3.2 Carrera Fuel Rail Pressure Testing

[steve84]

Has anyone actually measured the fuel pressure on a 3.2 Carrera at the test port on the end of the driver’s side fuel rail? Yesterday, I was finally able to remove the cap over the male threaded test port, which was substantially tighter than the 9 ft-lbs specified in the Bentley’s Manual. I previously bought a Betooll Pro fuel injection pressure test kit from Amazon and none of the female threaded adapter connectors fit the male-threaded test port on the fuel rail. So, for those of you who have actually measured the fuel pressure at the test port, I’d greatly appreciate hearing what you used to do so. Thanks in advance.

Steve

[boyt911sc]

Originally Posted by steve84

Has anyone actually measured the fuel pressure on a 3.2 Carrera at the test port on the end of the driver’s side fuel rail? Yesterday, I was finally able to remove the cap over the male threaded test port, which was substantially tighter than the 9 ft-lbs specified in the Bentley’s Manual. I previously bought a Betooll Pro fuel injection pressure test kit from Amazon and none of the female threaded adapter connectors fit the male-threaded test port on the fuel rail. So, for those of you who have actually measured the fuel pressure at the test port, I’d greatly appreciate hearing what you used to do so. Thanks in advance.

Steve

Steve,

You will need a pressure gauge with 12-mm x 1.5 pitch to do a pressure test at the fuel rail test port. The standard CIS gauge has this fitting.

Tony

[steve84]

Thanks Tony. My Betooll kit does have a separate set-up for CIS testing and I’ll take a look at it when I get home later today. Last night I search around for the Porsche special tool P378 mentioned in the Bentley’s Manual and came across the M12x1.5 dimensions you just mentioned. From Amazon, I then ordered several different adapters having M12x1.5 female threads at one end and varying sized NPT male threads on other hand. This morning, I started to have doubts about the usefulness of those adapters. Thanks again

[steve84]

Good morning Tony and thanks again for the advice. I used the CIS test rig with the two 12Mx1.5 female connectors that came with my test kit, with the isolation valve closed on the line not connected to the test port. With the engine not running and DME sockets 30 and 87b jumped, I measured 38 psi and 2.6 bar. So the fuel pump works and fuel pressure is within spec for that mode.

I then switched off my jumper and the pressure dropped as follow: 34 psi/2.4 bar (5 minutes); 33 psi/2.3 bar (10 minutes); 32 psi/2.2 bar (multiple readings over next two hours); and 30.0 psi/2.1 bar (@3 hours after toggling off jumper). I haven’t seen any spec’s on retaining pressure in Bentley’s Manual. Do these readings indicate that FPR is good?

Later in the evening, I attempted to do the test again and see if reading are the same. Before turning the jumper back on, I depressed the pressure relief button on the gauge and there was a puff, but no release of fuel in the release tube, and the gauge zeroed out. I then turned on the jumper and heard the fuel pump working but 0.0 pressure shown on gauge. I then opened the isolation valve on the CIS test rig and fuel freely flowed out of the non-connected end, showing that the fuel pump was working and fuel was getting to the pressure test port on the rail. Right now, my hypothesis is that the cheap gauge from Amazon crapped out. Any suggestions? Thanks in advance.

[boyt911sc]

Find a good and reliable pressure gauge kit. The results from the first test were OK. And should be reproducible to be valid.

Tony

[dtwa]

I saw similar behavior at the test port on my 85. Usually correct, or close, but sometimes zero or very low in static tests (w/o the engine running).

I didn’t trust my cheap gauge at first. Then I tested the pressure upstream of the regulator (at the fuel filter outlet) and saw something like 60psi when the test port said zero.

I replaced the fuel pressure regulator and no problems since. Not saying that is the problem here, but it is worth considering.

—Dave


Sent from my iPhone using Tapatalk

[steve84]

Thanks for your comments/suggestions Tony & Dave. I bought a new Maddox Deluxe Fuel injection service kit, which has a separate 12Mx1.5 adapter, so I didn’t have to rely on the double-ended CIS rig. I measured 36 psi with engine off and DME sockets 87b and 30 jumpered. With the jumper toggled off, the fuel pressure dropped to: 35 psi (immediately), 34 psi (5 minutes), 32 psi (10 minutes), 31.5 psi (20 minutes), 31 psi (30 minutes), and 29 psi (45 minutes - 2 hours). So, fuel pump and FPR seem to be ok.

I tried to start engine but it continues to only crank and no start. I tried some starting fluid but same result. While cranking, I noticed that the tachometer didn’t move at all, which suggests that the problem lies with the speed/reference sensors.

[BoxsterGT]

For future needs, I have this M12 Hose Nipple & Nut.....



...available, and I ship by Priority Mail.

Please email only...len.cummings @ Verizon.net

[wazzz]

Was wondering, when checking pressure with a test rig connected to test port, do you need to remove the ball that's covered by the plug?
Asking this because I once removed the plug when refurbishing my intake and fuel lines and the ball was stuck inside. No way to grab it.
Sorry to the OP for trolling this. Thanks!

[BoxsterGT]

Cannot test Fuel Pressures unless that Ball can be removed.

Only way I can think of to release this ball is with Pressure from within along with some heat. Perhaps loosen the Cap Nut and leave this in place, then add pressure & heat.

This could be dangerous, so be careful.

Good luck.

Len

[wazzz]

Thanks! Will try next time I need to remove ramp.

[BoxsterGT]

This means removing the fuel rail from vehicle and connecting hoses to pressurize with water.

Do NOT leave in place and try with fuel !!

Len

[FA-18C]

Wazz, mine was stuck, I removed with small Vice grips. Over time the ball had worn a groove. Replaced after testing everything.

[steve84]

Wazz, I agree with everything Len just posted. Here’s a picture of the inside of the 12Mx1.5 adapter and you can see there’s a spherical element with a passage through it which would hold your ball in place and not allow it to be freed by fuel pressure during test.

[wazzz]

OK thanks to you all. Len don't worry, I have no plans to pressurize with the rail still in place. I'll do it with water or air or try the vice grip method next time I need to remove the rail, which should not happen soon I hope.