1993 mercury efi 150hp cuts out

[paul828]

I have a 1993 mercury efi 150hp, I can be driving down the lake and the engine just quits like the someone turned off the key or hit the kill switch, everythings to test good when the service person checks it out

 

[CharlieB]

Re: paul828

Re: paul828

Does the motor restart and run fine?

Has the WOT RPM changed?

First suspect is intermittant failure of a wire connection providing power or ground to something. Always start with the battery, check to be sure all connections are clean, bright, and tight, some for the motor ends of the cables.

Then check the main harness plug, check that all pins are clean and tight, if any seems 'loose' take a small exact-o-knife and slide the blade down the 'slot' of the male pin causing it to swell just a little. NOTE: You may want to disconnect the battery ground first, it is very easy to short across two pins.

Check the wiring harness throughout the boat for any movement, chaffing, that may have worn thru causing an intermittant short or break in a wire.

Idle the motor while you 'wiggle' everything that will move to see if you can reproduce the motor killing.

 

[paul828]

Re: paul828

Re: paul828

engine starts fine after stopping, connections are tight and clean,

 

[paul828]

Re: paul828

Re: paul828

engine starts fine after stopping, connections are tight and clean,

we have narrowed it down to the electric fuel pump not always turning on, is there a way to test it, it makes alot of noise when it does turn on

 

[Faztbullet]

Re: paul828

Re: paul828

A noisy pump is usually on its way out....is the fuel pressure a tad low or brass/gold partiles in fuel when VST is drained??

 

[paul828]

Re: paul828

Re: paul828

do not have a gauge to check fuel pressure and have not drained the vst, will go check that out now, I want to check power coming into the fuel pump when it quits to verify it is not the ecu

 

[CharlieB]

Re: paul828

Re: paul828

The fuel pump always has a 12V supply, the ECU driver controls the ground to switch the pump on.

Use a test light or volt meter to determine which side is hot, disconnect the pump ground wire to the ECU
, then again, verify power to the pump, rig a jumper wire and ground the pump to the engine block, the pump should run so you can test pressure.

If the pump is noisy, start pricing a new pump thru all available sources to find your best price.

 

[paul828]

Re: paul828

Re: paul828

Thanks Sir.....ordered new pump, fuel filter and a new hose yesterday.....found a good price for original merc parts....should receive Thursday,........will let you know how it turns out.......I noticed Wright City Mo, there used to be a place that served family style chicken dinners are they still in business.

 

[CharlieB]

Re: paul828

Re: paul828

The original Big Boys was shut down a few years ago for non-payment of taxes, the City took over the land and just now bulldozed it, intending to build the new City Hall there. A few of the old employees have recently re-opened, somehow able to use the Big Boys name and serve the original menu, same food, now just on the North side of the freeway and only a block or so west.

 

[paul828]

Re: paul828

Re: paul828

Still having same issues with motor quiting and hard start , can I connect the elec fuel pump directly to the key switch and by-pass the ecu or will this cause more problems

 

[CharlieB]

Re: paul828

Re: paul828

Not the key switch.

As I spelled out earlier, the ECU pump driver controls the GROUND on the fuel pump. Disconnect one wire to the pump, use a test light to find which wire is 12V, you want to disconnect the ground wire from between the pump and the ECU. Now you can rig a separate ground wire to control the pump to test the motor. the pump should run as long as you have it grounded.

Any failure of the primary low pressure pump, or fuel hose, primer bulb, pick-up tube in the tank, etc., and you could still have a fueling problem.

 

[paul828]

Re: paul828

Re: paul828

Have rebuilt the low pressure pump, checked fuel hose, replaced primer bulb, removed pickup tube and checked screen all clean. when the elec fuel pump kicks on I have 60psi, but after the pump shuts off it the pressure drops to almost 0psi, should the system maintain pressure, I believe the normal is 36 to 39 psi

 

[CharlieB]

Re: paul828

Re: paul828

This could be an 'aha' moment, the fuel pressure regulator should control pressure and keep it within a vary narrow range, dumping any excess back to the VST but keeping the factory set pressure. With the motor NOT running, not cranking, injectors NOT firing, the pressure should hold for minutes after you unground and stop the pump.

 

[paul828]

Re: paul828

Re: paul828

Good Morning Sir, I will take it that you believe that the pressure reg. is the culprit, bleeding down and not telling the ecu about the loss of pressure. I am thinking replacing it, but I was also thinking I should maybe replace the float and needle valve in the vapor sep, while I am tearing into it.

 

[CharlieB]

Re: paul828

Re: paul828

The ECU runs the pump for a few seconds when the key is first turned on, since some people turn on the key but do not start the motor, the ECU only runs the pump those few seconds to build enough pressure to fire the motor, once you crank it.

After starting, the ECU senses the running motor and turns on the pump until the key is turned off.

Thus, the pump is not left on and burnt up if the key is just on without the motor running.

Anytime you are inside a component it would be wise to go ahead and service any normal wear items in there.

 

[CharlieB]

Re: paul828

Re: paul828

The clear hose works well to identify a problem between the primary LOW pressure pulse pump and the carbs, or to the VST on an EFI motor, but in this case we are dealing with the HIGH pressure of an EFI system. These electric pumps can reach in excess of 100 psi of the regulator sticks closed, and on the other hand, if a regulator is NOT maintaining adequate pressure the motor will not be able to make consistent power.

Verify fuel pressure, at idle, and again under load at throttle. If pressure is erratic yet the pump remains on and no change in sound, then drain the VST and inspect the fuel for metal particles indicating a worn pump. If clean, suspect the regulator.

 

[paul828]

Re: paul828

Re: paul828

Have not had time to re-check the pressure yet, but when I was looking at fuel filters and such I did see what looked like brass metal shavings, and little black pieces of maybe rubber

 

[CharlieB]

Re: paul828

Re: paul828

Have not had time to re-check the pressure yet, but when I was looking at fuel filters and such I did see what looked like brass metal shavings, and little black pieces of maybe rubber

If you found this in the VST, then the metal is what Fazt was pointing out, signs of wear in the high pressure pump.

The black particles are often bits of deteriorating fuel hose or flakes off the diaphragm of the low pressure pulse pump.

If you haven't already, it could be a good idea to rebuild the low pressure pump. The kit is cheap enough.