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Engine Specific Info and Questions => IDI Engine => Topic started by: zolorin on January 18, 2013, 10:56:28 am
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So I finally got a bit fed up with the smoking start on my diesel pickup and finally decided to do a compression test
So here is what I have found once I pulled the injectors
#3 injector had a black body and did not have a ring that is indicative of it being properly seated against the steel insert. I could not find the steel insert what so ever -- hmmm I guess this was first reason to be worry about a low compression worries.
I then tested all of the pistons with the diesel compression tool
1. 220 (retested at 210, same way that I did all 4 other, about 10 rotations)
2. 300
3. 290 (did not tested without the insert)
4. 310
I did the test cold (how much does doing it hot increases by? 40 psi, 50psi????)
So from what I am reading I am below the wear limit by a lot and number 1 is below the delta limit of 71 psi
So what else would you guys recommend to test before plunging into an engine rebuild?
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The compression reading isn't from a certain number of revolutions, but rather the reading when the needle stops moving up regardless of the number of revolutions.
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Agreed, I just did not have a helper who can tell me when the needle stop going up. So I did one cylinder for trial to see how many revs did it stop rising and then added couple more.
The question is is the HG blown?
and should I be thinking of replacing pistons and rings??
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Question on procedure. Did you do it by pulling the injector and replacing it with the test tool? I think that is what you did. Correct if I am wrong.
Once you have these readings you could squirt about a tablespoon of oil in the top then place the adapter in the injector hole and try again. If rings are the issue you normally will see an increase in pressure. Try it and see what you get. I have one cylinder that is bad and oil gives me 80-100 lbs more on a stone cold engine.
Isn't the normal 480 lbs per cylinder? And wear limit some where about your best cylinder? Bentley check. Wow your hosed!!!
Bentley says this for my 81 1.6 NA: Normal compression pressure is 398 to 483 psi. If pressure for any cylinder is below the 398 psi limit or pressure is 71 psi different between any two cylinders the valves, rings, or cylinders may need replaced or bored out.
Time for a teardown and measurements to be taken I'd say.
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could be a blown headgasket causing #1 to be so low. But the other 3 are really close together so you're going to need rings at a minimum, you'll have to check if the bores are within their wear limit and also if there is too much ovaling. and you'll have to inspect the head while its off. if you're lucky you can get away with just a hone, new rings, headgasket, headbolts rod bolts, and rod bearings. but you'd have to be really lucky haha.
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Sounded like this thing still runs just smokes on start up. Wait till he rebuilds it and he will have a thread that his starter won't turn it over anymore. Or the battery is weak. Buhaawwwaaa
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"starter will not turn" -- that is funny.
But yes it does/did run but smokes and has a low power (max speed is about 65 to 70 on a straightaway).
Yep pulled the injectors (all 4 of them), installed the tool/converter
So ya, I am hosed -- way low.
BTW who do you suggest for parts (and please don't say prothe)
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Did you do the test with the engine at normal operating temp? Does it have solid lifters?
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Be careful with that "wet test"... these engines run on oil.
As Andrew alludes, valves are not yet ruled out.
>270psi in each could still be a reasonable runner, if the engine starts and the blowby is managed to avoid runaway.
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If it isn't running away and you are just mildly upset about the smoke you could run it until you have a real problem. If it starts and runs it could keep going like this for anothe 100,000 miles. I would take the shot and find another block to rebuild in the meantime. That is me though. I just know the more you dig on these engines the more needs replaced and sometimes you could have done without it, sometimes not.
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I can't suggest many places for all your parts. And if the valves are the problem you may not need many just some cleaning and polish about the inside. I just picked up a set of Gotez (sp) rings for 80 off of Ebay. Still haven't had time to get them in. Like you I am smoking out the neighborhood instead of tearing it apart. Oh, and checking the oil all the time. :-[
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Have you checked your timing? I had mine a little too retarded when I first timed it and it smoked really bad when cold, but once warmed up it didn't smoke at all and ran fine.
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Normally smoke on start up can indicate poor timing, but with the numbers he has, he is in need of more than a few degrees of advancement.
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Before settling in on the idea of a total rebuild rule out the head/valves. Pulling the head will tell you a lot about the wear though. Personally if I have to go with new rings, I'll change the pistons, and the mains.
How many miles on the engine? How tight is money?
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Before even considering pulling the head, make sure the valves are opening far enough. Compression check should be done with the engine up to temp.
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And a simple check on the valve clearances would be good to do. A few of mine were way off somehow. One like no clearance.
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Yes, that's what I've been trying to say. The mechanically operated valves wear to being tighter and will eventually lower compression especially when the engine is cold. Hydraulic lifters can similarly cause compression test issues if they are not operating properly or have been allowed to bleed down prior to the test.
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Before even considering pulling the head, make sure the valves are opening far enough.
I followed it but didn't think he would know how to determine if they were indeed opening far enough. So I put it in different terms.
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OR Coaster, you are the guy with the best idea
So I have tested the valve clearances and :-[ :-[
Lets just say there was about 0.20 ++ mm of excess valve clearance (again done cold)
The readings were
0.025 inch for all exhaust valves (nominal is .014 to .018)
intake
1 -- .019
2 -- .016
3 -- .014
4 -- .020
with nominal at .006 to .010
Based on Bentley
So very low compression numbers could have been a result of the cam having a smaller window to open and close the valves, Hence a big power drain at higher rpm (say at 70 mph).
So will do get the shims and go
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Once you have these readings you could squirt about a tablespoon of oil in the top then place the adapter in the injector hole and try again. If rings are the issue you normally will see an increase in pressure. Try it and see what you get. I have one cylinder that is bad and oil gives me 80-100 lbs more on a stone cold engine.[/quote]
Did you do the test with the engine at normal operating temp?
Be careful with that "wet test"... these engines run on oil.
this test while being real good for reading ring sealing, especially while engine is at normal temps; oil will fire. while engine is dead cold you shouldnt get firing, but cylinder is live and has a fuel that it can burn. dont have your helper holding tester while doing this. its possible to lose your tester; if cyl fires(done cold)
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Actually I have to pass credit on the valve clearance to Libby. I thought oil would be the check for ring wear and just restated the clearance as another possible before you started to tear the head off. Maybe no need to do that? Reset the clearance proper and retest cold. Report numbers and then try oil and retest.
Cautions on the oil kicking the engine over. If you pull all four injectors I doubt this will be a problem. That is generally how I do it. Get the injectors and lines out of the way and then have room and easy spin of engine. I have never had one fire off the oil when completely cold and no glow plug juice. I pull my pimp wires but anyone with stock setup could remove the fuse on the firewall. I also pull the lead from the IP so diesel isn't squirting all over from that.
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I always take the plugs (gas) or injectors (diesel) out before doing the compression test. Extra pressure on the other 3 cylinders slows down the rotation speed and makes the reading numbers low. Learned that from my datsun days. Anyway will unbolt the glow plug harness too. Dont want to have an explosion in my garage.
Oil fires are hard to put out
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Wouldn't unhooking the stop solenoid prevent fuel from coming out of the injection pump?
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Wouldn't unhooking the stop solenoid prevent fuel from coming out of the injection pump?
Ja... the IP spits fuel, unless the stop wire is off. (Messy; and fuel is bad for the hoses.)
The concern is for adding oil into a cylinder for a wet-test.