93 V6 fuel pressure release.

[sgould]

I've been playing with the fuel pressure sensor today as the P0089 code has returned.  It's the third time in the last few years.  I've found that running neat fuel cleaner through the fuel rail seems to work. 

However, access is via the fuel pressure sensor in the line.  There's a Schrader valve adjacent to the sensor.  I released the fuel pressure via the valve.  Pressed it several times and there is no pressure and no release of any more fuel.  But when I take the sensor out, fuel sprays everywhere.  I'm puzzled.

[carrera]

I say your 2020 UKS thread and the video also linked there, then looked at WIS.

Do you have the kit to do the pressure checking with Tech II ?

I note in the instructions there is a mention of "unsecuring" and "safety on" with the adapter. Perhaps it isn't a simple Schrader valve & there is someting on the adapter that allows the valve to operate to be able to read pressure.... to stop people like me & you simply depressing it to get sprayed in fuel 

Rather than the multiple cleans, why not simply soak the sensor in a bath of fluid. I would be tempted to carefully clean it as well. Nothing stronger than a finger tip, so long as the fluid doesn't irritate you.

As to system cleaners, the best is Forte, last time I looked it was about £25 for a bottle, so probably £35 now, it's what the up market garages use, because it works

Final point. In the testing there are references to having a minimum fuel level of 12% and the DTC being set when you run out of fuel. I seem to remember you have a fuel gauge problem as well, perhaps one fault is falsely triggering another ?

[sgould]

Now it's a bit warmer and my fingers are working a bit better, I will investigate the two fuel level sensors.

But the P0089 code for fuel pressure error is recurring and was happening well before the level sensor failed.

It's difficult to pin down.  The word on the forums (mainly American) is that the fuel pump is failing and that you need to drop the tank and replace the pump.  But I was dubious that it was the cause as the car ran well on full throttle without any hesitation. And has done so in the 5 years since it first occurred  At first I thought it was the sensor.  A new one seemed to fix the problem, but it returned after 6 months.  The sensor is closed off and is easily wiped clean, but actually shows no sign of any coating.

Then someone else suggested cleaning the fuel rail.  I tried that and the light went out - again for about six months.  The last time the engine light came on I cleared it without doing anything and it stayed off for several months.

I'm inclined to think that there's a short intermittent fault.  I have run a pressure test on a drive with both Tech2 and CarScanner and the pressure stays high.  It's not constant on the V6 as the pump is controlled by the ECU and varies the fuel pressure depending on demand.

Since the fuel rail cleaning seems to work, I'm thinking along the lines that there's a deposit of fine particles nearer the  far end, and maybe they break off and briefly prevent an injector closing, reducing the fuel pressure momentarily.  I would take out the rail and clean it properly, but it's quite an involved process on the V6.

[carrera]

I was thinking along the lines of two independent failure modes, but from you decription, but perhaps the main one is nothing more than an irregular sensor result.

From reading around, it seems that this issue does only occur at start up or shut down. Does your scanner app have a logging capability so you can "see" the DTC being thrown ?

I see where you are coming from on the injector. That could be dirt, or simply a "sticky" injector, in which case perhaps clearing the code and 1/2 tank of fuel plus Forte might just do the trick

https://www.forteuk.co.uk/product/petrol-specialist-injector-cleaner/

You can get this, along with the general system cleaner for £25 on ebay

[sgould]

I'll put the investigation on hold for a few days.  As the level sensor only fails to read when the tank is over ¾ full, I planned to check a reading at the connectors behind the left hand headlamp.  There's a 10 pin and a 24 pin shown beside the battery.

Two things have stopped me.  Firstly I can't see any connectors where the WIS shows them.  They may have been moved as that area has the control box for the swivelling headlamps.  Secondly, the fuel in the tank was high enough yesterday evening for the gauge to show zero.  Today the level seems to have dropped a teaspoonful in refilling the rail and the gauge is reading correctly, so there's no failed circuit to find. Frustrating...

I'll just have to wait for the next tankfill.  I know that i could go and do it now, but I resent driving a six mile round trip to Tesco for two gallons. 

But a bottle of Forte wouldn't hurt.   But after messing about with the sensor yesterday evening, I cleared the code and it hasn't returned.  I can record the fuel pressure with CarScanner and save the graph.  I will try that, but it will be a bit hit and miss as it's not the car I usually drive, so it won't be monitored all the time.

[carrera]

I'll put the investigation on hold for a few days.  As the level sensor only fails to read when the tank is over ¾ full, I planned to check a reading at the connectors behind the left hand headlamp.

