Fuel pressure questions ? - Saxperience

citroensaxo · 11th September 2014, 21:02

Dear All,
Firstly, some very kind person ( from this forum

) has said that I need to check the fuel pressure on the Saxo, with reference to the car not starting very well and not running to much better either.
Secondly, would I be right in saying that to check the fuel pressure you need to remove the very small phillips screw ( thats used as a blank off ) in the three pronged black rubber pipes that fit right next to the fuel pressure valve ? and that the pressure should be 50 psi/3.5 bar too ?
Thirdly, all the kits that I can find, ( although they aren,t cheap ) they all seem to have some sort of " schrader " valve set up and that is how they are connected to the fuel rail somewhere. could anyone kindly point any out that would be suitable for testing the Saxo

Another question is that I have made a length of plastic hose to act as a gradual increase in diameter, will this be a correct way of carrying out this task, or does the pipe have to be all of the same diameter as the pipe is quite small. Would the gradual increase in the testing pipe diameter affect my pressure readings ?
Many Thanks indeed

Vince,

jbrady72 · 11th September 2014, 21:12

Just get this and it'll be piece of piss
http://pages.ebay.com/link/?nav=item...d=181210733935

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oxass · 11th September 2014, 23:09

There should be a schrauder valve on one end of the fuel rail is the engine managment magnetti morreli or bosch?
If the car is drivable a local garge should beable to test the fuel pressure it's a 2 minute job so it should not cost more than £10.
Has the car had a diagnostic scan?

citroensaxo · 13th September 2014, 20:09

Dear Jbrady72,
Firstly, thank you so very very much indeed for your very kind reply

Secondly, today I took out the air filter assembly completely to try and find this schrader valve

sadly there doesn,t appear to be one fitted on anywhere on the fuel rail

Thirdly, I have saved the special tool on my favourites on ebay

and thank you very very much indeed for your very kind advice

Many Thanks,
Vince,

jbrady72 · 13th September 2014, 20:20

If your fuel rail has the fpr in it then it won't have the schrader valve. Just use the little t piece to put it in the pipe going to the fuel rail and measure the pressure

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citroensaxo · 13th September 2014, 20:54

Dear Oxass,
Firstly, thank you very very much indeed for all of your great help and advice too

Secondly, you are absolutley " bob " on

it is a magetti marelli E.C.U management system

Thirdly, I have taken the air filter assembly out today but sadly no schrader valve that I can find on the fuel rail

Fourthly, the Saxo is an automatic and at present runs so badly that the car wouldn,t make to our local garage ( even though it is only 4 miles away ).
I remember you asking before if the car has been diagnostically scanned

but no it hasn,t. Unfortunately the people we take the cars to for their M.O.Ts have never heard of a Lexia

Plus also even with all the problems we have had on the Saxo, it has never once had the management light on at all

and it isn,t on either

Many Thanks indeed for all of your invalueable kind help and advice

Vince,

stevo67 · 13th September 2014, 21:57

I believe and sorry if i'm wrong that the fuel pressure regulator on later saxos is on or next to the fuel pump.

oxass · 14th September 2014, 00:27

Hi Vince even if the management light is not showing it is still possible to run diagnostic test with a scan tool the can read live data but this would need to be compatible with your management system.
For example you could monitor the fuel trim,maf sensor,tps and the o2 sensor so if the throttle is wide open and the o2 reads lean this will be a fuel issue or a maf issue however by monitoring the maf frequency you can diagnose if the maf sensoor is good or bad also with some scan tools it is possible to measure fuel pump rpm.
Try the following tests
1) Does the car run better in neutral?
2) If you have a multimeter measure the pump current it should be at least 6amps and should spike on initial startup.
If you get a fuel pressure guage the following will apply.
Drop in pressure when throttle is snap tested = faulty fuel pump,fuel regulator or fuel filter.
If the fuel system is working properly you should see a rise in fuel pressure when the throttle is snap tested.

oxass · 14th September 2014, 08:14

The current draw of these pumps should be 4 amps not 6 amps.

citroensaxo · 14th September 2014, 14:55

Dear Stevo,
Thank you so very much indeed Steve for your very kind reply

Firstly, as far as I can see Steve, the fuel pressure regulator is on the end of the fuel rail right next to the no1 cylinder plug lead ( the one nearest to the flywheel and the coil pack ) and it has 3 of very small bore black rubber pipes fitted to it ( one of which is the one that has the very very small phillps screw used as blanking off. ) This is the pipe that I feel that this should be the one that I need to be fitting the fuel pressure tester to

Would that be correct Steve ?

