Please help me find the problem with my GTV6... - Page 2 - Alfa Romeo Bulletin Board & Forums
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post #16 of 100 (permalink) Old 11-13-2017, 09:57 PM
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Check the valve clearance on the cylinders with low or no compression. If you have a bent a valve the clearance will be as wide as the degree of bend in the valve head or the opposite if the clearance is very tight the valve might be sitting open slightly. It is easy to check and eliminates valve issues if they check out OK
Also confirm you have spark with a spark tester or ground a plug against the plenum and crank as you check for spark.

Cheers
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post #17 of 100 (permalink) Old 11-14-2017, 06:43 AM
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those compression numbers are very low - like the engine desperately needs a rebuild low... with a fresh motor, cold, numbers should be 150-175 psi. hot should be over 200.
so either measurement process was wrong, or something in setup wrong.
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post #18 of 100 (permalink) Old 11-14-2017, 06:17 PM
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Got new spark plugs? They can make a hell of a difference...
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post #19 of 100 (permalink) Old 11-16-2017, 12:36 AM Thread Starter
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Hmm honestly not sure where carbon could have come from when the heads, valves, manifolds etc were all cleaned... But I wasn't going to rule out the possibility.

So - two days and nights plugs out to let the fuel evaporate, followed by drying them with the air line down the plug holes. Should have gotten rid of most if not all of it.
Checked the valve clearances again on the no-compression cylinder, followed by the suggestion of tapping it a few times with a punch and hammer. Check clearances again, one goes down - just a fraction, but it went down a tiny bit. Aha!
Test compression again: still zero (sigh).
Try starting the car on 5 cylinders, with the suspect cylinder plug disconnected to avoid potential back firing, it did more than it's done in a year but still didn't start. Initially there was a bit more of a cough, it tried to fire more than it did the other day when I eventually realised it was flooded, but then just stopped and didn't try any more. Possibly down to the faulty CSI at this point (possibly...) Althoughh I have seen people say even with that out of order it should still start on the normal injectors.

Still waiting on the guy with the CSI to come back to me with a shipping quote... Really just want to get this done. On the off chance does anybody here have a working one I could buy? Or know anybody that might?

In the meantime looks like Sunday is going to be take the head off day and figure out where the lack of compression is coming from.

1975 Giulia GT1300 Junior, 1981 GTV6, some modern German stuff, and a 1958 Messerschmitt KR201.
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post #20 of 100 (permalink) Old 11-16-2017, 05:58 AM
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So your cam timing is still correct? Wouldn't you want to know that before you disassemble things?

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post #21 of 100 (permalink) Old 11-16-2017, 08:29 AM
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A fresh rebuild with new rings that haven't been seated can show very low compression. I don't know about zero (did a ring get broken during installation?) but if you get it running long enough to seat the rings, re-check. Undoubtedly the compression should rise.

If you have checked the clearances on the cylinder that shows zero and they're fine, it is unlikely you're going to see anything obvious by pulling the head.

I suggest getting the engine running first if you can, it's not bad to try and use some starting fluid (ether) in one of the vacuum ports to get it running. If possible, have a helper with you to adjust the timing slightly (advance-retard) while cranking. It should start without the CSI but you'll need to find a happy timing zone to do so.
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post #22 of 100 (permalink) Old 11-16-2017, 11:51 AM Thread Starter
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Hmm yeah I'm confused to be honest, the valve clearances do check out, they're what they should be. I'm not aware of any rings being broken, I was careful inserting them, using a proper ring compressor tool. If anything broke, it wasn't audible...

No, I don't *want* to take the head off, just not sure how one cylinder can not be reading any compression at all, or aware of any way to find out or remedy it without doing so :/

I guess next step is get over my fear of spraying down the hole after last time, knowing this time that the timing is spot on all over and it's not going to backfire and make flames again. And see if it starts from there. Doesn't help we're having such cold days at the moment, but got to try!

Maybe I was lucky with my other Alfa, the GT junior. After rebuilding the engine on that one it started first time and has been ever so reliable ever since. It's got lucky number 7 on the side as it's rebelling against everybody asking "doesn't it break down?" , "don't bits fall off?", "doesn't it rust?" and the usual 'Italian car comments' and not actually ever going wrong. This one however has 666 on the side initially because I thought it was a bit of a beast (compared to anything else I've driven anyway) but now I've decided it's the devil in car form...

Will get back on here once I've tried a little spray into the plenum to compensate for the lack of CSI functionality.

Out of curiosity what would 'normal' compression be? Good to know it might improve with use regarding the rings being seated.

1975 Giulia GT1300 Junior, 1981 GTV6, some modern German stuff, and a 1958 Messerschmitt KR201.
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post #23 of 100 (permalink) Old 11-16-2017, 12:39 PM
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Well, one more time...

Do the marks on the cams line up with the marks on the bearing caps at TDC on the compression stroke-(with the distributor rotor pointing at no. 1 plug wire)???

