1996 Geo Metro.
Engine condition: 5000 miles on ring and valve job. All ignition, fuel,
compression and sensor functions within specs.
I hooked up a vacuum gauge, and cranked the engine with the fuel injector
“off”: vacuum was oscillating between 0 and 5 Hg, as expected.
When the injector was turned “on”, the engine fired, vacuum went to 12 Hg
for about half a second, then fell to flat zero, with no oscillation, RPMs
increased by about 75 while cranking, and absolutely no hint of cylinders
firing, as if the spark plugs had been removed.
NO vacuum while starting explains why the fuel just pools up in the
manifold, and why it won’t start- no fuel/air mix is getting to the
cylinders!
After sitting about 5 to 10 minutes, cranking again draws 5 Hg of vacuum,
but craps out again when injector is turned on and the engine fires up.
After several times of doing this, it will reluctantly start and idle, with
about 3-9 Hg of vacuum. When it warms up vacuum is a normal steady 17 Hg,
and it starts and idles perfectly, and gets 40 MPG at 70 MPH…
Now this has been going on since September, when I rebuilt the engine.
(Which I did because the old one did the same thing- we won’t even discuss
all the things I thought it was and diddled with for no good reason)
It is possible the shop that did the valve job reused the old lifters
without reconditioning them, transferring the malady to the new engine, just
like last time.
Or?
So what is happening here? Are the valves staying open or closed? (HVL
failing to drain or failing to pump up?)
What is the difference between the old style lifters and the “improved”
lifters?
Why does it suddenly happen when the engine fires up for the first time?
Would an additive like SeaFoam (kerosene/detergent) help or make it worse?
I suspect the final answer is to replace the lifters, but if there is
something to ameliorate the problem while I wait for the parts to get here,
I sure would like to do it.
Stupid thing can take two hours and two batteries to get started when it
gets below zero…
Has the temperature dropped significantly and do you have 20-50 oil in the engine. If so the lifters will not bleed down when the engine starts.
While thinking this over a bit (and I’m no Geo expert at all), let me ask this and it’s just to remove the question in my mind right off the bat.
What are the compression readings on each cylinder?
It would seem to me if the lifters, or lash adjusters, are loose enough to cause the engine to refuse to start, etc. you should hear them clattering away in there.
I’m not familiar with the emissions and vacuum system on this car at all but was wondering if the problem is related to a vacuum accessory that is ECM and/or temperature controlled.
Depending on the altitude, barometric pressure, timing, etc. 17" of steady vacuum is good so in essence that should weed out a compression fault but sometimes things can get a bit funny on engine internals.
I would get compression readings and leakdown on each cylinder. If you’ve already done that, what were the readings and leakdown behavior?
looks like you were thinking the same thing a few seconds ahead of me…
Plug every vacuum take-off to the intake manifold. Check any sensor, or control valve, which uses vacuum, for leakage.
A leakdown test would show if the intake and exhaust valves aren’t sealing.
If the exhaust is plugged up for any reason, you will not see any vacuum…But even if you get it started, it will barely run…
I am thinking of a botched ring job,what is the experience level of the person that did the “ring job”?
Very true. The ring scenario has also occurred to me.
Maybe a lousy hone job, poor fit, or even installed upside down. Poor fit when cold and better fit when heat swells things up a bit.
installed upside down
I’ve seen that done a few times myself.
This is the part that seems to preclude a bad ring job unless it’s a huge coincidence-
Now this has been going on since September, when I rebuilt the engine.
(Which I did because the old one did the same thing- we won’t even discuss
all the things I thought it was and diddled with for no good reason)
When the OP leaves the conversation, or as in this case never joins it, you are all wasting your time…
Agreed, unless the old engine was junk and the new one was improperly done.
That’s why the first thing I asked was to post the compression readings that are claimed to be in spec. Apparently that ain’t gonna happen.
When the OP leaves the conversation, or as in this case never joins it, you are all wasting your time…
Arguably, every post to this BBS is a waste of my time. I do it for entertainment value. I’ve skipped by countless posts that I felt were not worth the effort. As time goes by, that bar keeps getting higher. But occassionally, perhaps in a moment of weakness, I still like to speculate with the regulars, even if the OP is MIA.
There are so many forums and some posters are really desperate and clueless. My posting is often determined by how ragged my patience is for the day.
Compression is firm 135 in all 3 cylinders before turning ignition and fuel on. Then it is flat zero in all three. Leakdown (done with compressed air) in all three held air for five minutes, through six rotations of crank.
So- no valve is opening at all when it is in this mode, my guess is the lifters bleed out and lose prime.
Talked with the shop that did the valve job, and they said they did nothing to the lifters except clean them. I’m thinking the likelyhood of all six lifters going bad is not great, and am now pondering an oil pressure/delivery insufficiency. The oil pressure light goes out while dead cranking, but that’s probably only 10 - 15 PSI- an actual pressure guage will tell the story there. If the pump is putting out, then there may be some pice of debris restricting a passage somewher…
The compression readings of 135 PSI in all cylinders is bad. It should be up in the 180 range; give or take a little.
It’s a recommended and accepted practice to replace valve lifters during an engine rebuild.
Have you removed the valve cover, cranked the engine over, and verified that the valves are not opening? My feeling is that if lifters are involved in this problem then it’s not likely due to non-opening. It’s more likely due to not allowing the valves to completely close. (Maybe during this valve job the stems were not ground, the valves were seated too deeply, and this is leading to the valves being wedged open. Checking the valve stem height during a valve job is part of the process)
Would you expand on these statements: "Compression is firm 135 in all 3 cylinders before turning ignition and fuel on. Then it is flat zero in all three. Leakdown (done with compressed air) in all three held air for five minutes, through six rotations of crank."
I’m not following the test criteria; and, I think there might be something pertinent to the problems in those details.
It sounds like the valves are not opening after first fire. Maybe lifters are becoming air locked at start up… almost like air is blowing the oil out of the lifter.
Could it be a large amount of blowby the instant it fires up?
I don’t know if a completely air locked lifter will result in zero valve lift in this engine, but it sounds like you are describing zero valve lift. That alone should not case zero lift in a properly assembled engine.
Perhaps some error in reassembly has resulted in very little valve lift to begin with.
Can you remove the valve cover and measure pushrod travel cold?
Does this match cam lift?
I only get into town for internet connection about twice a week, so replies are spaced.
Dead cranking (cold, with ignition off) compression is 135 all across.
No-go cranking is flat zero in all three.
Leakdown with compressed air holds for five minutes, through six revolutions, with no air escaping from exhaust or intake. Not rings, not valves. Sounds like lifters are bleeding out and losing prime, and no valves are opening.
Shop that did the valves said they did not recondition the lifters, but it is unlikely all six would go bad anyway.
I’m now looking at oil pressure/flow problem, as that would make some kind of sense.