92 Ls400 Barely Running

[Mike523]

HI,

I have a 92 LS400 with 99,000 miles on it. The engine barely keeps running, almost dieing then reving up to 1000 - 1500 rpm. Driving is awful, you jerk down the road with top speed of 20 mph.

It seems just like a problem I had 1 1/2 years ago. I changed the fuel filter and the car worked fine for about 10 miles, then started again. Took the car to our Toyota Dealership, a pretty good mechanic worked on it for a couple of hours.

When I changed the fuel filter I was catching as much gas as I could and noticed how watery and dirty the gas was.

Not knowing what else to do at Toyota, the mechanic drained the gas tank and installed another filter. The car ran fine the next day all the way to Denver, about 400 miles. I dropped the car off at Lexus to have a traction control problem fixed and get the 120 work over. They did the timing belt, plugs, wires and all the other stuff. Ouch!

We quit buying gas from the same place and haven't had any trouble since.

No engine light. Took it back to Toyota, mechanic before is gone and the new guy looked like a deer in the headlights. He struggled for two days and gave up. But, after he changed the fuel filter and drove it out of the bay the car died and wouldn't start at all. Thats where he spent all his time. He finally found that the 20Amp EFI fuse behind where the battery sits was blown. Then they were happy to get rid of me and the car.

QUESTIONS:

What do the fuel pumps act like when they fail or begin to fail?

Has anyone ever had this problem?

If it's fuel, I should be able to measure a severe pressure problem, right? Though I don't have the tools.

Any other suggestions or thoughts?

Thanks!

Mike

[spiller91ls]

i'm not sure if toyota did it, but ford, jeep, chevy put fuel filters on each of the injectors, kink of last change to catch anything that get trou the regular filter. all they are are little strainers, you'll have to ask a toyota/lexus mechanic if they are that way. i'll look in my repail manuels and see if they have anything, can't do it now since i'm in work.

[VBdenny]

The fuel pump on my Chevy Caprice went out about three weeks ago on the I-295 in NJ. I was going about 80mph. I felt the engine starve for fuel briefly, then it went back to normal. After about 10 seconds, I felt it starve again, even worse. The the check engine light came out and the engine began cutting off. I was near an exit so I whipped off into a Wendys parking lot and coasted to a stop. Went real quick.

If it is a fuel problem (90% of all engine problems are electrical) it is probably due to getting a load of water in some gas. This most commonly occurs when you are filling your tank, as a tanker truck is dumping fuel. The water gets stirred up by the mix and use suck it up. Dump in a bunch of dry gas and see what happens.

[Lextreme]

Possible problem:

1. MAF

2. ECU

3. Fuel system

There is an article in my site has diagnosis with symptom at www.lextreme.com/misc.htm Good luck. Have a friend with a 1990-1994 LS400 and try to switch parts and test things out. What does OBDI say? Any check engine light?

[Mike523]

Thanks for the advise!

Mike

[ToddLS400]

Gas rises to the top of water, it's lite, water is heavier. If there was a bunch of water in the gas storage tanks below ground then the tank was near empty when you filled up. Why don't you syphon out the bad gas from your tank and refill with good gas?

Did you check your computer codes on your top LCD? Hold the OFF and the REC button as your turn the key in your ignition to the on position (right). Tell us what codes come up.

[132]

There have been problems with failed fuel pumps in the first generation LS. Two different companies supplied fuel pumps for these vehicles. I believe it was Aisin and Denso. The Denso pumps seem to last forever, while the others fail at 100K+ miles. Failure usually occurs when fuel level is below 50% and car is driven for an extended period. I suggest taking the vehicle to a dealer or Lexus specialist, as there have been ignition problems that will exactly mimic a failing fuel pump. Good luck.

[ToddLS400]

There have been problems with failed fuel pumps in the first generation LS. Two different companies supplied fuel pumps for these vehicles. I believe it was Aisin and Denso. The Denso pumps seem to last forever, while the others fail at 100K+ miles. Failure usually occurs when fuel level is below 50% and car is driven for an extended period. I suggest taking the vehicle to a dealer or Lexus specialist, as there have been ignition problems that will exactly mimic a failing fuel pump. Good luck.

Where is the fuel pump(s) located on the gen 1s?

[JPI]

Fuel pump located in the tank. Where did you get gas for the past year? Same place? You can turn your key on DO NOT START THE CAR. Hook up your gauge to check for reading. If you don't have any pressure your pump is out. But I would take the car to a Lexus dealership.

JPI

[Mike523]

I have the cover off the tank and don't see any water or debri.

In order to get the car to a Lexus dealership, I would have to trailer the car. Denver is 350 miles away.

I checked the resistence on the pump and it's within spec.

Is the "union" to check the fuel pressure a special part?

I emailed Lexus in Denver, but haven't heard back yet.

Seems like the pressure test would give me a clear answer on the fuel pump.

I'm going to go and check to see which pump is on my car also.

[Lextreme]

To test the fuel is flow or not. There are two site you can attack. The return line right by the fuel pressure regulator near the throttle body and loose the screw and turn the on... the pump should eject fuel out from the loosen screw.. if you see fuel... then your pump is working.... How much pressure is it produce is another story.. u have dont have a fuel gauge and there is no way of finding it out.....

The fuel pump is behind the rear seat... remove the rear seat to get access to the fuel pump.... This article might help

http://www.lextreme.com/FMU%20Article.htm

[Mike523]

I pulled the pump out and hooked it up to the battery as the manual said. It spun just fine. For some reason, luck I guess, I tried it a couple more times and it wouldn't work.

So, I'm waiting on a fuel pump from Lexus. I have the pump that someone said fails quicker. Aisis or something like that.

Called Napa, they said they have a "best line" in stock. So, I went down to look at it. First off it wasn't the one I have and second, it's not nearly as well built. So, I'm spending the extra $170.

I'll let you all know.

Mike

[Lextreme]

U should not have done that. You burned your pump by running it dry. Secondly, the pump spin doesnt mean its good. The motor might (or was) good, but the seal might be bad.

[Mike523]

All is well.

A new fuel pump fixed the problem.

So when your car acts as I mentioned above and you don't get an engine lite, beware of a failing fuel pump.

[ToddLS400]

All is well.

A new fuel pump fixed the problem.

So when your car acts as I mentioned above and you don't get an engine lite, beware of a failing fuel pump.

I'm glad to see you got it fixed. How much did it cost you?

[Mike523]

The new fuel pump with tax and shipping ran $440. A lot for such a small part. But worth it when such a fine car isn't running.

[ToddLS400]

Yikes! $440 for the part only? Jeez, this Lexus is killing me... Hehehe....But I love the ride...