DerSchlechtSpecht

Hi, I have 2 questions,

1: What is the 3 pronged elictrical type plug sticking out, near the back of the fuel rail?? nothing is plugged in it. Should something be?

2: How can I attach a pressure gague on the fuel rail to see fuel pressure?

Thanks
Christian

pikey7

Sorry to be really lazy, but have you tried a search on here for the gauge info? I've seen at least 10 threads!!!

Personally, I've just gone for an Autometer ultralite electronic job. Aparrantly, all you have to do is remove the plug at the end of the fuel rail, tap it, and then fit the guage or adapter!!

Dead easy!

Devildog2067

Hey, when you do that the ball bearing comes out, right?

Perry 951

Yup.

fletch.

I wrote this a few years back....


I recently built a new engine for my 87 944 Turbo; during some of the many days of down time I had waiting for parts, I decided to install a fuel pressure gauge. The gauge was a great deal of help in locating a fuel line leak.

Not long ago when at the track I experienced an intermittent engine shut down. I suspected the throttle position sensor or air box at first. During the two-hour drive home from the track, the problem was got worse. Both the air box and throttle position sensor seemed to be functioning correctly. The fuel pumps and filter were next in line for question.

After running the car, I noticed that the fuel pressure gauge (installed at the end of the fuel rail) would read zero very quickly after I shut the car down. This led me away from suspecting the fuel pump and filter, and I began to focus on a leaky injector fitting on the fuel rail or fuel pressure regulator and dampener.

I decided to start the car, and then shut it down and quickly take a look at the gauge; the second time I did this I heard a air leaking sound. Turns out the fuel line from the tank that mounts into the fuel dampener (line going to the front of the fuel rail) was cracked under the hard plastic cover. I solved the problem, with help from the fuel pressure gauge. Replacing the high pressure fuel line is another of my present concerns (currently in progress and waiting for parts).

Here is how I did it and what I needed.

First come the gauge; I got a 100psi moon liquid filled gauge for thirty-five dollars. Stock fuel pressure is about 28psi at idle, but will bump to 40psi at full throttle before dropping back. If you ever go to an adjustable fuel pressure regulator or bigger injectors, you will want the 100psi gauge. Lower psi readings are available, but I recommend the 100psi. VDO has one as well for about the same money. These gauges have a 1/8th pipe thread (tapered) fitting and are about 1.5 inches across (gauge face). Next, I got a pipe thread drill bit, this is a special size bit; it MUST be a 1/8 pipe thread size bit. It is the same for the tap, the tap must be pipe thread, the same size as the fitting on the gauge: mine was 1/8th. The tap and drill bit cost about twenty-five dollars. You should also have some PTFE (commonly known as Teflon) plumbers tape, about another three dollars.

First mark the top of the nut; this will give you approximate orientation for the gauge. Use a punch or permanent marker. The next step is to release the fuel pressure from the rail. Since my engine was already apart; I did not have to do this. When I did release the pressure, I disconnected the battery, then loosened the nut on the front of the fuel rail. Under that nut is a steel ball bearing; this seals the nut to the fuel rail, and is nice in gently releasing the fuel pressure. As I loosened the nut, the bearing kept the pressure release slow, and I regulated it by tightening or loosening the nut. I stuffed a rag under the nut and let the fuel release slowly. This method does work, but is not recognized by Porsche or any other literature I have read. I recommend this step be done according to Porsche specifications.

Once the nut and ball bearing are off, look inside the nut, there is a dimple that is created by the ball bearing. This dimple is perfect to start the hole because it is centered in the nut. Start the first hole with a very small bit, and work up to the pipe thread size bit. Once the hole is drilled to the pipe thread size, it's time to set up the tap.

Tap from the outside of the nut; use lots of oil (clean motor oil is fine). After every full turn of the tap, back the tap out one-half turn to release the shavings. Go about one third of the total length of the tap, and check to see it the gauge will thread in. You want the gauge fitting to stick out of the inside of the nut a couple of millimeters. The gauge will get tighter as you thread it in, if it does not go in deep enough, tap a little more. DO NOT TIGHTEN THE GAUGE IN ALL THE WAY YET! Do your best to estimate the location of the gauge when tight, make sure your happy with your estimated final location in relation to your reference mark on the nut.


Once your hole is tapped, wrap the threads on the gauge with PTFE thread tape, then install the gauge to the nut. Wrap the threads on the fuel rail with the same tape, and install the nut and gauge to the rail. The ball bearing is not re-installed; it will hit and damage the gauge, the Teflon tape will seal the nut. Now, with luck, the gauge is not upside down; mine was at about a forty-five degree angle. (I can live with that.) Reconnect the battery, and start the car to check for leaks. You're now "Gas-on" with your new fuel pressure gauge. Total cost is sixty-five dollars.

instigator

i was under the impression that you had to drill it off center in order for the gauge to clear the hood (when ever its installed it is supposed to be angled down to avoid this)