Timing Chain Jumped?
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Printed Date: 23 November 2024 at 1:01am
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Topic: Timing Chain Jumped?
Posted By: Capt Fiero
Subject: Timing Chain Jumped?
Date Posted: 17 March 2008 at 10:27am
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In my entire history of running modified 2.8's I have never heard of or seen a timing chain on a Fiero break or jump a tooth. In most cases, a 2.8 will lose a rod bearing well before a timing chain can wear out. However I think I may have found my first case of it.
Shirley (my mother) said on the way home from work, it felt like it lost a lot of power. However she made it home. I went out to try and start it and it would not start. If you held your foot to the floor and cranked it, it would sorta try to catch and even sometimes get a couple burbles before dying. I was figuring weak ignition. So in this order I changed. The Coil, no change in issue. The Ignition Module, still no change. The entire distributor shaft with new pickup coil. No Change. So I started advancing the dist shaft, well above what I knew it should be. I got it to fire up long enough to get it in diagnostic mode and put timing light on it, and it was at my best guess about 35 degrees BTDC. Way in front of the timing marks on the Timing Tab. I knew, this couldn't be right. So I swapped out the MAP Sensor, still no change. I changed the ECM and no change. Then I was really fighting to get it to start, and all of a sudden the noise from the engine changed. Instead of a steady, attempt to fire, it started spinning over with a "no compression sound" Kinda like if you were setting the valves on a 2.8 and had them all extremely over tight. I put a compression tester on it, and got Zero across all 3 plugs on the trunk side. At that point I knew there was something major wrong. As for the mileage, the odometer reads 312,000 kms, (about 190,000 miles) however we are pretty sure this is a reman motor, done by the previous owner. It has great oil pressure; great pick and go for a 2.8, passed Aircare. In general ran pretty good until now. Well I started the tear down yesterday. I jacked the car up, popped off the rear tire, removed the battery, zipped off the crank pulley, popped off the balancer, and zipped off the water pump. I removed all the bolts and knew something was not right. The previous owner had snapped off one of the 15mm large bolts that go through the water pump and on through the timing cover. Enough water had seeped out to rust everything solid. The timing cover would not budge. I gave up on the idea of saving the cover, so I started prying. I had a 3 foot long try bar with my 220lbs of weight on the end of it, prying as hard as I could. I got a 2.2kg sledge hammer. (5lb) and started pounding wedges in where I could. Then took a propane torch and started heating around the busted stud. I managed get to the aluminum hot enough that it would twist on the stud. After a bit of pounding beating, swearing and cussing. I finally got the cover off. The chain guide looks like new. There is about ˝” of slop in the chain. Defiantly more than it should be, not nearly enough to allow it to skip on the gear. What I did find, and this is going to take some more checking before I name it as the problem. The key in the crank that keeps the crank gear from spinning on the shaft appears to be broken. However it was still in tact, or at least looks to be completely there. I don’t know if it is even possible to somehow spin or slip and then line itself back up enough to “look” in tact. I am doing this job in my driveway as my 85GT V8 is in the garage with the motor out of it and the 2nd bay in the garage is reserved for tools and replacement parts supply for the Fiero fleet. Just my luck as I was starting really find out what went wrong it started to rain, which turned into downpour. I will update again as things come apart. Well here are the pics. 
 ------------- Capt Fiero 88 Fiero GT 5spd V6 Eight Fifty Seven GT V8 5spd. |
Replies:
Posted By: grokan
Date Posted: 17 March 2008 at 10:35am
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is the key sheared? ------------- Lets get it sideways |
Posted By: Capt Fiero
Date Posted: 20 March 2008 at 12:59pm
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Well I have not had much time to play with it the past few days, but today I got in there again.
Looks like it is a simple shot chain. Just watch the video. Ignore my old codger of a voice. I can’t believe I did not notice this earlier. I must have had the crank backed up just enough that the slop did not show. When I started turning the crank so it got tight on one side the slop really showed up on the other side. I did manage to get the bent stud out as well. I was lucky enough to grab it with a pair of vice grips and twisted it out without it snapping off in the block. Took me the better part of an hour inching it out, but it came out and even had clean threads. http://www.members.shaw.ca/hotrodfiero/timingchainloose.wmv - Video See Video Above. David ------------- Capt Fiero 88 Fiero GT 5spd V6 Eight Fifty Seven GT V8 5spd. |
Posted By: Capt Fiero
Date Posted: 12 May 2008 at 5:41pm
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An Update to this.
I finally got back to working on this car when Lisa and I got back from Vacation. We bought a new water pump, new timing gear, new crank gear and new timing chain. I bought an entire front end gasket set as well. I had to pick up a used timing cover from the good Doctor as the old one got bent all to hell with me prying on it to get it off. There was a busted stud in the front of the engine. I popped the old chain and gear set off, installed the new one, it was much more of a pain than I thought it would be to get the chain to go on with the gear set in the correct positions. When I went to install the cover I had an idea. Why not install the water pump to the timing cover then install the cover and pump as one assembly. It was a bit of a pain to snake the cover and pump into the engine bay as one big piece but it worked out really well. I was able to get to all the water pump bolts nice and easy while it was out on the ground. Once in the car it was just a matter of lining up the cover gasket and the cover and snugging up all the bolts. After a bit of tweaking with the plug wires and distributor to get everything where it needed to be, the car fired up and runs like a top. It must be one of those rare occasions / odd problems that we just don't see much of. However that is all the problem was, a bad timing chain, and it had skipped a tooth. Now I am back to working on getting the new trans in the 4.9 and putting it back on the road as well. ------------- Capt Fiero 88 Fiero GT 5spd V6 Eight Fifty Seven GT V8 5spd. |