V4 Looper experts needed, barely idles trimmed down

[RoyE]

Sorry for the long post:

1995 Evinrude V4 looper 130 HP
Oil side of VRO disconnected and VRO wiring harness disconnected
Running fresh gas, 1:50 ratio
Champion QL78YC
New rectifier
New power coils and plug wires

This issue has been bustin my balls for two months now.

I started chasing an ignition problem but it seems I have a fuel problem too. Started thread at S&F but no response there.
For reference: http://www.screamandfly.com/showthre...on-3-cylinders

Engine ran fine for whole season, until the idle started to be rougher and rougher, until the point where I am now. It will still run perfectly mid-range and WOT.

Engine will start up always within a few turns after using the primer, altough pretty rough, and runs rough in general at idle. It will idle around 900-1000 rpm in the water when trimmed level or higher. When trimming fully down, idles drops to like 500 rpm and it runs really really rough, dropping cylinders. It smokes pretty much in general, more than I can remember from the past season. Since I'm not that close to the water the rest of the tests below were performed on the hose - the problem also occurs on the hose, so it's not related to backpressure, engine does not sit too low in the water, idle relief holes are above the water line at all times.

At the hose, I find that when the engine is trimmed lever or higher, and I trim it full down, the engine drops to like 500 rpm, but will clear up after 30 sec or so and be back at around 1000 rpm. Still runs rough though.

I am pretty sure the engine is running rich. My shining SS prop is now covered in grey/black deposits and the motor smokes a lot.

I noticed that carbs are spitting fuel through the intermediate or idle orifice, not sure which one. I think the upper one, which is intermediate.

What I did:

- Checked compression, 125 PSI on all four.

- Checked ignition to make sure that was all good. All values (stator, timer base) are within spec, altough resistance of the stator is 395 ohm, bit lower than the value in the book.

- Timing is set to 4 ATDC at idle. Timing does not jump around, is spot on and not intermittent or something, on all 4 cylinders.

- QuickStart is working properly.

- Openend up carbs, looked perfectly clean, set floats dead level with gasket surface. Two of the floats were set too low.

- Discovered that the (#^#$^#$ plastic) float bowls were warped, wet sanded them on 600 grit until it was level again.

- Checked head temps while running, both in spec (around 150 degrees).

- Checked VRO pump for fuel leakage through the pulse fitting, no leakage was found.

- Cleaned all recirculation hoses, none were dirty.

- Cleaned all fuel lines, none were dirty.

What I did find:

- Discovered that all 4 check valves in the intake manifold and the check valve from lower to upper bearing were

broken, let fluid through in both directions, need to replace them.


Now, I didn't buy rebuild kits for the carbs yet. But none of the carbs are leaking fuel, and I can pump the primer bulb as hard as I want, when the carbs are full, they are full. I cannot keep priming the bulb. I think that tells me that the needles are properly seating? Carb kit that is in now is about 2 years old.

Now my main question is, can these broken check valves cause these problems? Since they are ALL broken, I can't imagine that they all were good during the season (when the motor ran just fine).

Any more questions, input or advice is much appreciated. What more can be trim-related? What makes this engine run rich? This thing is driving me mad and I feel like i'm missing something.

 

[daselbee]

Clean the calibration pockets in the throttle bodies. It is part of the whole carb system.
Search "calibration pockets" here.

 

[RoyE]

I'm sorry but I'm not sure what you mean. I've seen gaskets on the side of the throttle plates on some loopers, but not on mine.

This is the part diagram for my motor, there is only a core plug (number 2 in the diagram) where other motors have the cover plate and gasket:




Or do you mean the small holes at the front (carb side) of the throttle body?

 

[daselbee]

Behind #2...the core plug. There are tiny holes back in there that meter the idle fuel. Do the search. Search for posts by me. I nag on this subject.
Probably too much!!!

Your carb kit will have the replacement core plugs. The TB is part of the complete carb system.

 

[boobie]

Get the check valves and ect in the recirculation system repaired before you do anything else. It may cure a lot of your problems. The procedure for checking out the recirculation system is in the OMC factory service manual.

 

[RoyE]

Behind #2...the core plug. There are tiny holes back in there that meter the idle fuel. Do the search. Search for posts by me. I nag on this subject.
Probably too much!!!

Your carb kit will have the replacement core plugs. The TB is part of the complete carb system.

Ok I read all your posts regarding the calibration pockets here on iboats and I learned a lot. I understand now why the calibration pocket is in the TB instead of in the plastic carbs. I don't understand why OMC placed the core plugs there instead of the cover plate with a gasket, it would make it much easier to reach. I agree it is a good idea to at least clean the calibration pockets, I overlooked it.

Now, there is still something I don't understand and I hope you can explain it to me. In all the topics I found in which you posted about calibration pockets, the topic starters had issues that pointed to a lean running motor. My motor is definately running rich. How can dirty calibration pockets cause a rich running motor?

Also, I read about brass tubes reaching in the float bowls, some have one, some have two.
Just to be clear, in my carbs I find two brass tubes reaching into the float bowl.
I have two jets at the front of the carb, both numbered 33 (as in the BRP parts catalog)
I have one adjustable idle AIR bleed at the front of the carb.

My 1995 V4/V6 looper OMC factory service manual describes the initial idle mixture setting 2 1/2 turns out. It says turning IN will make the engine run more lean, while the sticker on my airbox says turning IN will make the engine run more rich. I think the service manual is describing adjustable FUEL bleed? Why does my carb have an adjustable idle AIR bleed?

