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2001 5.7L EFI Flooding at Idle

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ou05648

Member
At idle engine will almost flood out and die, with increasing RPM to 1000/1200 up to full load engine runs great. Dealer change Map Senser and made some adjustments but still hasn't solved the problem.

The engine has 110 hours on it and the dealer suggested I add Sea Form to the fuel and after 40 gals. it still floods at idel.
The other option is the dealer wants to pull the engine to work on the fuel pump, I'm not at that point yet but wanted to get feed back before I let him do it. I'm not real happy with the dealer either so hopefully i can find a better solution here.

Thank You
Fred
 
Why the fuel pump, did they test pressure at the rail first?
Did they say anything about the regulator?
Did they check the IAC and filter?
Is the engine warming up properly?
If you manage to keep it running after it starts and go to full load as mentioned, have you tried shutting down, then restart right away to see if it's still flooding?
 
WoodieMan, I will try to answer your questions.
1. Why the fuel pump, did they test the rail first?
Answer: I'm not sure, I have to assume they did, the dealer owns a large Mercury/ Mercruiser/ Yamaha dealership and I would hope he has preformed these test. But as mentioned earlier I've not been real happy with the service, for one he seems to be more focused on the big HP outboards.
2. Did they say anything about the regulator?
Answer: As above.
3. Did they check the IAC and filter?
Answer: As above.
4 Is the engine warming up properly?
Answer: Yes, starts find and warms up normal, even at WOT temp is normal, does increase some but i consider it normal.
5. If you manage to keep it running after it starts and go to full load, shut down then restart right away to see if it still floods?
Answer: It only seems to flood when at idle, after full load I can shut it down and it will start right up and after a min. or so its starts running rough at idle again.
If I continue to let it idle it will eventually foul the plugs, and I want be able to get more then 2000 RPMs until I clean the plugs. I carry a second set of plugs in the event it happens to me again.

When the engine is at idle and you are looking down into the thottle body you can see the gas almost pooling above the butter fly below the two injectors, also at idle the water around the stern is full of black soot floating on the water.

I feel it's something simple and I'm confident enough to handle major overhauls...... I'm just not good with the electronic side or EFI side.
Thank you for your input it's appreciated.
ou05648
Fred
 
If I pull the plugs after say 15/20 mins after I let the engine idle, the plugs that are not foul with carbon/soot are wet with gas.......

In addition to the above you do smell gas when it's at idle and the water around the stern is full of soot and a gas sheen will appear on the water.
 
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My wild ass internet guess:

If it is dumping excess fuel into the engine, and it has a vapor separator tank with a vent hose connected to the bottom of the throttle body, that could be where the fuel is coming from.
Remove flame arrestor. Look down throttle body while a helper turns the key just to the on position. Fuel pump should cycle on and build pressure. If u see any fuel leaking into throttle body from vst vent, replace needle and seat in vst.
 
The engine has 110 hours on it and the dealer suggested I add Sea Form to the fuel and after 40 gals. it still floods at idel.
Click to expand...
That's the dopiest thing I ever heard. Your dealer is an a$$. Sea Foam is less than useless. So's he I think.

EFI can't "flood".
EFI Isn't all that complicated. It consist of a computer (ECU or Engine Control Unit) sensors and injectors. The sensors tell the computer how much air is flowing into the engine based on either vacuum or by an air flow sensor. There are other sensors like air temp, fuel temp, throttle position and so on. Those sensors are minor players to the air flow sensor. Even if all of those sensors fail the engine will still operate based only on air flow. The computer calculates the volume of air entering the engine and adjusts the duration that the injectors are open so as to keep the air/fuel mix ratio at a constant 14.7:1. There's way more to it of course, but that's the meat of it.
The computer has preset "mapping" that determines how it will react to the sensor input under various conditions. It knows, for instance, that the engine is cold at start up and adds extra fuel to get things warmed up faster. It knows when the engine is warm and idling. It knows when the throttle is wide open.
BUT, it only knows these things if ALL the sensors are doing the job properly. Super rich condition at warm idle means you have a bad sensor, either the Manifold Air Charge sensor, the Air Temp sensor or the Coolant Temp Sensor. This is telling the ECU that the engine is cold, needs more fuel and is running it very rich.

