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'96 Ls400 Won't Start; No Compression Readings


latintxn54
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Greetings to all LS enthusaists! I need your insight into the problem I've got with my LS400. I've replaced the timing belt with an OEM belt (to insure the markings line up exactly). I've actually replaced a few LS400 timing belts and the procedure has become 2nd nature to me. This time, the vehicle will not start. I'm getting spark, fuel, I've confirmed the Crank & Cam Pulleys line up beautifully just as the Lexus Manual instructs. My problem is this - no compression in any of the cylinders. I've come to accept the undisputed fact this is an Interference engine and that I may have bent valves. I've come to the point where I need to decide which directions to take. My neighborhood Lexus/Toyota mechanic said if it truly is bent valves, I can either replace and/or repair the heads, replace the motor or just sell the car as is. Is there any way to be absolutely sure I've got bent valves and that this truly is the culprit to the engine not starting? Any replies would be so appreciated. Regards,

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Was it running properly before the timing belt replacement?

VERY good question. No! A little history behind the problem. I replaced the timing belt before this problem occurred and everything started right up. Shortly after replacing the belt (1-2 days), I went to start the engine but while spinning, it made a odd stumping noise and from that point on, it would not start. My first & immediate thought was "sounds like it's out of time". I removed everything to inspect the timing belt and I did notice 2 of the rubber grommets (that fit on top of the distributor caps used for sound cushioning) had fallen off and were sitting right under the crankshaft pulley and belt. they looked shredded as if they got caught up in the crank gear teeth. My thought is that these grommets caused the belt to jump and valves to bend. Does this sound possible to you? Again, thanks for your insight & reply! V. Gonzalez

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Maybe you could remove the sparkplugs and insert a camera. You know the type they sell in hardware store for inspecting hvac and such. It should fit in the hole of the plugs.

Thanks for that suggestion. Someone previously mentioned using one of these but I couldn't find where to purchase one. I was also told that using one of these tools, I should be able to see 'nick' marks on the top of pistons. Off to the hardware store. Thanks!!

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Maybe you could remove the sparkplugs and insert a camera. You know the type they sell in hardware store for inspecting hvac and such. It should fit in the hole of the plugs.

Thanks for that suggestion. Someone previously mentioned using one of these but I couldn't find where to purchase one. I was also told that using one of these tools, I should be able to see 'nick' marks on the top of pistons. Off to the hardware store. Thanks!!

You can buy them at Home Depot or check on-line like at Amazon.com, it think it is cheaper on Amazon.com. But you might prefer HD since it is easier to return in case the camera is too large for the hole.

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Another way to check for bent valves is to pull a cam cover and check the lash on a few. When the valve bends it doesn't return all the way the seat so if you have say .060 lash on a valve that should have .008, you know it's bent. If one or two are, most are. Which of course would be bad news.

Good luck with it.

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My thought is that these grommets caused the belt to jump and valves to bend. Does this sound possible to you? Again, thanks for your insight & reply! V. Gonzalez

If the crank and cam pulleys line up beautifully, as per your first post, then I would not think that the belt jumped. If it did jump, I would expect it to remain in its new position. There should be a lot of tension on the belt.(you did remember to pull the tensioner pin, right?).

Still, the fact that you now have no compression is both disturbing and puzzling. IF valves did get bent, I would think you would have a little compression on several cylinders, even if ever so slight. Are you sure the compression gauge works correctly?

You might want to use an air compressor and try pressurizing several cylinders after you have confirmed that the valves are (should be) closed.

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...My first & immediate thought was "sounds like it's out of time". I removed everything to inspect the timing belt and I did notice 2 of the rubber grommets (that fit on top of the distributor caps used for sound cushioning) had fallen off and were sitting right under the crankshaft pulley and belt.....

Did you happen to check the timing marks before you pulled it apart? If pieces fell between belt and gears that might have made it easier to jump a notch.

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Another way to check for bent valves is to pull a cam cover and check the lash on a few. When the valve bends it doesn't return all the way the seat so if you have say .060 lash on a valve that should have .008, you know it's bent. If one or two are, most are. Which of course would be bad news.

Good luck with it.

thanks for your tip. Should I decide to investigate further, I'll consider your suggestion.

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My thought is that these grommets caused the belt to jump and valves to bend. Does this sound possible to you? Again, thanks for your insight & reply! V. Gonzalez

If the crank and cam pulleys line up beautifully, as per your first post, then I would not think that the belt jumped. If it did jump, I would expect it to remain in its new position. There should be a lot of tension on the belt.(you did remember to pull the tensioner pin, right?).

Still, the fact that you now have no compression is both disturbing and puzzling. IF valves did get bent, I would think you would have a little compression on several cylinders, even if ever so slight. Are you sure the compression gauge works correctly?

You might want to use an air compressor and try pressurizing several cylinders after you have confirmed that the valves are (should be) closed.

Yes, the TB tensioner was reinstalled at the appropriate time. And as you say, I would expect some reading from the the Compression test but ALL 8 not showing compression? So strange. And yes, thinking my new compressor might be defective, I borrowed my neighbor's compressor and yet still no readings. I'll try your air-in-cyl suggestion to see if this changes things.

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...My first & immediate thought was "sounds like it's out of time". I removed everything to inspect the timing belt and I did notice 2 of the rubber grommets (that fit on top of the distributor caps used for sound cushioning) had fallen off and were sitting right under the crankshaft pulley and belt.....

Did you happen to check the timing marks before you pulled it apart? If pieces fell between belt and gears that might have made it easier to jump a notch.

Oh yes! I made sure the markings were lined up (just as the Lexus manual instructs) prior to removing the belt and was also careful not to turn the crank once belt is off.

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