LS400 stalling problem solved!
Rookie
Joined: Feb 2011
Posts: 82
Likes: 1
From: La
The fuel pump relay resistor is not inside the fuel relay switch enclosure, it is underneath and to the rear of it. It is about 2" x 3", aluminum, mine has a 4 stamped on it. It is held in place by 1 10mm bolt and has 2 wires leading to it. Mine was getting too hot to touch. I replaced it with one from Pick N Pull ($5) and it ran fine for a week and then the used one went out, so I have now just cut it off and connected the wires together (thus bypassing it), the car runs fantastic like this. But from what I read, this may caure pre-mature fuel pump failure, so I am ordering one from Discounttoyotaparts.com, for $52.52.
Another side note is that my radio had not been worth listening to due to too much static. Once I bypassed the fuel pump relay resistor my radio came in clear again.
Another side note is that my radio had not been worth listening to due to too much static. Once I bypassed the fuel pump relay resistor my radio came in clear again.
There is a fuel pump control module in the trunk on the '94 although replacing it didn't ever effect drivability of my '94 at any time.
My '94 had a dying ECM that I wasn't aware of when I bought it at 180k miles, and then the original Aisin fuel pump failed at about 195k miles on the car. The brand new Advance Auto Parts store's Airtek "exact fit" replacement fuel pump failed about 8k miles later.
A new "exact fit" Bosch is currently running the car as that's all I could get locally in a hurry.
I never bypassed anything. As far as I know the wiring is all original on my car and yet it still killed that auto parts store pump surprisingly quickly... We'll see how the Bosch holds up...
Bypassing the fuel pump control module on the '93 - '94 LS will make a good working pump run and a weak/tired pump seem to be good and make the car feel a bit stronger/faster but it will also kill the pump within anywhere from 2-3k miles on a tired original pump to 20-30k miles on a brand new pump at the most...
It will likely also make the pump run any time the key is on, even when the engine isn't running and you're not trying to start the car, instead of the pump only being turned on when it's needed.
The Toyota Supra guys used to do that fuel pump relay/module bypass trick and swore it was fine and that it worked great until 2-3 years later most of their Supras began leaving them stranded on the side of the road with a dead fuel pump...
It's the same basic setup on the LS, or at least the same exact technology concept although the parts may not be directly interchangeable with the Supra...
The main point of the pump control relay/module is to run the pump at a somewhat reduced voltage under light loads and drastically extend the life of the pump which works great.
Driver School Candidate
Joined: Jul 2014
Posts: 17
Likes: 0
From: California
The fuel pump relay resistor is not inside the fuel relay switch enclosure, it is underneath and to the rear of it. It is about 2" x 3", aluminum, mine has a 4 stamped on it. It is held in place by 1 10mm bolt and has 2 wires leading to it. Mine was getting too hot to touch. I replaced it with one from Pick N Pull ($5) and it ran fine for a week and then the used one went out, so I have now just cut it off and connected the wires together (thus bypassing it), the car runs fantastic like this. But from what I read, this may caure pre-mature fuel pump failure, so I am ordering one from Discounttoyotaparts.com, for $52.52.
Another side note is that my radio had not been worth listening to due to too much static. Once I bypassed the fuel pump relay resistor my radio came in clear again.
Another side note is that my radio had not been worth listening to due to too much static. Once I bypassed the fuel pump relay resistor my radio came in clear again.
I have a '92 LS400 and I have a stalling problem. I also have a radio audio problem. It may help solve my problem. The stalling problem is intermittent and my mechanic cannot read any diagnostic code. I also upgrade my ECU electrolytic capacitors. So I am left with the Fuel Pump area.
Michael
Last edited by mjkwee; Nov 14, 2014 at 05:01 AM.
Driver School Candidate
Joined: Mar 2014
Posts: 45
Likes: 1
From: ca
He found the clicking to emanate from the fuel pump relay however the relay checked out OK. He then disconnected the fuel pump resistor, also in that area of the engine compartment, and bypassed it with a jumper wire. The engine immediately smoothed out. He found that the resistor's resistance changed greatly as the unit heated up and he measured the local temp reaching 200 degrees.
Replacing that resistor completely solved the problem. It is P/N 23285-50010-LX. Unit price $63.28 plus $95 for labor.
Ray
Replacing that resistor completely solved the problem. It is P/N 23285-50010-LX. Unit price $63.28 plus $95 for labor.
Ray
Driver School Candidate
Joined: Mar 2013
Posts: 14
Likes: 0
From: CA
this is what I did before throwing out my old resistor. I keep the bypass in the trunk,.
There are several Toyota's that use the same resistor and you might find the same resistor cheaper because it is for a cheaper car (even though they are exactly the same).
Driver School Candidate
Joined: Mar 2014
Posts: 45
Likes: 1
From: ca
What they do is make a bypass plug out of an old resistor wire connection (just cut the wires and solder them together. Then when they suspect the relay is bad they simply un-plug it and plug in their homemade bypass.
this is what I did before throwing out my old resistor. I keep the bypass in the trunk,.
