Car randomly sputtering and switching off. Then working normal.

[Don Mario]

Hi team,

New here, please let me know if this is not the right place to ask this.

The car starts and has unstable rpms, then switches off.
The car can't start (but cranks).
Battery is brand new.
The car starts and runs perfectly without issue.
No error codes whatsoever (except one time for misfires in cilinders).
Car is a 2017 GT Cabrio. European version.

I have videos of the symptoms but I can't upload them due to some error.


Is this a fuel pump that went bad? Could randomly go bad? Could it be I caused something by refueling 15 liters with a fuel canister (3 mo this old European 95 fuel)?

Mechanic doesn't know what this could be since now car starts and runs without issues. (American Cars mechanic specialized).

Thank you for your time

MARIO

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[SheepDog]

Could be fuel related, but sounds more like a grounding issue to me. Could also be a Purge solenoid issue, especially if you top off the tank when fueling, meaning you pump a few extra clicks to fill the tube from the tank to the gas cap.

 

[Don Mario]

Hi, thank you for your reply. I only refuel until the first click.
Last time I fueled 15 liters from canisters that were sitting for three months.
Now has about half fuel tank.

 

[SheepDog]

Hi, thank you for your reply. I only refuel until the first click.
Last time I fueled 15 liters from canisters that were sitting for three months.
Now has about half fuel tank.

I don't know what the fuel quality is like in Poland, but 3 months isn't enough for the fuel to go bad, and if it were bad, the car wouldn't run intermittantly.

A bad Fuel pump can certainly do this, or a loose connection, bad ground.

If you want to test the fuel pump, you really need to have a fuel pressure gauge hooked up when the car isn't starting, but your mechanic should know that.

 

[Don Mario]

Mechanic proposed to leave the car there until problem appears again, seems now the car starts and runs good and problem doesn't show.

Sorry, what is "bad ground"?

 

[SheepDog]

Mechanic proposed to leave the car there until problem appears again, seems now the car starts and runs good and problem doesn't show.

Sorry, what is "bad ground"?

Meaning that one of your ground wires are not making good contact. There are several locations in the engine bay that have ground, or negative wires attached to them. As an example, one of them is right in front of the passenger strut tower. Several black wires come together and are grounded there. Vibration, corrosion, aftermarket parts can all cause these connections to be loose

 

[ORRadtech]

Since the car is operating normally right now there's really not much to be done except drive it and see if the issue recurs. Since it's only done it once, and randomly at that, it's possible you may never know what it was.
If I were speculating my first thought would go to the fuel from the fuel canister. Not that it was bad but possibly contaminated. Perhaps the fuel was mixed with something like diesel or water. A failing fuel pump is also a consideration as is a loose connection (connector or ground wire. You may know it as an "earth" wire.
I'm currently chasing an intermittent fuel pump issue in one of my cars. Occasionally and randomly I will get a thrumming noise reminiscent of a bad bearing and then the car dies. So far it has always restarted but I do believe I have a failing fuel pump. But until it gets worse, or at least more regular, I'm stuck waiting.

 

[Don Mario]

Thank you all for your opinions.
Car is now magically working perfectly and no issues.

We bet is the fuel pump that somehow got "unstuck".

That being said, I'd like to buy a new fuel pump, a really good one. Any suggestions?

Thank you!

 

[SheepDog]

Thank you all for your opinions.
Car is now magically working perfectly and no issues.

We bet is the fuel pump that somehow got "unstuck".

That being said, I'd like to buy a new fuel pump, a really good one. Any suggestions?

Thank you!

OEM. your original lasted 8 years. You could also install the DW400

https://www.beefcakeracing.com/dw-9-403-1047/

 

[Don Mario]

OEM. your original lasted 8 years. You could also install the DW400

https://www.beefcakeracing.com/dw-9-403-1047/

I've been looking around and seems OEM and this DW400 cost the same? If price almost equal would you go for the DW400?

Thanks again for the help!

MARIO

(car stopped working and had to tow it home).

 

[SheepDog]

I've been looking around and seems OEM and this DW400 cost the same? If price almost equal would you go for the DW400?

Thanks again for the help!

MARIO

(car stopped working and had to tow it home).

Sure,
Yeah why not, if they're the same price.

 

[Don Mario]

Sure,
Yeah why not, if they're the same price.

Thanks! Just ordered.

