I have recently acquired a new purchase of a 1997 ls400 with around 146,000 and only 2 owners and very few mechanical issues. One that has had me quite stumped. Some back story to the problem. The first round of small repairs was to replace the Maf and idle air control valve connectors since the tabs were broken off of it. Later in the day the vehicle was driven around town and parked at the store for around 30 minutes, upon returning and attempted to start the car I got a crank no start, it wouldn't even attempt to catch. My first thought was the connectors I replaced but after double checking everything looked good. So down the checklist of diagnostics. I was able to confirm spark by arcing one of the leads onto a strut tower nut. I had a can of brake cleaner and had someone spray it into the intake while cranking and it would catch and run for around 5 seconds or so. My suspicion is fuel. The vehicle unfortunately wasn't able to be started and was hard towed home with the headlights and hazards on which killed the battery completely. The next morning the vehicle was attempted to be started and it cranked right up first crank without the battery having any charge applied to it. Weird. Fast forward a month, same situation vehicle is driven and parked for around an hour and once again crank no start. The battery leads were removed and touched together to remove all stored voltage in the system, still no start. By some miracle, with a random sequence of locking and unlocking the driver door with the key, leaving the key in the ignition and opening the trunk it was able to be started and driven home, took around 1hr of waiting for it to crank and start back up. After the second time that happened I replaced the positive battery terminal and rebuilt the negative since it's a $700 wiring harness and replaced both circuit opening relay and fuel pump relay with the updated Toyota part number. The problem wasn't able to be duplicated again so the vehicle was driven around town with no problems. Yesterday the car was driven to the local locksmith to have a key cut and once again attempting to go home the car cranked but didn't start. I tried to use a jumper cable and jump the battery terminal to the fuel pump terminal in the diagnostic port under the hood but no luck getting it started. I gave up and had it towed to a friends house a couple blocks away where it sits now. We sprayed some starting fluid and were able to get it to start for 15 seconds. I have heard the ls400s having issues with Ecu capacitors failing and causing issues, however I would think that would cause me weird drivability issues. The vehicle has an aftermarket viper alarm system installed and I didn't get a factory key fob with the vehicle. My suspicion was an immobilizer fault but from my understanding the viper system works with the factory system which in 1997 according to the owners manual only cuts the starter. Can the viper system be interrupting the fuel wiring and causing a fuel cutout. Do I have a failing fuel pump that is intermittently going at the worst opportune time? I apologize for the long post but I wanted to give as much details to help with the diagnosis, any help is appreciated. Thank you!

 

Based on the symptoms that you've described, either your fuel filter is clogged or your fuel pump is at the end of its service life. If you're a DIY'er, these aren't hard to replace. The fuel filter is in the back of the car near the rear axle & to replace the pump, just pop the backseat & the round metal cover then you can get to it. Good luck.

 

Fuel pump and fuel filter were going to be the next items I was going to replace. I was however questioning it because I have not had issues with loss of power, fuel economy, cutting out or weird idling. Also, with it randomly restarting after a period of time. Around town the vehicle runs normally with no issues or drivability concerns. Just for discussion, can a clogged filter be causing excessive strain on the pump causing it to have excessive resistance? I have the issue narrowed down to lack of fuel I believe, but I don't know if it's electrical or mechanical.

 

As the pump reaches the end of its life cycle, it can operates intermittently for a short time before it completely goes out. Your car is 24 years old & most likely the pump is still OG so you're due for a new one. In regards to the filter, if it's clogged, sure it'll make the pump works harder & in turn will shorten the life of the pump so my recommendation to you is to change both of them so you can sleep better at night.

 

I ordered a Denso fuel pump kit with screen and a wix filter. No parts store had a fuel filter in stock of any manufacturer for some reason. Once it arrives I will install and report back. Is there any fuel pressure test points on the 1uz-fe?

 

The 97 doesn't have a test point for you to hook up a pressure gauge. If you want to perform a pressure test, you can remove the union bolt at the end of the delivery fuel rail then hook up the pressure gauge there or break the fuel line connection right next to oil filler cap & install a Tee adapter.

 

My parts have arrived. Not a fan on ordering from Amazon but their price was so much cheaper than anything locally. When reading reviews for Denso fuel pumps alot of people were saying that they were made in China now. Thankfully when the box arrived, right on it Made in Japan. Also, plan on running 2 cans of Toyota fuel injection cleaner that they use for EFI services at the dealership just for good measure. Hopefully this random crank no start is a failing fuel pump.

 

So today I replaced the fuel pump. Pretty straight forward procedure, out with the old and in with the new. Had to do it with a full fuel tank which was quite difficult. After the fuel pump replacement I decided to do an efi service. I pulled the fuel pump relay, and started to disconnect the fuel connection that leads to the fuel regulator on the driver bank. It felt like it had pressure behind it so I decided to start the engine and let it die out to get rid of some residual fuel pressure. Cranked the engine over and it started and ran, and kept running with no fuel pump relay in place. I pulled the efi no.2 10 amp fuse and that stalled the engine. But upon restarting it, it fired right back up with no fuse in place. Same thing happened with the efi no.1 fuse. I even disconnect both battery terminals while it was running and it kept idling fine, ecus must have really good capacitors. Could any of that possibly have anything to do with my random crank no start issue, still have the ecu suspect. Does anyone have a wiring diagram for the fuel system for a 1996/97? Or a way to disable the fuel pump so I can run a can of injector cleaner through?

Also, I noticed weak exhaust pulses. I was able to cover both exhaust tips without much force. It is possible that my catalytic converters are clogged up and causing the engine to not breathe properly?