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Fuel pump getting weak, how hard to change?

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Old 02-18-12, 12:27 AM   #1
ImWildBill
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Default Fuel pump getting weak, how hard to change?

I have a 1990 LS 400, is the pump hard to replace in this car? I'm thinking it's in the tank, I've done fuel pumps before just not on the Lexus yet.
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Old 02-18-12, 03:42 AM   #2
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on a 95-97 it's easy, no need to drop tank, just have to remove trunk floor mat, trunk trim cover, seat cushion and back and then 8 bolts on the set plate on top of tank, 3 nuts on fuel pump bracket, disconnect hose and pull it out!

not sure if a 1990 is the same but I bet it is a very similar procedure
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Old 02-18-12, 06:54 AM   #3
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The location appears to be the same per the attached diagrams. You might want to check the fuel filter before replacing the pump.
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Fuel pump getting weak, how hard to change?-1990-ls400-fuel-pump-figure-1.jpg   Fuel pump getting weak, how hard to change?-1990-ls400-fuel-pump-figure-2.jpg  
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Old 02-18-12, 09:21 AM   #4
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Maybe this information could help, http://www.lextreme.com/fp.htm
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Old 02-18-12, 09:33 AM   #5
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How do you know the fuel pump is getting weak? What symptoms are you experiencing? Could it be that you just have a clogged fuel filter that needs replacing?
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Old 02-18-12, 11:27 AM   #6
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What are the symptoms first?
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Old 02-18-12, 10:23 PM   #7
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The car has been harder to start the last couple weeks and now acts at times like it's starving for fuel when I hit the gas then runs ok. The other night on my way to work, I took the exit ramp off the highway and my car stalled out when I was almost stopped. It started back up and stalled again at the next light.

My Nissan did the same thing when the fuel pump was going out a few years ago. I'm planning on changing the fuel filter first then the fuel pump if it doesn't fix it.
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Old 02-19-12, 05:25 AM   #8
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Originally Posted by ImWildBill View Post
My Nissan did the same thing when the fuel pump was going out a few years ago. I'm planning on changing the fuel filter first then the fuel pump if it doesn't fix it.
I'd suspect other causes of this problem before the fuel pump - like the MAF.
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Old 02-19-12, 12:13 PM   #9
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Gas stateside isn't dirty with lots of particulates in it, I doubt a fuel filter. Any codes?
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Old 02-20-12, 10:31 PM   #10
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Have you tried bypassing the fuel pump resistor? It's fairly easy to test and could possibly be causing the problems you've described.
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Old 02-24-12, 04:40 AM   #11
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It isn't throwing any codes, it's been running rough for a few months now. I installed new plugs and wires and it helped a bit but not much. I was looking online for a MAF and they are almost $400 for what I've seen from a couple I found that were rebuilt.

I've been planning on changing the filter and pump before my son starts driving the Lexus here soon and doing the maintenance it's needed due to previous owner not doing maintenance or repairs on the car for several years. If it's still having issues after replacing the pump and filter I'm taking it in to get diagnosed so I'm not wasting money on replacing good parts....
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Old 03-20-14, 03:25 PM   #12
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[/SIZE]
Quote:
Originally Posted by LScowboyLS View Post
on a 95-97 it's easy, no need to drop tank, just have to remove trunk floor mat, trunk trim cover, seat cushion and back and then 8 bolts on the set plate on top of tank, 3 nuts on fuel pump bracket, disconnect hose and pull it out!

not sure if a 1990 is the same but I bet it is a very similar procedure
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Old 03-20-14, 04:50 PM   #13
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on the 8 bolts, these have a very light torque of 29 inch pounds - that is just about 2.5 foot pounds, use a torque wrench meant for this range, or you will get it too tight and then the plate will be warped and you will never get it to seal and the inside of the car will smell like gas from now on!

message me if you need a high quality small torque wrench for this, I probably know of a deal on one!
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Old 03-21-14, 05:52 AM   #14
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ive yet to sell or even hear of a ls 400 fuel pump going out...doesn't mean it hasn't happened,but just like our master cylinders,they are very very reliable
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Old 03-21-14, 09:50 AM   #15
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Has the OP checked the fuel pressure specs as per the factory manual? Might be an idea before condemning a part and replacing it.
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