Missing Petrol Cap - pressurized fuel system

[Toptrumps2]

Car : 2000 Suzki Swift 1.0
Issue - Fuel Filler Cap Left on the Roof - Pressurized Fuel System.

My Partner went out for a drive in her little swift the other day and it started spluttering @ 60mph, when attempting to Sharply accelerate the car slowed down, knocking it out of gear stops this. Rolling onto the throttle slowly allowed the car to accelerate off the duel carriage way.

Discovered that the fuel cap has been left on the roof when it was last filled up (2 weeks ago). The issue we have is its a pressurized fuel system, what would you recommend using to keep the system pressurized.

Im thinking fill the tank then zip-tie part of a rubble bag over the filler neck. Until we get a new cap.

Would this work?

Any advice will be welcome!

Edited by Toptrumps2 on Monday 13th February 13:33

[LarJammer]

The missing fuel cap is not the problem but feel free to tie a bag around the neck, this will at least keep water out.

[GreenV8S]

Toptrumps2 said:

its a pressurized fuel system

I don't know what you think this means, but you're suggesting that fuel supply to the engine is somehow dependent on the fuel tank being pressurised then that seems unlikely to me - the fact you've been running with the tank open to the air for two weeks and only noticed the problem today also doesn't suggest that the missing fuel cap is causing the engine running problem.

Maybe you have fuel starvation - perhaps aggravated/caused by filters blocked by contamination. Maybe you have some other problem such as a faulty sensor. If you can reproduce the problem then I suspect this should be reasonable easy for a mechanic to diagnose.

[texaxile]

GreenV8S said:

I don't know what you think this means, but you're suggesting that fuel supply to the engine is somehow dependent on the fuel tank being pressurised then that seems unlikely to me - the fact you've been running with the tank open to the air for two weeks and only noticed the problem today also doesn't suggest that the missing fuel cap is causing the engine running problem.

Maybe you have fuel starvation - perhaps aggravated/caused by filters blocked by contamination. Maybe you have some other problem such as a faulty sensor. If you can reproduce the problem then I suspect this should be reasonable easy for a mechanic to diagnose.

Tanks I don't think are pressurised, more than likely the fuel system is (injectors and fuel lines post pump). As GreenV8S said, and I'd agree, it is more than likely contaminants in the fuel which have entered via the filling hole.
You should be able to buy a cheap replacement temporary / emergency universal cap from any garage or even poundland, I'd fill the car right up and hopefully and excess water or contaminants in the tank will be diluted with the fresh fuel.

[lufbramatt]

A missing fuel cap is going to result in a huge vacuum leak for the EVAP system (controls how fuel vapour is released into the atmosphere via a charcoal filled canister and solenoid valve). I wonder if this could either be dropping the engine into limp mode or allowing unmetered air into the intake system, resulting in the stuttering and loss of power.