Hi I bought a 1.6 Nissan Primera 1999 model from somebody. The mechanic working on the car wants me to purchase a FUEL/PETROL SENSOR. I'd like to understand what it is and what it's function is. Please assist. Sorry the Primera is not listed on your list so I just chose a model for the request to go through.

what a great question!
no year told, no country , no car told just raw engine
QG18 comes in many types QG18DD,,1999 to 04
QG18DE, 1999 to 2007 QG18DEN is the natural gas version?

lacking all key facts.
I go GENERIC (full bore)

the answer is super simple..
causes spark misfire. (and scanned PCM see P03xx errors DTC)

loss of engine horse power. and wasted fuel.
or engine dead. fully and no spark at ALL.

why worry it at all.??? if scans are clean this is it if CKP does not trip CKP errors DTC

must we guess all of these and if yes why?
and more,

The QG18DE is used in the following vehicles:

• 2000-2006 Nissan Sentra B15 and N16
• 2000-2005 Nissan Pulsar N16
• 1999-2002 Nissan Primera P11.144
• 2002-2007 Nissan Primera P12
• 2000-2006 Nissan Almera N16
• 2000-2006 Nissan Almera Tino
• 1999-2006 Nissan Primera
• 2000-2006 Nissan Expert
• 1998-2006 Nissan Avenir
• 1999-2005 Nissan Wingroad/AD van Y11
• 1999-2005 Nissan Bluebird Sylphy G10
• 1998-2004 Nissan Sunny B15
• every one sold in USA all scan easy as eating cherry pie !

the CKP and CMP sensors are the base line inputs for all spark and fuel injections and timing and timing advance of spark
if spark dies the PCM cuts all fueling dead( no crash&burns)

Hi,it dose seem to much,maybe there is a leak in the fiel line.
all the best.

Ignition modules have two sections -- one for low rpms, one for high. Could also be clogged air filter, converter, muffler, low fuel pressure, speed sensor.

Fix your car right away by clicking the link I attached
https://www.reliable-store.com/products/1999-nissan-primera-workshop-repair-service-manual-pdf-download

Sounds like a vacuum leak or a bad intake manifold gasket. Take engine cleaner and spray the gasket where the intake manifold bolts onto the motor while running. If there is any change in the idle, your gasket needs to be replaced. Spray all vacuum hoses too. This is the best and cheapest way to test. Let me know how you do please

Your 2003 nissan primera has a timing chain.

It has a timing chain.

TRy with 5523

The best way to remove the fuel tank. You can't get all of the fuel out of the system without tank removal.

You will also want to flush the system out to remove the incorrect fuel from the filter, lines etc.

It may be best to have a mechanic do this for safety reasons.

OR

The fuel line could be removed in the engine compartment and pump all of the fuel into a container (can be dangerous if done improperly). You would need to use the vehicles fuel pump to empty the tank.
Then you can add the correct fuel and flush the system.

You may even want to change the fuel filter also.

dont know the year ur car which would of help but the fuel sending unit in ur gas tank usualy the cause of this