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low compression-timing issues
Topic Started: Jul 26 2012, 11:40 AM (1,936 Views)
toocolts
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I have a 93 geo metro with a 3 cyl. Had a complete rebuild done by an engine remanufacturer. From the very begining I had only about 140 lbs compression. Had a miss at higher rpms. Every part on this motor is new. Timing marks all line up but this motor will not run at factory spec. Timing is now at 18 advanced. Still has no power and large hesitation before rpms start to go up. Doesn't seem to miss with no load on motor. Slow rpm build up as you start to take off. Compression is now 130-135-140. Only 12k on motor. Mechanic told me that 140 in earch cylinder was fine as long as they were all the same. I know that minimum is 156 but I let that go figuring he knew what he was saying. This was a new motor and even then it was 140. I thought that after a complete rebuild it shoud have been substatially higher like at lesast 175 or so. Can anyone agree with his comments about compression so low? Also why would I have to run so far advanced that there is no adjustment left on dist.? Once again let me say all parts are new, injectors,dist and wires, map sensor,eger valve, all hoses etc. Motor has warranty but this guy seems like he does not want to take care of this. 4k invested and my little car runs worse than before the rebuil! I need some guidence on this.
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Old Man


at 12K after a complete rebuild you shoud be around 200 compression.

Every indication you have mentioned points to the timing belt being off a tooth or two.---

hang on.....someone with more experience will log in soon and let you know exactly what is wrong
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toocolts
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thanks. Very disturbing that the engine rebuilder could not figure that out
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starscream5000
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Got 70 MPG?

Timing is off and I would also question what was replaced internally in the engine...
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toocolts
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Thanks. I want to ask some things. If the cam timing is off would that mean that on compression stroke that the intake valve is not open long enough to bring in the air needed to create the correct compression or is it that the valve opens to late to create the correct compression. I will surely ask this guy in Spokane about the rebuild. My problem is there is no way to tell if he will be telling the truth or not. As much as I feel he has jerked me around for the past 1 and 1/2 years I don't really know if he will lie about the work. i hate to work on this myself since I have a written warranty ( 7 yrs/70k miles) and a major investment in my little car.. He still hasn't returned a call made to him 2 days ago. That is how it has been all along. Hope he will just bite the bullet or I guess I will have to take him to small claims court for a resolution. I am still seeking anyone who will say below factory specs upon completion of a complete are acceptable. I will need all the info I can get if I go to court.
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Shinrin
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Compression should be around 200 if it was a good rebuild. Your timing belt definitely sounds off a tooth. Most shops see these as disposable, crap cars, and they will jerk you around. You need to be fighting this or he'll just try and blow you off.
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clarkdw


The valves, intake and exhaust, are open the same number of degrees of engine rotation now as before. What has changed is the relationship of when they are open to the crankshaft position. The intake valve should be open while the piston is traveling down in the cylinder.

If the cam timing belt has been installed one or two teeth in either direction of where it should be the intake valve may open too soon while the piston is traveling up near the top of its' stroke or open too late while the piston is already well down on its' down stroke.

If it is only one tooth or possibly two teeth out of position the engine will still run but badly and will show bad numbers on a compression test.

It is a sad thing when someone will not admit the fact that they have screwed up. We all make mistakes should be willing to make good on it when we do. I hope you are able to get this corrected without the hassle of small claims court.

If it is in fact the case that the cam timing is out a tooth or two it requires only a small investment of time and no parts to fix it. one hours labor will easily set it straight.
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toocolts
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I hope so also. I can do the timing belt change if I have to. Which way should I go. I am way advanced on timing now. Will the belt move clockwise or counter clockwise to get me where I need to be. Thanks
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clarkdw


If you have this style of camshaft sprocket then the only trick is to make sure that you align it to the mark that has the dowel in the end of the camshaft opposite it. As you can see in this pic there are two marks. Whichever one has the dowel is ok. The marks only make an insignificant 2 degrees difference. So, mark on the rim at the top aligned with the notch in the valve cover and at the bottom is the dowel in the alignment hole peeking out from under the bolt. If yours is the stamped steel style of cam sprocket then you don't have to worry about this. You only have one timing mark. It goes at the top and the dowel opposite.

