1998 Mercury 150 EFI Flooding Out

[CLi87]

Hey all, i'm working on a 1998 Mercury 150 EFI and the issue is it keeps flooding out, I can get it started by holding the throttle all the way down but if I let off it'll immediately die. At first I thought it was too much oil mixing into the gas as I saw a lot of blue smoke, but I completely disconnected the oil feed line to rule that out and still the same issue just with a lot of white smoke. It seems to me the injectors are stuck open, I did an ohm test from the red wire to the other 3 and they each ohmed out at 0.9ohms. I also opened up the VST to make sure it wasn't dirty and the float wasn't sticking but it's super clean no issues, and I had just replaced the check valve at the bottom of the VST recently. Any ideas what could be causing the injectors to stick open or what to test next?

 

[Faztbullet]

TPS wide open?

 

[CLi87]

Do you know where the TPS is on this motor and how to test if it's stuck in WOT?

 

[dingbat]

Do you know where the TPS is on this motor and how to test if it's stuck in WOT?

How and where will not cut it working on an EFI.

You need an understanding of electronic component testing, a factory (Mercury) manual and a good voltmeter.

 

[CLi87]

I do have an understanding of electronic component testing with a good voltmeter, I'm an inboard Mercruiser tech with 7 years of experience, I'm just not too familiar with these old EFI 2 stroke outboards and I just didn't want to spend $80 on a manual if this was just a simple problem, it's a friend's old fishing boat I was trying to help him get back running.

 

[Faztbullet]

Check you PM

 

[CLi87]

Check you PM

Thank you!!

 

[CLi87]

In the diagram, should line e to the upper manifold lower fitting have fuel shooting out of it when cranking over? I had disconnected that line originally to see if the VST was overfilling but to my surprise the hose was shooting fuel out when cranking over, not running, just cranking, no throttle applied.

 

[dingbat]

In the diagram, should line e to the upper manifold lower fitting have fuel shooting out of it when cranking over? I had disconnected that line originally to see if the VST was overfilling but to my surprise the hose was shooting fuel out when cranking over, not running, just cranking, no throttle applied.

EFI uses both a high and low pressure pump. The LP is pulse driven but the high pressure pump is electric. Starts running when you turn the key on.

Fuel coming out of the overflow is typically a bad (float valve) HP fuel pump.

 

[CLi87]

EFI uses both a high and low pressure pump. The LP is pulse driven but the high pressure pump is electric. Starts running when you turn the key on.

Fuel coming out of the overflow is typically a bad (float valve) HP fuel pump.

It's not coming out of the overflow from the VST, it's coming out the hose that connects to the VST, I also did some more testing to see if all the cylinders were flooding or just some, seems it's just cylinder 6, I'm not sure if that's because it's the lowest cylinder causing all the fuel to pool up there or if it's just cylinder 6 stuck wide open.

 

[CLi87]

Opened up the cover to see the injectors and noticed injector 6 has the wiring o-ring popped out. And on a side note, I don't know what idiot engineer decided to mount the fuel rail from the back side instead of the front, so to remove the fuel rail I have to remove the entire manifold just to get the to screws on the back

 

[dingbat]

Don't think the diagram you posted above applies to your motor.....EFI typically don't have an oil supply inlet (I) on the Vaper separator

Here is the test procedure for the EFI fuel system

Vapor Separator Fuel Delivery Test - Mercury 150 EFI Service Manual [Page 253]

Mercury 150 EFI Manual Online: Vapor Separator Fuel Delivery Test. Purpose: Verifying there is adequate fuel flow to the electric fuel pump (through full RPM range) will deter- mine components in low pressure fuel system are functioning correctly. 1. Remove vapor separator drain plug...

www.manualslib.com

Then again, what are you working on........an EFI is a 4 stroke?

 

[CLi87]

Found the problem, the fuel inlet to the rail was broken and not sealing properly and causing fuel to just spray into the manifold and fall to the bottom where it was sucked into cylinder 6.