Eating Humble Pie in my '78 on I64. Yum! Failing pump? Fuel tank siphon tube leak?

[Love my 72 240Z]

Some of the guys with older 280's place header insulation around the rear rubber fuel lines to keep the heat away. Yesterday - saw a 260Z that had this same "covering" over the fuel hoses near the rear diff. BTW, if there are wires connected to a the fuel pump terminals make sure they have not been melted by heat from the rear diff - saw that a few years back on an early 280Z. Heat can be a cruel enemy :0

[FastWoman]

Eric, no idea about fuel pressure yet, although I'm assuming zero at this time. I haven't been able to carve out time to test my fuel delivery yet. Probably this weekend.

Steve, David, I hadn't really thought about a differential throwing off that much heat. It makes sense, as a lot of diffs have heat sink fins (e.g. on my Miata's LSD). That would be another thing to test. I can perhaps throw some (mild) heat up towards the fuel intake line with a heat gun and see what happens. David, I've been into the wiring at the fuel pump and haven't seen any signs of hot/melted insulation. Anyway the collapsing intake line sounds like a plausible theory. I suppose it might be all the more likely if the fuel in the tank gets warm from road heat and circulation through the engine compartment. It was a fairly hot day, BTW -- the hottest I've driven my car since having reworked the fuel and intake systems. We were flying down the interstate at 70'ish (VA speed limit) with the AC burning on high and the temp gauge a couple of needle-widths above where it normally lives.

I think I'll try some of that exhaust insulation. Sounds like a great idea.

Thanks, guys! More theories to test this weekend!

Edited April 28, 2011 by FastWoman

[cozye]

Hey Sarah,

Get one of those $15 mini inline fuel pressure gauges from summit, and put it inline between the fuel filter and the fuel rail. That way when you have the issue you can pop the hood and get a real time FP reading.

Personally I don't think it's anything heat related at the rear of the car. There are plenty of FI Z's running around with no special heat shielding around the differential, gas tank etc.. The fuel pump may be getting hot just under it's own operation. I suspect you have a faulty fuel pump, or something in the fuel circulation that is causing the issue. Do you have a fuel pump pre filter ? Have you looked at the inlet screen on your fuel pump? Are you sure your gas tank is clean? Also, you should be able to take an air hose and blow out the return line after the FPR, and make sure there are no blockages there.

[240260280z]

Compressed air blowing out the lines backwards from the engine compartment could be a preventative measure/grenade to throw at this.

Maybe drain the tank too to see what comes out.

[240260280z]

Oh yeah check for spark too when it dies. Sudden dying is often caused by heat and ignition circuits... even a capacitor can intermittently short when hot and kill the sparky stuff.

[FastWoman]

Eric, I think I'll add a gauge permanently for matters just like this. I do have a pre-filter before the pump. I haven't checked it yet. (It's not a clear one. I think I'll replace with a clear one like I have on my tractor.) I'm positive my tank is clean, at least as of last August. I dropped the tank, opened it up, peered through the holes, etc. There was so little rust inside (in only a couple of tiny spots near the drain plug) that it wasn't worth de-rusting. I didn't want to disturb the galvanized coating. I pressure-washed the inside, rinsed out with acetone and B12, repainted the outside, and reinstalled. Unfortunately there was no way to view the inlet screen without cutting apart the tank, so I can't say anything about its condition. (That's why I installed the prefilter.)

Blue, I would be amazed if anything surprising came out of my tank through the drain. I've used my car regularly since putting it back in a full operational state last fall. There's been no old gas, and rust just doesn't happen that fast -- even here.

Compressed air through the return line is something I didn't do. I'll try that. But wouldn't that just make my pressure spike to 42 so that I run rich?

I didn't check ignition or even check much of anything. Way too much steel flying past me on the interstate only feet away. I wasn't going to risk it. Next time my engine fails, I'll certainly check those things. That said, I did an HEI retrofit, and I have the HEI module pretty well heat sunk.

[ZCurves]

Related to what Cozye was saying - When I was rebuilding my engine, I took the Fuel Rail and brazed in a Ford fuel pressure fitting so that I could easily run the 3M cleaner through this port as well as check the fuel pressure. It comes in handy to check pressure without having to pull any lines, etc.

I use an Actron Fuel Pressure Test Kit - CP7818 to monitor.

http://www.actron.com/product_detail.php?pid=16174

Attached is a stock drawing of the setup. I'll see if I can take a pic of my install.

[FastWoman]

Hey Andrew, that looks like the way to go. Very nice. I think I'll do that.

Anyway, I connected some clear vinyl tubing from the return line of the fuel rail to the fuel tank, hooked up a fuel pressure gauge, hooked up a battery charger to the battery, hotwired the fuel pump, and observed. The system quickly came up to pressure, but I noticed the return fuel flow was not particularly energetic. So I watched and watched, and the fuel flow started slowing down more and more until it stopped. Pressure stayed up until I put vacuum on the FPR. I found the pump did not restore the pressure, even though it was still running. Therefore I had a fuel starvation issue. But was it the pump, a blockage in the supply, or a rusted siphon tube?

Rusted siphon tube theory: I topped off the tank with gas (no air to draw through a hypothetical rust hole in the siphon tube. Same problem. Therefore not a rusted siphon tube.

Collapsed fuel hose hypothesis: Nope.

Clogged intake screen, pre-filter, or filter: I hooked the vinyl tube to the outlet side of the fuel filter and ran the pump. I didn't get a rapid flow, but it flowed and continued flowing. I should have been able to pass the same volume of gas out the fuel rail's return line, where none flowed. Therefore not a blockage.

I'm pretty sure that rules out everything but the pump, which I'm assuming just wore out. I know the pump would supply approx 45 psi static pressure last fall, but perhaps it was growing weaker even then.

Any recommendations for a replacement pump?

[FastWoman]

MSA has rebuilt OEM ones for $135. Are these good rebuilds?

http://www.thezstore.com/page/TZS/PROD/SFC02/11-3064

Their new ones are $283. Are these genuine Nissan -- new old stock?

http://www.thezstore.com/page/TZS/PROD/SFC02/11-3063

Factoring in a bit of overdesign, I figure I need a max delivery rate of about 25 gal/hr at 40 psi. There are lots of aftermarket fuel pumps that will do that, but I understand many of them are junk. For instance I heard the aftermarket fuel pump on a friend's truck the other day. It was pretty loud. You could hear it maybe 20 ft from the truck. I definitely don't want that. Who makes a good pump?

[FastWoman]

Has anyone tried this one from Summit Racing?

http://www.summitracing.com/parts/SUM-G3138/

[FastWoman]

Maybe this one:

http://highflowfuel.com/i-6227286-walbro-gsl393-190lph-universal-inline-fuel-pump.html

40 gal/hr, 60 psi max.

[FastWoman]

Ah, good ol' Ebay. I found a new OEM one from Chesapeake Nissan for $222. Sold.