Fuel pump lose power from time to time

[magnartbl]

Hi,
I've got a Maxum 2900 SCR from year 2001 with 2x Mercruiser 4,3L V6 190Hk Thunderbolt V engines.

The problem I experience is that the starboard engine starts up but dies again after a very short time (varies from 5 seconds to 10 seconds after startup). But the next day, the engine might work flawless for a whole day as long as it is in operation. If I shut it down and try to restart it, I might get unlucky and have the issue again.. When the issue starts, it is consequent until I come back to the boat another day or so..

What I've done so far is:
- Clean the carburetor
- Exchanged the Fuel/Water separating filter
- Exchanged all of the sparkplugs
- Exchanged the fuelpump
- Put carb cleaner in the gas tank

Still the problem exists.

It seems to me now that the problem is more and more related to the fuelpump losing electricity power; thereby does not pump fuel to the carburetor.

Does anyone know where the electricity Power Relay is that feed this engine's fuel pump?
And also, does anyone know the the replacement part number of it?

Any other suggestions to what might cause and fix the issue is also welcomed.

Cheers,
Magnar

[Nehalennia]

Have you verified that is it losing power or is it a theory at this point?
It could be the IAC (Idle air control). These commonly will go out mimicking the symptoms you're describing.

[magnartbl]

Originally Posted by Nehalennia

Have you verified that is it losing power or is it a theory at this point?
It could be the IAC (Idle air control). These commonly will go out mimicking the symptoms you're describing.

It is just a theory at this point as I need someone to assist me again when the issue occurs to perform the power tests.
The IAC is a good advice, I'll have a look on that too.

Magnar

[Nehalennia]

Best of luck.

[magnartbl]

Hi, and thanks all for nice feedbacks.

The engine serial numbers are: 0M023679 / 0M023695.

What I mean above with "exchange part", is that I've actually bought brand new parts from the local marine store and put into the boat. This has set me back financially since I've also had a boat technician to assist me with the installations (I'm 6.3ft long, so it's hard for me to work in the tight engine space even though I do my best to try fix it all myself). So, around 850 USD already spent in new parts and boat repair costs (the billable hours).

As an add-on to the problem description:

The engine might coughs and sputters at start point (like it has happened once or twice) and using the FULL throttle when the engine is about to go down in rpm and die, full throttle might save it from dying and you might get it up to full rpm again and then it will just die helpless after another few seconds... It is therefore not possible to keep it running by having full throttle all the time.

As we've exchanged the pump with a brand new one, I now think it must be the pump relay. Or bad connection somewhere that randomly disconnects power to the fuel pump. Or it might be the IAC.

With the knowledge of the serial number per above, do anyone of you know somewhere I could look up a drawing or find out where the placement of the engine pump relay could be? I've looked around, but I can't really see it anywhere..

Really-really appreciate help on this.

Many thanks.

Magnar

[mmwjr]

6' 3" working on a 2900 SCR is easy;-) I am also 6' 3" and I have a 2400 SCR now that's tight!

The 190 HP 4.3 has a carb as you mentioned so no IAC (only on fuel injected). I suspect it's the oil pressure switch. This is a saftey device that detects low oil pressure and removed power to the fuel pump on models with an electric pump such as yours. Of course you may actually have low pressure and this devise is saving the engine from destruction.

The switch is mounted next the the oil pressure sending unit that connects to the guage, both are located on the port rear of the engine where he oil filter or remote kit attaches to the engine.