Merc 2.5 175hp Fuel Pump getting low voltage

[Keaten]

Merc 2.5 175hp EFI Lazer
Fuel pump only getting 9.6 volt
Battery cables on motor side have 12.2 volts
Fuel pressure = 35psi with key on pump running.
Motor fires trying to run for 1-2 sec then dies slow like lack of fuel/pressure. Help please.
Connection at electric pump are good very clean.

[tlwjkw]

mechanical pump?.. tried pumping bulb when starts ta die?.. whats pressure when motor start dyeing?.. is pump still runing when motor dies?.. is tha 9.6 reading + to - on pump or pump + to - on motor ground?

[Keaten]

Positive to neg. On pump is 9.6 pump still running when motor dies yes.

[Keaten]

I'll try others

[tlwjkw]

sounds like tha mech pump may need some attention....

[Keaten]

I'll try hand pumping , and test psi while running with out my help then kinda get some info..

[tlwjkw]

.........:thumbsup:

[Keaten]

Tried hand pumping bulb to help mechanical pump out no change.. didn't really ever start just hit and fired 1/2 sec

[tlwjkw]

filter at bottom of pump?.. fuel in vst when it dies?.. 'bout ta run out of "computer ideas".. jus ta make sure its a fuel delivery problem ya might squirt some pre-mix inta tha open butterflies when ya crank it...

[tlwjkw]

jus for questioning tha pump and/or driver circuit ta make sure they aren't doin' something stupid.. disconnect tha + and - at pump.. find a purple anywhere on tha motor and add it to + on pump.. add a block/motor ground to tha - side of pump.. this will by pass tha ecu driver circuit and supply a continuous 12+ volts to tha pump when key is on.....

[25two.stroke]

jus for questioning tha pump and/or driver circuit ta make sure they aren't doin' something stupid.. disconnect tha + and - at pump.. find a purple anywhere on tha motor and add it to + on pump.. add a block/motor ground to tha - side of pump.. this will by pass tha ecu driver circuit and supply a continuous 12+ volts to tha pump when key is on.....

Thats what it sounds to me, the fuel pump driver is failing or the two wires feeding the pump are bad. Like he said, send 12v to the pump direct and see if it starts. That pop and die is the motor trying to start too lean.

[Keaten]

Ok I'll run 12 volt to pump directly then try starting. And also see wat psi is with full 12v when motor runs normal electric pump runs solid correct. Bc I know it shuts off with key left on past 10-15 sec. Just want to make sure it doesn't run then rest then run then rest..

[tlwjkw]

goin' thru tha ecu it is supposed ta shut off after a few seconds unless tha motor starts.. by passed (switched purple hot and solid ground) it will run as long as tha key is on..

[rock]

This is a motor Keaten got from me. 175 efi that ran good but something let loose and destroyed a cylinder cracking the register to the bottom. I was not confident enough in my welding to make the repair so I had James Perry do the repair. He then replaced 2 sleeves, bored, decked, and cleaned the block ready for building. His work looked outstanding. Chris Carson cleaned injectors and supplied new reeds. Motor was assembled with 6 new standard bore pistons and metal caged bearings. I got ill (heart attack) and did not start motor. This is not Keaten's first rodeo so I figured it was OK to sell it without starting. Now I wish I had it back so I could get it going. My guess is also the driver so anyone with a digital ecu for sale or loan please let me know. This is my responsibility and I want it to be correct. We can certainly try the bypass but I don't want to have it that way permanently. Needs to be used as Mercury planned. Appreciate the help guys.

Rock

[25two.stroke]

This is a motor Keaten got from me. 175 efi that ran good but something let loose and destroyed a cylinder cracking the register to the bottom. I was not confident enough in my welding to make the repair so I had James Perry do the repair. He then replaced 2 sleeves, bored, decked, and cleaned the block ready for building. His work looked outstanding. Chris Carson cleaned injectors and supplied new reeds. Motor was assembled with 6 new standard bore pistons and metal caged bearings. I got ill (heart attack) and did not start motor. This is not Keaten's first rodeo so I figured it was OK to sell it without starting. Now I wish I had it back so I could get it going. My guess is also the driver so anyone with a digital ecu for sale or loan please let me know. This is my responsibility and I want it to be correct. We can certainly try the bypass but I don't want to have it that way permanently. Needs to be used as Mercury planned. Appreciate the help guys.

