crisavelli2002 Posted October 30, 2011 Share Posted October 30, 2011 My 94 LS 400 just shutdown on me while driving home on the highway. Waited about 20 mins attempted to restart pumped the gas pedal,motor ran for about 7 seconds and shut off repeated the same steps same result. Replaced fuel pump and filter car still wont start. What could it be?? trying to get a heads up before so I will know how costly it will be to repair it. crisavelli2002@yahoo.com someone please help!! car has alot ofsentimental value to me,it was therapy for me to drive after returning from Iraq all(3)tours. Quote Link to comment Share on other sites More sharing options...
crisavelli2002 Posted October 30, 2011 Author Share Posted October 30, 2011 My 94 LS 400 just shutdown on me while driving home on the highway. Waited about 20 mins attempted to restart pumped the gas pedal,motor ran for about 7 seconds and shut off repeated the same steps same result. Replaced fuel pump and filter car still wont start. What could it be?? trying to get a heads up before so I will know how costly it will be to repair it. crisavelli2002@yahoo.com someone please help!! car has alot ofsentimental value to me,it was therapy for me to drive after returning from Iraq all(3)tours. Quote Link to comment Share on other sites More sharing options...
curiousB Posted October 30, 2011 Share Posted October 30, 2011 To start with thanks for your service to our country. 3 tours is an impressive level of commitment. As to your car what led you to replace the fuel punmp and filter? Had you already narrowed the problem down to fuel and not ignition? If you are sure its fuel then it could be the fuel pump relay and/or series resistor. If you have a voltmeter you could probe at the connector leading into the fuel tank to comfirm +12V is present while cranking the engine and after the motor starts running. If you are unsure of fuel vs. ignition then search this forum for issues with one bank of ignition coil going bad. Its a well documented problem for these cars but usually the car will run but very roughly (runs on 4 cylinders instead of 8). Quote Link to comment Share on other sites More sharing options...
crisavelli2002 Posted October 30, 2011 Author Share Posted October 30, 2011 To start with thanks for your service to our country. 3 tours is an impressive level of commitment. As to your car what led you to replace the fuel punmp and filter? Had you already narrowed the problem down to fuel and not ignition? If you are sure its fuel then it could be the fuel pump relay and/or series resistor. If you have a voltmeter you could probe at the connector leading into the fuel tank to comfirm +12V is present while cranking the engine and after the motor starts running. If you are unsure of fuel vs. ignition then search this forum for issues with one bank of ignition coil going bad. Its a well documented problem for these cars but usually the car will run but very roughly (runs on 4 cylinders instead of 8). Quote Link to comment Share on other sites More sharing options...
crisavelli2002 Posted October 30, 2011 Author Share Posted October 30, 2011 I did not know what was wrong I immediately "thought fuel" not igniton but like isaid after leaving the acc switch on and pumping the gas pedal the car would turn on and idle for less than 10 seconds and shut down. fuel pump relay switch you say? or igniton coil?? I will try both Quote Link to comment Share on other sites More sharing options...
steve2006 Posted October 31, 2011 Share Posted October 31, 2011 The 1st thing you need to do is determine whether it is fuel rated or spark related, so check your fuel pressure and check for sparks. From what you say it does sound fuel related but you need to be sure before throwing $$$ in there. Once you have a diagnosis of either fuel or spark repost and we can go from there, at the moment there are too many possible causes to cover. Quote Link to comment Share on other sites More sharing options...
steve2006 Posted October 31, 2011 Share Posted October 31, 2011 I didn't realize there were 2 post the same. The diagram on the link below may help you find the problem if fuel related. Pumping the gas pedal shouldn't make any difference on a fuel injected engine. Also have a good look at all the vacuum pipes a leak here could cause mixture related problems. http://www.clublexus.com/forums/ls400/373766-90-ls400-fuel-pump-system-problem.html Quote Link to comment Share on other sites More sharing options...
LEXIRX330 Posted October 31, 2011 Share Posted October 31, 2011 Merged the two post. Quote Link to comment Share on other sites More sharing options...
crisavelli2002 Posted May 9, 2012 Author Share Posted May 9, 2012 Fuel pump is not getting power...its a new fuel pump, hot wired it and it came on but when reconnected to the harness turned the ignition and the pump does not come on SMH!!! HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Quote Link to comment Share on other sites More sharing options...
steve2006 Posted May 9, 2012 Share Posted May 9, 2012 If the pump runs by hot wiring it there is a break in the circuit somewhere. If you look at the diagram you will see the "Check Connector" this is the oblong shaped black box located on the top driver's side of the engine it should say "Diagnostics" on the cover. Remove the cover and connect the pins marked FP and +B together this will effectively by pass most of the circuit and allow the fuel pump to run and the engine should then start and run. It is then a case of checking for the correct voltage at each component, start at the fuel pump and work backwards towards the fuses looking for 12 volts along the way, when you get to the point where the 12 volts has disappeared that should be the component which has failed. This link provides a bigger image All the points with +B on them should have 12 volts present. http://images.ttyr2....l-schematic.jpg Quote Link to comment Share on other sites More sharing options...
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