Gumart1 Posted February 2, 2005 Share Posted February 2, 2005 I am getting some great advice on my "new" 98LS400 and would like another recommendation. The prior owner had two unrelated issues in the past 6 months. The first was that he would get an "intermittent" no crank from the starter. The Lexus Dealership diagnosed the problem as a bad starter (isn't this pretty rare for a '98 or any year for that matter?). In addition to the bad starter, the owner noticed that when the engine was warm and had just been driven, when he would attempt to restart, it would crank for an extended period before turning over. When the engine is cold it turns over fast like it should. The Dealer found no codes stored, but installed a fuel pressure gauge and the pressure was found to be low at 28-30psi (what is normal pressure?). The service ticket states that after shutting off the car, the pressure dropped to 0psi after a few minutes. Their recommendation at the time was to replace the fuel pump, regulator, fuel filter screen, and second fuel filter. The prices for the parts from the Dealer were $290 for the pump, $145 for the regulator, $9 for the fuel filter screen, $31 for the fuel filter, and $6 for an o-ring. I don't know what the labor charge was, but I would have my independent mechanic tackle the job. My question is, from the info above, do I have a bad fuel pump? Or should I change the fuel filter and see if that helps first? Or is there a separate issue that may be causing the long warm start symptoms like a computer related issue or bad or dirty injectors? Remember the problem does not occur with a cold engine. Thanks. Quote Link to comment Share on other sites More sharing options...
Lexus_Luxembourg Posted February 2, 2005 Share Posted February 2, 2005 Just my 2 Cents... Remember it's hard to make a diagnostic over The Net. Let's see what can cause this. Your engine doesn't fire up immediately like it should do. 1. Electric problem. Maybe the starter just draws too much power so it literally pulls off the juice from the ignition. Not very probable but I'd have the batterie checked. Also remove the connectors and look if there's white deposit. No, it's not enough to look at it from above, you must remove the connectors and also check the insides. Also wiggle at the starter connectors. Might be a loosened one on that side. Not very probably either. Finally it may be an ignition spark not strong enough to ignite the mixture. Hm, have the spark plugs be changed at 60.000mls? 2. Fuel supply. If so the fuel mixture is not correct at start up. A faulty pump can not feed the engine and takes time to build up pressure. (Now wit restrictions as I may be wrong on this:) Injectors need a certain pressure to "open". If the pump is bad it takes a longer time to build up that pressure. Regulators have similar effect if they go bad. Pressure remains in a sound system for a long time as all those who ever opened a fuel line can attest. It will be necessary to put a fuel pressure gauge into the line. This will tell you what's happening. You will see if there's residual pressure, how the pressure builds up and if there's any fluctuation. Yes, a gauge will set you back at least 50$ but consider how much you will spend when a pro does this. :( Another possibility are shot injectors. They should last a long time, almost indefinitely IF the fuel filtration system is always in top condition. But if metallic particles entered the lines they will have worn out the injectors. Diesel or high pressure injectors are easier harmed than the "low tech" injectors the LS400 used. Injectors can be tested and refurbished by specialised companies. It's not difficult to take them off (on most cars, not sure about the LS) but flow testing is not possible at home. Beside this it's always possible this is caused by an altogether different fault. So to resume: 1. Check batterie under load test. Even when it's almost new. Have had brand new batterie with a broken cell. 2. Change plugs if not already done. 3. Get a pressure gauge and see what it reads. Hope this helps. Quote Link to comment Share on other sites More sharing options...
Lexls Posted February 2, 2005 Share Posted February 2, 2005 I just looked at my 98 repair manual.... It says normal fuel pressure for your car at idle is 44-50 psi. When the car is shut off fuel pressure should remain at 21psi or more for 5 minutes. If pressure is not as specified, check the fuel pump, pressure regulator and/or injectors. Now I rarely hear of fuel pumps or injectors going bad in these cars. My best guess according to your info is that you have a shot fuel pressure regulator. You can rule out the fuel pump as the culprit by testing it.... normal is 0.2 - 3.0 ohms at 68 degrees. You can check it by removing the back panel in the trunk then unhook the wiring harness to the gas tank. The wires will probably have a yellow cover and will wrap over the tank behind the back seat. The fuel pump and regulator are in the tank on the rear seat side of it. No need to take the back seat out right away. Quote Link to comment Share on other sites More sharing options...
Lextech23 Posted February 3, 2005 Share Posted February 3, 2005 The reason for the fuel pump suggestion is that there should be pressure in the system at all times. If the meachanic said it dropped to 0 after a few minutes, the problem is the check valve in the fuel pump. In a returnless fuel system like the 98 ls there is a valve in the fuel pump that keeps the line pressurized even when off. As far as the starer it is very possible for it to be going bad. I have seen a lot of starters go bad on any lexus model Quote Link to comment Share on other sites More sharing options...
Gumart1 Posted February 8, 2005 Author Share Posted February 8, 2005 Thank you for the research and the very intelligent answers. It seems like the problem is either in the pump or the fuel pressure regulator, but I don't think I need to replace both as the Dealer recommended. I feel they didn't exactly find the problem besides confirming the PSI drop. I am not too mechanically inclined to tackle it myself. I will be seeing my mechanic this week, but wanted to mention a few observations about the long cranking when the engine is warm. I've noticed that about a minute and 10 seconds after shutting the engine off, I will hear a pump noise that lasts about 2 seconds and sounds exactly like what one would hear when starting a cold engine when the pump is activating. What I don't understand about the pressure drop is why it starts on a cold engine and not a warm one. Is it because with a cold engine the pump is introducing fuel on command at ignition vs. a warm engine which does not ask the pump for fuel? Quote Link to comment Share on other sites More sharing options...
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