1988 Mercury laser XRI no power in gear

[swoodruff]

I have a 1988 Mercury Laser 220 XRI Electronic Fuel Injection motor. It idles fine but has no power when in gear and a load on it. I have drained all the fuel out, replaced all filters, fuel line, primer bulb, spark plugs. I have had it into a shop and they checked the timing and compression was 120 psi on all cylinders. The spark is good on all cylinders. It appears that the fuel pump is working fine. However, I don't know what it's pressure is. If I disconnect the hose and pump it into a can it pumps fine. I have been having this issue probably 4 out of 5 times I take the boat out. Once in a while it will run fine. It only gets about 1600 rpm when under a load. Any help would be appreciated.

 

[CharlieB]

Re: 1988 Mercury laser XRI no power in gear

Two things to check

Small hose from the intake manifold to the ECU box, has a small brass oriface that sometimes plugs with oil/muck, not letting the ECU read the drop in intake vacuum indicating the throttle opening.

Also check the throttle position sensor, with the engine off and the key off, disconnect the wires and attach a digital ohms meter to the sensor, record your readings, slowly open the throttle and watch the smooth change in readings all the way to WOT. Compare your notes to those in the factory service manual.

 

[swoodruff]

Re: 1988 Mercury laser XRI no power in gear

Where do I find the throttle position sensor? I have ordered a service manual for the motor but I have not received it yet.

 

[swoodruff]

Re: 1988 Mercury laser XRI no power in gear

I figured out the problem. I received the manual today. It states that it should have 40 psi for fuel pressure. I had measured it yesterday and it only had 35 psi. The manual states 35 and below should replace the pump. I went out today to test it again and the pump has completely stopped working. I will replace it and let you know. However, I'm sure that is the problem.