Seems to indicate that one of the rheostats has dead spots at the top of the range ??

[sgould]

That's my assumption, but to add a bit of confusion, SWMBO was out at her concert last night and the gauge dropped to empty again.  So either the heat of the sun has expanded the fuel, or the level sensor has failed completely.  She has been using the car, and needs it tomorrow, so it may be a while before  I can investigate further.

In the meantime the 9-5 is playing up.  Erratic starting.  Starts and misses, then stalls, try again and it'd fine.  Hopefully not the CPS, that's barely a year old.  No codes.

[sgould]

Had a brief go at the 9-3 fuel pressure. Bit of an odd one.  I cleared the codes with the "Car Scanner" and got the option to "Clear found codes" and "Clear all codes".  That may have been a mistake as the car refused to start.  All the sign of a flat battery.  I attached the booster pack and it started straight away.  The green indicator on the battery is there and turning the car off and trying to start on the battery alone was fine.  It must have confused something.  Hopefully just a fright.

Another oddity is that the CarScanner picked up a code for the failed fuel level sensor which Tech2 didn't.  It's P0463.  WIS says "Fault in wiring or component", which I had already surmised.  The engine light and code returned after a day.

But the codes are cleared and the engine light has stayed off for now.

[aerojon]

The green indicator on the battery is there

learnt long time ago they mean squat,as it only covers one cell..

[sgould]

I put the battery tester on the battery and it said "Bad - 23%", but I'll check it again after a run as the tester requires a fully charged battery, and I'm not sure that it is.  If it is bad, it's not quite 4 years old and it has a five year guarantee,

I've dismantled the fuel pressure sensor again.  The engine light stayed off this morning, but came on on the way back home at lunchtime.  I had no problem with the fuel pressure release, not much fuel came out of the valve and none when I pulled the sensor out. More oddness.  I've left a slug of fuel system cleaner in overnight as it started to rain again...

I cannot find the connectors at the front for the fuel level sensor.  There's nothing that looks like the WIS.  I'll have to go in under the back when i can guarantee a warm few days.

[sgould]

I have found the connectors on the front wing for the fuel level sensor wiring.  But, sadly, I feel it's too risky to have go at splitting them. 

They might be more accessible if I take off the bumper and remove the LH headlamp.  The connectors are low down, fixed to the inside of the inner wing, under a lot of loom, and bits of the loom are clamped and tied down.  It could be done, but I took the battery tray out for access, and it showed that a lot of the plastics are now very brittle.  The battery tray was easy as the battery is dead and was out of the car anyway.

I think it's the first time I've needed a T40 Torx screwdriver!

Picture of the 24 pin connector, looking straight down. usually hidden by the battery tray...

[aerojon]

are yes the good old H24 or H42 connector,designation dependant on MY..

[carrera]

, and it showed that a lot of the plastics are now very brittle. 

That reminds me of testing for current on the auto gearbox on the 9-5. I have found that with some WD40 and the right size screwdriver in the groove at the top of the red securing clip these connections do usually give in to gentle persuasion.

I suppose the alternative is to measure the values at the ECU.... but of course if there is a problem, you then need to disagnose where, and while you really don't want it to be in the loom, the alternative seems to be a tank out job

[sgould]

There is supposed to be an accessible connector in front of the tank.  That’s my only hope for a DIY diagnosis.  Once (if) I have pinned down which sensor is damaged, I’ll probably get the garage to fix it.  It’s due a service/MOT by the end of June and they will be around the back of the car as the rear Haldex is due a service and clean out.

New battery this morning.  Halfords were closed by the time I got there, due to a road closure, diversion and subsequent traffic jam.

[carrera]

I have looked again at WIS and the wiring diagrams.

Connector H10-3 "should" be visible and possibly testable, depending on location.

While searching for a photo or something to assist, I came across this https://www.youtube.com/watch?v=_5eOlhrC-gM which may be of interest. At least it doesn't have images of the rear seat floor being cut to get access to the pump. Final comment may be of interest.

Perhaps the best route forward is to fill the car up again (to replicate the problem) and then measure the readings at the ECU connector. At least that will be accessible which will allow you to get a reading for both sensors.

Interesting that the EU and US markets appear to have the rheostat wiring reversed (if you believe WIS). Intuitively it seems NG9-3 is incomplete, the NG9-5 is considerably worse, I can't even find preload settings for the TTiD turbo, which is something I may do a thread on later