1993-VG30E-GXE

Guys, is it safe to hold a screwdriver in the sparkplug hole of the VG30E to feel for TDC physically, with flexbar on on crankshaft pulley nut (I guess i'll need a second person)? The instructions for the leakdown test say for some reason to find a little bit before TDC, I can't see how to accurately do that from looking at the distributor. So I figured, is it possible to feel it then back it off slightly.

What do you suggest.

CapedCadaver

iTrader: (8)

line the crank pulley up so that the last notch is on the pointer mark sticking out of the timing cover. make sure you are on the compression stroke too (ie, valves on that cylinder both closed) or else you will just dump all the air out your open valves.

LvR

............. and for the other 5 cylinders?

The screwdriver method is probably the easiest and only method if you don't have a calibrated dial guage fitted to your crank pulley.

Leak-down tests generally gets done with the rings under the compression stroke mechanically (iow don't go past TDC and then turn it back!), but still on its way to the top so as to prevent (about 15 degrees before TDC for the particular cylinder) the rings sitting in the normally slightly more worn TDC position where the rings generally tend to wear a radial groove in the barrel.

IMO its very close to a waste of time since a well controlled compression test can tell you the same and much more under the actual working conditions of all the mechanical bits involved in creating a chunk of compressed mixture in any given cylinder.

WERNER1

Yeah,.. what is the deal with all the references to leak down test anyway?.. I've read that a lot on here in just the short time I've been lurking around (??) . .. I've sort of come from the school of doing a good compression test on all the cylinders and get an idea of how they relate to each other in terms of performance and wear (??) ...

1993-VG30E-GXE

LVR, if the engine is out on a stand and one is rebuilding it - can the compression tester somehow function then? Update: I bought the compression tester real cheap on sale for 14 bucks. I did the Leakdown tonight when the plenum was back on, and the test seemed to work BUT, here's something I ran into.

With the screw driver method - I couldn't figure out which up movement in the screwdriver is on the compression stroke - is there some way to differentiate?

The feeling with the screwdriver didn't seem to line up with the cap numbers, so I just went by feeling (and ignored the distributor alltogether)....but unsure which was compression stroke so I tested both up movements. Also, when I rotate, if I leave the screwdriver without me holding it and move towards top, the screwdriver can actually get jammed in there, and I have to back it off to get it out or wigle it out. It starts tilting to one side then jams.

The results of my tests were each cylinder ranged from 0% Leakage to 4% Leakage out of 100% Leakage.

LvR

Using any sort of "hope for the best tester" when a motor is already open and being rebuilt is an exercise in futility imo - including the "compression tester" ............... and if you look at the compression tester operating instructions, then it cannot possibly tell you anything useful about your motor while rotating it by hand.

When you have the motor open and anything is either suspect or known to be suspect, do the proper thing and attend to it there and then - you simply cannot do better fault finding than actual individualized item inspection and comparison with the FSM design specs

I still don't know what it is you are trying to do with either the compression tester or the leak-down tester - are you tracing a known symptom or are you just farting around?.

............. as I said before - the plenum can have absolutely no influence on the creation of a compressed slug of mixture in a cylinder.
Your sparkplug hole sits at an angle relative to the top of the piston - that angle is varying as you rotate the engine and the piston travels up or down becoming more acute as the piston reaches the top in the cylinder - any straight solid object stuck into the cylinder will/may get bent along your experience if you rotate the motor fast enough without adjusting the location of the item/screwdriver whatever. I cannot possibly again write a war+peace on all the mechanics involved - you will need to get acquainted with general 4 stroke internal combustion engine mechanicals before you continue.

As for the direction to turn the motor - BTDC on the crank pulley means exactly that - ie - the timing mark on the crank pulley is still on its way to TDC - in general, you need to only turn the motor in that direction to move from BTDC to TDC while following the particular engine's exact firing order - if you do it right, then the compression stroke on any given cylinder (detected by the "screwdriver method") will and must necessarily correspond to the rotor's position in the distributor cap - no 2 ways about it.................... and I can only repeat again what I said in your other thread

The amount of variables playing a role in drawing a sensible conclusion from a leak-down test is simply staggering - not least of all being a decent mechanical knowledge of the particular motor you are dealing with and compression mechanics in general .................... and this is simply not in the realm of the avg home mechanic trying to maintain/troubleshoot a 15+ year old motor

1993-VG30E-GXE

Cool - thanks bud - no, there's no known symptoms or problems - I'm just farting around with it. I just replaced an injector and I had the thing open so I figured i'd fool around with it. It's very strange how I couldn't get the distributor to line up when the screw driver was actually at the crest of the movement. Some cylinders seemed to be way off...there were 2 crests I think in one full rotation of the distributor. I'll try it again maybe next year.

So far the motor seems OK, no problems, except a leaking exhaust manifold - and i'm concerned that even when I replace the gasket with a new one, it's going to be warped....I've been driving around with this ticking/crackling sound for a year or two now...maybe more. Actually, is there anything you can recommend I do once the engine is removed, how I can be certain that manifold won't leak after I put the new gasket in? Would high temp flange sealant stand up to those temps?

whitealexander

if the screwdriver has a rubber grip or plastic grip on it.. i think its safe..

LvR

Safe for what? - The rubber grip is not the problem - the problem is the metal bit between the piston top and the side of the sparkplug hole.

If thats the holy truth then your motor is fubar
Then you didn't do the job right or followed the FSM - sorry cant help you with that one.............
If you did the job right it wont leak ............ me? - I use Indian Head on all gaskets I fit with no hassles - but that is only me...............

Greeny

iTrader: (43)

Indian head

1993-VG30E-GXE

I'll check it out - but maybe another brand - that ones too racist