red90 driver Posted January 17, 2011 Share Posted January 17, 2011 Had a 3.9 V8 sat in the challenge truck for nearly 12 months now, and 2 months ago, filled the engine with oil and cranked her over until I got oil pressure. Today was a good day, until I tried to set the crank at TDC so that I could set the timing for the VR pickup for the megasquirt. Tried to put a ratchet onto the crank pulley bolt but no movement. Put the cracker bar on, and still no joy. The starter failed to turn the engine over, and after checking the flex plate had not shattered in the auto box, decided to whip the sump off and inspect. 7 of the bores look well lubricated, and I have managed to remove the big ends on 4 of the conrods 1,2,5 and 8. Of those, 3 pistons move in the bores. Number 8 won't, but as it is sat at the highest point in the stroke, I don't know if it should. The bore of number 8 is extremely dry under the piston skirt, and there is a rust mark on one point of the piston skirt, so I am wondering if it has seized in the bore? Although I can rotate the crank back and forth by hand (cracker bar on crank pulley bolt) by about 5 degrees, all it does is rotate 7 & 8 around slightly around their TDC point. Number 8 bore is extremely dry under the piston skirt, so I am assuming that it has seized in the bore.... I have managed to squirt some WD4 onto the piston crown in the hope that some will permeate down the side of the piston, I can't get much in there because it just drain out of the plug hole again! Do I: wait and see if the WD un-seizes the piston? Take the cylinder head off and try to 'send' the piston and conrod out through the top of the block? Any other suggestions? Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 17, 2011 Share Posted January 17, 2011 I'd give the WD some time to do its thing before having it apart. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted January 18, 2011 Share Posted January 18, 2011 Yup ^^^ Or try something a bit more de-seizing, like Plusgas or duck oil. Quote Link to comment Share on other sites More sharing options...
red90 driver Posted January 18, 2011 Author Share Posted January 18, 2011 I'll see if anything has loosened when I get home tonight..... I see a trip to Halfrauds tonight to get plusgas.... Quote Link to comment Share on other sites More sharing options...
Diff Posted January 18, 2011 Share Posted January 18, 2011 What about a valve stuck down? Regards, Diff Quote Link to comment Share on other sites More sharing options...
red90 driver Posted January 21, 2011 Author Share Posted January 21, 2011 After now removing one cylinder head, and number 8 piston (which was not actually stuck), the problem still exists. I fear it is now autobox out time! Whats going to have failed in a ZF 4 speed to cause non rotation of the spinny thing that makes the up and downy things go up and down? Bear in mind that said auto box was working fine, but has not had any oil in it... Number 8 piston has had water sat in the bore, and the rings are stuck in the piston, so it's a good job I've pulled it out for inspection as it looks like a ring set is needed. Anyone tell me what the ring gap should be on a std 3.9? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted January 21, 2011 Share Posted January 21, 2011 I'm struggling to think of any reason why the autobox would stop the engine turning, unless it's a stuck loose bolt in the bell housing... Quote Link to comment Share on other sites More sharing options...
fozsug Posted January 21, 2011 Share Posted January 21, 2011 Anyone tell me what the ring gap should be on a std 3.9? Compression ring gap 0.40-0.65 mm Oil control ring rail gap 0.38.1.40 mm Quote Link to comment Share on other sites More sharing options...
RoaryV8 Posted January 21, 2011 Share Posted January 21, 2011 The only thing i would say would be valves hitting pistons at TDC. Cant see how the box would stop anything TBH. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted January 21, 2011 Share Posted January 21, 2011 You've not jammed the dizzy drive or something have you? Pull the dizzy out and try again.... Quote Link to comment Share on other sites More sharing options...
