Z19DT Fuel Pressure Dropping

[eddyz1122]

Hi All,

I own a Vectra C Estate and frequent the forum a lot, so i know there's plenty of guys on here than know their stuff. The vehicle in question isnt a Vectra but uses the same engine.

My missus owns a 1.9 (Z19DT 8V) 2009 Grande Punto, EGR delete, FMIC and mapped by Tom Procko. Currently seeing drops in fuel pressure when you accelerate hard. (Getting a Fiat specific P0091-22 Fuel Pressure high pressure pump input regulator code).

Ive included a photo below of the live data when the fault happens, in this instance i was cruising at 1.5k rpm in 3rd gear and then put my foot to the floor on the accelerator. This shows the desired fuel pressure spike as it should, actual fuel pressure drops but then tries to climb to where it should be. It then puts the EML light on and goes into limp mode. Limp mode can be cleared by cycling ignition. Accelerating steadily doesn't produce the fault.
Live Data
https://i.imgur.com/EbJdVKz.png
Fault Code
https://i.imgur.com/LETasqg.png

I've read a lot of the posts regarding fuel pressure fault, but none seem to include any live data and seem to just throw parts at the vehicle. Any ideas guys?


PS: Couldn't insert the images directly, was getting an "invalid file" error.

[Dog_Book]

Any service info? When was the fuel filter changed and what brand?

[eddyz1122]

Any service info? When was the fuel filter changed and what brand?

Vehicles currently on 65k miles, owned since 30k miles. Full Fiat service history every year since new, until our ownership. Roughly 9 Fiat stamps.

Since our ownership, its had engine oil, oil filter, air filter changed every 6-8k miles. Fuel filter changed every other service. Gearbox refurbed at 61k miles (good old M32).

Just checked invoice and the last Fuel filter was September last year at 60k miles and it was a Crossland branded filter. The filters on the Grande Punto use the same metal canisters you find on the 1.9cdti Combo D van (https://www.ebay.co.uk/itm/353410730694)

Cheers.

[Jon1796]

On pictures I find if you edit it save then add works.

[Dog_Book]

You could also ask Tom, I know its not his problem but as he does live data mapping he might know pretty quickly. In all my time with these engines I dont know if the SCV is a separate part or how the pressure is controlled like other common rail diesels.

[eddyz1122]

You could also ask Tom, I know its not his problem but as he does live data mapping he might know pretty quickly. In all my time with these engines I dont know if the SCV is a separate part or how the pressure is controlled like other common rail diesels.

Thanks mate, already dropped Tom a message, he suggested renewing the fuel filter first as a precaution, but it could be the fuel pump on the way out. Which would be odd as the cars only done 64k miles and had more fuel filters than probably 80% of cars with this engine. Somebody else on here may be able to confirm, but I'm led to believe the regulator is on the pump itself and ECU controlled. There's a lot of used pumps for sale with the regulator included, so failing the filter fixing the issue I might need to bite the bullet and replace them both. Use pumps seem to go for £30 to £100 not the end of the world if it doesn't solve it.

Doesn't seem too difficult to replace the pump and looks to be possible without removal of the timing belt. Will get a genuine GM fuel filter on order and update my post when its been fitted.

Cheers.

[Jon1796]

Just a thought as I don’t play with deso’s does rail pressure drop straight off when engine has stopped then I would look at leaking injectors and pressure release on rail.

[Dog_Book]

Sounds like the SCV as it’s making the commanded pressure but is slow to react. The control valve is held on with 3 bolts I believe but I’d assume it needs learning once replaced. Don’t have a Cdti infront of me so can’t plug my tech2 in to check if there’s an option but my Mokka certainly has it as I just replaced mine.

[eddyz1122]

Just a thought as I don’t play with deso’s does rail pressure drop straight off when engine has stopped then I would look at leaking injectors and pressure release on rail.

I haven't checked rail pressure when the engine is stopped via live data, at idle fuel pressure is basically the same as desired fuel pressure. I have measured injector quantity deviation/correction and across a 5 mile drive the maximum deviation across all 4 injectors was +2 and -1. They all seemed to be roughly the same. Which I would think would rule out leaking injectors?

Sounds like the SCV as it’s making the commanded pressure but is slow to react. The control valve is held on with 3 bolts I believe but I’d assume it needs learning once replaced. Don’t have a Cdti infront of me so can’t plug my tech2 in to check if there’s an option but my Mokka certainly has it as I just replaced mine.

Slow to react is what i am seeing in live data, yes. If you ease into a hard "pull" having your foot to the floor by 3k rpm, measured fuel pressure will always stay with desired, all the way to the hardcut rev limiter. But why it slow to react I haven't been able to work out. In theory "slow to react" could be caused by both the Pressure Regulator and the Fuel Pump?

Perhaps you are right and it might be wiser to replace the Regulator before the fuel pump since it is easier.

[Dog_Book]

I’ve never done one so can’t advise but if it’s easy to do it’s the first port of call as that small part does the controlling of the pressure bit. If the pump was gone it wouldn’t be able to make the higher pressures? Look out for relearning though.