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89 930.
 
Benny771's Avatar
 
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Lightbulb Fuel pressure test video.

Found this on you-tube. It appears to be quite good for someone who wants to test their own pressures.
Hope it helps.

Porsche 911 Turbo CIS Pressure Testing - YouTube
Old 09-07-2011, 08:36 AM
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Good video...takes the mystery out of a simple procedure.
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Old 09-07-2011, 09:32 AM
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He forgot an important step.

After turning on the fuel pumps and before taking a pressure reading you're supposed to push in the button under the gauge to purge the air out of the line leading up to the gauge. They put that there for a reason and if you skip that step you won't get accurate pressure readings on the gauge.

You can see the aluminum push button to let the air out of the line in the aluminum block just below the gauge and his gauge is a fancy expensive one that has a clear poly vinyl vent hose coming out below the button so you don't get gasoline all over your hand and on the motor while holding the button down and letting the air purge out.

Some gas squirts out once all the air is purged out of the gauge hose so that clear bleed hose is a nice safe feature.
If the gauge doesn't have a bleed hose rap a rag around it to absorb the gas while pushing the button
Old 09-07-2011, 09:56 AM
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very good,, that should be a sticky on the top of the board
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Old 09-07-2011, 10:29 AM
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Good catch, Jim.
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Old 09-07-2011, 01:21 PM
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Quote:
Originally Posted by JFairman View Post
He forgot an important step.

After turning on the fuel pumps and before taking a pressure reading you're supposed to push in the button under the gauge to purge the air out of the line leading up to the gauge. They put that there for a reason and if you skip that step you won't get accurate pressure readings on the gauge.

You can see the aluminum push button to let the air out of the line in the aluminum block just below the gauge and his gauge is a fancy expensive one that has a clear poly vinyl vent hose coming out below the button so you don't get gasoline all over your hand and on the motor while holding the button down and letting the air purge out.

Some gas squirts out once all the air is purged out of the gauge hose so that clear bleed hose is a nice safe feature.
If the gauge doesn't have a bleed hose rap a rag around it to absorb the gas while pushing the button

Ok, Ive never understood that. Why clear the line?
If fuel is pushing/compressing air at 60lbs is the air pressure not 60lbs? I could see a slightly slower reaction time but it still would quickly even out?
Am i wrong?
Old 09-09-2011, 02:08 PM
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Quote:
Originally Posted by Benny771 View Post
Ok, Ive never understood that. Why clear the line?
If fuel is pushing/compressing air at 60lbs is the air pressure not 60lbs? I could see a slightly slower reaction time but it still would quickly even out?
Am i wrong?
I'm not an engineer so I can't answer that.

Any air bubbles being compressed in hydraulic brake lines reduces pressure at the calipers along with making the brake pedal spongy so you're supposed to bleed the brake lines to get them out, maybe there's a relation there?

All bosch k-jetronic/CIS fuel pressure gauge kits have the air purge button just below the gauge for that reason and the instructions say to purge the air out of line going to the gauge before taking pressure readings so it must be important for an accurate reading.
Old 09-09-2011, 02:22 PM
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Always thought that the "button" was just to let the fuel out that found its way in... bleeding the line.
Old 09-09-2011, 04:13 PM
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When the pumps are running, the injectors are squirting, right? I've always wondered how much fuel is dumped into the intake ports during a pressure test, and how long you should let the engine sit before starting it up to let it evaporate.

Thoughts?
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Old 09-10-2011, 07:58 AM
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Quote:
Originally Posted by PrimeMvr View Post
When the pumps are running, the injectors are squirting, right? I've always wondered how much fuel is dumped into the intake ports during a pressure test, and how long you should let the engine sit before starting it up to let it evaporate.

Thoughts?
No, the injectors dont squirt by just having the pumps run. Pressing on the metering plate will make the injectors squirt.
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Old 09-10-2011, 08:30 AM
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No fuel sprays or drips from the injectors while only the fuel pumps are running as long as the airflow metering plate is at rest and it's height is adjusted correctly in the middle of the cone. If they drip even the slightest amount there's something in the fuel head is wrong and leaking, or the sensor plate is out of adjustment or stuck.

You may doubt what i'm saying so do an injector flow test on your car to confirm that. Every old CIS car should have that done periodically to see if the injectors are clean, the spray pattern is good, and they all flow equally or very close to it. If two injectors flow a little more than the others put them in the #2 and #5 injector blocks.
Old 09-10-2011, 08:41 AM
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Good info thanks. Full CIS tuneup is planned for the winter as I can't get cruise afr over 12.6 or on boost over 9.5. BL WUR is planned along with a boost solenoid. Have a great weekend guys!
Old 09-10-2011, 09:32 AM
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Quote:
Originally Posted by PrimeMvr View Post
Good info thanks. Full CIS tuneup is planned for the winter as I can't get cruise afr over 12.6 or on boost over 9.5. BL WUR is planned along with a boost solenoid. Have a great weekend guys!
Wow, she be drinking fuel at those AFR's. Something aint right. An adjustable WUR is a nice thing to have, but it won't fix your rich problem unless it's the result of your current WUR being FUBAR. Stock WUR's do a pretty good job controlling fueling for a stock car. But if a person is to replace the WUR, then by all means go with an adjustable one.
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Old 09-11-2011, 12:32 PM
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I believe my wur to be fubar because it's gotten progressively worse. I'll take it apart when summer driving season is over.
Old 09-11-2011, 02:52 PM
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I have stupid Question , can any of these tests be done with the car running?
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Old 11-29-2011, 06:32 AM
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Quote:
Originally Posted by heliolps2 View Post
I have stupid Question , can any of these tests be done with the car running?
No tests i have seen have the car running. They are all off, enging hot or cold (2 different tests).
Old 11-29-2011, 06:53 AM
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Originally Posted by heliolps2 View Post
I have stupid Question , can any of these tests be done with the car running?
With a CIS pressure gauge kit connected in series with the control pressure line leading to the WUR and the ball valve open you can check control pressure while the motor is running.
If you close the ball valve to check system pressure in the WUR control pressure line the motor will go way lean from hydraulic control pressure raising way up and equaling system pressure and it will shut off or stumble alot and barely run from being way too lean but you'll get the system pressure reading as long as the pumps are running.

With the same CIS pressure gauge connected in series between the front and rear fuel pumps at the rear fuel pump inlet (same compression fittings as the WUR) like is being described in this picture with the ball valve open you can check the fuel pressure from the front pump while both pumps and the motor is running. Remove the rear fuel pump relay so only the front pump is running and you'll get an idea how well the rear pump is working but not the actual fuel pressure from both pumps running together at the same time.


Close the ball valve and the motor won't get any fuel and it will shut off but you'll get the static fuel pressure reading from the front pump while no fuel is going to the fuel head and being returned to the tank by the fuel head system pressure regulator or squirted out the injectors while the motor is running.
Old 11-29-2011, 07:34 AM
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