OMC 5.0L EFI Idle surge problem

[93fourwinnshorizon]

I have an 1993 OMC 5.0L EFI 200 HP I/O that is garage kept when not in use. The boat has been trouble free until this perplexing problem.

The boat starts up and runs great and idles well and runs perfectly under load and operates at normal temps. (I don't remember the temp number, needle is in the middle of the guage. Never had overheating issue.)
When the motor is shut off after running at normal operating temps, everything is normal. I'll let it sit for at least 2 minutes and when I start it again while it's warm, the idle will surge until it eventually dies.
The computer is trying to compensate for the surging. Surge will go up to 1700 RPM, it does eventually die. If I start it up and put it into gear, it will run fine until I put it back into neutral. It will then go into the idle surge cycle.
If I let the motor cool for a few hours or overnight, the boat starts up idles perfectly again. If I shut it off and let it sit, and try again, the idle surge cycle continues. Gas is fresh and changed over a few times, tried STP gas treatment too.
I even drained the boat gas tank into the family car. Car ran fine.

I brought it into the shop and did a full tune up, and hooked it up to the computer with no error codes.
I changed out the IAC valve, temp sensor, and water sensor.
Areas of interest this spring are: High and low fuel pumps and the coil.
I plan running again, and cooling each of these to see if that has any effect.

Some blog suggested checking the tightness of the "salt and pepper" EFI connectors, but I don't see how those would be affect by temp. Checking the vaccuum as well. I don't have a clue where these are yet.

If anyone has any other ideas, please offer them up as the shotgun approach is getting expensive.
Thanks.

 

[havasuboatman]

Re: OMC 5.0L EFI Idle surge problem

While reading your list of things checked, I didn't see "I changed the water separating fuel filter"
If you haven't changed that, do so and run it again.
Also, just because your temp guage says it aint hot, doesn't mean it ain't. Can you rest your hand on the exhaust elbows while the engine is running?

 

[93fourwinnshorizon]

Re: OMC 5.0L EFI Idle surge problem

While reading your list of things checked, I didn't see "I changed the water separating fuel filter"
If you haven't changed that, do so and run it again.
Also, just because your temp guage says it aint hot, doesn't mean it ain't. Can you rest your hand on the exhaust elbows while the engine is running


Thanks for your reply. Yes, the water separting fuel filter and was the first the change out. It was changed out again after the tank was drained as well.
The engine is not running any hotter. A hot engine would not necessarily cause an idle problem unless there was a vaacuum leak. The exhaust elbows can be touched. I do notice that the fuel pump on top of the fuel filter is really warm, and it could suggest vapor lock. I plan on isolating that in a few weeks.

 

[shdw2001h]

Re: OMC 5.0L EFI Idle surge problem

I had the same problem with mine 96 5.0 efi. it Happen to be the low pressure fuel pump was on its way out. If you have the repair manual there is a section in the book to test the fuel pumps. I hope this helps.

 

[93fourwinnshorizon]

Re: OMC 5.0L EFI Idle surge problem

Thanks for the feedback.
The pump you had a problem with sits on top of the OMC Fuel Filter (feeding from the gas tank), is that correct?
I only have the Clymer shop manual which does not go into too much helpful detail. It's going into the shop for U-joint lube and bellows changes. I'll have them test the fuel pumps.

 

[shdw2001h]

Re: OMC 5.0L EFI Idle surge problem

Yes, it is the pump that sits on top of the filter. it should be the low pressure pump, If it is intermitant it will be hard to check for.

 

[93fourwinnshorizon]

Re: OMC 5.0L EFI Idle surge problem

Yes, it is the pump that sits on top of the filter. it should be the low pressure pump, If it is intermitant it will be hard to check for.


Thanks for the response. I'm going to try and cool it off with a cool rag after it acts up again to see if that isolates the problem. I've located the part and what's another $207 if I can do the work myself.

 

[shdw2001h]

Re: OMC 5.0L EFI Idle surge problem

The pump heating up was another clue that the pump when bad. The pump would stop working and just heat up to the point you could not touch it.. You can do the work your self it is fairly easy. Also you maybe able to turn the key on and listen for the pumps to see if they are coming on or not.
Well good luck I hope this helps you find the problem.

 

[93fourwinnshorizon]

Re: OMC 5.0L EFI Idle surge problem

Say, How did my post disapear?
I realize it's a tough problem, but alittle more direction would be appreciated.

 

[Samps]

Re: OMC 5.0L EFI Idle surge problem

95 OMC I/O EFI 5.0L -

Hope this is not hijacking a tread but seems I'm looking at the same problem, only mine will Fire-up but not run... but cools down, then it does???

The "fuel pump sound (1-2 sec.)" that you get when you first turn the key on is gone and the lower pressure pump looks "ash" in color. It started right after I had run the boat hard for a few miles this past weekend...

Ordering a new low pressure pump and filter- Best service and prices?