There are several Toyota's that use the same resistor and you might find the same resistor cheaper because it is for a cheaper car (even though they are exactly the same).
this is what I did before throwing out my old resistor. I keep the bypass in the trunk,.
There are several Toyota's that use the same resistor and you might find the same resistor cheaper because it is for a cheaper car (even though they are exactly the same).
Driver School Candidate
Joined: Aug 2017
Posts: 1
Likes: 0
From: Texas
This is an old thread but I wanted to let anyone out there know that I was experiencing similar problems with my 91 Lexus. The car would konk out at stop lights in hot weather especially when it was very humid or the air conditioner was on. But the solution suggested of simply replacing the resistor solved the issue for me. The problem is that now Lexus now longer makes these parts so I needed to use a used part. The good news is that it has been a couple of months and it still works great. In addition, the part is something you can replace yourself so the cost will be under $100. I was also told by the repair shop that they would need to replace the computer and so on (which of couse are more expensive tasks) but the reality is that simply changing the resistor has worked great. So if you have an issue similar to this, I would recommend trying out this solution. Thank you to all who posted the information above because it makes the summer months so much more enjoyable in my car now.
Driver School Candidate
Joined: Jul 2018
Posts: 1
Likes: 0
From: CT
I am having this rough running/stalling problem with my 1990 LS400. Does anyone know where can I get this fuel pump resistor, P/N 23285-50010-LX? Toyota doesn't make this part anymore. The only resistor I found on Ebay is P/N 23080-50010. Is this resistor compatible to my car? Any advise is greatly appreciated.
Lexus Fanatic
Joined: Sep 2010
Posts: 26,190
Likes: 4,380
From: Alberta
Maybe this will work for you? It's an injector resistor but looks very similar.
https://www.ebay.com/itm/113146293393
https://www.ebay.com/itm/113146293393
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Driver School Candidate
Joined: Sep 2015
Posts: 3
Likes: 0
From: CA
In my original note I described 1990 LS400 problem as the engine seemingly running out of fuel and RPM winding down while driving and sometimes stalling. But never a problem restarting. Most of the time the engine would surge back as if the fuel supply suddenly returned which did turn out to be the case. There were no engine codes and the problem was intermittent and no fun to experience.
The local Toyota dealer in Hyannis MA (no Lexus dealers within 50 miles) cleaned the throttle body that he said was badly carboned up after 160,000 miles but that did not solve the problem and he gave up because during his checkout the car ran fine. While I was driving home the intermittent operation came back and I limped back to Toyota.
With the engine idling badly and going from high to almost stall speed by itself, the Service Manager (Brian Scarpellini, heard a faint clicking noise in the right front fender area that would come and go as the engine RPM fluctuated and be in sync with the surge frequency.
He found the clicking to emanate from the fuel pump relay however the relay checked out OK. He then disconnected the fuel pump resistor, also in that area of the engine compartment, and bypassed it with a jumper wire. The engine immediately smoothed out. He found that the resistor's resistance changed greatly as the unit heated up and he measured the local temp reaching 200 degrees.
Replacing that resistor completely solved the problem. It is P/N 23285-50010-LX. Unit price $63.28 plus $95 for labor.
I thank those of you who took the time to help and thought you might be interested in the final (I hope) solution.
Ray
The local Toyota dealer in Hyannis MA (no Lexus dealers within 50 miles) cleaned the throttle body that he said was badly carboned up after 160,000 miles but that did not solve the problem and he gave up because during his checkout the car ran fine. While I was driving home the intermittent operation came back and I limped back to Toyota.
With the engine idling badly and going from high to almost stall speed by itself, the Service Manager (Brian Scarpellini, heard a faint clicking noise in the right front fender area that would come and go as the engine RPM fluctuated and be in sync with the surge frequency.
He found the clicking to emanate from the fuel pump relay however the relay checked out OK. He then disconnected the fuel pump resistor, also in that area of the engine compartment, and bypassed it with a jumper wire. The engine immediately smoothed out. He found that the resistor's resistance changed greatly as the unit heated up and he measured the local temp reaching 200 degrees.
Replacing that resistor completely solved the problem. It is P/N 23285-50010-LX. Unit price $63.28 plus $95 for labor.
I thank those of you who took the time to help and thought you might be interested in the final (I hope) solution.
Ray
wow thanks alot for this, i am having the same problem exactly how you described. It only happens on very hot days and when the fuel is low (about 1/4 low) the engines stalls like is running out of gas but i am able to start it again no problem but when i come to a stop it feels like it is about to bog dow and the rpm has drastic surge up & down. If i am able to pull up to a gas station (car on “limp” mode) and fill her up then it runs no problems. Hopefully the part you mentioned will solve the problem, i love my 91 LS400 w/ 130k miles
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