Secondly, the fuel pump on Nats Saxo is a VDO unit that is fitted in the top of the petrol tank. Would that be correct Steve ?

I am still tying to get my head around all this

Many thanks indeed Steve you are most kind

Vince,

citroensaxo · 21st September 2014, 15:03

Dear Oxass,
Firstly, Thank you so very kindly for your invalueable help and advice

Secondly, please accept my apologies for not replying sooner

it just took me quite a while to make sure that I was doing the checking " correctly "

With regards to your question 2, the checking of the amperages readings from the 4 pin connector on top of the fuel pump ( when I had the multimeter set on 5 amps, I got no readings at all. ) So I switched the multimeter to read 20 amps

and I got the following readings

on all 4 wires. They started at about 7A 8A 8A and 9Amps and then they spiked upon starting upto 15A and they ranged from that upto 30A. Is that the readings that I should expect ? or are these from a not very well fuel pump ?
With regards to your question 1, No the car will satisfactorily go through all the gears without any change to the running of the engine.
The " only " thing that will make the engine run any better, is if I disconect the jubilee clip that holds the air filter assembly and create a gap to the throttle body. The air filter element is quite grubby and definately needs a new, so I have removed it out of the eqation and refitted the air filter assembly and now the engine is back to running poorly again

I will be renewing the fuel filter next.
Many Thanks Indeed for the kind advice

Vince,

stevo67 · 21st September 2014, 16:37

With regards to the fuel pump,give it a tap then put back in the tank.if the car runs better then it's likely to be the pump at fault.

oxass · 21st September 2014, 16:57

Hi Vince sorry i forgot to mention that the reading was taken from the number 9 fuse in the main fuse box under the bonnet.
Try the test again from the number 9 fuse if they are as high as your first test this may suggest the pump motor is under more load and as you have sugested a new fuel filter would be a wise move.
It is very odd that the reading spiked at 30 amps as the fuse has a 10 amp rating I'm not sure what the awnser is to that.
I will have a look for the specifications of the said pump motor to see if the manufacture gives details of current draw.

citroensaxo · 26th September 2014, 21:01

Dear Stevo
Thank you very very much indeed for your kind advice Steve

I havn,t thought of doing that

I think it may have to be my next move most probably Steve.
Today I fitted a brand new air filter element as it needed a new one anyway and I also fitted a new fuel filter too. But to avail

Many Thanks Steve

Vince,

citroensaxo · 26th September 2014, 21:36

Dear Oxass,
Firstly thank you so very very much indeed for all your invalueable advice

Over the last few days I have been taking amperage readings from F9 as you so kindly advised

three times a day I have been taking readings and they as follows;- 1st day it was 1.72 A, 2.73 A and 2.24 A. 2nd day it was 2.26 A, 2.50 A and 2.34 A. 3rd day it was 2.50 A, 2.70 A and 2.34 A. And today it was 1.63 A, 1.59 A and 1.62 A, all taken whilst the engine was cranking so as to start the engine normally.
I fitted a brand air filter element as it needed a new one anyway and I also renewed the fuel filter aswell

But still no difference.
The only thing was that I noticed today that the fuel gauge seems to be playing up aswell now, the car tries to startish and the fuel warning comes on as it should do, but then after a few seconds the needle just starts to rise and continues on up to full and then it comes back down again and the gauge does this 3 times every time you turn the ignition on, doesn,t do again if you leave the ignition on.