In both cases the arrow on the engine at the top of the crankshaft sprocket must be aligned to the tooth with the dimple.

Last thing is don't be overzealous in tightening the belt tensioner. The little spring on the tensioner sets the tension and then rotate the engine a couple of full turns with a wrench. Recheck the timing and lock down the tensioner bolt.


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toocolts
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Ok. Now let me ask this question. If I find all marks lined up what then? My engine was running quite well at one time. This mechanic said that the camshaft gear had moved on the end of the cam. He claimed it happens a lot although I have not heard of this before then. He said he made it so it could not move again. If he placed it on the cam differently than where it was originally and the marks line up ( I recently looked at this on a trip and found all the marks lined up) which direction of rotation on the cam will I turn it. Counter clockwise or clockwise. Also I think that if I turn the cam in any direction the marks will no longer line up. My cam gear ( if memory serves ) was not open like the pick. It seemed to have a full cover on it. Is this the stamped one you were speaking of? I do remember that the crank mark did line up with the dimple. I just exploded the pic so I could see the marks better. I can now see what you are talking about the mark oppisite the dowel. Looks like the one at seven oclock is also where the ring gear comes together. There is also a dimple. If he used that other mark with the dimple would that be retarding the engine? Maybe when I looked I saw the dimple lined up with the valve cover not knowing that was not the correct mark. I will wait until I get my other car back to open and inspect again. I wish I could be positive about my type of gear. I guess I will soon find out. I bet I will remember this time around. Looks like a lot of difference between the two mrks. 14 teeth=28 degrees? Right now with dist advanced all the way it is about 18 degrees adavanced ( with the wire in the connection to set timing) after computer is back on it looks like 22. It is past the 20 degree mark.
Edited by toocolts, Jul 27 2012, 03:15 PM.
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starscream5000
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Got 70 MPG?

It sounds like he may be talking about the crank gear, not the cam gear. The crank gear has a woodruff key that is known for shearing when someone doesn't torque the crank bolt down to the factory recommended torque and use locktite on it. I bet if you pull the lower timing gear you'll find all your problems there.
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toocolts
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I will be sure and clarify that with him when he finally gets back to me. If that is the case once again it was a failure on his part to make sure all was well with the rebuild.

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clarkdw


Oh boy, lots of confusion here.

I think it boils down to what starscream said. The crankshaft sprocket or the camshaft sprocket has most likely moved. It could be either but is more likely the crankshaft one.

If the crankshaft sprocket has moved you need to find someone with a little more experience to assess the damage. In all likelihood the crankshaft is pretty much wrecked. If the mechanic has in fact managed to remount the sprocket so that it will not move again then you will need to reset the camshaft position using a degree wheel and some in depth knowledge of what the process involves.

BTW: The two different timing marks on the camshaft sprocket are way more than two degrees apart but if you move the dowel from one hole to the other and align the opposite mark then the relationship of the crankshaft to the camshaft changes by only two degrees.
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starscream5000
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Got 70 MPG?

clarkdw
Jul 27 2012, 03:50 PM
I think it boils down to what starscream said. The crankshaft sprocket or the camshaft sprocket has most likely moved. It could be either but is more likely the crankshaft one.

If the crankshaft sprocket has moved you need to find someone with a little more experience to assess the damage. In all likelihood the crankshaft is pretty much wrecked. If the mechanic has in fact managed to remount the sprocket so that it will not move again then you will need to reset the camshaft position using a degree wheel and some in depth knowledge of what the process involves.
I'm curious to see what Billy Bob Mechanic did to "fix" the problem...
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Old Man


starscream5000
Jul 27 2012, 05:36 PM
clarkdw
Jul 27 2012, 03:50 PM
I think it boils down to what starscream said. The crankshaft sprocket or the camshaft sprocket has most likely moved. It could be either but is more likely the crankshaft one.
I'm curious to see what Billy Bob Mechanic did to "fix" the problem...
I would give 10 to 1 odds that the "mechanic" told him to get lost
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