1987 Johnson 120hp V4 idle issue - only idles when air bleed is removed

jimmyneutron

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Sep 1, 2015
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15
Hello,

i’m trying to diagnose the issue on my 1987 Johnson 120hp V4 VRO.

It starts in high idle (muff or water) but engine rpm gradually dies and stalls out after few minute.

if I disengage high idle to normal idle, it immediately dies.

I found that if I remove the 4 intermediate air bleed orifices and 4 idle air bleed orifices. The engine will idle perfectly at 1500rpm in water.

I’m guessing it’s running rich. I checked the 8 air bleeds and they are not jammed.

Why does my engine only run when air bleeds are removed? Can I run my engine with these removed?

The engine is J120TLCUR. The air bleeds are #13 and #19 in the carb diagram.

Thanks,
Jim
 

Joe Reeves

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Feb 24, 2002
Messages
13,262
What are the actual ID sizes of "all" the intermediate and idle air bleed jets... and how many of each?

(Example... 4 of #45, 2 of #16, 2 of #30...)

It makes a difference as to what jet is installed in which carburetor affecting its related cylinder.
 

jimmyneutron

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Sep 1, 2015
Messages
15
What are the actual ID sizes of "all" the intermediate and idle air bleed jets... and how many of each?

(Example... 4 of #45, 2 of #16, 2 of #30...)

It makes a difference as to what jet is installed in which carburetor affecting its related cylinder.

I have 1 of #16 installed on the bottom hole (idle air bleed) of each carb, so 4 of #16 total.

I have 2 of #45 installed on the intermediate air bleeds on the two port side carbs.

I have 2 of #42 installed on the intermediate air bleeds on the two starboard side carbs.

So here's the confusing part. I may have fixed the above issue. It turns out someone left the primer solenoid bypass valve in the 3 o'clock position (halfway open). It should be in the 6 o'clock position, right?

I flipped it to the 6 o'clock, and the engine idled perfectly on muff and in a bucket. High idled around 4500 to 5000 rpm, and normal idled around 1500 rpm.

But when I put everything back and took it to the lake, it started and high idled around 6000 rpm, then I heard a loud beeping tone (once per second). The engine gradually died down and stalled. I was able to start it again by turning the ignition key while someone held the throttle lever (on the carb) manually open to WOT.

It high idled around 3000 rpm and died again after several seconds, and could not get it to start again.

I opened the plug screw on the bottom of each carb and lots of gas poured out. Is this normal or is this my problem?

Any thoughts?
 

flyingscott

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Apr 8, 2014
Messages
8,199
The carbs should be full of gas.You need to do a compression test before you do anything. You may have lost a piston skirt.A beeping once per second is a no oil alarm.
 

racerone

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Dec 28, 2013
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38,765
You should not be running this motor at " 6000 RPM in high idle "----Bad things can happen.
 

Joe Reeves

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Joined
Feb 24, 2002
Messages
13,262
All of your intermediate and idle air bleed jets are exactly where they belong.

Racing any outboard over say 1800 rpm in neutral or even in gear if on a flushette is inviting a runaway engine which immediately goes into diesel mode, of which by the time you figure out how to stop it, it has connecting rods flying out the side of it. In short.... it explodes! Don't do that! Racerone's statement of "Bad things can happen" is a understatement.

The "Fuel Primer Solenoid"?... Yeah, you betcha, having that RED lever aimed anywhere excepting straight at the other end (automatic running position) would be the same as running a engine with the choke butterfly shut.. Don't do that either! :)

Note that we have no way of knowing just how that Fuel Primer Solenoid is attached... horizontal, straight up vertical, whatever. It's best to describe where that RED lever is pointed in relation to the solenoid body itself.

As "Scott" above states.... a beep every other second indicates "No Oil At The VRO Pump"! (Not good!!)... Prime the VRO as follows if that alarm sounds under normal circumstances.
********************
(Priming The VRO Pump)
(J. Reeves)

When hooking up or installing a VRO whether it is a new or original VRO pump, it must be primed in order to dispel any air that might be in the oil line.

Have the Oil line attached to the engine fitting BUT detached from the VRO. Add a piece of fuel hose if necessary to the oil line so that it can be aimed into some sort of container.

Pump the oil primer bulb, catching the oil flowing out of the line into the container until you are absolutely sure that you have rid the oil line of every bit of air that might have been trapped there.

Now, connect the oil line to the VRO and secure it. When the oil line is secured, apply pressure to the oil primer bulb ONE TIME only. That's it.
********************
Having a cold engine race away to 6000 rpms when starting, in my opinion, could only take place if perhaps the timer-base was set at the Full Spark Advance setting, or if the throttle butterflies were open, or a combination of the two. Check those two areas.
********************
(VRO Horn Warnings)
(J. Reeves)

NOTE: I retired around 1991/92. Possibly some of the later V4 engines and others may also incorporate a fuel vacuum switch that would enable a fuel restriction warning to sound as mentioned below, an unknown factor to myself.

1 - A steady constant beep = Overheating - The V/6 engines, possibly some others, have a fuel restriction warning which is also a steady constant beep.

2 - A beep every 20 or 40 seconds = oil level has dropped to 1/4 tank. (Late model engine = Every 40 seconds)

3 - A beep every other second = VRO failure, air leak in oil line, oil restriction, (anything that would result in a lack of oil being supplied to the engine).

NOTE - If the warning horn is the black plastic (overpriced) three wire type horn, the warning horn should beep once when the ignition key is turned to the ON position. If it does not, it is either faulty or someone has disconnected it (a stupid move!). At any rate, if it does not beep which indicates that the horn is non functional, find out why and do not run the engine until the problem is corrected.
********************
 
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jimmyneutron

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Joined
Sep 1, 2015
Messages
15
Compression
I checked the compression using two different testers, they gave different results.

Tester 1: all 4 cylinders show 60psi.
Tester 2: port cylinders are 135psi and 130psi, starboard cylinders are both 120psi.

Does the results from tester 2 seem to be in spec? I will likely get another compression tester to compare values.

Primer Solenoid
The red lever was pointed perpendicular to the solenoid body. But I turned it clockwise to face towards the body.

Beeping
The beep once per second went away by itself this morning. But the alarm was acting up and had a constant beep (overheating alarm) as soon as I turned the key to the ON position. This was when the engine is completely cold. Strangely, the beep went away after I started charging the battery???

Spark coil
I switched out 3 of the 4 ignition coils couple days ago because they had weak sparks. I verified that they were solid sparks at 1/2" right after I changed them. However, today all the coils are only producing tiny thin sparks at maybe 3/8". What is the spec on the spark length? Any reason why the coils may be going bad so fast? I tested all of their primary and secondary resistance:
All coils primary are 0.2 Ohm. Three of the coils had 240 Ohm in secondary, but one of the coils had 300 Ohm in secondary. Does this seem right?

Timing-base
I am not familiar with the throttle butterflies and timing base adjustments. Can you provide some information on that? Could this cause my idling issue and engine not starting while on the lake?
 
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