mercury 150 efi fuel pump

[pancakes]

i have a 2000 mercury 150 efi salwater series. i'm experiencing a problem with the fuel pump. when i turn on the ignition without cranking the motor, the electronic fuel pump does not come on unless i jump the negative pole on the fuel pump to ground. also, once the jumped pump does turn on, it just runs forever as if it's not able to build up enough pressure in the tank. i thought it was just a bad ground but even when grounded, i'm experiencing very rough idle and motor dies quickly. does anybody know if the negative pole fro the fuel pump is just a standard ground or something more complicated? what's the best way to check the fuel pump? any help would be greatly appreciated!

 

[Faztbullet]

Re: mercury 150 efi fuel pump

Without getting technical,the ECU controls the ground to the pump. You need to test the fuel pressure when pump runs to see if within spec's and check all the grounds to front mounting plate(ECU mounts) and check the ECU connector. If all is Ok the fuel pump driver may have failed in the ECU.

 

[pancakes]

Re: mercury 150 efi fuel pump

great, will troubleshoot today. can you tell me the part in need to test the fuel pressure? i assume it connects to the brass valve on top of the VST, correct? does the engine need to be running to test pressure or just the electronic pump in the VST? the engine won't run for more than about 10 seconds. if it turns out to be the pump driver, do you know the cost of that part? thanks so much for the help!

 

[Faztbullet]

Re: mercury 150 efi fuel pump

can you tell me the part in need to test the fuel pressure? i assume it connects to the brass valve on top of the VST, correct?

You will need a fuel pressure tester guage, either rent one from a auto parts house or buy one a Harbor freight for $25.

does the engine need to be running to test pressure or just the electronic pump in the VST?

Just the pump....below is how to test pump.
(1) Install fuel pressure guage
(2) Prime engine using fuel primer bulb.
(3) Turn ignition key switch to ?On? position.
(4) Operate electric fuel pump for approximately 10 seconds.
NOTE: Fuel pump will only operate for approximately 30 seconds. By turning the key switch to ?OFF? and then back to ?ON? the pump will operate for 30 seconds more.
(5) Take reading on fuel pressure gauge.
Results: If pressure reading is 34 to 36 psi (234 to 248 kPa), the electric fuel pump is providing
fuel with enough pressure to be used by the injectors. Pump malfunction is not the cause
of EFI trouble. If fuel pressure is well below 34 psi (234 kPa), fuel delivery to electric fuel pump, mechanical fuel pump failure or other related problem exists.

if it turns out to be the pump driver, do you know the cost of that part?

A new Merc ECU is about $1900 but if it turns out to be driver I would send it to to Tony Brucato @Brucatosvs.com and have it tested. If it is bad he has a aftermarket for about $1200(I sell these to customers and 100% satisfied with unit)

 

[pancakes]

Re: mercury 150 efi fuel pump

excellent, thank you for the thorough response. i'll try this today.

 

[pancakes]

Re: mercury 150 efi fuel pump

okay, i tested the fuel pressure. i had to turn the ignition on and off three times to get pressure to max out right at 35 psi. does this indicate a bad ECU driver? on a side note, once the motor is hot, the pump seems to come on for the appropriate amount of time without jumping the fuel pump to ground. i was able to run motor up to operating temp by removing negative lead from vst pump while jumping that pole to ground. before, i had simply jumped to ground with factory leads still attached which resulted in a motor that would start but quickly die. thanks again for the help!

View attachment 120879

 

[pancakes]

Re: mercury 150 efi fuel pump

i posted the wrong photo before...

View attachment 120880

 

[Faztbullet]

Re: mercury 150 efi fuel pump

Check all your grounds and connections first but it sounds like the ECU , call Mrs Linda and tell her you want to send it in for testing (about $75). CDI charges about $800 to fix this problem but for around $300 more you can get a new adjustable ECU from Brucato.

 

[1Crazymechanic]

Re: mercury 150 efi fuel pump

You shouldn't have to energize fuel pump three times to get it to pressure. Are you getting good voltage to vst, when running? Also have you drained the vst to see if it has contaminants. If you have debris in vst, it could clog strainer filter for elec fuel pump.

 

[pancakes]

Re: mercury 150 efi fuel pump

i think i had not primed the line the first time i took a fuel pressure reading. seems like it takes about 8 seconds to come up to 36psi now. also, did a cylinder drop test this morning and found that #3 isn't firing. maybe a separate issue but wonder if the ecu could be to blame for all?

 

[Faztbullet]

Re: mercury 150 efi fuel pump

If #3 injector isnt firing that cylinder wont run....

 

[pancakes]

Re: mercury 150 efi fuel pump

could a faulty ECU cause intermittent cylinder drop out?

 

[pancakes]

Re: mercury 150 efi fuel pump

okay, i swapped the ECU with a working used one i found on ebay for 150.00 and everything seems perfect! thanks, faztbullet, for the bulls-eye diagnosis.

 

[Colinj]

My problem is I have2 e c u box I have a good one but I put it on the bottom ofmotor a 225 and now the warning lights are blinking motor and pump are still not running