It may also be a faulty Idle Air Bypass stepper motor that is conked out. This is a $40 part at Auto Zone and the marine version is no different from the car one.

Now I'm basing this only on the information you wrote. It may be something else all together. You should first try reseating ALL your connectors to all your electrics, as it may simply be a loose connection.
 
Thanks for the help and suggestions, I plan to use the boat this weekend and will try some of the things suggested here. I did speak to the dealer service mgr. in Kenner, La. this afternoon and he indicated all the test that you guy's have mentioned here were done...........
 
What is the fuel pressure? Maybe you need to hit the local Harbor Freight and get a fuel pressure gauge. If the regulator is plugged up you will have excess fuel pressure and that will cause the symptoms of flooding at idle.
 
What pressures should I be looking for, were do you attach the gauge, and what is the brand name of the gauge?
On-line Harbor Freight shows one for under $20.00 that is 10 psi, is this the type you recommend?
Thank You
 
Sounds like it's TBI. Have you looked at the spray pattern from the injectors? It should be an even consistent spray pattern. If you see fuel dripping or a stream squirting from the injectors during operation, you need injectors serviced or replaced.
 
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I was able to run the engine today and the EFI injectors are a operating at a perfect cone, no drips, or uneven spray. I shined a bright small flashlight through the fuel below the injectors at idle and it look good to me.
I also removed the IAC, it looked good, I cleaned it up and reinstall it , don't know if it works or not so did the TPS. I did order a new TPS and a fuel pump test gauge with fittings and it should be here tomorrow.
Sense I decided to fix the flooding problem myself and now have done my homework with the help of this forum, I'm leaning toward the fuel regulator, I hope that's not it but I've read this could be the causing the problems.
Again thanks for everyone's help.
 
I take it this motor is TPI, if so by looking at spray you can't till what's going on with your eyes....
Here is Tech Tip use a timing light, this will show you if flooding with larger droplets, or you will see nice even spray...
Some one say a EFI can't flood, well yes it can.... EFI with VST like old 502 flood # 8 when needle got stuck...guys in Marine trade know all all about this.....


Steve
 
Changed the throttle position sensor and IAC sensor this P/M no change to rough idle and excess fuel at idle. Should recieve TBI throttle body fuel pump test adapter early next week ............It must be the fuel regulator thats allowing excess fuel at idle, if it is it will be a major project to get at.

Question: An IAC filter was mentioned earlier, I've looked for this filter and I'm unable to find it. Any help would be appreciated.

Fred
 
I ordered the Temp sensor from Perfomance Product Technologies today, should have ordered it last week as suggested by a posted here.
The IAC sensor did help, ran the boat hard today and I can tell it does idle better.
 
Installed the new Temp. Senser (805218T) today, cleaned spark plugs (ACDelco MR43LTS @ 45 Gap) srarted right up as usual but no change, still idles rough ............. I'm now leaning more to the fuel pump / regulator.
Spoke to service mgr at dealer again today and he indicated when they tested the engine it did not show any bad codes, but his mechanic felt like it was the regulator and that was the reason they wanted to pull the engine to get at the regulator.

Question: Has TBI been a problem, I understand my engine is a 2001 5.7 EFI but it only has less then 200 hrs on it, I hope to recieve the fuel pump test adapter Friday, if this test out ok I may just have to live with the problem.
 
I've checked it from the flame arrestor to were it enters the back of the cool box, I been test running it with the flame arrestor removed..........it will hold a vacuum.
 
Spark plugs were carbon up with a couple wet with gas, dealer did a compressure test back a month ago and he indicated it was find.

I also did a press. test and found everything normal, I have the numbers but they are in my tablet in the boat.

Thank you for your help.........

Fred
 
just wondering, have you check your temperature sensor... if not working it will cause motor to have more fuel about 10 to 20 % more...99% of the time this will not show up on scanner, guys in the marine business this
Steve
 
M043680, Yes I did timing light, I did see fine spray in almost perfect cone, but in my opinion gas is really coming out of the injectors at idle, to me it seems the gas is almost pooling on the top of the throttle plates. RPM is right at 600.
fred
 
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