Engine problem has me stumped

Panda54

I’ve been all over the forum but have not found anything identical to this. Here are the specs:

03 250 FV
5.0 Merc MPI
540 hours

In my last two outings, I would get out of the marina (engine has been on for at least 10 minutes by now) and go to get up to speed but the engine would not get above 2700-3000rpms. Each time I would back it off then go again and would have no problem getting going and cursing around 25mph at 3500. Anchor for a few hours, start up and go home with no issue.

All I could think were the fuel filter and/or fuel water separator. Being a new to me boat last year I changed both today. I forgot new fuel so I filled the new separator with the fuel from the previous one, only enough to fill it about 2/3 (maybe this is where I went wrong) Went to start and it would just turn and turn. No fire. Battery and kill switch were all proper. 

Pulled a plug on each side of the engine. Both were dry. With the amount of cranking I did, the engine should have been flooded and the plugs wet. 

Searched high and low in here and across the web. My best guess was maybe I ruined some injectors? I had fuel all through the fuel rail. Fuel pump would prime the system each time, verified by the valve on the fuel rail. I pulled off the fuel rail, fuel came out of each injector connector. All nozzles on injectors seemed clear. 

Other than the rpm limit when first leaving, boat ran fine until I swapped the filters today. Any ideas?

Pat310

Maybe pull the separator and check if it filled?  Make sure you didn’t knock a wire loose while working in the bilge. 

davidbrooks

First thing i would do is hook up a scan tool and see if any codes are showing and it isnt in guardian mode. If none then i would do filters. Do you have a cool fuel module? Check the fuel pressure? Last time wires, plugs and dist cap was replaced. It may not be one thing but several little things.

aero3113

Do you have in-line fuel filters also?

Panda54

Pat310 said:

Maybe pull the separator and check if it filled?  Make sure you didn’t knock a wire loose while working in the bilge. 

After trying with it 2/3 full I removed it and filled it to the top with fresh gas. I’ll double check wires. 

davidbrooks said:

First thing i would do is hook up a scan tool and see if any codes are showing and it isnt in guardian mode. If none then i would do filters. Do you have a cool fuel module? Check the fuel pressure? Last time wires, plugs and dist cap was replaced. It may not be one thing but several little things.

Would guardian mode show up through VesselView? There were no faults when I checked it that way. As for the cool fuel, I haven’t been able to verify this. I read that if you have the spin on fuel separator like an oil filter than you do not have the cool fuel module. Which would be my case. Plugs were done last year. It ran fine until the inline filter change and fuel/water separator change. I can’t see numerous components failing together at once?

Panda54

aero3113 said:

Do you have in-line fuel filters also?

Yes, it was changed at the same time as the FWS

My thought now is when I used the old contents from the previous FWS (dumb) I may have mixed water into the system. I could still have too much water between the FWS and intake preventing a start. Or I may have damaged the fuel regulator?

I won’t be back at the boat until tomorrow. I’m going to try to get it to fire on starting fluid. I cleaned the injectors today, whether they needed it or not. 

Ian

My mechanic told me to fill the separator and leave for 10-15 to let the media soak and fill it to the top; be prepared to spill a little so have it in a can. Apparently it may not prime if not full. Did that and they started up straight away first time after winter storage. 

Panda54

Update:

went to try and start it today after putting all the injectors back in, it sounded like it tried to fire briefly, but nothing. Tried starting fluid. Nothing. Put all new plugs in. Nothing. 

VesselView is showing a IAC valve and throttle position sensor fault. Would these prevent the engine from even starting?

Dream_Inn

IAC could prevent it from starting. But, you could give it more throttle to see if it starts. If so, it'd be IAC.

Panda54

Second update. 

I pulled the cap off and cleaned off some light corrosion on the points. Got it started after that. 

Not sure if that was the whole issue or not. Took it for a test ride. All good, including the limiting at 2700rpms at first.  Will replace the IAC to clear the fault. The throttle position fault has disappeared. 

Aqua_Aura

Points could definitely do that. I had a Ford 302 in my car in high school and it was bad with the points and would die on occasion while driving and I would file off very little on the points and it was like new. 

I forgot about ignition points and this is the first I have seen it brought up on the forum. 

aero3113

@Aqua_Aura , I think he’s talking about the contacts on the cap. He did say he was fuel injected.

Aqua_Aura

Oh well then that makes much more sense. Anyway disregard my high school days 😐. 

There has been so many posts like this especially now that I joined the FB group I got them all mixed up. Everyone is starting their boats for the season and none of them seem to run right.