Hi, I bought a car about a week ago, had a thrown rod. Went and picked up a new block and internals at a pick n pull junk yard. Threw it all back togeather, think I got it timed correctly, when I go to start it, it sounds like it has no compression at all and backfires white smoke out of the intake every once and awhile. Any help? There is one sensor that isn't hooked up, right behind the timing chain crap. I can't find the hook up for it, anywhere. Any help? This is my first rebuild project, ever lol. The radiator isn't hooded up right now, I just want to hear it run before I put those kinda things back in. Any help at all would be greatly appriciated.
I honestly don't know how to do a compression test. But, its not the timing. I've had 3 people check it and they've said its right. They're all dumbfounded on what could be wrong...I know its got spark, and fuel (air is a given). So I don't see what could be wrong......plugs aren't new, but they're clean NGKs. When I turn it over, all I hear is the starter just turning over. (If I take the plugs out and try it, it sounds the same.) I noticed their is a sensor right behind the timing chain cover, that I can not for the life of me, find the plug for. Could that plug be it? There is also another one, on the harness that I have no idea what it goes to. Its right above the tranny, next to the intake. Any help would be greatly appriciated.
Buy a compression tester gauge. It screws into the spark plug hole and you can check the compression on each cylinder one at a Time. It's really hard to diagnose with not knowing what you have done completely. Take a video of what is happening and post it. Might be easier to figure out. Also see if you can take a picture of the timing chain and let's see if ALL the marks are lined up.
Well, I'm having my friend who works at a GM dealership as a mechanic bring me a compression tester after work. I had taken out the spark plugs and had someone put their hand over the whole. Usually, it'll blow your hand off of it. But they said they didn't feel ANYTHING. I've figured that since its occationally backfiring thru the intake, something about the timing is off. Like its just pushing the compressed air out the intake, and occationally igniting. Timing is set at cylinder 1 @ TDC (2nd mark on the left), both of the first cam lobes are pointed 180 degrees away from the center of the engine. I will get some pictures and maybe a video on here after the compression test. Ive been told that it could be bad rings, but even if it did have bad piston rings, it would still have atleast a little compression, right?
Its best to relieve the fuel pressure and unplug each coil pack when you do a compression test. You wouldnt want to flood the engine with fuel. Yes you should/will still show compression with fried/blown rings...just wont be within specs..... Remove each spark plug and test each cylinder 1 at a time by plugging the compression tester into the spark plug hole and cranking the engine for about 3-5 seconds, record the number on the tester and move on to the next. All figures should be fairly close to one another which would comfirm a healthy engine internally. If one or more cylinders are 15-20 or more psi off, those are the affected cylinders and will warrant closer inspection. Hope this helps
Well, depressing news /: compression of all cylinders = 0. Took the head off, EVERY single valve, SMASHED. Anyone know where I can get decently cheap vavles? Orielys is 10.50 each, ebay is 90 for a set. I don't have a lot of money right now, so does anyone know a cheaper place?
IF the valves are all smashed, your best bet is a reman'd head because that head is going to require significant machining. There is damage that you simply cant see with your eyes. IF you do just replace the valves, valve stems, locks, and guides I guarantee that when your all done you will be pulling it back apart. Its like having a spun rod bearing and going the cheap route and just replacing that rod bearing. Sure it will hold for a little while but its only a matter of time before it "spins" again. Why? Because the spinning of the rod bearing has caused internal damage perhaps to the journals of the crank and left small metal flakes in the engine where close tolerances mean everything. in your case the replacing of the valves is not recommended. Atleast have the head inspected by a machinist/machine shop if for nothing than piece of mind.
After reading your original post, consider this...being an interference engine, your timing was infact off. This is why the valves were all smashed. A way to prevent this is after putting it all back together, use a large breaker bar on the crank pulley nut, and slowly rotate the engine several times. IF you feel any resistance, STOP. The valves are coming into contact with the pistons and the timing is not set correctly. Never put it back together and start cranking the engine. If your off, it will bend every last valve.
those motors are really cheap to find. Just get another motor. it's gonna cost you more to fix this one than to just get a long block. Check out the Sentra forums for details on how to put in a SR20 motor if you can afford it.
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