75 280Z - Updating fuel feed & return lines in the engine bay

[HusseinHolland]

I made a start on redoing the fuel lines. I used sleeved 10mm nitrile line with quick-connect fittings. The ends are clamped to the hard lines, and are not intended to be removed moving forward. The quick connect fittings allow you to disconnect the rail from the feed & return.

Did the return first. Rerouted behind the filter to get it away from the motor. Support bracket previously attached to the filter clamp is now secured it at the inner fender 

 

QC fittings for the (Volvo application, Mahle KL 196) filter 

needed a longer M5 bolt

while I was there I added a branch to allow me to add the fuel pressure gauge (M10x1 w/QC, 1/8" NPT)

Used a left over silicone elbow from my C30 turbo upgrade, perfect fit for the torn filter-AFM elbow

Edited April 20, 2023 by HusseinHolland
typo

[HusseinHolland]

Dropped the (aftermarket) fuel pump & feed hose today. I don't like the way the pump is fitted either.

Original schematic of layout

redrilled the mount plate to rotate & move the (new Bosch) pump up & out the way somewhat, adding Quick -Release fittings, to get rid of the large loop on the low pressure suction side

Volvo fuel hose 1312257 11.5mm ID sold by the meter . I was going to put an inline filter here, however both versions I purchased were less that 3/8 OD, probably close to 5/16

Have to fit the pulse damper above. I won't need it with the VQ35DE install, so I'm going to make it easier to remove

Edited July 8, 2023 by HusseinHolland

[HusseinHolland]

Finished up the fuel pump/pulse damper install today

Used some preformed nylon line cut from a Volvo, mostly likely. That put the pulse damper where it needed to be to connect to the feed hard line

With that figured out, I made a bracket to support it welded to the fuel pump bracket

hook up the pump wires before installing the assembly

All up out the way now

Installed the correct return line , that was also the wrong ID

 

[HusseinHolland]

Forgot to add here - I had removed the Datsun FPR, and installed a Volvo FPR pod that incorporates the return, so no return on the motor

I subsequently replaced the fuel rail & injectors, which meant modding the feed line

I didn't care for the transition from the AN braided, and the barbed FPR port hanging out, so I reworked the feed side to tidy it up. 

Single 6AN braided hose from the rail to the fitting for the fuel gauge, then barbed 6AN 90º elbow into the FPR outlet hose. Not a huge fan of 90º fittings for the fuel supply, however it is all larger ID than the stock setup, and a smooth arc would have sent the line way to far forward

Ignition wires need a new standoff, now the one on the stock rail is gone - I have a tie wrap holding them down so they don't rub on the underside of the hood

 

[Captain Obvious]

So I'm not sure how that pressure regulator is designed inside, but it looks like you've moved to a dead-headed setup at the rail?  The original system is bypass scheme.

[Zed Head]

I thought the same.  That won't help the hot start problem, might even make it worse since the vapors can't be purged except through the injectors.

[HusseinHolland]

23 hours ago, Captain Obvious said:

So I'm not sure how that pressure regulator is designed inside, but it looks like you've moved to a dead-headed setup at the rail?  The original system is bypass scheme.

22 hours ago, Zed Head said:

I thought the same.  That won't help the hot start problem, might even make it worse since the vapors can't be purged except through the injectors.

It's the same as any of the 90's-2K gen systems used before they went to entirely returnless in tank modules. Return is moved from the rail to the regulator, so only regulated pressure enters the feed and rail. Works as expected, and no additional heating of the returning fuel. 

Did you mean it may aggravate the hot start condition when used with a stock rail? That is conceivable. In any event, using the larger volume Billet rail seems to have removed the issue. I expect the extra material and volume within is what did the trick.

Besides that, I still made the heat shield today, off the previous template. I used some left over T-304 sheet I had bought pre-covid, when the prices were still reasonable

Had to chop 3" off the left end, I miscalculated that. Several in/outs to get the fitment right between the injector holders

EDIT - going to have to re-wrap the injector harness to align with the new rail - not happy with the way it looks now 🙄

Edited November 17, 2023 by HusseinHolland

[Zed Head]

Just an observation.  The pros and cons of return style versus deadheading is a popular topic.

 

https://www.bing.com/search?q=return+style+versus+deadheading

[siteunseen]

Would slightly slowing down the return cause the fuel to be cooler in the rail? I've wondered if it flows too fast it wouldn't cool down. My aluminum rail is sort of cool if you grab it but I've got one of those ceramic coated headers from MSA. 

Restrictor for the return line?

 

[HusseinHolland]

2 hours ago, Zed Head said:

Just an observation.  The pros and cons of return style versus deadheading is a popular topic.

 

https://www.bing.com/search?q=return+style+versus+deadheading

I think you guys misunderstand the Volvo FPR - it's not deadheaded as in the examples given in your link - it's still bypass with the return off the bottom of the regulator pod. The difference is that you don't have the return gas heating in the return section of the rail as with the stock setup. It's not going to make any difference to vaporization, since that issue is on the feed side of the stock system, not after the FPR, since that fuel is not part of the feed side equation

I put pics of them in the FPR thread

[HusseinHolland]

11 minutes ago, siteunseen said:

Would slightly slowing down the return cause the fuel to be cooler in the rail? I've wondered if it flows too fast it wouldn't cool down. My aluminum rail is sort of cool if you grab it but I've got one of those ceramic coated headers from MSA. 

Restrictor for the return line?

There is no return on the motor, so it's not getting radiant heating as the stock system does.  It's the same unit I put on my 91 Volvo pickup, which had a regulator & return on the manifold previously. Volvo started using the pod style (also used by VAG) in around 93 with the 850 series Bosch M4.3/4 EMS

 

[Zed Head]

The "dead" part of the deadhead is the non-moving fuel in the rail.  Dead flow.

If the fuel doesn't pass through the rail, in one end and out the other, then it's a deadhead system.