Running Rich Stalls

I have a 1999 7.4 MPI
Had engine replaced ( Michigan Motorz Reman long block ) by a Mercrury Mechanic. Change out went well however engine now runs very rich. So much so they will not release the boat to me for fear of engine damage. When they rev the engine and bring it back to idle it stalls.
Summary of engine info:
New motor is Michigan Motorz 7400RRR
existng engine ser # 0L077447
fuel pump replaced 2007
Changes during troubleshooting.
No error codes
Eng temp sensor normal and reading correctly
New Map sensor
New fuel pressure regulator ( manifold vacuum only at 12" at idle )
New plugs
Injectors cleaned and tested

My mechanic has come to the end of his patience and does not want to spend any more time on it. I will say I feel he has been very fair just does not know how to go forward.

Re: Running Rich Stalls

there are two fuel pressure regulators on that fuel system

one is located on the fuel cell mounted low, PORT side of engine

there is another one located in-line at the fuel rail - this regulator has caused problems exactly like the one you describe, i have seen it a number of times - this is GM installed part and does not always show up in merc nomenclature

have your mechanic check the vaccuum line at the regulator on the fuel rail, betcha there is fuel there

there are two styles of fuel rails, one has the regualtor built into it and the entire rail must be replaced, the other has a "serviceable" regulator

Re: Running Rich Stalls

Had engine replaced ( Michigan Motorz Reman long block ) by a Mercrury Mechanic. Change out went well however engine now runs very rich. So much so they will not release the boat to me for fear of engine damage................

My mechanic has come to the end of his patience and does not want to spend any more time on it. I will say I feel he has been very fair just does not know how to go forward.

Click to expand...

Howdy,

And welcome to iboats....

In view of the above, there are many of us here that can probably make suggestions, but my next question would be where is your "Mercury Mechanic" going to send the boat to get it fixed if he doesn't know how to fix it?

It appears that the shop is sort of "on the hook" to get it right or pay to send it somewhere else before you go out on your own to find your own "fix"........


Just saying......



Rick

Re: Running Rich Stalls

He checked the pump regulator on the port side down low. It was putting out 43PSI which he said was normal. He then checked the one on the rail and it was putting out 43 psi which is high suppose to be around 30 psi according to him. We replaced with new and still have problem. He checked the vacuum it was 12" at the manifold and at the regulator. I may not explain this right but my understanding was that he advanced the engine timing and the vacuum went up to 18" and fuel rail pressure dropped to 34psi and engine ran normal. Howver timing was advanced too far to run engine that way. Another post indicated that the knock sensor if defective would retard the timing causing my problem.

Re: Running Rich Stalls

HT32BSX115 said:

Howdy,

And welcome to iboats....

In view of the above, there are many of us here that can probably make suggestions, but my next question would be where is your "Mercury Mechanic" going to send the boat to get it fixed if he doesn't know how to fix it?

It appears that the shop is sort of "on the hook" to get it right or pay to send it somewhere else before you go out on your own to find your own "fix"........


Just saying......



Rick

Click to expand...

Fair comment. However he has to date been very fair he has spoken to Mercury who only comment was send the ECU back for an update 5 weeks turnaround. He has ried the suggestions from 2 other merc dealers. Doesw not know where to go from here and is being up front about it.

Re: Running Rich Stalls

HFXJACK said:

Fair comment. However he has to date been very fair he has spoken to Mercury who only comment was send the ECU back for an update 5 weeks turnaround. He has ried the suggestions from 2 other merc dealers. Doesw not know where to go from here and is being up front about it.

Click to expand...

Based on what they've done so far and barring any electrical wiring or fuel flow etc.. problems, It sounds like the next step might be to reflash/update the ECU processor. I think you will be "on the hook" though for that. I have a hard time believing (everything else being the "same) that the ECU reflash will "fix" it though....

You're sort of stuck. I would not be very happy either.....

Re: Running Rich Stalls

Another thread mentioned that a defective knock sensor may retard the timing. This may be causing the low vacuum pressure. Unless someone has an explanation for low vacuum pressure on a new engine.

Re: Running Rich Stalls

HFXJACK said:

He checked the pump regulator on the port side down low. It was putting out 43PSI which he said was normal. He then checked the one on the rail and it was putting out 43 psi which is high suppose to be around 30 psi according to him. We replaced with new and still have problem. He checked the vacuum it was 12" at the manifold and at the regulator. I may not explain this right but my understanding was that he advanced the engine timing and the vacuum went up to 18" and fuel rail pressure dropped to 34psi and engine ran normal. Howver timing was advanced too far to run engine that way. Another post indicated that the knock sensor if defective would retard the timing causing my problem.

Click to expand...

so both regulators have been replaced??

ignition timing and engine vaccuum have nothing to do with fuel pressure, it is controlled by the regulator(s) and fuel pump output

how is he checking the vaccuum??

yes, a knock sensor would tell the ecm to retard timing and increase injector pulse width, a CDS data list with the engine running would be the best bet to check the output of the knock sensor(s) - testing them is easy, run engine at 1500-2000 rpm and rap the block with a hammer next to the sensor and note change in engine rpm/sound