If the marks do NOT line up, on the head where you have no compression in that cylinder, then there's your answer as to what happened.
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post #24 of 100 (permalink) Old 11-16-2017, 01:10 PM Thread Starter
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Yep, everything lines up perfectly as it should, at the right time with piston 1 at TDC. I've been following 'the proper manual' for every step of the rebuild and for the most part referring to these more accurate cam marks inside the head over the plastic triangles in the belt cover holes that line up with the pulley marks.

If it were out then surely the other two cylinders in that head would show lower values too... ? I've got five out of six showing near enough the same value (the other one that was a bit low initially went a bit higher the second time I tested them all) but only one reading nothing at all.

(P.S. not being unappreciative! Anything is possible, and worth double checking everything - after all it was such a silly mistake I'd made with the ignition timing the first time around...)

1975 Giulia GT1300 Junior, 1981 GTV6, some modern German stuff, and a 1958 Messerschmitt KR201.
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post #25 of 100 (permalink) Old 11-16-2017, 01:12 PM Thread Starter
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Quote:
Originally Posted by martym00se72 View Post
Got new spark plugs? They can make a hell of a difference...
Yep! Wouldn't be a very good rebuild if I hadn't bothered with the simple things like that.

1975 Giulia GT1300 Junior, 1981 GTV6, some modern German stuff, and a 1958 Messerschmitt KR201.
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post #26 of 100 (permalink) Old 11-16-2017, 01:15 PM Thread Starter
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Quote:
Originally Posted by barboncino105 View Post
those compression numbers are very low - like the engine desperately needs a rebuild low... with a fresh motor, cold, numbers should be 150-175 psi. hot should be over 200.
so either measurement process was wrong, or something in setup wrong.
Wow, that's a bit of a concern... Like it hasn't just had a rebuilt, valve seats recut (due to new guides) and ground, new piston rings and head gasket torqued up as per the manual's instructions... [scratches head] what on earth could possibly be wrong here?

Although I'm not convinced on the integrity of all of the spark plug threads (not guilty for overtightening! car was like that when I bought it) which could be a possibly culprit for loss of compression. Possibly, not necessarily.

1975 Giulia GT1300 Junior, 1981 GTV6, some modern German stuff, and a 1958 Messerschmitt KR201.
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post #27 of 100 (permalink) Old 11-16-2017, 01:16 PM Thread Starter
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Quote:
Originally Posted by sportiva View Post
Check the valve clearance on the cylinders with low or no compression. If you have a bent a valve the clearance will be as wide as the degree of bend in the valve head or the opposite if the clearance is very tight the valve might be sitting open slightly. It is easy to check and eliminates valve issues if they check out OK
Also confirm you have spark with a spark tester or ground a plug against the plenum and crank as you check for spark.

Cheers
Yep, all six plugs tested and sparking, at the moment of compression in each respective cylinder. One of many 'elimination tests' I've tried.

1975 Giulia GT1300 Junior, 1981 GTV6, some modern German stuff, and a 1958 Messerschmitt KR201.
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post #28 of 100 (permalink) Old 11-16-2017, 08:25 PM
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ok Dan... something simple you might want to try, once you have verified there is really zero psi compression in that cylinder.

If you have compressed air, turn the regulator down to about 20 psi max. Use clean, filtered dry air for this test. An assistant would come in handy, by the way.

Remove the spark plug from the suspect cylinder. Pull the vacuum hose to the brake booster off the intake plenum.

Get you a Milton rubber tipped air blowgun, or a similar long blowgun with a soft end (see photo). Make sure the cam lobes on this suspect cylinder are not contacting the bucket tappet or rocker arm. So both valves ought to be closed, right? Make sure there is actually daylight between the cam lobe and the tappet/rocker arm heel.

Jam the rubber tip of the blowgun down into the spark plug tube and hold it tight against the threaded hole. Shoot low pressure air into the cylinder and listen/observe where it might be escaping from. If either the exhaust pipe or intake plenum, then you likely will have a bent or leaking valve. If you get air flow or bubbles into the coolant, or oil passages, suspect a head gasket. And as Rob suggested, you could also have a ring issue.

If the cylinder holds air pressure, then you ought to look closer at the spark plug threads and/or your compression gauge fitting. I assume it has an o ring on the threaded end to seal against the top of the plug hole, right? It needs a seal ring there for accurate repeatable readings.
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post #29 of 100 (permalink) Old 11-26-2017, 04:50 PM
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The low compression on one cylinder is a red herring with regard to the engine starting. It needs to be looked into but that's not why she's not starting. Once you are certain that the cam timing is correct, and then rechecked it again, you need to confirm that the other tow necessities are present, spark and fuel. One of your posts confirms spark on all 6 plugs, now you need to confirm fuel is getting to the injectors and then that the injectors are firing. I wouldn't pull the head yet, I can't imagine finding anything in the combustion chamber that is preventing it from starting, but you might find out why one hole has low compression. Good luck and keep posting your progress (or obstacles).

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post #30 of 100 (permalink) Old 11-26-2017, 10:23 PM
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You can use a circuit tester to check if the injectors are receiving a signal. pull #5 injector plug connect a circuit tester and crank the engine the tester should blink in time with the pulses from the ECU. I use a male EV1 plug wired to a 12volt LED. If you get a signal it means the ECU is working, the next thing is to bench test the injectors to ensure they are working.
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