Fuel Press gauge installation...

[Guest Ricter]

I've searched both here an on zcar.com, and I've found lots of references to in line fuel pressure gauges, but no instructions on installing one. Can anyone point me to some documentation on installing one on my '77 280Z? Such as the best place to mount them, best method of doing so, etc..?

 

Thanks,

Ricter

[Dan Juday]

Best place to mount any mechanical fuel pressure gauge is on the other side of the windshield. Mount it inside the cabin and a failure of the gauge or the line has a high probability of being catastrophic and/or fatal. This goes double for an FI system due to the higher pressures.

 

Burning is at the absolute bottom of my "List of ways I'd chose to die".

[technicalninja]

Dan is absolutley right!

I've been wrenching for 20+ years and always duct tape the gauge to the windshield (outside!) on customers cars that I am diagnosing for F.I. issues.

It sounds like you want to permanetly mount a gauge which can be very useful for tuning and monitoring. This is amost neccessary for a max effort turbo engine.

Having a gauge permanetly mounted in the engine comp that can not be seen while operating the car is almost useless and not worth the cost.

 

The solutions are

Mount a mechanical gauge on a bracket sticking out of the hood

rear parting line (or possibly through the hood). This is often seen

on bracket racing cars. The gauges are hard to see and ugly

hanging out in the breeze. They also represent a fuel hazard.

 

Using an isolator- These critters isolate bad things and keep them

out of the interior. Two styles available

 

Mechanical. - Used with a mechanical gauge, Installed between

gauge and F.I. basically a fixed volume system that allows

the fuel pressure to push against a diaphram which applys the

same pressure to the isolators fluid- usually a thin oil. Line from

isolator to gauge is steel, aluminum, or hard plastic and can be

difficult to route. Diaphram unit is installed at or close to fuel

source in E comp.

 

Electrical. - Changes fuel pressure into an electrical signal close or

at fuel source. Requires Electrical F Pres gauge. Very easy to

install. Plumb isolator into F.I. Run wires to gauge inside car.

Much more expensive and far less accurate!

 

I dislike electrical gauges. The change to an electrical signal tend to smooth out the signal and you are seeing an "average" instead of a pure signal. IMO electrical gauges are reading a "range" and although movement within the range are accurate the markings of the range (on the gauge face) may not be. Often times a sensor signal is digital which further averages the signal. Often the readings are digital which I hate!

When watching E.F.I. fuel pressures how fast and smoothly the pointer moves is important to me. Watching how the needle of the gauge darts around can give you as much diagnostic help as the pressure readings.

Try to watch a digital tach at WOT.

 

Analog swept pointer gauges can usually be installed clocked so that the needle points straight when readings are the best. When you have multiple gauges all clocked this way your dash will look weird but during operation you can spot problems earlier and have less distractions. A quick glance lets you see if ALL pointer are pointing the same way.

I've seen race cars that had their gauge markings blacked out to further reduce distractions. Digital requires you to focus on the gauge and take your eyes off the road.

 

Tap into fuel system between fuel filter and fuel rail (on engine). Common brass tee with 5/16 barbed connections will work. Make sure you F.I. hose is in good shape and not old (old stuff some times cracks soon after teeing into it). My test rig is nothing more than a 6' peice of F.I. hose connected to one of these tees and a simple mechanical gauge. Close hood only untill first latch and duct tape to middle of window. Good duct tape can hold a gauge at 100+ mph! but don"t leave it on long. Baked in the sun it can form a epoxy like bond to the window that is hard to remove.

You can install the isolator anywhere in E comp but I suggest the right side fenderwell close to fuel filter to keep pressurised fuel lines short.

Use teflon tape on all brass to brass connections. (barbed ends into tee).

Any gauge install should be checked for accuracy by a known good test gauge. IE use a real thermometer to check coolant temp gauge accuracy.

 

One last note. The faster ,more accurate, mechanical gauges are usually much cheaper than the electrics.

 

Hope this helped to answer your question.

Rick

[Guest Ricter]

Thanks for th replies. I had no intention of putting the gauge in the cabin of the car. In fact actually having mounted in the engine bay would suite my needs. As I'm under the hood diagnosing my EFI problems 99% of the time.

[z-ya]

My regulator is mounted in the driver's side firewall. I made a fixture so that I could look at fuel pressure while driving. I made it from 1/8" copper turbing, compression fittings and NPT fittings (all hardware store stuff). I bent it so I could route it through the gap between the hood and the cowl (need the hood popped to do this). When I need to see the fuel pressure while driving, I wait for the system pressure to drop, then I remove my pressure gauge from the FPR, and screw it to the test fixture. I then screw the fixture to the FPR. I then tape it to the windshield. Works great, and it very safe.

 

Pete