Rock

Dammit, now I wish I hadn't thrown those 3 I had away a few weeks back. I tossed 2 200s and a 175. I may have a 200 ECU left, do you know if that would run with a 175 porting and exhaust, or would it flood out?

[H2Okie]

Merc 2.5 175hp EFI Lazer
Fuel pump only getting 9.6 volt
Battery cables on motor side have 12.2 volts
Fuel pressure = 35psi with key on pump running.
Motor fires trying to run for 1-2 sec then dies slow like lack of fuel/pressure. Help please.
Connection at electric pump are good very clean.

If you have access to a multimeter you can perform a couple of simple wiring tests . With the battery disconnected and the black /red wire lifted off your fuel pump negative terminal set your meter on OHMs.

Now separate the laser ECU plug in connector . With one meter test lead On pin 2 of the plug with the locking ring (the one going to the engine harness) read the lifted black/red wire going to your fuel pump . Should read low resistance .1 to .3 ohms .

Now read between the large stud that the Positive red battery cable connects to on your motor and the red wire on your fuel pump terminal . again this should be a low ohmic reading .1 - .3 ohms

Next read positive red battery cable to the negative fuel pump terminal where you lifted the black /red wire off of . this will be a higher read due to the resistance of the fuel pump motor windings . 6 ohms +/-

These tests will prove wire continuity of the pump wiring . I found a bad connection on a fuel pump wire a few years ago and had to trim the wire back a little and put a new ring eye terminal on to fix the problem . (broken strands of wire inside insulation )

Inspect the #2 pin contacts in both plugs for burning , corrosion , or bent before Reconnecting the ECU plug and terminate the black/red wire on the fuel pump . Now reconnect the battery for making voltage tests . The red wire on your fuel pump terminal should be "Hot" all of the time .

With meter set to DC "volts" black meter lead to engine ground and red meter lead to red wire on fuel pump terminal meter reading should equal battery voltage .

Now when you turn the key on and fuel pump starts read the voltage across the fuel pump terminals . Since you have previously tested the wires if voltage is still low most likely cause is a bad fuel pump driver in ECU or bad pin contacts on pin 2 of the ECU plug in connector

[25two.stroke]

If you have access to a multimeter you can perform a couple of simple wiring tests ...

Everyone who owns a lazer efi motor should print\archive that.

[tlwjkw]

send it to 'em.. bobby v. has run justa 'bout every combination of all tha production ecu's (includin' tha three PM's) on every horsepower (mix n match) and found tha hp rating didn't mean squat.. if they were good they would run on anything.. if they were bad they were BAD....

[Keaten]

Tired pump with a solid 12 volt keyed source and still had the 35psi and motor fires 2-3 sec then dies. Next step like Rock said find another ECU 175 HP

[25two.stroke]

Its too lean. How is the enrichner circuit hooked up? To solenoid or to the choke on the key?
Also, ohm the head temp sender and the IAT...if either of those is bad it will not start right cold. Check those prior to getting a new ECU...

[Keaten]

This help this crazy good thanks guys..!!

[H2Okie]

It sounds like when you're turning the motor over with the Key it "starts" , you let go of the key and then it stops ? Is the +12 v purple wire staying hot when you go from "start" to "run" with the key sw.? If the purple goes down so does the ECU.
I wonder if your enrichment circuit is working but when you stop cranking the extra fuel stops and so does your motor

If your are not getting enough fuel when starting if you disconnect the manifold air temp sensor it will cause the ECU to increase the fuel delivery by 10%
If you disconnect the TPI the ECU will increase fuel delivery by up 40%
Mercury advises against running an engine with sensors disconnected but say you can do it on a short limited basis to troubleshoot problems
If you try these things and the motor keeps running it definitely was not getting enough fuel . Just remember to connect everything back up

[Keaten]

The yellow wire with black strip coming from motor harness is cut and taped up.

