350 Mag mpi leaky exhaust gasket

[silver_power]

The temp reading at diacom while running is 69-71οC ( 156-160oF) which is very good. The injectors were bench tested with very good results 40hrs before...anyway the escaped air I felt at my hand while engine running seem to be a leaky exhaust gasket. Am I correct? I was suspected the head gasket as well but with these compression numbers I think that the head gasket is fine.

 

[alldodge]

A leaking exhaust gasket won't make it run rich, and while your compression numbers are a bit low they are all even enough. Low numbers can be caused by the gauge or method of how readings were taken.

 

[achris]

If you have a PCM555 (3 connectors on the 'Computer') then you will be able to 'misfire' each cylinder individually. If you have the ECM555 (2 connectors), then as AD's diagram shows, only one bank or the other. Module is mounted on the port exhaust elbow.



Chris...........

 

[silver_power]

How can I find the correct ecm555 service manual for my engine? The reason is that till now I knew according to sm I have that my ecu is 2 bank fire , but I just read that there is the ecm555 sm36 rev1 (90-864573001) which sais that newer v8 ecm fires the injectors in batches (4 groups of 2injectors) and not 2 groups of 4 injectors.
My engine has serial:1A348183.
does anyone know where can I find it?
thank you very much

 

[alldodge]

I'm finding
864260 manual 31
864573 manual 36

The drawing posted above came from 90-864573001 December 2006

 

[silver_power]

That is correct, I just found the 90-864573001 sevice manual and it describes that there is 2 versions of injector wiring. The first is the known wiring of 2 groups of injectors ( 4 injectors/group) and the other is the semi-batch firing wiring of 4 groups (2injectors /group). At the second wiring the ecu has 4 pins at the A ecu plug to trigger the injectors. I was searching this service manual because my ecu has A1,A2,A17,A18 pins wired . This also explains the fact that when I used my diacom scanner to execute an induced misfire test, because my ecm 555 fires the injectors in batches when I tried to fire cylinders 5-8 I received an error code which carried through cylinder 8. I could only test cylinders 1 through 4 and the grouping is obviously cyl1= 1&6, cyl2= 2&3 , cyl3=5&8 cyl4= 4&7 .

 

[alldodge]

Well I be dang :facepalm: , all I needed to do is go down a couple more pages and would see the other drawing. Don't know how many times I have looked through this and not notice it

In any case thanks for noticing

 

[silver_power]

Yesterday pulled out the manifold and the gasket was burnt at #8 Cylinder. So the air was escapping from there. So i will put new gasket and then i must find why #4 & #6 cylinder plugs has carbon by rich condition even the compression is very good.Is there any possibility that the blown exhaust gasket #8cyl related with the rich condition at #4 & #6 cylinders as they are the closest to the blown gasket point?

 

[achris]

Blown exhaust gasket can affect the 'read' on spark plugs of other cylinders.

Chris.....

 

[silver_power]

what do you mean telling "read"? I think it is obvious that the two plugs at the middle shown at pics telling that these cylinders run rich......since compression is good, i probably must check fuel injectors, spark plugs, wires......and offcourse the diacom pluged...i will post as soon as possible....

 

[achris]

what do you mean telling "read"?

"Read the plugs". Look at the firing end and work out what it's indicating.

Run the engine with the exhaust manifold gasket fixed and see how it goes. You may be chasing ghosts.

 

[silver_power]

I hope so.
Many thanks.