gman44116

iTrader: (11)

A little history first.

Last year I changed both filters on my fuel pump (120k miles) for the sake of preventative maintenance.

After the filters were replaced I had trust in my fuel gauge but ended up running out of gas a few times. I used to run the tank to 'E' and fill up. After reinstalling the pump it seems that the gas gauge needle was off by approx 10-12% on the high side, hence running out of gas prematurely.

I got used to the needle not being as precise as it used to be prior to replacing the fuel pump filters. But always wondered what happened to change its accuracy when I did the maintenance.

NOW!! On to last weekend:

I had a 500 mile round trip over the weekend. 346 miles on the tank (highway). About a quarter tank on the gas gauge and it happens!! stutter, and dead!!! I'm coasting on the highway. Pull over in a quandry as the gauge says I have at least another 40 miles or so based on my experience with the gauge. Try to start her up and it's not getting any gas. The low warning fuel light didn't even light up!!

So, I scratch it up that I ran out of gas but just could not understand why the gauge says I have about 1/4 tank remaining...

Needless to say, I got a gallon of gas, drove to the gas station and filled up.

Here's the other problem......... It only took 13 gallons!! So it seems the gas gauge was correct as it has been but the engine wasn't getting any fuel...

Any suggestions?? I am thinking it may be time for a new fuel pump. I have ran out of gas probably 5 times and I run it down 90% of the time to an 1/8 tank before refilling...

#1 - Why when I changed the fuel filters did my gauge lose its dead-on accuracy? (Still wondering which sending unit to replace)
#2 - Why did I run out of gas when I had several gallons in the tank? (This has been answered. Replaced FPR & Pump)

I don't want to just 'live with it' and fill it up at a 1/2 tank. I want to know why I had at least 3-4 gallons of gas in the tank and the engine was getting none of it.

Anyone have a similar issue? I would like to DIY this but don't want to blow $250 on a new pump and have it be something else...

Any thoughts from the savvy mechanic would be greatly appreciated...

Wicked GS

iTrader: (4)

I know us guys that have done the swaps are having the same issues, As of right now I go by counting my miles,and when it reaches a certain # , I just refill ... I've too have run out of gas because of the 1/4 mark not reading beyound that. First time I've heard of someone this has happened to that hasn't done the swap. Wish I could be of some help to you but we're in the same boat. Good luck though because it is a headache

GS4_Fiend

iTrader: (22)

Your fuel sending unit/float is no good.

gman44116

iTrader: (11)

Is this in reference to the gauge inaccuracy?

Or the running out of gas when there is plenty of gas in the tank?

I don't see a replacement part for this at Sewell.

GS4_Fiend

iTrader: (22)

The fuel sending unit/float controls that fuel gauge and fuel light. Unless the gauge itself is stuck.

HI98GS

Check the siphon system. Since your tank only took 13 gallons, the tank guage was reading correctly. You are not getting the last 1/4 tank of gas that is located on the "other side of the hump" on the passenger side. The usual cause is that the siphon system isn't working. Check the hose that connects to the regulator and the plastic siphon piece. I suspect the hose slipped off.

It is part 2032A on this diagram
http://lexus.sewellparts.com/oem-cat...S400-1998.html

gman44116

iTrader: (11)

Thanks for the thoughts but the hose was attached to the regulator, just checked. No loose connections anywhere. Could it be the regulator itself?

mphsatty

Is this a common problem that occurs when the fuel filters are replaced? Are the sender units being damaged or not properly reinstalled? I'm getting mine from Sewell today when FedEx runs but now wonder if I should actually install them. Like OP, I planned to do it only as preventive maintenance.

gman44116

iTrader: (11)

Is there a way to check the other end of the siphon system? I don't see where the line runs. Just about 8-10 inches of the hose that connects to the regulator. How would I check to see if the other end is in its correct place on the other side of the tank?

HI98GS

If your tank is about 1/4 on the guage, the driver side tank should be up to the "max" point that it can fill without spilling over to the passenger side tank. The passenger side tank will look lower than the driver side. There is a secondary sending unit on the passenger side. It is much smaller. You could also check to see if the siphon is working by removing it and attaching one side to liquid (the feed side) and blowing or having fluid flow on the siphon side to see if liquid is being pulled through it.

The other thing you can do to make sure that the connection to the passenger side is intact is to push/blow air through the tube and see if there is air bubbles on the other side.

gman44116

iTrader: (11)

??? Driver side would be 'max' point at 1/4 tank?? this post is practically useless without photos or a diagram for reference. Man oh man, blowing in gas tubes sounds like fun

HI98GS

Sorry if I wasn't clear. I agree that pictures would help, but I can't take apart my fuel system as of yet. Let me try again.

If you look into your gas tank, there is a hump that separates the right and left side. That hump is negligible if the tank is full. The gas just flows over it. When the tank is drained to about a 1/4 tank, the hump becomes a problem because the gas cannot get from the right side of the tank to the left due to a physical barrier. That is where the siphon tube comes in.

as far as blowing gas, I would use compressed air attatched to the tube that comes off the regulator to the siphon. It definitely won't be as fun if you do like blowing on the tube with your mouth.

I'll see if I can find a pic of what I'm talking about

wise2k

Same here, ran out of gas without notice several times after replacing fuel pump. I now just go by 20 miles for each gallon of gas I put in the tank, reset trip A at each fill up.

Inside the gas tank there is a black hose which to me is the suspect, probably interfering with the floatation towards empty, and not allowing it to drop completely. I don't even know what it's for.

Mike813

iTrader: (5)

you should check the sending unit that sakataj mentioned. when replacing it alot of times the unit gets caught onto that black fuel line which kind of kinks it upwards making it seem "off". it happened to me and i just reinstalled it carefully making sure the float was free and was not obstructed by the line or anything else.

make sure youre not topped off on fuel though before you check or youll make a mess inside your car.

gman44116

iTrader: (11)

Yesterday I replaced the fuel pump with a Denso 951-0003 unit and I also replaced the fuel pressure regulator. Maybe this will take care of my issue with running out of gas on a road trip with 3-4 gallons in the tank (about a 1/4 tank).

I was hoping the gauge would correct itself as since last year when I replaced the fuel filter(s) the gas gauge reads about an 1/8-3/16 higher than it should. My gauge used to trigger the low fuel light when it hit the 'E' on the gauge. Now it does it with about an 1/8th of a tank remaining. I just want it to be like it was, perfectly calibrated. BTW, the float does not hit the black hose. It's nowhere close to the float in the tank.

Seems I am now at a point where I am narrowing it down to what the actual issue is. Do I just go and replace the float (which is basically the top part of the fuel pump housing) ????? Anyone got a solution based on similar issue??