Step 4:

Plumbing and Flow Testing

Caution: This involves high pressure fuel spray and electricity. If you don't have fire extinguishers and/or you are not qualified then get help from someone who is qualified to do the following safely.

The flow path will go from the tank through the filter to the pump to the first rail with 3/8" line. Then with 5/16" line from one rail to the other through the regulator and back to the fuel tank. This arrangement keeps all the injectors and the same pressure and any excess fuel goes back to the tank.

Fuel Pump:

The fuel pump is off a VW Rabbit with CIS injection. On those Bosch pumps there is a check valve that keep the fuel system pressurized. Take the check valve off. It restricts flow and the computer will prime the system. In addition because the check valve isn't there the fuel lines can quickly depressurize when you turn the engine off. In other words it's safer that way.

The inlet of the pump is about 7/16. I couldn't find that line so I used regular 3/8 fuel line and jammed it on. The outlet of the pump is a metric fitting that just happens to be the same size as a VW lug nut. Drill and tap the end of the lug nut for a 1/4" NPT and you got yourself an adapter. Use a copper washer between the adapter and the pump.

The pump should be mounted as close to the bottom of the tank as you can get it so it primes itself quickly. Below is my quickie mount made from a piece of angle iron. A hose clamp goes on the wide slot and the notch on the filter fits in the small slot. Another clamp goes on the bottom. I wrapped the pump with inner tube to isolate the vibrations a little.

Fuel Filter:

I chose to use a Fram fuel filter with a 10 micron screen. It is plumbed before the pump...yes...before the pump. As Tim said "there's a right way, a wrong way, and there 's how we do it." Fuel pumps are not good at sucking so typically cars will put the filter after the pump. Sometime they will use a less restrictive filter before the pump and put the good filter after the pump. Off roading is dirty business though and a piece of sand or dirt could kill the pump...so the good filter is going before the pump.

Pressure Regulator:

Below is the regulator off a 68 or so fuel injected bug. I found a nut that fits the threads and welded that to my old cooler mount.

((Insert PICTURE HERE))

Fuel Line:

You must use fuel injection rated line after the pump. Steel braided high pressure line is best but that was too hard for me to obtain at this point. Remember to blow the lines and fittings out so they are clean.

Fire Extinguisher:

Once you got all the lines tight and double checked, grab the fire extinguishers and put out any sources of flames.

fire_extinguisher_DSC01194.jpg (217705 bytes)

Cleaning:

So now we have the rails plumbed and the tank filled. You may still have small pieces of dirt in the system so here's what I suggest. Set the rails over some canisters. Wire the pump up temporarily to a switch and let some fuel run through the lines to get any small grit out that could later affect the injectors. Put some gloves on and cover the holes on the first rail to blow the gas to the second rail. After you're sure the lines are clean wire tie the injectors to the rails.

Note: The wiring and wire nuts are temporary. The final wiring was soldered with heat shrink over the joint.

Now turn the pump on and off quickly and look for leaks. If there's no leaks let the pump run. After the air has been purged turn the rails upside down to better allow any more grit to flow out the exit port. Please be careful and use proper safety procedures...we're talking about a lot of high pressure gasoline here.

Flow Testing:

The purpose of this test is to make sure that the fuel system you have can handle all four injectors running wide open at full pressure capacity with some fuel still being returned to the tank.

The Bosch regulator is good for about 45PSI so that's what we're going to test it at. With the pump running, adjust the regulator to read 45PSI.

Wiring:

The injectors are basically little solenoid switches that operate very quickly. If you wire them directly to the battery they will be fried in short order so you need to limit the current by wiring them through a tail light bulb.

Each injector has two wires. Use some scrap wire and connect one wire from each injector to the battery.

Then connect the other side to the injector pigtail on the brake light. Tape or use electrical twist connectors on the wires so there is no chance of sparks. At this point when the bulb is grounded, the light will light up and you should hear the injectors click open. Turn the pump on, look for leaks, click the injectors a few times and make sure all 4 are spraying. Also make sure all 4 turn off. If one continues to "pee" click them open a few more times. Now turn them back on and while they are spraying check to make sure that there is fuel returning to the tank. If the fuel is flowing back to the tank with all 4 injectors open at 45PSI then you know the fuel system can handle the required fuel flow.

I also clamped the line to the regulator while the injectors were running wide open. Fuel pressure rose to 52PSI when the pump was deadheaded which would mean that is about the limit for my pump and plumbing.

Spray Pattern:

Look at the spray pattern and check it for defects. The spray should be uniform.

Good Pattern	Bad pattern

Cleaning Injectors:

If you used junkyard injectors they may need to be cleaned. Read More here

Injector Flows:

With port injection it's critical that the injectors flow about the same. The proper way to measure injector flow is with an injector flow bench that simulates real world conditions by pulsing the injector open and closed. You can have this done professionally or you can build a flow bench as described here: http://www.diy-efi.org/diy_efi/projects/inj_flow/inj_flow.html

I choose option 3 (the wrong way) to get a very rough estimate on the flow rates.

Put some 1/2" line on the bottom of each injector and run them into 4 separate containers for exactly 1 minute. The flow should be within at least 3 or 4 percent of each other. I used a burette but use what ever way you can find that's accurate.

Cylinder 1:	374.2cc	Difference
Cylinder 2:	382.2cc	2.14%
Cylinder 3:	382.8cc	2.30%
Cylinder 4::	386.4cc	3.26%

So now the manifold is bolted on, the injectors are in and spraying properly and the next step will be to mount the computer and wire it up.

[ Step 1: Fuel Tank ] [ Step 2: Flanges and Plenum ] [ Step 3: Runners and Rails ] [ Step 4: Plumbing and Testing ] [ Step 5: Computer Wiring and Tuning ]