 

[shdw2001h]

Re: OMC 5.0L EFI Idle surge problem

Say, How did my post disapear?
I realize it's a tough problem, but alittle more direction would be appreciated.

Sorry I dissapered, I had some problems I had to take care of.
Did you get the pump tested by the mech? If not I will see if I can post the test I did to check the pump. One other thing check you gas for water, not just the filter, the gas tank. If too water gets to the pump the pump will seize up.

 

[shdw2001h]

Re: OMC 5.0L EFI Idle surge problem

95 OMC I/O EFI 5.0L -

Hope this is not hijacking a tread but seems I'm looking at the same problem, only mine will Fire-up but not run... but cools down, then it does???

The "fuel pump sound (1-2 sec.)" that you get when you first turn the key on is gone and the lower pressure pump looks "ash" in color. It started right after I had run the boat hard for a few miles this past weekend...

Ordering a new low pressure pump and filter- Best service and prices?

That 1-2 secounds tells me the pump is bad or the fuse needs to be reset.
Sounds Like it heated up. check fuel for water filter and tank. that is what siezed mine up. as where to get them I think they sell them here on Iboats. But shop around.

 

[93fourwinnshorizon]

Re: OMC 5.0L EFI Idle surge problem

Thanks for replying. Yes, I checked for water in the gas.

I bought the following low pressure fuel pump from eBasicpower.com

CARP60965 Fuel Pump, Inline, OMC, Volvo, Electric, Low Pressure, Carter.

I plan on starting to install it this weekend and should have an answer. I'll report back with the results.

 

[shdw2001h]

Re: OMC 5.0L EFI Idle surge problem

Ok, I hope that is the problem.

 

[93fourwinnshorizon]

Re: OMC 5.0L EFI Idle surge problem Resolved

Re: OMC 5.0L EFI Idle surge problem Resolved

The new low pressure pump solved this problem: Details below.

I changed the low pressure fuel pump on Saturday afternoon. The new pump did not come with o-rings and had the foresight to order a fresh set as well. I replaced the gas filter...again as long it was off.
Of course during re-assembly the threads never line up to the original orientation so it took some time to line everything up. I checked for leaks during the week. Turning the ignition engaged the pump with it's distinctive new sound. It was cold and rainy the rest of the week and let her sit.

I started it this evening with the muffs in the driveway. Turned over right away (the benefits of EFI) and let it warm up. Tach held steady at 600 RPM.
Shut down and let it sit for 5 minutes and fired right up and held it's idle at 600 again. I repeated this for a half hour and the idle surge problem did not occur. I'll do an in-the-water shakedown in a couple of weeks when the ramp opens at Tower Road.

Thanks for your feedback and support.
I hope this post is preserved for reference purposes.

 

[shdw2001h]

Re: OMC 5.0L EFI Idle surge problem

Glad it worked. if it acts up again check the gas tank for water. That is were my problem stared from. I also added a racor filter witch seem to have help a lot too.

 

[jdblya]

Re: OMC 5.0L EFI Idle surge problem

How much did you pay for that pump? They have them for $73 at autzone.

 

[shdw2001h]

Re: OMC 5.0L EFI Idle surge problem

How much did you pay for that pump? They have them for $73 at autzone.

I think you are looking at the wrong pump. these low pressure and high pressure pumps sit on top of the filter and in back o the intake. the sell them here on iboats. or other marine stores. here is the link for the pumps.

http://www.iboats.com/Volvo_Penta_E...1711996--**********.860117492--view_id.269847

 

[jdblya]

Re: OMC 5.0L EFI Idle surge problem

I think you are looking at the wrong pump. these low pressure and high pressure pumps sit on top of the filter and in back o the intake. the sell them here on iboats. or other marine stores. here is the link for the pumps.

http://www.iboats.com/Volvo_Penta_E...1711996--**********.860117492--view_id.269847

No, it is the high pressure, and the lower pressure pump. The High-Pressure is a Carter # p61171 and the low pressure is a #P60965 or a Airtex/Master E8263. Autzone and Advance sell the low pressure for $72.99. I ended up getting the high pressure from napa for $123. Both of them are not normal stock, of course and took a day to show up.

The low pressure sits on top of the fuel filter on the front of the engine where the feed line from the tank is, and the high pressure mounts on top of the fuel reservoir on top of the engine behind the intake manifold.

 

[shdw2001h]

Re: OMC 5.0L EFI Idle surge problem

No, it is the high pressure, and the lower pressure pump. The High-Pressure is a Carter # p61171 and the low pressure is a #P60965 or a Airtex/Master E8263. Autzone and Advance sell the low pressure for $72.99. I ended up getting the high pressure from napa for $123. Both of them are not normal stock, of course and took a day to show up.

The low pressure sits on top of the fuel filter on the front of the engine where the feed line from the tank is, and the high pressure mounts on top of the fuel reservoir on top of the engine behind the intake manifold.

That is a really good price. the only thing that would worry me is if it for marine use. It might be worth looking in to.