I will keep the post updated in case this process is useful to someone else.

 

[Don Mario]

Went to the car and it started without problems at all. Ground cables were checked and are ok; can this still be the fuel pump? Working randomly?

 

[sk47]

Hello; First let me say I do not see the point of buying a new fuel pump on speculation such is the problem. However it is your money to spend.

Here is my WAG (wild a__ guess). We in the USA are plagued with ethanol in our fuel. However, ethanol does have a benefit with regard to water in the fuel. Ethanol alcohol will mix with water and so allows any excess water +alcohol in the fuel to burn. May not burn super well but good enough unless way too much water gets in. Fact is back before alcohols were mandated in our fuel we would buy small bottles of alcohol to add to the tank in the winter.
Back in the day we also had metal fuel tanks. Also the fuel tanks were open more to the air. During cold weather the air in a partly full fuel tank could and often would have moisture in it ( see relative humidity or just humidity). Some of the moisture would condense onto the inside of the tank and drip into the fuel. Gasoline is less dense than water so over time a layer of water would form at the bottom of the fuel tank with the gasoline floating on top of the water layer.
Get enough water in the tank and eventually some will be sucked into the fuel lines. Would cause rough running and worse. In cold temps fuel lines can freeze up. There were two effective ways to deal with this back then.
Easiest was to never run less than half a tank (preferably not below 3/4 tank) during very cold weather in day to day driving. OK to run the tank down on long trips as you were filling up often. Ideal being to keep the air space above a partly full tank to a minimum, thus preventing some condensation. The other was to use the alcohol additive. I did both.
(Side not some very older (1950's) vehicles had drain plugs on the metal tanks)

Back to my WAG. I suspect the containers you filled the tank from had water in them after sitting for a few months. I figure the issue is over and the car will be fine unless grit or some other dirt was in the containers. The excess water is run thru the system by now.

 

[Don Mario]

Hello; First let me say I do not see the point of buying a new fuel pump on speculation such is the problem. However it is your money to spend.

Here is my WAG (wild a__ guess). We in the USA are plagued with ethanol in our fuel. However, ethanol does have a benefit with regard to water in the fuel. Ethanol alcohol will mix with water and so allows any excess water +alcohol in the fuel to burn. May not burn super well but good enough unless way too much water gets in. Fact is back before alcohols were mandated in our fuel we would buy small bottles of alcohol to add to the tank in the winter.
Back in the day we also had metal fuel tanks. Also the fuel tanks were open more to the air. During cold weather the air in a partly full fuel tank could and often would have moisture in it ( see relative humidity or just humidity). Some of the moisture would condense onto the inside of the tank and drip into the fuel. Gasoline is less dense than water so over time a layer of water would form at the bottom of the fuel tank with the gasoline floating on top of the water layer.
Get enough water in the tank and eventually some will be sucked into the fuel lines. Would cause rough running and worse. In cold temps fuel lines can freeze up. There were two effective ways to deal with this back then.
Easiest was to never run less than half a tank (preferably not below 3/4 tank) during very cold weather in day to day driving. OK to run the tank down on long trips as you were filling up often. Ideal being to keep the air space above a partly full tank to a minimum, thus preventing some condensation. The other was to use the alcohol additive. I did both.
(Side not some very older (1950's) vehicles had drain plugs on the metal tanks)

Back to my WAG. I suspect the containers you filled the tank from had water in them after sitting for a few months. I figure the issue is over and the car will be fine unless grit or some other dirt was in the containers. The excess water is run thru the system by now.

Hi Sk47,
Thank you for your input.

The cans were 5 liters each, (hard plastic?), and were stored in the trunk of the car. They were never still and they basically "bounced" around the trunk for 2.5 months.

I thought, if I ever want to increase the HP of the car I will need anyways something like the DW400 so I went for it.

The day I had to tow it: I went and tested the car 30 minutes and it run perfectly. Let it rest. Test 30 minutes more (fast, slow, you name it). Run perfectly.
Lastly took it home and failed 4 minutes after starting. Check engine light.

Today I went to it and it started like nothing. 0 sputtering, 0 gurgling. No engine light. Smooth as a baby.

I had a KD2006 ghost immobilizer the mechanic cut off because he said it was not giving the right power to the fuel pump. Could this lack of power fry it somehow? The thing is, sometimes it works, and when it does, it works great.

What are your thoughts on this?

MARIO

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