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5.0l MPI question

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danilo

New member
I have a 5.0L mpi that only delivers 3200 rpm at WOT.When i take back the throttle about 50% the rpm's don't decrease.Could this have to do with the TPS or do i have another problem.Are there any tips on this issue.
 
Misfiring or dirty fuel injectors may be the cause. I seem to remember a few similar postings last summer that concluded dirty injectors and corroded injector wiring were the issues. Idle in the water at 1500 RPMs and disconnect each injector one at a time and watch for NO CHANGE in RPMs...that will be the problem injector(s). The TPS rarely fails. When they do the engine will fall on its face for a moment as the TPS passes the dead spot on the TPS.
 
Can you pull codes on this?
In addition to a fuel related issue, see if the ignition advance is doing what it's suppose to be doing.
A progressive advance or a TA (total advance) that is not meeting OEM specs, can hold back RPM while under load.

Another thing to possibly consider, would be if any changes have occured to the bottom condition, prop condition, etc.
If hull growth or an incorrect prop pitch, or even damaged prop is preventing you from reaching the OEM spec's WOT RPM, then you'll want to correct this ASAP.
 
Thanks guyjg,
today i,m going to perform a spark test and a compression test just to be sure
after that i,m going to do the injector test.thanks for the tip.
 
Rick
there are no changes to hull and prop condition. the boat doesn't stay in the water so there is no growth.
I,ll keep you guys posted.
 
danilo said:
Thanks guyjg,
today i,m going to perform a spark test and a compression test just to be sure
after that i,m going to do the injector test.thanks for the tip.
Click to expand...
By spark test, just what do you mean? Spark quality.... or spark timing?

I know that your harmonic balancer is not marked off for a dynamic TA check, so you will be limited to using a digitally advancing timing light.
With this type of light connected, increase RMP and strobe the OEM timing marks up to approx 3.2k rpm.
Compare what you are reading to the OEM specs.
It could be that your ignition module is delaying the EST too much..... of which may take us back to the TA being too little for any performance above your WOT RPM of 3,200.
Perhaps a crap shoot, but perhaps worth checking.
P of E...... process of elimination..... one item at a time. :D


danilo said:
Rick, there are no changes to hull and prop condition. the boat doesn't stay in the water so there is no growth.
Click to expand...
Well, that's a good thing!
 
Before you start doing all the testing, When is the last time "ALL" the fuel filters were changed. Especially the ones(Both) inside the fuel module? I would start with a fuel pressure check.
 
I did the compression and spark test both were good .
I'm sure now its a fuel problem .
Gonna check the complete fuel system now.
thanx
 
have you verified the tach with a calibrated shop tach. also checked the throttle cable operation and adjustment?
 
WPAGE,

We must be careful what we tell others to do with chemicals here.........

What you do is your business but to just say use acetone with no explantion is not considered good practice.

There are too many viewers who may not understand the full impact of using or handling chemicals such as pure ACETONE and may cause more damage than good.

If acetone is the "base" for many fuel cleaners than maybe suggest the actual cleaner that the acetone is the "base" for. That way they are using a premixed packaged product with INSTRUCTIONS on how to use it.


Pure acetone vs a mix may not be a good thing for many....just sayin........
 
kghost said:
WPAGE,

We must be careful what we tell others to do with chemicals here.........
What you do is your business but to just say use acetone with no explantion is not considered good practice.

There are too many viewers who may not understand the full impact of using or handling chemicals such as pure ACETONE and may cause more damage than good.

If acetone is the "base" for many fuel cleaners than maybe suggest the actual cleaner that the acetone is the "base" for. That way they are using a premixed packaged product with INSTRUCTIONS on how to use it.

Pure acetone vs a mix may not be a good thing for many....just sayin........
Click to expand...
+ 1 ............
I don't mean to bust your chops here, but I too would ask that you not offer this as a suggestion!


There may be certain materials use that are very sensative to chemicals such as acetone.
We don't necessarily need to view acetone as being "HOT"........., all it requires is for the chemistry to be incorrect and/or incompatable, and we have a problem.
Petroleum products contacting certain rubber components, for example!
Problems caused to MPI components could be very costly to an owner who took this advice at face value.

I too am just say'n!

Kghost 4:15 We must be careful what we tell others to do with chemicals here
Rick 7:22 Chemistry..... be careful!:D



.
 
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Taken from the website above...
...Using a solution of 1:160 I noticed a slight swelling of the gaskets, just enough to be noticeable. 1:160 is DOUBLE the maximum recommended ratio for acetone usage. ...
Click to expand...

Using it outdoors for proper ventilation to clean metal carb parts may be OKAY. I use lacquer thinner to do that. Both chemicals are dangerous to use in an uncontrolled environment. The last time I used them I wore a respirator. A retired professional mechanic only advises on YouTube to use lacquer thinner at a 10:1, gas:LT, ratio to clean catalytic converters.

Kghost 4:15 We must be careful what we tell others to do with chemicals here
Rick 7:22 Chemistry..... be careful!:D
Click to expand...

Couldn't agree more!
 
Wpage, understood! However, I'd be more interested in reading where Mercruiser recommends using any form of acetone for any portion of thier MPI system.
Then I'd be interested in seeing the chemical dilution ratio, etc.

The page that you referenced mentions a ratio of 1:160.... that's quite a dilution, and you made no reference to this ratio dilution when you posted earlier.

The thing with open forums is that someone may poke their head in and read one tid bit only. Then they may leave thinking that this is all they needed to hear.


Rick 7:157 Yea though I dilute my Acetone, I caution those behind me!


.
 
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The thing with open forums is that someone may poke their head in and read one tid bit only.
Click to expand...

We all must remember that not everyone is equal in experience, knowledge and procedures for using ALL TOOLS (for the novice; including chemicals) for maintenance of everything.
Give a man a fish and he'll eat. Teach a man to fish and he'll survive...or something like that...
Click to expand...
 
Yes, it's something more like; "give a man fish and bread, and you've fed him for a day! Teach a man how to catch fish and harvest wheat to make bread, and you've fed him for a life time!".... or sump'n like that! :D Whatever it is.... it's a good one!

As to your first point, this is exactly why I will seldom post torque specs, ignition timing specs (other than general), or p/n's without specific information, etc.
Not unless I'm comfortable knowing just what the OP is asking about.
There is just too much room for misinterpretation by either party, IMO.

.
 
I wonder if the site moderators have any disclaimers for anyone/all to read? It may be a good idea to have some to protect the contributors from frivalous lawsuits by those that may not have enough sense to come in out of the rain.
 
I knew a guy who used to add Acetone to the fuel he ran through a supercharged small block Chevy. He added just a little too much one time and melted the top end of his engine at Island Drag Way.

I would never advise anyone to add any chemical to there fuel that was not prepackaged, designed to clean or help with combustion.
 
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