I know I have a lot of questions, I hope you are willing to answer them. I appreciate the help.

Get the check valves and ect in the recirculation system repaired before you do anything else. It may cure a lot of your problems. The procedure for checking out the recirculation system is in the OMC factory service manual.

I have the OMC factory service manual. I checked the recirculation system according to the procedure in the manual. I turned out that all the check valves are broken, their one-way function is bad. Now I want to replace them all, but why are these so expensive for such simple parts.... [I live in the Netherlands]

 

[tblshur]

RoyE ,ebay has some plastic in line checks that may work 4 for 10 bucks. may be worth a try,. good luck:joyous:

 

[daselbee]

Ok....guessing from your carb description...your model number is E130TLEOA.
Just for grins....look at the other model number's carb setup (the E130TXAOR) and note the difference in the air bleed jets, and the idle mix screw.

So....when you take the black carb body off....you have the idle mix screw sticking out the face of what? The throttle body. In your case, on the "A" suffix motor, the idle mix screw meters AIR. Turning out will lean the mix...i.e. add air into the idle fuel mixture.
Turning it in, will decrease the air added, and cause a richer mix.
The air that is metered by those needles has to come into the TB somewhere...right? What if the small inlet hole to that air circuit was clogged?

I had a Yamaha 20 hp engine, single carb, that had the idle air inlet hole plugged up with foam dust from deteriorating sound deadening foam applied to the
inside of the engine cowl. Took many months for that foam dust to fill up the small hole...but it when it came to me, it was extremely rich, and would not idle.
Crap like that happens.

So, do you know if the air passages in the TB are clean and clear? Not without pulling the TBs and making sure.

Did you read about the straw in the air bleed jet method? Put the straw of an aerosol carb cleaner directly in the opening of each #33 air bleed jet and shoot the cleaner in while the engine is running.
If you can, remove the idle air adjusting screw, and do the same...engine running. If you idle it up to 1500 or so, it will probably stay running for this carb cleaner trick.
That might clean out your TBs adequately. It surely is easier to try than a complete RandR of the TBs.

My point is this: guys say they cleaned the carbs. No they didn't, IF they failed to clean the TB's also. That applies to the plastic carbed engines....
Metal carbs have the same tiny holes and a calibration pocket......but they are almost automatically included in the cleaning because you pull the carb...clean it...put it back...voila.
But the plastic carb calibration pockets are almost universally excluded from the cleaning because the guys don't realize the critical metering that the TB does.

Regarding the recirc valves. I just have not ever seen a bad recirc valve cause any real problems. Or at least a problem where the engine just would not idle. Maybe a rougher than normal idle...but not No IDLE. I know others here have. But I haven't.
While experimenting, I have clamped off the lines with needle nose vice grips, and really could not tell a difference.
I have NOT experimented with a case of "open check valve" like you describe. My experiment would resemble a clogged check valve.
It would not surprise me at all that if you replaced all of them, you still had the same issue. Just my 2 cents.

Boobie is absolutely right tho. The engine will not be fixed until those recirc valves are corrected.

 

[daselbee]

One other thing......you say your check valves are open. They pass air both ways.
Well, why not try the "clamp off the line" trick? That would create a "fault" exactly the opposite of your "open check valves" fault.

If the open check valves are truly causing this rich, loaded up, no idle situation, then creating the exact opposite fault should make some sort of difference, right?

 

[boobie]

The check valves have to be working when the motor is idling as they take any excess fuel that builds up in the intake manifold and recirculates it back into the motor cylinders. Which by the way is calibrated into the carb jetting. Now if the valves aren't working excess fuel builds up in the intake manifold and when you tilt the motor all the way down this excess fuel just dumps into the motor and causes it to run real rich. I've cured what somebody thought were carb probs for a bad idle by just fixing the recirculation system. 'Nuff said.

 

[RoyE]

Thank you all for the advice and the extensive explanation of things. To clear things up, my idle mixture screw does not screw into the throttle body. My carb looks like this, the upper passage is the passage in which the idle mixture screw is located.

Carb:


The throttle body looks like this, with 2 openings, one for the intermediate jet and one for the idle jet


And the back of the carb looks like this:


I did several things at once, so I don't know what exactly cured my problem. What I did:

- Cleaned the calibration pockets using carb cleaner, did not take out the core plug.
- While the carbs were off, I dissambled them, cleaned all passages with carb cleaner, followed by an ultrasoon treatment.
- I gathered 4 new check valve fittings and the check valve between the bearings from a scrap block. All were in good condition.
- I redid throttle plate synchronisation, one side seemed to be off very, very slightly, was not even sure. Redid it just to be sure.

Then assembled everything again:
- Redid link & sync
- Set idle mixture screws to 2 1/2 turns out, according to service manual.

Factory service manual calls for 8 +/- 2 degrees ATDC idle timing. My engine died in gear at 6 degrees ATDC (probably due to the relatively heavy prop I run on my light boat). Manual states to increase idle timing if rpm is too low, I did this and ended up at about 4 degrees ATDC, achieving around 700 rpm in gear.

and... idle is good again!! (as far as idle is good on these loopers). Definately running on all four again, and achieving 700 rpm in gear all trimmed down.

Thank you for all the helpful responses

 

[RoyE]

Up.

For some reason my topic doesn't show at the top, just want to let you guys know that my problem is fixed.

 

[boobie]

Thanks for the feed back.