How do you check the engine compression on a Gen 3 Prius?

i think there's a way to spin the ice for testing, but don't know what it is.

 

it could be. i'm sure there's a thread or post buried in here somewhere.

 

Don't forget that this engine is an Atkinson cycle, the intake valve closes quite late. The correct reading should be much less.

 

you may want to download the service manual. 15 bucks a day or something?

 

With a laptop running Toyota's Techstream software plugged into the diagnostic port, you have a command that tells the engine to crank at 250 rpm for your compression-testing pleasure. The acceptable range of pressure readings can be found in the service manual at techinfo.toyota.com.

If that's not convenient, your leakdown test idea is a perfectly good one. That's a nice test because you've got less cranking noise and you can really hear if you've got hissing into the exhaust or intake manifolds, bubbles in the coolant, etc.

There doesn't seem to be a single standard size for the orifice in a leakdown tester, so it's difficult to give figures to compare between people using different makes/models of tester. On the other hand, it doesn't depend on whether the engine is Atkinson or Otto cycle, so whatever numbers are considered good in the literature with your leakdown tool ought to be good.

-Chap

 

You're in for a world of hurt just getting a spark plug out: Google "youtube nutzaboutbolts spark plug". About an hour's disassembly, the wiper arms, motor and bottom of windshield cowl all have to come out.

 

Per alldatadiy (to which I subscribe) compression test pressure is 118 psi (813 kPa), min pressure is 89.5 psi (617 kPa) and difference between cylinders should be no more than 14.5 psi.

 

Compression test is about 2/3 of way through this. Didn't really read it; Techstream is mentioned, and to have the car in maintenance mode.

 

I can't help noticing those 'alldatadiy' numbers are all different from the ones in Mendel's attachments (which I trust are from the service manual on techinfo.toyota.com).

That's one of the reasons I don't go anywhere for my service info except the Toyota manuals....

I forgot to answer that part earlier. It's a really low friction engine, so the answer is

1. make sure the system is OFF so nothing will try to start the ICE
2. put hand on crank pulley
3. turn until timing mark points where you want it.

The tricky bit is holding the crank in that position when you put the air pressure on. I just used a breaker bar and socket on the crank pulley nut, wedged the handle against the ground with my foot while standing up to open the air valve and note the readings. It worked, if the contortions were a little awkward.

-Chap

 

Mine are from a single pdf, file titled "Repair Manual". Could be some supersceding going on. This is page one:

 

Toyota's wiring manuals are super. You don't just get circuits, but the routing of all harnesses, locations of all junctions and ground points, a whole section dedicated to identifying any connector by location, color, and shape (and with part numbers in case you need to replace one) ... anybody doing electrical work or diagnosis and trying to do without is playing a big self-imposed handicap.

The "New Car Features Manual" might have a forgettable title, but it's a hugely useful manual. All the other volumes tell you how to diagnose what's wrong with stuff or fix it, but they are filled with assumptions that you know what all the stuff is in the first place and why it's there and how it's supposed to work. That's all what's in the New Car Features Manual.

-Chap

 

I have to agree. Big difference between 118 psi and 199 psi.

 

That’s an easy one