Mercruiser MPI Won’t Stay Running

Croftie said:
Interesting, so I assume the HP pump is after the fuel filter?
Click to expand...
Yes the pumps are after the fuel filter, the problem is these pumps don’t suck too well unless they are primed, once they have fuel in them they pull it up from the tank easily. If the system has been dismantled then I fill the filter with fuel to get the system primed and once the pumps are wet they will push the fuel around the cooler and rail. You can hear when they are dry as they are quite noisy and quiten down once they have fuel in them. If they are still loud when the system is primed and the engine running then thats usually a sign that they are worn.
 
All injection engines run the pump for a few seconds when you turn the ignition on to build up rail pressure which inevitably falls away after the engine is turned off over a period of time, I use that feature to fill the system after working on the fuel injection on Mercruisers, only ever connected to the schrader valve to check pump pressure which can be in spec at idle but too low under way and the demand increases, thats how I confirm a diagnosis of a worn pump if its not screaming that its knackered.
 
spannerman said:
He’s already replaced the distributor cap.
Click to expand...
Hi spannerman. Just catching up...never trust those crap caps, as you’ll be well aware. They are just terrible things. I’ve had one fail right out the box and went through 5 including that in as many years. Terrible things. Although I’ll admit to cracking one putting it on too. Haha.
 
Wow QBhoy you have been unlucky, I have think I’ve only changed 5 in the past 20 odd years! But they can give misleading faults as I have found from experience.
 
spannerman said:
Wow QBhoy you have been unlucky, I have think I’ve only changed 5 in the past 20 odd years! But they can give misleading faults as I have found from experience.
Click to expand...
Yeah. Can be a total bugger of a thing. Especially known for failing after winter and trying to start in spring. Can cause so many random issues from rough running to not starting at all. They gather moisture by their very design.
My issue over the years is likely accelerated by putting a 150 odd hours at least on the engine each season, but still. They ain’t called the crap cap for nothing.
 
Hi

have worked on a few merc Mpi mag 350 engines And standard carb 5.7 l v8 and have a few that all that had the same problem of cutting out for what seems like no reason
on your port hand riser the ecm module is bolted and into two it go two wiring looms which seem to end up making poor connection

run the engine the wiggle those wires with the engine running if the engine cuts out that could be your problem

way we have fixed it if that is the problem is to use cable ties to stop the wiring loom moving while the engine is running

hope that help
 
You must log in or register to reply here.

Share this page

Top