91 Ls400 Won't Start-no Fuel

[70 140]

Hey,

I just found this forum and read a bunch of stuff on lextremes site (nice work). I have a 91 LS 400 that has had no previous problems until now...it doesn't start. I verified that there is spark. I reset the alarm and tested it out just in case that was the problem, it seems to work as normal. So I sprayed some ether in the air filter and got the car to cough and stumble. So I figure I have a fuel problem.

I checked all of the fuses, both under the hood and in the kick panel. I checked the M4 EFI relay and switched it with the horn. I pulled the fuel pump relay and tested it with a 12v source - it works. With the key "on" and the yellow cased wire to the pump unhooked in the trunk I get no reading on the voltmeter. I also get no reading at the terminal where the fuel pump relay goes.

I just read that I can bypass the fuel pump ecu by connecting fp to B+ on the diagnostic connector. This should give me a V reading at the fuel pump right? I will try this in the morning.

Any other ideas or suggestions ?

Thanks,

Erik

[ArmyofOne]

Hey,

I just found this forum and read a bunch of stuff on lextremes site (nice work). I have a 91 LS 400 that has had no previous problems until now...it doesn't start. I verified that there is spark. I reset the alarm and tested it out just in case that was the problem, it seems to work as normal. So I sprayed some ether in the air filter and got the car to cough and stumble. So I figure I have a fuel problem.

I checked all of the fuses, both under the hood and in the kick panel. I checked the M4 EFI relay and switched it with the horn. I pulled the fuel pump relay and tested it with a 12v source - it works. With the key "on" and the yellow cased wire to the pump unhooked in the trunk I get no reading on the voltmeter. I also get no reading at the terminal where the fuel pump relay goes.

I just read that I can bypass the fuel pump ecu by connecting fp to B+ on the diagnostic connector. This should give me a V reading at the fuel pump right? I will try this in the morning.

Any other ideas or suggestions ?

Thanks,

Erik

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that is correct, you can bypass the ECU. but it sounds as if the pump may be bad anyway. either that or the relay is gone.

to check for fuel flow, disconnect one of the fuel lines before one of the rails. if it squirts fuel, you have gas until that point. if that happens check your injectors.

[70 140]

I guess I will pull the pump out this afternoon and test it. I can't figure why I don't get a voltage reading though.

I have been reading that the fuel pumps last a long time. Theres only 350 000 on the car :D

[daffy]

Hi 70 140,

I am curious, before the car quit, were there any noises coming from the back seat area? I was told that this would be warning that fuel pump is about to go. If you didn't hear anything, then I'd best change my pump soon to prevent being stranded somewhere and having to tow it somewhere. It would be cheaper (I think) to replace pump here at home. I have over 250,000 miles so far, so maybe at 300.000 miles I will change the pump unless you find something else wrong. Thanks, Daffy

[stockgixer]

I agree w/ Army One. If you're not getting fuel across, then you could have a bad pump. Also worth checking the fuel filter.

However I doubt it's a clogged filter unless you tossed a chunk of dirt into the tank during your last fill-up.

Just some thoughts. Good luck.

Sonny

[Lexls]

Erik,

You won't get a reading on the yellow cased wire in the trunk because when it's disconnected there is no power ;) . What you want to do is check for resistance, not voltage. Measure the resistance on the terminals of the yellow cased wire in the trunk. 0.2 - 3.0 ohms means the pump is good, above or below the repair manual says to replace the pump. Tell us what ya get! Sounds like the pump...

[70 140]

Sorry I'm new to this whole thing......Lexls I knew I should have typed that differently . I disconnected the yellow cased (pump) wire and tested the hot terminal (black wire). So with everything normal I get no voltage at the terminal the pump hooks to. When I jump the fp to the B+ on the diagnostic connector I get 12v at the back. The pump gave me 2.2ohms resistance, so its ok? I guess I have a bad pump ecu?

(sorry for the following bad description) Now the "fuel rail" I assume to be under the black plastic covers on each side of the engine, just above the valve covers? There is a 14mm (if I remember correctly) bolt with alloy washers that has a hose hooked to it (like a motorcycle brake hose) just to the rearside of the engine lift hook on the passenger side of the car. This looks to be attached to the fuel rail? Should I crack this open and crank the car?

Daffy: The car was running fine with no noticable noise from the fuel pump. It just wouldn't start one day. Pumps from the dealer look to be worth a couple of bucks. I would wait until it goes. If your lucky like I was it will die in the garage.

[Lexls]

Ok, well you got a normal reading for the fuel pump so that must be ok...something else then. You'll probably have to do what army said and check to see if you get fuel at the injector rails.

Other possibilities... fuel pump resistor? Pressue regulator? Once you see if you're getting fuel you can rule more things out.

[ArmyofOne]

Sorry I'm new to this whole thing......Lexls I knew I should have typed that differently . I disconnected the yellow cased (pump) wire and tested the hot terminal (black wire). So with everything normal I get no voltage at the terminal the pump hooks to. When I jump the fp to the B+ on the diagnostic connector I get 12v at the back. The pump gave me 2.2ohms resistance, so its ok? I guess I have a bad pump ecu?

(sorry for the following bad description) Now the "fuel rail" I assume to be under the black plastic covers on each side of the engine, just above the valve covers? There is a 14mm (if I remember correctly) bolt with alloy washers that has a hose hooked to it (like a motorcycle brake hose) just to the rearside of the engine lift hook on the passenger side of the car. This looks to be attached to the fuel rail? Should I crack this open and crank the car?

