1998 250 EFI takes a break every afternoon

[rvaha]

Ok, I've done the following since last post. Pulled reeds out, checked both sides - fine. Swapped coils and coil wires from one side to the other. Swapped in some other plugs. Pulled connections on both ecu's. They look ok but have grease in them which I think I may have added after the motor got wet last year.

Ran it on muffs - not running as well. Ran it in water yesterday. Pulled ok for the 1st couple of tubers, then wouldn't pull anymore past 2000 rpm's. So the problem is getting worse which may help. I got it home last night, still warm. Checked with timing light and getting spark on all 6 but motor is not smooth now. Change out some more plugs. No change.

One thing that I have noticed all summer is that I have to keep adjusting the Tps down. I did replace it. It's getting close to running out of range. I need to recheck all voltages on it. I set it at .98 but after running it goes up. The throttle is coming back to the stop.

I spoke to Eric Simon today about the ecu's. He said this vintage (830044 and 830046) don't go bad often. When they do they usually burn up. He said they either work or don't. He said they can't leak due to the epoxy poured around them. He said he would be happy to test to confirm. What he did say is that this vintage engine often had corrosion in the harness. This may explain the problem. I'll going to use electric cleaner to clean all ecu's connectors and get the grease off.

Last, I was in error about the stator being pristine. I looked after dark last night and noted some minor surface rust on the flywheel side. Not sure if this is normal. I am getting spark so not sure. Thx

[EuropeanAM]

On the TPS... make sure you snap the throttle open/closed 3-5 times, and verify it's consistently returning to your setting. If it does not, back up and try again.

Sometimes may require you "set" below your target, then snap throttle and check. Repeat as necessary until you obtain a consistently "in range" TPS reading at idle.

You mentioned "redundant grounds" in your first post. Given the circumstances, want to make sure those are the grounds we really need: Please provide a very precise description of each of the grounds added.

[rvaha]

Update, I installed all new plugs gapped at .035. I marked the flywheel on every cylinder. Checking timing on each cylinder on muffs a number of times. All are firing and timing is advancing as it should. I'm beginning to think its not a problem with spark. I cleaned every connection I could find. No corrosion. This includes the plugs to both computers, the big plug that ties them together, all the sensor connectors, etc. Also in your above post you asked about grounds. I have grounds run from the bottom right bolt
on ignition (bottom) ecu, stator post, and a few other places. I checked and all have .2ohms or less to the main ground. Also I checked crank position sensor. Moved it just a tad closer to the flywheel. A bit less than 40 thousands. Tach works fine so I guess crank sensor is ok? Also I get an alarm if I unplug the MAP and an alarm if I unplug the air temp sensor.

One note, the engine runs a bit better right after a cold start. It runs faster I guess due to the enriched mix. Once it gets warm it starts to stumble.

None of this has helped so I must be on the wrong path. The engine is stumbling badly at idle on the muffs and struggles to advance rpm's when I move the throttle. The problem has definitely gotten worse. I did pull the injector box to check the reeds. Reeds were ok but maybe I didn't get something back quite right with injector box as it seems to have gotten substantially worse after I checked the reeds. It may be time to take it to a local mechanic with a fresh set of eyes. I'm also thinking about pulling the box and sending the injectors to you for service. I was hoping to salvage the summer and this weekend but that looks doubtful. Thx Rick. 540-521-5211

[EuropeanAM]

Rick- might need to check that all injector harness connectors are securely fastened, make sure the #6 injector harness pigtail isn't pinched or chafed/shorting, verify that you're not losing fuel pressure after you turn the key OFF, and verify all synchronization settings (including TPS). If you unbolted or loosened the intake, things moved.

Should you decide to send your system in, please send the entire intake (fuel management assembly) for best results. Very important that we have the brass flange where the fuel lines connect.

VST is optional... but may be wise in your situation.

[rvaha]

Update,

installed brand new plugs. No change
Swapped back to original mercury spark plug wires as I had automotive. Original wires I believe are fine. No change.
Took it to a local mechanic. He did put a ddt on it. All tests passed. I'm not sure if the ddt would tell anything or not. He and I both believe that it's a fuel issue, either the computer, harness or injectors
I did put an osciloscope on the injector drivers checking each one separate. I could see the pulse on each which would get shorter when revved which I believe is normal.
I looked very closely at the harness. The plug on the bottom ecu (fuel) has a couple of sockets that are slightly discolored. The top ecu plug looks good. I may replace the bottom harness 1st

Engine is still stumbling badly.

Don, I have the injector assembly and VST pulled. I'm going to send to you tomorrow. I figured it wouldn't hurt and may find a problem. Thx guys Rick 540-521-5211

[EuropeanAM]

Make sure you fill out and send in an Injector Service Request Form (download from our website).

