Diacom recording wanted
 

I have a 7.4 MPI 2000 with MEFI 3 ECU witch is running real rich on idle.
I have used the Rinda Diacom scan tool on the engine and found some unusual data (vacuum level injector time etc).
My question is, does anyone have a Diacom recording from a 7.4 MPI running well on idle? I think it would be a great help to see a recording of healty engine and compare it with my engine.
Or does anyone know of a site where i can find recordings from a similar engine?

Thanks!

Re: Diacom recording wanted
 

I have some Diacom files from a 2000 7.4MPI I can email you. I recently did a top end rebuild on one that ingested water and had a stuck exhaust valve. Just for fun I attached a graph of the data before and after the repair that I combined for comparison.

I wish there was a site where recorded Diacom files could be shared. I have about 1,400 files ready to upload. If you want, I would be happy to review your data.

Dave

Re: Diacom recording wanted
 

Hi!
This winter I took the engine out of the boat an took it apart completly and checked everything, the cam is perfekt the valves also and nothing bad could be said about any mechanic parts on this engine, but still I have this low vacuum reading that makes the ecm to overfuel the engine at idle, as soon as I rev it up it runs fine and just after cleaning the spark plugs (or replacing them) it runns fine on idle (but rich).
After a while at idle the spark plugs get very black an it starts to missfire and run rough on idle.
There is no vacuum leak.

Does anyone have any idea?

I have attached a diacom reading, maybe you have any idea Dave_N?

Re: Diacom recording wanted
 

I would be happy to look at it. Don't see an attachment.

Dave

Re: Diacom recording wanted
 

Here is the Diacom-files.

/Thomas

Re: Diacom recording wanted
 

By the way!
Could my problem be that here in Europe we can only find 95 and 98 octan fuel.
Could it be that the fuel table have to be changed?

Does anyone know if it is possible to add a o2 sensor to the MEFI3 ECM, and if so where to connect it (pin #).

Does anyone know of a good tool for altering fuel table in MEFI3, and where to get it?
Because if i could give the engine a little less fuel on idle I would get rid of the dirt on the spark plugs, because on higer rpm everything is just fine.

/Thomas

Re: Diacom recording wanted
 

I don't think so.
In the US they use PON (Pump Octane Number) and in Europe we use RON (Research Octane Number) for gasoline. PON is really (RON+MON)/2.
So if you use European 95 octane (RON), then depending on the fuel quality it is probably the same as 90-91 octane in the US.
I have been using 95 octane (RON) in a 454 MAG MPI from 1999 without any problems.
Brian from Denmark.

Re: Diacom recording wanted
 

No O2 ability, no programability. For about $1700 you can get a program and programmable MEFI4 from Arizona speed and Marine. Check their web site out.

Re: Diacom recording wanted
 

thomasen,
Finally had a chance to look at your recordings. You are right, the engine is being driven rich by high MAP (low vacuum). There really is not much to indicate the problem in the recordings, or at least not that I can see.

Has the MAP sensor been changed out, or has the manifold pressure been confirmed with a standard vacuum gauge? If the MAP readings in these recordings are correct, there must be a mechanical cause such as vacuum leak, valve leakage, valve timing issue, or exhaust restriction.

Do you have any recordings with the engine under load?

Dave

Re: Diacom recording wanted
 

Thanks Dave_N!
Yes, The MAP sensor has been changed and the vacuum level has been checked with a standard gauge.
As I said the engine was completely rebuilt and there is no vacuum leak or restriction in exhaust, all valve checked and so on, no mechanic problem found.
Last week I built a electronic box that sense the TP value < 0.6 V that tells my box the engine is in IDLE.
If that is true the box lower the MAP sensor signal enought to give a MAP reading of about 16 InHg.
This lower the injection time so the engine runs much better (still a little rich so I probably could lower the MAP even more).
After using this little box this weekend I have a lot cleaner spark plugs and engine runs much better when idleing.
This works but it feels strange that I have to do something like this on a stock engine.



Dave N!
I have attached some readings when the engine is under load, without my box.

I am very thankful for your help on this, i would really like to find the REAL reasen for this problem and not have to cure it with my own electronics.

Thomas E N