I keep reading that the 928 motor must never be turned backwards.

I would like to do a leakdown test, but am concerned that if I stop the relevant piston before TDC, the pressure may rotate the motor backwards.

What is the easiest way to accurately find TDC on the cylinders that do not correspond to the TDC mark on the crank pulley ?

Degree wheel ?

Is there any relevance in a compression test over & above a leakdown test ?

 

Dis nie die ergste nie Miles. As kompressie hom bietjie terugstoot sal daar nie skade wees nie. Ek het my 32-klep motors al teruggedraai (versigtig natuurlik) sonder skade. Ek dink die idee is om net nie mal te gaan nie. Iedergeval, in jou gevel ... geen probleem nie boet

 

Hm ek verstaan jou vraag nou beter. Ek dink ek het nie die tegniese kennis nie jammer, ek sal nou shaddap.

 

H, when did you start using the Dvorak keyboard?

 

Try that crazy keyboard out at these 2 places:

http://typingtest.com/test/default.asp - Use 1 minute, Strategic Alliances, and WPM. I got a 99WPM NET

http://www.offthewrist.com/frenzy/index.jsp?gameId=0 - How fast can you type the alphabet? I got 3.67

Those numbers were on my laptop. I can type faster on a normal microsoft keyboard.

 

LOL

 

Ya boet, unfortunately ek is a verdompte engelsman ! Please use your original keyboard.

 

"O" on the balancer, then use the firing order as your sequence.
tip..pull the plug boots out first, then blow air in there to removed any dirt and debris.
By removing them you will be assured you can easily get them out when the engine is hot/warm for the test. Not fun trying to pull a plug boot of a hot engine.
reinstall boots and go for a drive and get the car up to operating temp.
Remove the boots and all the plugs and go ) TDC on #1....then move to the next cylinder in the firing sequence after you turn the crank to around to TDC again

 

Thanks Tony, but I am still a bit confused.

Looking at a picture of the crank, the crank throws seem to be 90 degrees or less apart, with 2 conrods on each throw.

Surely in 720 degrees of crank rotation there will be 8 cylinders firing, which to me seems that to work from one cyl to the next in firing order, one would only turn the crank 90 degrees (if the throws are 90 degrees apart). But does it have equal spacing between firing ?

Is this correct ? Therefore I can only think of making a degree wheel to accurately find the TDC positions of each cyl, if one knows where they are.

Or have I missed a chance to keep quiet ?

 

I don't worry about small backwards turns of the engine. Exactly why they say not to has been discussed at some length. It's either to not stress the tensioner or to not jump a belt. Either way, 10 degrees won't hurt.

Yes, turn the crank 90 degrees and move to the next piston in the firing order to get TDC. For a leak-down test hold with a breaker bar. If you're not right on ) and I expect not) it'll torque the crank and you'll know which way to correct.

As for compression vs. leakdown, I prefer compression in the car as a diagnostic check. If the numbers are nicely even then there's no problem. A leak-down test will help identify what is failed. Rings or valves? Can't be conclusive as a major failure of one (broken ring) will mask the failure of the other (burned valve).

 

Thanks Glen, makes sense.

 

I did the leakdown test yesterday, and my worries about the applied pressure turning the motor, if not exactly at TDC, were groundless.

I did a few cylinders with them just after TDC, and there was no tendency for the crank to turn. It's pretty tight !

Results, 2 cylinders at 6%. all the others 5%, using a Crypton 66 tester.