No compression

I’m new to all this y’all so bare with me.
I’ve got a 2000 Toyota Tundra with the 4.7L engine. Just had to get an entire new wiring harness put on the truck.
When you turn the key everything works and the motor spins as it should. Just don’t have any compression. Everything I’ve read so it’s more than likely the timing belt, just want to get some other opinions before I tare into it.
Any and all advice and information would be greatly appreciated.
Thanks

 

No compression with a tester?

could be rings, valves, or timing (like you said).

put a couple tbsp’s of oil into each cylinder, spin it over a few times and test again, how long has it been since its ran?

 

No sir didn’t have a tester.
And it hasn’t ran since late 2018, but was running up until rats got the wiring harness. I drug it out the weeds and had to start with harness, and now I’m at this point.
I read last night to take the oil cap off and see if you can see the cams move while turning it over, if not then it’s the timing. I did that, and couldn’t see a thing moving while I had someone turn it over. That’s why I was leaning more towards the timing. But I’m not real sophisticated when it comes to mechanics, so I’m kina just learning as I go

 

If the cams arent moving then you might need head work. These are interference engines, so if a valve is stuck open it could kiss a piston. Take the plastic cover off the timing gear to verify, i think most people open the pass side, but not sure.

 

I hope that’s not the case, but I will give it a check.
Thank you

 

Does it have the original timing belt? If it sat 4 years I wouldn't be surprised if that old belt snapped. You can take off the timing cover easily and look at the belt.

 

Question: No compression on ALL cylinders? And how can you be certain if you're not using a compression tester?

Here's another vote for "if things aren't moving, check the timing belt 1st". See if it's intact or not, and if it's in good health. The timing belt cover itself is only a few 10mm bolts and easy to remove, even though some ppl find the passenger side cover is easier than the driver's side cover or vice-versa.

If I were you, the first things I'd check:

1. Pop timing cover back on whichever side is easier. Is it in intact? If not, there's your issue, but I gotta say, if it snapped during operation, that engine is toast.
2. If it is intact, is it in good shape? If not, like it has cracks in it, I probably wouldn't be turning it over anymore until it's replaced. The Aisin timing+water pump kit (Aisin and Denso make Toyota OEM parts) isn't too expensive, if you feel confident in the work.
3. If it's intact and it appears to be in good shape, then get a proper compression kit and test.

On that #3 point, at least one person on here within the last year or so replaced their entire engine because one cylinder had no compression. He tore down the original engine after and it turns out it was just a stuck valve on that cylinder, something that could've probably been confirmed with a bore scope and resolved with a flush or two. The new engine (and the swap) came with a whole host of issues, which I think just added insult to injury..

 

That didn't make any terrible crunchy noises? If you spun the motor but the valve train isn't moving, it's gonna smack the valves.

 

No crunchy noises.

 

It does have the original timing belt, I pulled both covers yesterday evening and the belt looked to be in pretty good shape. No tares or big cracks and no flaking of the rubber where its looking dry rotted. I
was able to get a couple fingers under it on each side and pull, could feel no slack.

Looks like I need to get a proper compression kit and test and go from there. Thank yall for the input.

 

I like marvel mystery oil, but everyone has their favorite flavor. A little bit of oil in the cylinders will keep a dry engine from scouring the bores, and thinner oils will let you know if theres ring problems quicker on a leak down test.

 

I just realized the wording in my original post is wrong. I said the motor spins as it should when you turn the key, but its actually just free spinning.

 

But i do have a thing of Marvel Mystery oil at the house, that would be my go to as well.

 

the motor is free spinning? Or just the starter? You won’t be able to see the valve train through these covers. There’s a guard in there that would prevent that. So far thoroughly puzzled…..

 

Sadly you can't just pop the valve covers off on the 4.7 then reinstall, you need to clean everything up, then re-FIPG the two corners and potentially the half moon plugs also, unless you like oil leaks. You can sort of see inside the driver side, at least, if you remove the oil filler tube. But it's not very substantial.

 

OP could have someone crank the motor and check that air is being pumped through the engine.

 

Then how do you know you don't have compression?

 

Without actually testing compression, a dead fuel pump will let it crank but no start too.

 

Are you mistaking the starter not engaging the flywheel as no compression?

 

Digging up graves here, found this while looking for highest mileage on timing belts. @Sharp27 any update on this one?