Vapor lock year two, the good fight is back on.

[5thhorsemann]

Okay, so I had to waite till today to do the install as I had to order the gauge for the regulator.

The pump is a little bigger than it looks, the only nice place to mount it, and have room for a high quality filter, was on the bracket that the jackpot mounts to. I was having a hard time manipulating the mounting hardware on the back side of the bracket around the moushtash bar and such, so instead of drilling and bolting I used two beam clamps to mount the pump, it works really well.

I put the regulator up in the front corner on the inner fender which makes all the hoses as short as possible.

So I presurized the system and checked for leaks, it's all good, started the car and adjusted the pre mechanical pump regulator to 3 to 4 PSI and let her run for a while to make sure the bowls on the SU's were not overflowing, again, all good.

So now I wanted to see if Blue's idea of inlarging the return restriction was necessary. I removed the returne line from the fuel rail and put a quart glass jug on it, I turned the pump on with stopwatch in hand, the electric pump alone pumps a quart in 8 seconds thru the return pipe. So thats almost 2 GPM and I think that should be plenty of bypass to combat the vaporlock, so I'm gonna reserve the drilling of the rail as a last resort.

I'll report back on the next hot day.

[epsark]

I have a very similar set up on my 240Z, only I have the Holley red pump. 4 year old pump died, so I bought a replacement. That one was dead out of the box. Took me a while to figure that one as I never expected that to be the issue. Next one now has "locked up" twice on me. By that I mean that the pump sounded like it was on, the humming noise (loud) that it usually makes, but no pressure. Took everything apart and thought vapor lock since the issue, no pressure, finally went away. The second time no pressure again, but pump was a little quieter. Checked a few things before deciding to knock on the pump. Once I did that, the pump jumped in volume and pressure was flowing.

Just not sure about Holley quality any more is what I am trying to say. Hopefully you have better luck. I am going to try a pump from Airtex, I think that is their name, who makes most OEM pumps for the major manufactures. It is said to be much quieter and more reliable. Time will tell. Good luck with your set up and I hope it takes care of your vapor lock issues!

[d240zx2]

Amazingly, 721 never had a vapor lock issue with either the SUs or Mikunis. I had removed the mechanical pump and installed a Stewart Warner "thumper" pump years ago (40). I had the fuel lines routed adjacent to the original lines, up the firewall, over to the center of the car, then forward to a fuel block mounted with the intake/exhaust studs then to the carbs. Pressure was regulated at the pump at just below 6psi. No return line was used.

Vapor lock is a varying mystery, isn't it?

[5thhorsemann]

I've used the Holley pumps in the past, never had a problem with them. Since I'm using the returne circuit, the pump should run stress free, as long as there is pressure at the suction side of the mechanical pump, it should be fine.

I will be watching everything closely for a while to make sure I don't overfeed the bowls and wash the motor down. Like you said, time will tell.

[5thhorsemann]

Update, looks like this did the trick, it's been in the high 90's for the past two days and no sign of the problem. I do still have to get used to the buzz of the new pump, it's loud compared to the old thumper.

[rcb280z]

Try running a rubber insulator between the pump and bracket.

[5thhorsemann]

Try running a rubber insulator between the pump and bracket.

The pump bracket has a rubber isolator built in, I dont see how to further isolate the noise and still have a secure mount, I just have to learn to live with it.

Is that a FG hood or just a 3" scoop mounted to the stock hood? I like it, and just ordered a FG cowl scoop for mine. http://www.ebay.com/itm/150852819409?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649