5 Star Rising Posted January 16, 2019 Share Posted January 16, 2019 Hello, so I bought this non running 92 Z32 TT a couple months ago. Its pretty beat up, the PO bought it from some guy who had it sitting in a field for years. Zero history on the car..The PO couldn't figure out the electrical issues to get it to turn over. I fixed the electrical issues and I now can turn the car over with the key, i have fuel and i have spark, but no start. Did a compression test and the numbers were horrible something like 30psi,40,50,0, only tested the front cylinders I had access to at that time. The motor has that sound like there was no compression or like you didn't have spark plugs in the motor. Tonight I pulled the front of the motor down to check the timing belt. It looks like the timing belt hydraulic tensioner gave out and the belt loosened up and slipped a tooth or 2. I have the notches lined up at the crank but the upper sprockets do not line up perfect with their notches they are a tooth or 2 off.. I found The tensioner fully compressed and touching metal to metal with no gap. I have included some pictures of the sprockets not lining up uptop even though the crank is lined up at the bottom..When I turn the motor over manually I dont hear or feel any interference, unless the damage was already done.. (IS THERE A CHANCE THAT THE VALVES ARE NOT BENT AND BY RESETTING THE TIMING BELT CORRECTLY I COULD GET THE CAR TO START AND BE OK? HOW MANY TEETH OFF CAN YOU BE BEFORE YOU DO ENGINE DAMAGE?) Thanks Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 16, 2019 Share Posted January 16, 2019 The belt seems close and the numbers are very low. But if it's been sitting in a field for years the cylinders might be rusty. Adding oil to the cylinders would make that problem better. You could remove a valve cover and look at rocker arms and valve ends. You could also do a leak down test. The belt doesn't look terrible. Seems more likely that somebody just did a poor job on a belt change or some maintenance work. I think that they're usually much more worn when they slip. The teeth wear out or break off. Quote Link to comment Share on other sites More sharing options...
5 Star Rising Posted January 16, 2019 Author Share Posted January 16, 2019 1 hour ago, NewZed said: The belt seems close and the numbers are very low. But if it's been sitting in a field for years the cylinders might be rusty. Adding oil to the cylinders would make that problem better. You could remove a valve cover and look at rocker arms and valve ends. You could also do a leak down test. The belt doesn't look terrible. Seems more likely that somebody just did a poor job on a belt change or some maintenance work. I think that they're usually much more worn when they slip. The teeth wear out or break off. Should the hydraulic tensioner be sitting flush with the bracket and have no gap? That's the way I found it. According to the sticker under the hood. This timing belt has been on for 27,000 miles. When I did the compression check, I did it dry as the motor had already been turned over a few times trying to start it from the PO and my self which could have done damage to the rings di cyl walls.. I got those low readings..then i poured some motor oil in and watched the guage slightly go up. One cylinder was at zero and stayed at zero even after oil was poured in. Another cylinder on the other head was at 70psi and went to 150 when oil was added. While the others were 30psi and went to 50psi with oil added. I left the gauge on each cylinder and watched if the pressure leaked down but they stayed about the same reading. I just want to get this thing started so I can drive it out of my backyard on it's own power and put a For Sale sign on it lol. Not looking to rebuild this thing. I have 3 other 240zs I'm building right now. Quote Link to comment Share on other sites More sharing options...
5 Star Rising Posted January 16, 2019 Author Share Posted January 16, 2019 Even though the line on the timing belt is lined up with the dimple on the cover the dimple on the sprocket with the white paint is not lined up. Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 16, 2019 Share Posted January 16, 2019 (edited) I don't know the details of the 92 TT. I had a 95 Pathfinder though and it's belt was good for 100,000. The earlier VG30E models were good for 60,000 I think. 27,000 is almost new in either case. Yours is the rounded tooth variety which is the 100,000 mile design, the others had squared teeth. Doesn't seem like belt wear would be the issue. The fact that one cylinder climbed to 150 suggests that the valve timing is close enough, since they're all tied to the same belt. Probably bent valves or broken piston/rings on the bad ones. Turbos tend to damage pistons. You still might check the rocker arms and lifters though. I don't know if the hydraulic lifters leak down enough to keep the valves from opening. That would give a low pressure reading because no air gets drawn in, because the valves don't open. Is their oil in the crankcase? Dip stick at full? Most cylinder pressure gauges have a valve that needs to be opened to release the pressure between tests. Not sure that just leaving the gauge on will tell you about leak down, it will just read the last highest pressure in the gauge. You're supposed to pressurize the cylinder using an external air supply for a leak down test. Sounds like you definitely have dead and damaged cylinders though. Doesn't look like readjusting the timing belt is going to fix your problem. If you've already been spinning the engine maybe you should just put it back together and start it on the remaining cylinders. It will run like crap but it's messed up anyway. Edited January 16, 2019 by NewZed Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 16, 2019 Share Posted January 16, 2019 Nicoclub has their service manuals back up. 92 wouldn't load but 91 did. Might have some good info there. https://nicoclub.com/archives/nissan-300zx-factory-service-manuals.html Quote Link to comment Share on other sites More sharing options...
5 Star Rising Posted January 17, 2019 Author Share Posted January 17, 2019 (edited) Yeah this thing wouldn't even try to start when spraying starting fluid into the intake. I have fuel squirting across the yard, i put a gauge on the fuel pressure and it was rather high I think like 90 psi or so. I put a spark tester off one of the coils and got spark while cranking the motor. It was then that i found these horrible compression readings. The motor sounds like there is no spark plugs installed when cranking it. Thanks for the manuals. I had downloaded those already. Was hoping that being a tooth off or 2 might be the cause of the valves opening incorrectly and giving me those readings, but yeah as a interference engine its probably toast. Edited January 17, 2019 by 5 Star Rising Quote Link to comment Share on other sites More sharing options...
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