Intermittent no start/hard start - 01 Merc 150 EFI

[jarednr]

Boat is a 2001 Glasstron 18ft with a 2001 Merc 150 EFI just turned 700 hours

This all started about 2 months ago when I replaced the fuel bulb and line from the bulkhead to the motor with a cheap replacement from bass pro. After that the boat was very hard to start and almost always had to be in neutral with 1/2 throttle. We were able to use the boat as normal but it did seem that when I went to prime, it would take an excessive amount of pumps. We also did get stuck where the boat would not restart and seemed to lose pressure in the bulb after every attempt to start. After about 30-40 minutes of not cranking the motor it finally did start but after an excessively long crank (10+ seconds)

After that incident I did purchase a new fuel filter and mercury fuel bulb and it started right up in the driveway. We took the boat out and when at the dock I had to again put it at 1/2 throttle to get it to fire. We pulled out from the dock and putzed along and all of the sudden at a slow speed 1100rpm or so the boat just shut off. I restarted after priming again and it would not start until it was more than 3/4 throttle and a long crank. It would run for 5-10 seconds and die off like it was starving for fuel. Every time the bulb went limp and would have to re-prime. I just let the boat sit for about 2 weeks and when I went to start troubleshooting, the boat started up with slight throttle after a few tries. I did pull the vacuum fuel pump apart and everything inside looked like it was in good shape. The diaphragms were pliable and all springs and check valves looked to be intact. I had a good vacuum pulse signal from the engine also.

When I purchased the boat (45 hours ago) the engine had good compression (120+ and within 5lbs of each other.)

 

[Dave1027]

Re: Intermittent no start/hard start - 01 Merc 150 EFI

Are you using the choke? You never mentioned it.

Maybe the interior of the cheap fuel line and bulb broke down and deposited crap that is now lodged in your carb's passages and orifices.

 

[Faztbullet]

Re: Intermittent no start/hard start - 01 Merc 150 EFI

A EFI does not have a choke, the switch will push it but it does nothing. You do not mention if the fuel pump comes on when you first turn the key on. Here is what I would do/check if in my shop...
1) Check all fuel lines for blockage/debris if grey lines
2) Drain VST tank and check the sample removed for water or seperation
3) Turn key on and listen for pump in VST tank, should run 10-15 seconds and shut off.
4) Check fuel pressure at fuel rail (36-39 psi) and see if it holds, if not regulator if bad. If pressure low the pump filter is clogged or pump is failing.

 

[jarednr]

Re: Intermittent no start/hard start - 01 Merc 150 EFI

Alright did some troubleshooting today and found good pressure -34-36 lbs with key on but while cranking it would drop to about 20-22 and then pick back up with the longer I cranked it.

Checked voltage at + side of pump 12.5, - side 12.5, while cranking on - side 2.2-3.0.

thats a hell of a voltage drop. so from there I disconnected the ground and provided my own, motor literally fired up the fastest it has in 2 months and i had 36-38 lbs of pressure while idling. I also rechecked voltage drop on - side of pump and found .15 to .25 volts.

Sounds like a faulty ECM to me. Any ideas on getting it rebuilt or should I start shopping junk yards around me?

 

[jarednr]

Re: Intermittent no start/hard start - 01 Merc 150 EFI

today I bypassed the ground from the ecm via a relay off of the ignition switch. works fine except still have to start with 1/2 throttle in neutral. will double check fuel pressure tomorrow and clean plugs as they have 60 + hours on them.