Stumped

I am really stumped on this one. I own a few Toyotas and can almost always figure them out....well I need some help on this one....1988 4x4 extra-cab....rebuilt the motor (22re) a year or so ago and at the time it had been sitting a while....the fuel pump and whole unit was almost rotted away so they got replaced. Shortly after when you would be driving (around a corner or coming to a stop, seemed to make it worse) it would lose all power even if you put it in nutual and floored it, it would just sputter and almost die....that is until you shut it off and then you could almost immediatley restart it....power was fine. So of course after the rebuild I put on a new fuel filter (relocated to fender for easy change in the future), thinking it had picked up gunk from the tank....no difference so I dropped the tank and flushed it, changed the filter again, and even filed the contacts on the relay switch above the brain. Still happens....now here is the really strange part, if the tank is full, it never does it....once it gets to about a half tank, it starts up again. That leads me to believe its not an injector, pressure regulator, or fuel pump. Sorry for the long post....any ideas would be greatly appreciated.

waskillywabbit

iTrader: (-1)

Sounds pressure related to me. Full tank has greater static pressure. Half tank loses static pressure flow becomes sporadic due to loss in pressure.

:wabbit2:

xxxtreme22r

To me that sounds like the return and supply lines might be mixed up for the fuel. Considering before it started acting up the fuel pump was replaced. Make sure they didn't get mixed up at the tank.

IIRC, supply line is on the bottom of the tank, return line is somewhere in the middle and the vent line is on the top. (yes they are all connected at the top of the fuel pump bracket) So it would make perfect sense (at least to me) that if half tank or corners you would loose fuel because it uncovers the return line which is now a supply line.

Stumped

The return line could make sense, but where would they have gotten crossed? The supply line can only be hooked up by the fitting on top of the tank and if I remember correctly it was larger than the rest. I never unhooked any other lines beside the ones on top of the tank.

Stumped

Wait....it will run all the way down to empty, so how would the return line pick it up?

Stumped

@waskillywabbit....are you thinking fuel pump? thats about all I can come up with....it was a used one when I installed it. Thanks again

waskillywabbit

iTrader: (-1)

If the fuel system isn't getting pressure like it should then it's regulator or pump.

:wabbit2:

Stumped

Well I think I will replace the pump again anyway. I dont see much on pressure regulators going bad on these trucks, and i dont see how they really can effect it in the way I am having trouble. If I remember correctly regulators are just a diaphragm and when they go bad, the truck runs rich. Anyone ever seen a fuel pump do what I have discribed above? When I get this solved, I will post back and maybe it will help someone else....Thanks

john4wd

a pin hole leak somewhere that is high on the bracket/fuel pump assembly and when fuel level gets lower it's exposed? leaking seal on fuel level sender unit allowing air in? So many things in fuel system to go wrong, leaking gas cap? Are you getting pressure released when removing gas cap? Hummmmm????

Stumped

ugggg

Stumped

?????

Stumped

delete....

Stumped

It does have pressure when the cap is removed....i also tired a different cap from my 4runner and even drove around with out a cap, as I was thinking some kinda vapor lock. I know my sending unit is in need of replacing because it does the old "drop to empty on the gauge, at half tank trick". I think this week when I get around to it, I will replace the whole unit along with the pump. Thanks again

scope103

Have you put a fuel pressure gauge on it? You are assuming that's the issue (and it sure sounds like that), but without the gauge it's only an assumption. And a gauge will cost less than a fuel pump.

Stumped

I figured it would be a waste of time cause it only does it driving. Unless you can put a gauge on and drive with it?

scope103

You could get an electric Fuel pressure gauge with a remote indicator, but I've never found one cheap enough to use just for diagnostics. http://www.autometer.com/cat_gaugede...gid=2526&sid=3. You don't want to "hard-plumb" a mechanical fuel gauge into the cab -- too dangerous.

But you could hook up a diagnostic gauge, drive til it stumbles, then open the hood and take a look. Not too effective, though, if you can't cause it to stumble in a mile or two.

Stumped

Thanks, but it may just be easier to replace the pump....I found one for 33 bucks...yes its used, but worth a shot in my opnion....Thanks

thralldad

What about fuel filter?

Stumped

I have changed it twice already, but thanks anyway.

Stumped

Alright....after pulling the tank for the 4th time....I replaced the pump "sock"....Yes it fixed the problem....It just wouldnt allow the flow the pump needed....I figure the reason it started after half tank, is because when it was full, it had enough weight on it to pressure force the fuel in to it....but after half tank, the pressure was alot less, allowing the pump to starve....hope this can help someone else....