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Old 25-02-2018   #1
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Fuel rail pressure testing.

Hi to all,

The car is a 2004 panda 1.2 with 90k miles on it.

The problem is at higher rpm the engine struggles to go faster. Like fuel

starvation. I'd like to do a fuel rail pressure test.

I see there is a schrader valve ( I believe its called ) at the end of the

fuel rail.

I removed the plastic cap on top, now I need to screw in a connector or

adapter into the schrader valve. The inside diameter is around 8mm.

Is there any place that would have this adapter instead of buying the

whole fuel pressure test kit.

Thanks a million.

John.
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Old 25-02-2018   #2
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Re: Fuel rail pressure testing.

Quote Originally Posted by murfman53 View Post
Hi to all,

The car is a 2004 panda 1.2 with 90k miles on it.

The problem is at higher rpm the engine struggles to go faster. Like fuel

starvation. I'd like to do a fuel rail pressure test.

I see there is a schrader valve ( I believe its called ) at the end of the

fuel rail.

I removed the plastic cap on top, now I need to screw in a connector or

adapter into the schrader valve. The inside diameter is around 8mm.

Is there any place that would have this adapter instead of buying the

whole fuel pressure test kit.

Thanks a million.

John.
Hi,
A Schrader valve (same as fitted to tyres) is normally coupled by the threads on the outside. The Panda uses a quick release coupling with a Schrader insert. You need the proper coupler that fits the outside, not someting that screws inside. The only thing that might fit is an airconditioning coupler but the seals may be damaged by petrol. get a garage to check it or buy a chep kit off ebay.

Robert G8RPI.
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Last edited by g8rpi; 25-02-2018 at 12:03. Reason: changed to quick relese
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Old 25-02-2018   #3
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Re: Fuel rail pressure testing.

Should be able to indirectly see if it fuel starvation by logging the upstream O2 sensor.

As it leans out there should be a lower voltage from the O2 sensor


Not saying that this is the problem. A few people have had a problem reving. As they have pressed the accelerator it get to a point and the drops down again. This has been a faulty crank sensor. The quality of the signal is not good enough and the ECU gets confused
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Old 25-02-2018   #4
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Re: Fuel rail pressure testing.

Quote Originally Posted by g8rpi View Post
Hi,
A Schrader valve (same as fitted to tyres) is normally coupled by the threads on the outside. The Panda uses a quick release coupling with a Schrader insert. You need the proper coupler that fits the outside, not someting that screws inside. The only thing that might fit is an airconditioning coupler but the seals may be damaged by petrol. get a garage to check it or buy a chep kit off ebay.

Robert G8RPI.
Hi,

As you say, I need the proper coupler that fits the outside, and not something that screws inside. I'll see what i can find off ebay.
Thanks a million.
John.
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Old 25-02-2018   #5
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Re: Fuel rail pressure testing.

Quote Originally Posted by koalar View Post
Should be able to indirectly see if it fuel starvation by logging the upstream O2 sensor.

As it leans out there should be a lower voltage from the O2 sensor


Not saying that this is the problem. A few people have had a problem reving. As they have pressed the accelerator it get to a point and the drops down again. This has been a faulty crank sensor. The quality of the signal is not good enough and the ECU gets confused
Hi,

I've checked the upstream 02 sensor, and checked the short and long term

fuel trims, and the result is that its running on the lean side. Used a smoke

machine to see if any vacuum leaks, but all is good.............no leaks.

My logic is either too much air (which doesn't appear to be the case)

or, not enough fuel to injectors ( hence, my interest in checking fuel rail

pressure). Never considered the signal quality to the ecu from the crank

sensor.

Thanks for your reply.

John.
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Old 25-02-2018   #6
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Re: Fuel rail pressure testing.

Quote Originally Posted by koalar View Post

As it leans out there should be a lower voltage from the O2 sensor
Higher voltage.

It's the heat that causes the sensor to generate a small voltage.
The leaner the engine, the hotter the exhaust gas, so the voltage of the O2 sensor rises.

A car in good order will average out a reading of 0.45v or there abouts. (they peak and trough 0.9 and 0.1V about once a second at idle)
Lean the mix out and it increases, enrichen it and it drops.

But

Overall fuel status will cause it appear to be running the opposite (confusing I know).
It'll be trying to dump extra fuel in to compensate for the lean signal and take fuel away to lean out a rich signal, so the fuel trims are reverse.

Before diving in the deep end, swap the O2 sensors over, they are both the same.
I've had a duff O2 in the past and it caused similar issues and it didn't cause a DTC.
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Last edited by Goudrons; 25-02-2018 at 18:35.
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Old 26-02-2018   #7
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Re: Fuel rail pressure testing.