[rvaha]

Injectors and form went out today. Should get there Friday. Thx

[rvaha]

Update,

Got the intake, injectors and VST back from Don. He found a few issues including injectors out of tolerance, injector rail issue, cut oring, etc. Installed yesterday and ran on muffs. Idle is about perfect. The engine sounded crisp when blipping the throttle with no stumble as before. I ran it for a minute or 2 at 1500 rpm. Sounded good - an occasional miss about every 15 seconds. Not sure what that is but need to test on the water.

I likely wont know if the problem is completely fixed until next year as the original problem would mostly occur after running about half the day. However I feel much more encouraged about the engine. Thanks Don for your help!

[EuropeanAM]

Make sure the throttle roller/cam is properly aligned, and TPS set properly.

When you run it next time... get it up to temp, and check the idle timing. Non-adjustable, but it's a good indicator of the health of other settings.

[rvaha]

Update! I meant to post this earlier this season. Sending the injector assembly to Don last falll was a great decision as he found some items noted above. After I did a link and sync engine has ran great this summer. So, I spent quite a bit of time last summer chasing problems that were all related to the fuel injection.

I am having a slight problem. Engine starts great on cold start as well as warm start. However, when it sits for around 1hr to 2hrs sometime it will fire briefly but won't stay running. (Outside temps in upper 80's and sunny and the black cowl holds the heat). I continue to try and start and sometimes have to wait a few minutes. Happened this past Sunday twice. After it starts it's fine. I leave the throttle closed during starting to prevent lean start. Also tried trimming the motor up but still doesn't help. So, I'm wondering are the Ecu's treating it as a warm start (engine is still warm) when it may need extra fuel that cold start provides?? I don't think there's a enrichment system that can be manually activated (via a seperate enrichment switch)? Seems like there was some version of fuel injection that you could manually (via switch) add enrichment to. (Required wiring into the harness).

So, if manual enrichment is not an option should I look harder at something else, such as TPS? Also plugs are new and correct. Other than this it runs great.

Thanks so much for the help. This season has been much better than last! Rick. 540-521-5211

[rvaha]

Don or others - any thoughts on post 30 above? Thx

[JYoung022]

Just to throw a thought at ya, my XB had a similar issue except it would act like it was really rich when warm. It was the air temp sensor that was failing. If it's a warm start issue, check the ohms of the head/water and air temp sensors just to be sure they are in range when warm.

[rvaha]

Thanks. They were ok before but I'll double check.

[EuropeanAM]

Rick:

Try this: Pump bulb FIRM before EVERY START. Key ON for 3 seconds, then OFF. Key ON for 3 seconds, then start.

Any difference?

When the engine is warm, what is your ignition timing AT IDLE?

[rvaha]

Don, I have an electric fuel pump in boat so don't need bulb. I think pump is rated at 3-4 psi at 70gph. Also I still have the pulse pump as well. I'll double check timing. I did check tps the other day -.975 v at idle.

I'll do the key on for 3 sec and off sequence you suggest. I have not done that before.

I ran boat this past weekend and it started fine - but I didn't have any times that it sat for and hour or so between starts. Either started a few times with just a couple of mins between starts or a 3-4 hr lapse. No problems with either. Just seems to be finicky when it's set for 60-90 min. But - much better than last year thanks to your help with the injector and vst service you performed!

[Savage]

Why are you using a electric fuel pump and a pulse pump together? I would pick one only.

[rvaha]

I've thought about eliminating the pulse pump but I have a small surge tank between my main tank and the motor. My main tank is 28 gallons but is long and wide but only 7-8 inches tall. It's built in under the flooor. So, before I added the surge tank the engine would occasionally die on hard corners when below 1/4 tank gas. After I added the surge tank I've not had this problem. The surge tank holds about a gallon and is alarmed for low fuel and is kinda a reserve tank. So, if the big tank starves for fuel in a turn then the electric fuel pump would also starve - but the pulse pump will still pull fuel from the surge tank.

I i I had a more standard tank - i.e. Taller - i would eliminate the pulse pump and just go electric. Electric is nice as my boat design doesnt lend itself to easy access to a bulb. Thx. Savage.

[DiawaKid]

FYI, I had a friend that had a external fuel pump and his motor doing the same thing. Ended up being the fuel pump. The fuel was being discolored and the fuel pump impellor/seals or something inside the pump was breaking down. Probably not related, but on the VST, how long after you had the High pressure pump replaced in it did this problem start?

[rvaha]

High pressure pump was replaced a couple of years ago. It was sent to don last year along with injectors and tested. I'll keep that in mind. It's just been finicky when doing a warm start after sitting 60-90 min. Thanks!!

[EuropeanAM]

Understand your system doesn't leave a lot of choices, based on your description.

I really "loathe" external electric pumps. While they can resolve a number of problems (by pressurizing the entire system), they also leave a propensity to fuel leaks (sometimes quite massive). That makes for a risk of Fire or Explosion.

Be sure to report back... and keep your filters fresh/clean on this system.

That idle timing (when WARM) may be very beneficial information.