bypass valve that regulates the (low) pressure so you don't have to worry about straining the pump (the Carter flows more GPH lower pressure, the valve prevents strain). Just asking because people on the ACVW forums were telling me to run the surge tank in between the two, and connecting the return line to it to vent excess pressure buildup. But you sound like you've had good luck with a direct line.

Sorry to dig up an older thread, but I was wondering if your new fuel set up seems to be working well still? I found this thread on google and have had the exact same problem, even after several reconfigurations of the fuel system (including replacing the Walbro with a Bosch 044, addition of a dedicated surge tank, etc...). I have an aircooled volkswagen instead of a Z, and most people can get away with gravity feeding the high-pressure pump because our front-mounted tanks are fairly high and have plenty of places to mount the pump underneath. So before I spend money on a new high-pressure pump, I thought I might be able to resurrect one of them with a feeder pump, and was just curious if your problems are cured. Thanks!