[flabum1017]

With a volt meter, put the meter black on an engine ground and the meter red to the positive side of the pump. Turn the key on and read the voltage as the pump is running.... it will run only a couple seconds or so. If the voltage is low, check the fuel pump fuse contacts for corrosion. You can also ohm out the wire from the pump to the positive terminal where the battery cable hooks to the engine as said earlier. Should be real close to 0 ohms. If the voltage is good, remove the negative wire from the fuel pump and put a jumper wire from the negative terminal on the fuel pump to an engine ground and check the voltage across the terminals on the pump with the pump running. Do this with a fuel pressure gauge hooked up. Voltage should be at least 11 volts or more. If the voltage is lower, most likely a failing pump. If voltage and pressure are good, then fuel pump circuit in computer or the wire from the pump to the computer has a problem. Again, you can ohm out the wire and it should be close to 0 ohms.

I have seen wires that ohm out alright, but can't handle the amperage and drops voltage.... so be aware of that.

[tlwjkw]

The yellow wire with black strip coming from motor harness is cut and taped up.

thats normal on tha efi.. it should have two yellow reds on tha starter solenoid.. one of those is tha enrichner going thru tha ecu...

[rock]

I may have a 200 ECU left, do you know if that would run with a 175 porting and exhaust, or would it flood out?

If you have one send it and tell me what I owe you. Thanks

Rock

[Keaten]

Might have found the issue hold off for now... Thanks

[25two.stroke]

Yeah haven't had a chance to look and test yet, but keep us updated. Especially if you find an issue that is not the ECU!

[Keaten]

I will post the final fix so all and learn for future info..

[Keaten]

Ok got it fixed and running and idling normal..
The problem was.... Ready for it..!!
Dam water in the fuel so when I primed the fuel system for the first time (New motor for this boat) it primed the vst and water separator filter with a very high% of H20 and of course wouldn't fire correctly. I learned this by looking at the plugs to see if they were getting gas nope they had clear H20 mostly on them, I then drained a little fuel from the vst drain plug into a clear cup and omg looked like piss or beer.. I've since drained everything and replaced the fuel/ H20 separator filter and drained gas tank and replaced with new gas/oil mixture and bam !! Running like a beast..

[Keaten]

Thanks Rock love the Engine it's a bad ass hits Hard !!!!��

[tlwjkw]

alrighy then!!!! don't cha jus luv it when a plan comes ta 'gether......:thumbsup:

[TEXAS20225]

Tommy you hit it right on the head on these Merc ecus i have in fact ran more combinations of all horsepower ecus on every horsepower range you can dream up from the very early days of the sh%#$t pile analog ecu to the last of the digital units horse power sticker means nothing this i know for a fact i ran i 150 ecu on one my pumped up pmaxs for a while it was a scalded Dog for sure :eek: Do you remember the guy in california who tried to run the early analog with external tps on his brand spankin new 10,000.00 260 new motor that lasted 4 days then boom you bought the whole shootin match for a grand and redid it that was a sure nuff deal there:cheers: i cant member what happened to some of those bad boy motors you bought you had um flying off the chart for a lot of years along with assorted killer Allison's an Bullets but we both know those ecus were just trouble from the get go dont get me started on the old stuff but it was just livin and learning you more then me you started in the early 70's when i was tryin to figure out all the crap about lower units much later but i loved it for lots of years it was fun

[tlwjkw]

yeah bobby it was great times.. seems like a decade ago now though!.. all tha crap we did and i don't remember one motor gettin' destroyed like some of tha ones we see here and there.. jus lucky we were i guess..... i still miss that ONE bullet more than all.... still got your original?.. stupid question after i thought 'bout it....:reddevil:

[rock]

Glad to hear it's good to go.

Rock