Problem with the main tank

[JulianAugustus]

Hello Everyone,

im having some issue with the main fuel tank gauge in the dashboard. It’s a 1999 5VZ at 355,000 kms. Regularly serviced. The issue was noticed few days ago. Main tank was nearly empty, so filled up for $60 and the gauge went up to half way mark. Sub tank remains full 60lt at all times. Only use that on long drives, as the fuel economy is terrible 90 lt main tank give me 650kms.

Returning to the issue- drove the car for two days coving little over 70 kms and the gauge needle was at 1/3 mark, turned the engine off and the needle didn’t drop down. It remained there. Next day same and it didn’t move up or down. So wasn’t sure what was happening, so filled up the tank for another $20 and the needle went up to half way mark. And it remained there even after driving for an hour and half and back home, switching the engine off doesn’t work on that needle too. Still at the half way mark.

Cleaned up the under side of the car with high pressure hose and removed all the mud before trying to find if anything has gone wrong. Unfortunately I didn’t notice anything out of ordinary, everything the way it out of the factory.

i have checked all the fuses just in case Could get some help from the forum before I see a mechanic or an electrician!

Thanks team

[Rob Zombie]

I just drove the gibb river road and started on the main tank, as I use the sub just when she is acting up on the main and I didn’t have any problems at all for 500km or so on the main.
But I had a other problem coming up.
A morning the car started running rough. A mechanic in derby told me, it’s the spark plugs or leads, changed those and the car is running better but still not normal.
Will swap coils Thursday and see if that gets better.
Tank seems fine, could the 660km rattling solved anything?
What do you think about that coil thing? Why should just replacing the leads be a solution for anything? The “boots(?!)” for 1, 3 & 5 are combined with the coils and could be a cause for the problem as well, right?
Thanks for your help guys, appreciate that a lot!

[Leethal]

As the two tanks fill from the same filler most unlikely that it is the fill point.
To get to the fuel pump you need to first remove the bash plate then drain your tank before dropping it. Overall no a hard job just fiddly reaching the filler hose etc and a pain having to drain the tank. Once you have dropped the tank it is easy to remove the pump assembly complete.
One item not mentioned is the solenoid which switches the supply feed from tank to tank, I have seen where the return valve fails and all the fuel returns to the sub tank even when switched to the main. Perhaps it is not switching fully to the main tank on the supply side? This solenoid/valve assembly is in front of the sub tank on the passenger side.

Lee

[Rob Zombie]

I had a service done shortly and the mechanic said there is a dent in the bottom of that tank, I don't know if that could be a cause, so I guess it's the easiest, to check the fuel pressure and connections first and go from there?
The filler cap is the same for both tanks... So that should be fine, shouldn't it?
Does someone know what big of a job it is to get the main tank pump out to have a look at it and replace the sock filter?

[Pauls 95]

Sounds like a vacuum problem. What about the vent in the filler cap?

[dds]

the sock filter at the base of the main tank pump is still a fuel filter

[Leethal]

I doubt it will be the main fuel filter as both tanks feed through it, I would be checking the in tank pump, connections & the sock filter at the base of the pump.
If you have a fuel pressure gauge check fuel pressure at the engine to see if there is any difference between the two tanks.

Lee

[zoc]

+1 for the fuel filter

[dds]

have you check the fuel filter?

[Rob Zombie]

Hey guys,
I've problem with the main tank in my prado.
If the car is cold, it's running good on both tanks, but as it gets warmer, the engine studders, mainly when going uphill or overtaking (middle rev ranges).
The engine even stopped a couple of times while idling.
It seems to be getting worse as the tank is getting more empty. I can use the main tank in between and switch to the sub when it's rally bad. The sub tank is running without any problems.
Does it sound familiar to someone?
Could it be a defect fuel pump?