So it must be looking like the fuel pump may be the problem do think ?
Many Thanks

Vince,

oxass · 27th September 2014, 15:48

Hi Vince the readings you have taken from f9 are very low and would suggest an issue with the fuel delivery.
I think the wiring and associated connectors and relay should be investigated first before condemming the fuel pump.
Also is the fuel guage sender integral to the fuel pump or is the earlier model with a seperate fuel sender?
The location of the fuel pump earth e8 is on the right hand C pillar.
The instrument cluster earth e2 is on the base of the left hand A pillar.

VeiRoN · 27th September 2014, 19:37

Quote:

Originally Posted by citroensaxo

Dear Oxass,
Firstly thank you so very very much indeed for all your invalueable advice

Over the last few days I have been taking amperage readings from F9 as you so kindly advised

three times a day I have been taking readings and they as follows;- 1st day it was 1.72 A, 2.73 A and 2.24 A. 2nd day it was 2.26 A, 2.50 A and 2.34 A. 3rd day it was 2.50 A, 2.70 A and 2.34 A. And today it was 1.63 A, 1.59 A and 1.62 A, all taken whilst the engine was cranking so as to start the engine normally.
I fitted a brand air filter element as it needed a new one anyway and I also renewed the fuel filter aswell

But still no difference.
The only thing was that I noticed today that the fuel gauge seems to be playing up aswell now, the car tries to startish and the fuel warning comes on as it should do, but then after a few seconds the needle just starts to rise and continues on up to full and then it comes back down again and the gauge does this 3 times every time you turn the ignition on, doesn,t do again if you leave the ignition on.

So it must be looking like the fuel pump may be the problem do think ?
Many Thanks

Vince,

Hi,for the fuel gauge issue it might be helpful to have a look here for a possible fix.

http://www.saxperience.com/forum/sho...67#post4481167

citroensaxo · 13th October 2014, 20:05

Dear Oxass,
Firstly, thank you so very very much indeed for all of your invalueable help and advice

Secondly, sorry for my late reply

as I wanted to try and double check all of the work I have been carrying out on the Saxo

Today I fitted a new fuel pump relay and still unfortunately no change, so then I re carried out an electronic reset of the throttle position sensor but with no change either. The car is still running rhubarb.
Today I did check the amperages on F 9 again and I had the following readings 1.77 A and 1.82 A.
Today I also renewed the battery as it had died a death

One thing that has been bothering me is that with the old battery and with the new fitted, I have a voltage reading on the battery terminals of 12.30 V but on the ignition feed wire on the fuel pump under the rear seat I only have a reading of only 11.26 V ?
One other thing I did today was to disconect the cat to rule that part out.
With regards to your question about the fuel sender as of yet I haven,t disturbed the fuel pump at all so I don,t know what type is fitted at this precise moment ?
With regards to the fuel pump earth on the inside rear quarter panel, do I need to remove the interior panel completly to gain access to it

?
Many Thanks indeed

Vince,

citroensaxo · 13th October 2014, 20:20

Dear VeiRoN,
Firstly, thank you so very very much indeed for your very kind advice

Sadly, the only wire that rectified the fuel gauge problem ( when I connected to an earth ) was the ignition feed wire, which unfortunately kept on draining the battery over night

Many Thanks indeed

Vince,

oxass · 14th October 2014, 16:45

Hi Vince the fuel pump and the fuel sender share the same ground (e8) which is the one on the right side of this picture http://www.saxperience.com/forum/sho...d.php?t=355940
Have a good look at this connection if it is a good ground disconect it and continuity test it with the earth wire on the pump and the fuel guage sender.
Also you could do a loaded circuit test on the pump by removing fuse f9 and running a fused jumper wirefrom the battery to power up the pump and take a reading from earth point e8 if the ground is good the reading should be 300-400mv.
The current on the pump circuit is still very low i doubt 1.8 amps is enough for the car to run properly.
Also check the connections on the inertia switch on the nearside suspension turret andground (e9) on top of the gearbox which earths the injection relay and the ecu.