Have A 1990 Ls 400 With Problem When Try Starting It Will Run At 1,000 Rpm Then Drop Then Back Up To 1,000 Rpm Then Stall.installed New Fuel Filter (old One Was In Backwards) Car Ran A Little Better Then Same Problem. Check Engine Light Is Not On. When I Check For Power To Fuel Pump Relay There Is No Power To It. Do Not Want To Replace Fuel Pump If That Is Not Problem.could I Remove Pump And Test?have Rear Seat Removed And Acess To Fuel Pump.please Help!
Thank You.

 

Can u describe the problem a little better? What happens when u start the car when its cold? It should idle at 1500 or so until it warms up and then the RPMs drop to 650. Exactly when does your car stall? Is it almost immediately after u start it, or after u drive it for a while? What kind of mileage? What if u give it some gas to keep the RPMS up? Is it just an idle problem? Are you able to start your car again or it wont start?

Before you do anything with your fuel pump, remove the line from the fuel filter and switch the car on. If the fuel fountains out of the filter, your fuel pump is working.

Check your fuel injectors. If you are able to keep the car running, put some fuel injector cleaner into the gas tank.

 

Sometimes It Will Start And Sometimes It Won't. It Will Cold Idle (when It Starts)at 1,100 Rpms Then Drop To 400 Rpm Then Back Up And Stall Again. Then Won't Start.i Have In Side Of Filter Coming From Tank And Out Side To Engine. Fuel Kept Running Out Of Tank Side When I Replaced Filter. It Did Happen When Driving But Then Would Start Running Fine Again. Seem Worse Since I Change Filter. Car Has 225,000 Miles On It. Should I Hear The Fuel Pump Come On When Ignition Is Turned On? Thanks For Any Help.

 

Try removing the fuel filter completely and running a hose to let the fuel through. Sounds like your fuel pump maybe running out of breath, and with the filter it has to work harder

 

PROBLEM FIXED!TOOK OUT FUEL PUMP AND HOOKED 12V TO IT AND IT SPUTTERED AND STOPPED. REPLACED WITH NEW ONe ($225.00) and car runs like a dream. I guess it needed a complete circuit to activate the fuel pump relay which had no power going to it because of faulty pump. Thanks to everyone who tried to help.

 

PROBLEM FIXED!TOOK OUT FUEL PUMP AND HOOKED 12V TO IT AND IT SPUTTERED AND STOPPED. REPLACED WITH NEW ONE ($225.00) and car runs like a dream. I guess it needed a complete circuit to activate the fuel pump relay which had no power going to it because of faulty pump. Thanks to everyone who tried to help.

 

glad you figured out what the problem was but you could of just put it in the original thread for future reference. welcome to the club

 

i see the mods corrected it for you