Daffy: The car was running fine with no noticable noise from the fuel pump. It just wouldn't start one day. Pumps from the dealer look to be worth a couple of bucks. I would wait until it goes. If your lucky like I was it will die in the garage.

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there is an easier way. i keep forgetting you have an LS400. there shoudl be a cold start injector on your engine. it shoudl be in the upper intake manifold, it will hae a fuel line going to it. pull it off and DONT CRANK THE CAR, have a friend turn the key to the ON position (where all the lights come on and the door ding thing rings incessantly LOL).

if you cant locate the CS-i, try the Fuel Pressure Regulator line. shoudl have the same effect.

scratch that, you have no cold start injector. so try the fuel presssure regulator approach.

[70 140]

Ok, It runs.

I opened the bolts on the fuel rail and got nothing. I put a length of hose on the metal line inside the tank and blew air through it. It bubbled out at the rail so I knew the line wasn't blocked.

I took the pump out of the tank and hooked it up to a spare battery. I could see the impleller spin at about 5 rpm and the pump started to smoke!! I took the pump off the bracket and pulled it apart. Inside it was full of gum and varnish. I soaked it in carb cleaner and worked the motor until it spun freely. I put it back together and tried it again. This time the pump spun fast, I popped it back on the bracket and put it back in the tank. Hooked up the battery and fuel sprayed everywhere at the rail, I tightened everything up and the car started.

So it in fact was the pump. The ECU is fine, its running without the jumper on the diagnostic connector. The pump is noisy as heck now....I will have to buy a new one this week and put it in, I don't think my repair is long-term.

Daffy: If you have never been in the tank I would suggest you open it up and take a look. I found at 350 000 there was no rust or gum in the tank. But the filter screen on the pump was glazed up, and some how my pump was full of gum.

Thanks for all the input. :D

[ArmyofOne]

Ok, It runs.

I opened the bolts on the fuel rail and got nothing. I put a length of hose on the metal line inside the tank and blew air through it. It bubbled out at the rail so I knew the line wasn't blocked.

I took the pump out of the tank and hooked it up to a spare battery. I could see the impleller spin at about 5 rpm and the pump started to smoke!! I took the pump off the bracket and pulled it apart. Inside it was full of gum and varnish. I soaked it in carb cleaner and worked the motor until it spun freely. I put it back together and tried it again. This time the pump spun fast, I popped it back on the bracket and put it back in the tank. Hooked up the battery and fuel sprayed everywhere at the rail, I tightened everything up and the car started.

So it in fact was the pump. The ECU is fine, its running without the jumper on the diagnostic connector. The pump is noisy as heck now....I will have to buy a new one this week and put it in, I don't think my repair is long-term.

Daffy: If you have never been in the tank I would suggest you open it up and take a look. I found at 350 000 there was no rust or gum in the tank. But the filter screen on the pump was glazed up, and some how my pump was full of gum.

Thanks for all the input. :D

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DO NOT DRIVE THAT CAR ANOTHER INCH...DO NOT EVEN START IT!!!!!!!!!!!!!!!!

if the fuel pump smoked, that means there may have been a spark at one point, somewhere. that also means that you could explode. i wouldnt move it until you have a chance to fix it. dont even start it. if the pump is noisy, it probably only has a few hours of life left anyways. some pumps make noise (most notable chevy silverado/tahoe/subruban/k5blazer/escalade/yukon platforms fuel pumps, you can hear them INSIDE the backseat of some models at idle.

[70 140]

Don't worry. The pump is out already. I put the cleaned up pump in the tank....the car started I knew the pump was the problem. I pulled it back out and am awaiting the arrival of a new one. I don't think I ran it for more then 30 seconds, just long enough to unhook the jumper on the diagnostic box and establish that the ecu worked. It won't be driven until the new pump is installed. It sounded pretty bad, I don't think it would make it to the end of the driveway.

How much should I be paying for a new pump? Lexus is checking the price and availabilty for me now. Is their a better source?

[ArmyofOne]

Don't worry. The pump is out already. I put the cleaned up pump in the tank....the car started I knew the pump was the problem. I pulled it back out and am awaiting the arrival of a new one. I don't think I ran it for more then 30 seconds, just long enough to unhook the jumper on the diagnostic box and establish that the ecu worked.  It won't be driven until the new pump is installed. It sounded pretty bad, I don't think it would make it to the end of the driveway.

How much should I be paying for a new pump? Lexus is checking the price and availabilty for me now. Is their a better source?

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maybe me. :D Hang on and i will check.

EDIT:

FUEL PUMP, LS400, Aisan 90-94 List Price: $329.30 Your Price: $246.98

FUEL PUMP, LS400, Denso 90-94 List Price: $318.61 Your Price: $238.96

probably the best i can do ya.

EDIT again: bet you are wishin it was the relay:

FUEL PUMP RELAY, LS400 90-94 List Price: $63.13 Your Price: $47.35

[70 140]

Thanks for the info armyofone. I am waiting to see what Lexus wants.....no doubt a lot more. I have had so much fun doing this I may go to the wreckers and see what I can get. I doubt there are too many LS400's in the scrap yard though.

Yeah the relay would have been nice. A 20amp fuse would have been even better :D

Thanks for all the help everyone.

Erik

[Lexls]

thepartsbin.com has the pump for $178 :whistles:

[ArmyofOne]

thepartsbin.com has the pump for $178 :whistles:

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yeah but its not lexus, or its remaned, these are NEW. :)

but i dont blame you. i just offered the best that i can. :)