Roverbo Posted January 21, 2011 Share Posted January 21, 2011 After now removing one cylinder head, and number 8 piston (which was not actually stuck), the problem still exists. I fear it is now autobox out time! Hmmm...if you are gonna disassemple the engine, would it be an idea to remove the timing gears/chain? Not a too hard job, and would eliminate errors from valves/lifters. Or am I wrong here... Regards Bo Quote Link to comment Share on other sites More sharing options...
zim Posted January 21, 2011 Share Posted January 21, 2011 If i were you, i'd also remove the other head...and send both for pressure testing / skimming. Quote Link to comment Share on other sites More sharing options...
red90 driver Posted January 21, 2011 Author Share Posted January 21, 2011 Ok chaps.... Definately not the engine. There are now no pistons in the engine, and I still can only turn the crank about 10-15 degrees before it gets too hard to turn. I am seriously thinking we've knacked something on the auto box. Someone has suggested that because I have had no oil in the box, and I have cranked the engine over then the brake band in the box has locked, or the torque converter has become mechanically challenged. I did try putting the transfer box into difflock, auto box into Neutral and then rotating one of the output flanges with a bar to see if I can turn the back half of the gearbox over, which was OK. I am going to split the engine from the box tomorrow, and then drop the box out as well. So, any ideas what I can do? Quote Link to comment Share on other sites More sharing options...
cackshifter Posted January 21, 2011 Share Posted January 21, 2011 Hmmm...if you are gonna disassemple the engine, would it be an idea to remove the timing gears/chain? Not a too hard job, and would eliminate errors from valves/lifters. Or am I wrong here... Regards Bo Yes, or maybe just take off the valley gasket and confirm the cam is able to rotate before doing all that work. You'd be really annoyed if it was something jammed at the front of the engine....or even the starter. Not sure how it could be the autobox as the torque converter isolates it Nigel Quote Link to comment Share on other sites More sharing options...
SteveRK Posted January 21, 2011 Share Posted January 21, 2011 If the gearbox has locked then there should be no free play - I'd check that nothing is fouling the torque converter to flywheel/flex plate and also the camshaft/timing chain assembly Quote Link to comment Share on other sites More sharing options...
red90 driver Posted January 21, 2011 Author Share Posted January 21, 2011 Ok, before engine out tomorrow, I'll take off the timing cover and have a look. That is really the only thing left to check!! Then I'm lost..... Top tip for a friday: Stuck rings on a piston? Boil gently for 2-3 hours in a pan of engine oil on the stove. Top, top tip: Don't do this in the house as it tends to stink!! (Ask me how I know, and why I'm writing this outside......) Quote Link to comment Share on other sites More sharing options...
garyjrode Posted January 21, 2011 Share Posted January 21, 2011 Hi there, have you removed the starter as that was, as you said the last thing you used when cranking for oil preasure. Cheers Gary Quote Link to comment Share on other sites More sharing options...
woodytz Posted January 21, 2011 Share Posted January 21, 2011 If the gearbox has locked then there should be no free play - I'd check that nothing is fouling the torque converter to flywheel/flex plate and also the camshaft/timing chain assembly hmmmm 5 degrees or so sounds like the amount of stretch in a knackered timing chain, if you have the heads of you will see if the cam is moving or not.If in doubt take the timing cover off remove the chain and see if it turns over then ,its easier than taking the box out. hth woody Quote Link to comment Share on other sites More sharing options...
red90 driver Posted January 21, 2011 Author Share Posted January 21, 2011 Hi there, have you removed the starter as that was, as you said the last thing you used when cranking for oil preasure. Cheers Gary Yup, starter was removed, but I have not tried it again since. But, the starter would engage and you could see the pulleys move, especially if I moved the crank round to the beginning of the point of where the crank would actually start to move. Quote Link to comment Share on other sites More sharing options...
red90 driver Posted January 22, 2011 Author Share Posted January 22, 2011 Found it!!! Totally bent and buckled spray plate on the back of the crank pulley. Due to the 2 temporary bolts I used to hold the belt pulley on, one of them was ever so slighly longer than the other, and it had caught on the timing cover, bent the bolt, ripped the captive nut from the spray plate, and then flattened and buckled it. dead obvious really! But, it had worked without a problem when I had tested the oil pressure which is the really strange thing...... A new spray plate is £38 +VAT. So a trip to the local scrap yard has sorted it!! Good job this happened as number 8 piston had stuck rings, so setting up the Megasquirt might have been interesting!!! Quote Link to comment Share on other sites More sharing options...
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