Problems starting mercruiser 4.3L mpi

patsyjoe

Cadet
Joined
Jun 28, 2009
Messages
6
Hi folks,

I need some help. trying to get a Mercruiser 4.3L MPI (1999 I think) with an Alpha One sterndrive going again but I'm running into problems!!!

The history of the boat is that it was given to a relative who ran it aground breaking off the skeg and wrecking the prop. He also bent the prop shaft. I disassembled the drive and repaired all, but it justs seems as if we have had constant problems with it since. Because of a delay in getting parts delivered the boat was sitting up for a good while, i got it back together and serviced it and tested it and it worked fine. She was parked up for the winter and brought out as soon as the weather improved, but like I said we have had a lot of problems with it.

Since it was taken from storage, the fuel gauge won't work, appears to be the float which I am attempting to repair. There was a ball valve, I suspect this acted as a non return valve in the fuel line was very very stiff. When I tried to blow it through, it would hardly move. This was freed up and we got going again but there always seemed to be a hesitation in the acceleration. i began suspecting fuel pump problems as it would die, come back, splutter, back fire and then clear itself and go again. When the throttle was opened fully, it would die and sounded as if it was drawing air, but i suspect that it is not getting enough petrol for efficient burning.

Anyway, the latest is that the starter has stopped working, the bendix is spinning but not being sent out. I took this out and sprayed a lubricating solution in (WD40) but to no avail, made no difference. It is working intermittently. When it did engage, it would crank the engine but the engine would not fire and appeared not to be getting petrol. Now I cannot here the electrical fuel pump priming where I always could previously. Could the fuel pump have burned out as a result of having to draw the petrol past that half seized ball valve?

I am very frustated with it at the moment and really need some help to keep my sanity. Thanks in advance.

PS I followed the braided pipes from the Fuel/water separator and they go under the engine into a covered part on just under and behind the alternator, is this the fuel pump and is there any other way of getting it out without undoing the engine mountings and lifting the engine. Also do you know how much height I could get the engine with the sterndrive attached, don't really want to have to disconnect all that.

Sorry about the essay.
 

patsyjoe

Cadet
Joined
Jun 28, 2009
Messages
6
Re: Problems starting mercruiser 4.3L mpi

Anyone any help to offer at all please.
 

Fun Times

Moderator
Staff member
Joined
May 16, 2009
Messages
9,138
Re: Problems starting mercruiser 4.3L mpi

Yes that is where the fuel pump is, Not sure on how much room you have but some times you can un do the too nuts to the fuel bracket and slide it off the engine mount studs and let it hang lower in the bilge and work on it, That black cover will just pull off easy, no tools needed to remove the black cover, Will need a size 7/16 gear wrench to remove the too nuts that hold on the brass cover that holds the fuel pump in place, There is a 90 degree brass fitting hooked to it that will slide off once you get it apart and hanging,the 90 is held tight by too 'o' rings on each end of the brass fitting.Have you hooked up a fuel pressure gauge to the fuel rail on top of the engine to see what fuel psi you are getting at key up and while cranking?
 

patsyjoe

Cadet
Joined
Jun 28, 2009
Messages
6
Re: Problems starting mercruiser 4.3L mpi

Thanks, so far!!!!

No I don't have a pressure gauge, if i do this will it tell me if the pump is gone? What pressure should i have?
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,133
Re: Problems starting mercruiser 4.3L mpi

Ayuh,... The fuel pump can't pump fuel if the tank won't give it up....
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Problems starting mercruiser 4.3L mpi

1. Your outdrive has to come off before you lift the engine at all. Besides it should come off yearly for maintenance anyway.
2. You will need a proper fitting and high pressure fuel gauge to read the fuel pressure on an EFI system.
3. You will need an OEM service manual to locate all the things that could cause your problem and give you the specs on what, how, when and where to check.
4. A rough idea about year of your boat (not engine) isn't going to work. A real SN is needed for your engine to find the proper specs for your system.
 
Top