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Old 26-02-2018   #8
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Re: Fuel rail pressure testing.

Quote Originally Posted by Goudrons View Post
Higher voltage.

It's the heat that causes the sensor to generate a small voltage.
The leaner the engine, the hotter the exhaust gas, so the voltage of the O2 sensor rises.

A car in good order will average out a reading of 0.45v or there abouts. (they peak and trough 0.9 and 0.1V about once a second at idle)
Lean the mix out and it increases, enrichen it and it drops.

But

Overall fuel status will cause it appear to be running the opposite (confusing I know).
It'll be trying to dump extra fuel in to compensate for the lean signal and take fuel away to lean out a rich signal, so the fuel trims are reverse.

Before diving in the deep end, swap the O2 sensors over, they are both the same.
I've had a duff O2 in the past and it caused similar issues and it didn't cause a DTC.
I was thinking along those lines, and I replaced the 02 sensor. It made

alittle difference, but didn't cure the problem. I'm convinced its a lack of

fuel is my issue, I could be wrong, but a fuel rail pressure test will tell me

one way or the other. My long term fuel trims are at 69!!!! So with these

type of figures its something fairly major.

John.
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Old 26-02-2018   #9
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Re: Fuel rail pressure testing.

Thanks for this link. Interesting read alright. This car too has a square oil cap.

The systems I have would be slightly different in that I can reach higher rpms

but I must not overlook the crank positioning sensor.

John.
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Old 26-02-2018   #10
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Re: Fuel rail pressure testing.

The Latest,

I finally concocked a connection to the schrader valve on the fuel rail.

Rigged up the pressure gauge, then switched on the ignition.

The dial went to..............18 psi. And when the petrol pump motor finished its

cycle ( about 3 seconds ), and switched off, the dial on the pressure gauge returned

to zero immediately.

Firstly,I'm not sure of the panda fuel pressure spec, but 18psi seems very low, when

considering earlier punto fire engines were at and around 40-45 psi.

Secondly, once the pump switches off the pressure should remain there for sometime.

Is there a check valve in place along the input line, or in the petrol tank somewhere.

I honestly don't know to be honest.

Should I consider the pump motor has had it, and get another one instead.

I may have stuck open injectors, which might account for poor fuel consumption.

If I have to buy a petrol pump motor, is it possible to purchase the motor only.

John.
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Old 26-02-2018   #11
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Re: Fuel rail pressure testing.

Info here
Attached Thumbnails
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Old 26-02-2018   #12
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Re: Fuel rail pressure testing.

Quote Originally Posted by koalar View Post
Info here
Thanks for the info. Looks like all the interesting devices are located in the

tank.

You wouldn't happen to know the operating fuel rail pressure?

I suspect between 40 to 45 psi. Not 18 psi which this car shows.

The pressure regulator looks like one of the goodies in the tank.

If I knew the proper pressure then I'd know my next step.

The punto is basically the same engine, must have a look over there.

Keep looking.............name of the game!

John.
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Old 26-02-2018   #13
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Re: Fuel rail pressure testing.

3.5 bar
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Old 26-02-2018   #14
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Re: Fuel rail pressure testing.

Quote Originally Posted by koalar View Post
3.5 bar
Thanks for the info koalar.

Looks like the issue is with the pump seen better days. My guess would be that

its unable to hold pressure at all, because of contamination to the pressure

regulator or its non functioning.

At 3.5 bar (50 psi), is a big difference to the actual reading of 18 psi

(1.24 bar).

Whip out the pump tomorrow, and get a closer look at it in detail.

Again, thanks koalar for the info, much appreciated.

I'll keep all up to date on the progress.

John.
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Old 28-02-2018   #15
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Re: Fuel rail pressure testing.

Hi,

The latest,

Removed the fuel pump relatively easy enough, although the outer locking ring was

tricky but came loose after a little patience. Must make up a plywood outer ring

template with notches cut out on the inner diameter, so when its time to put back

in place the template will make tightening process easier.

https://www.ebay.ie/itm/173041704720...m=173041704720

I came across this fuel pump, not an original, an after market, but that doesn't worry

me at all. Comes with a 2 year Warranty. The one I took off the car is a carbon copy.

Second hand ones here, if you're lucky enough finding one is selling between 70-85

euros. Apparently, its a common fault on the panda......fuel pump fails. I'll wait until

it arrives, put it in place, check fuel pressure, and run it for a week. If all is ok, I'll

get another one, as I drive a 2007 1.2 skydome panda myself. At that price you can't

go wrong.
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