Alfa Romeo Forums banner

1 - 5 of 5 Posts

·
Premium Member
Joined
·
1,781 Posts
Discussion Starter #1
Folks,

Having eliminated timing, electrical (hopefully) and fuel supply as the cause of rough idle and lack of power I finally plucked up the courage to do a compression test as suggested.

Readings: 1=180, 2=175, 3=170, 4=185, 5=195, 6=190.

I am inclined to think the valves are OK.

Keep in mind that the engine is cold, all the plugs are out and the cranking is done solely by the starter and battery.

I noticed that all the intake valves are nice and shiny except for #6 which is coated in black substance all the way to the stem.
The black substance does not come off when I "touch" it with the end of a long screwdriver.
The valves don't look bent and appear to seat nicely when closed.

The photos below are not really clear but the shiny example is indicative of #1 through #5.

Any input regarding the compression readings and the #6 intake valve will be greatly appreciated.

#1 Intake Valve Photo is first and then #6:
 

Attachments

·
Premium Member
Joined
·
27,388 Posts
You did say earlier front cam timing was off and you reset cam timing and belt tension with engine at TDC on crank pulley and cams matching 1 and 11 oclock on template (69 and 72.5 degrees) right?

So with that set right rough idle and no power maybe bad plug wire, plug or injector or injector connector.

Does idle change with #6 plug wire unplugged?

As for black stuff on valve stem probably have a bad stem oil seal.

Higher compression reading maybe from carbon buildup on piston from oil leak.
 

·
Premium Member
Joined
·
1,781 Posts
Discussion Starter #3
Thanks Steve, see my response to each of your comments below.

You did say earlier front cam timing was off and you reset cam timing and belt tension with engine at TDC on crank pulley and cams matching 1 and 11 oclock on template (69 and 72.5 degrees) right?
Yes - rechecked timing today, as well as re-checked timing belt tensioner spring and all appears to be good in that area.
I am paranoid about why the belt jumped teeth in the first place.

So with that set right rough idle and no power maybe bad plug wire, plug or injector or injector connector.
Plug wires were swapped with good Carolina car wires.
Plugs are new Champion 415's - old plugs looked OK.
Distributor cap, coil, rotor, AFM and a few other related items were also swapped with parts from the good engine.
Injectors are going this week for rebuild - I did not swap these as I don't want to pull the good engine too much apart.......
I broke a couple of pintle caps removing the injectors as they were too tight which meant I might have the same problem on the good engine if I tried to pull those too.

Does idle change with #6 plug wire unplugged?
Cannot remember....I was pulling and testing spark at one stage early on and that was not a problem.

As for black stuff on valve stem probably have a bad stem oil seal.
OK I will not try and read more into that - I had hoped it meant there was a problem with the injector.

Higher compression reading maybe from carbon buildup on piston from oil leak.
Yup I figured that higher reading was due to oil in there for some reason.... long ago I used to do compression readings after squirting oil in each cylinder beforehand, not this time though.
 

·
Registered
Joined
·
5,993 Posts
Make sure your compression readings

are with the throttle held wide open, otherwise you wont get enough air to enter the cylinders to give you the true compression reading

On 24 V its easy since the intake plenum is pulled off thus allowing whatever the engine wants to breathe in!
 

·
Premium Member
Joined
·
1,781 Posts
Discussion Starter #5
Folks,

The dust has finally settled and I can report back on a great Alfa Week.

Bella Alfa has never performed as well as during this past four days on the daily work commute.
My twice daily high speed guilty pleasure is back......

In the end the fuel injector service did the trick although I cannot point a finger at the injectors themselves.
The local injector expert reported that the injectors were in very good shape but the contact points in the electrical connectors were not.
I had earlier cleaned the electrical points in place but obviously not very well due to their difficult location.
Even the copious amounts of contact cleaner had done no good.
I had to send the injectors in for service as two of the pintle caps had broken off when the O rings refused to come out of the seats.
This is what happens to 20 year old fuel injectors.......no complaints.
The injectors were totally overhauled for $120 in all including a bunch of printed graphs and figures I have yet to fully understand......

The engine starts easier, idles smoother and picks up smoothly throughout each gear range.
I have not yet gauged fuel consumption but it "feels" better - it was never really as good as everyone else claims, which always irked me.

I am still worried about what caused the original timing belt 2 tooth jump, and I don't really know which part of the injector service really made the difference.
Maybe it all just counted positively in little bits....or there may be a bad piece in the injector cables that I just happened to set right with all the fiddling.

Whilst the euphoria exists I will enjoy.....but at least I know the injectors are "new".

Thanks as always to the Forum for great input.

Ta,

Neville.
 
1 - 5 of 5 Posts
Top