Help interpreting vacuum test results 2001 Johnson 150 Non fitch

[rothfm]

J150vxsi non ficht, non EMM or computer

Did some testing tonight with vacuum guages for an issue I was having. Was hoping someone could help interprete my observations and test info.

Background: Was getting a Check Engine light on PORT motor only.These motors have no computer. Tach has 4 lights, the one coming on is CHECK ENG...Which means Fuel restriction. Was happening at Hi Speed, then at Med speed, then at near idle into port. And sometimes just putting the key to "on" without starting motor..it would come on.

Tonight went to Marina, did the following:

1. Removed all hoses, connections, primer bulbs and replaced..Down to the Tank pickup. Removed Previous owners splices and joiners. Opened new Racor filters, all good. Removed motor fuel filters to inspect all good. Found No issues anywhere.

2. Installed vacuum gauges on T's, between motors and primer bulb (this is twin engines). Used Clear hose up to engine input to look for air bubbles etc.

Started both motors and I was surprised to see basically the same thing on each motor. Was expecting to see motor in question with higher vacuum, or at least something different.

On each engine I saw, very low vacuum. See pics. On the scale, i'm guessing less than 1inch..They would come up a little depending on how I held the T'd-in gauge. Tight connections, all clamped well.

I then brought each motor up to 2500 to 3k at the dock, in the water (briefly)....Saw NO change in Vacuum at all.

I then pinched the Port (motor in question) fuel line before the primer, and I could make the gauge go up. When it got to about 4 in, it set off the Check Eng lite, and alarm. it went out in 15-20 seconds after releasing the blockage.

Then I did the same thing on Starboard (non-issue motor), same...It rose up and alarmed when it hit about 4-5in.

I"m not really sure what to make of all this...I thought I would see 3,4,5 inches of vacuum typically but dont know.

Does a low vacuum, meaning fuel is flowing pretty much unrestricted.

I'm leaving gauges attached to do a test cruise under load, Saturday to see how the gauges look.

**My suspicion is at higher RPM its going to rise ( didnt see this at the dock at 2500-3000 however) to near 4-5 inches and set the alarm.

**What is the normal low RPM readings??
​​​​​​​** What should it normally go to at higher RPM under load??

 

[achris]

A vacuum test on the fuel system was a standard installation check when I was installing new engines, outboards and inboards. The spec Merc suggested was no more than 2" at the engine, at full load (ie, WOT, on the water). If it was higher than that, engine damage was a risk (too lean)... The required fix is bigger lines, including the tank pickup. Or find the restriction (can also be a blocked vent line).

When I installed the first new engine in my boat, I put a 1/2" tank pickup and 1/2" lines all the way to the engine. I know the engine only has 3/8" lines between filter and fuel regulator (for the MPI), but I know the rest of the system is handling the 'full noise' fuel flow without breaking sweat.

In the case of fuel lines, bigger really is better, especially with 2 strokes!

Chris......

 

[rothfm]

Thanks Achris, Good info. Really appreciated.

So, not knowing what I was looking at...My readings of 1/2-1.0 inches on the Vac gauges sounds like its not an issue but could be normal. I saw no air in the clear lines either.

I have a new Tank and 1/2" pickups done by myself carefully. All 3/8 to OMS input.

Water test coming on Saturday...

Since this was repeatable, I"m expecting the Alarm to sound again on the water...I want to see what the gauge reads at alarm time.

Does anyone know what the Vac switch should truely be alarming at? Seems when I pinch each engines hose and the gauges go near 4 inches...Each motor will set its Check Eng light/horn.

 

[flyingscott]

Get a factory manual and do a.proper test on the motor. It will also have all the.specs you need in it.

 

[Faztbullet]

Vac will be low as VRO only cycles about once every 45 seconds at idle.It is slowly pulling fuel diaphragm till spring overcome it and "clack: fuel out to carbs and repeat... Leave it hooked up and run engine above 4500RPM with load.

 

[rothfm]

Thanks all.

Fazt...Thats very interesting. Yes, going out Sat with gauges still attached to see what is happeing at higher RPM.

Flyingscott: I have another post out there trying to obtain the manual. Seems this was thier transition year. I can get a year on each side of my year. Trying to determin of those are the same motor basically.

Been rebuilding crossflows for decades...But this is a tad different. But trying to get the correct OEM manual.

Vacuum should be vacuum really. I've proved pinching and creating Vac trips the switch at 4-5in and resets. Circuit works and at least at idle to 3000 rpm, my readings are good. Its not struggling.

More to come. Will post water results Sat if it can help anyone else.

Thanks again.

 

[rothfm]

For those asking. I've done tons of tests..Usual compression...and I have all DVA peak readings on these motors compared to the charts.....All is in order except the System-Check "check engine" light coming on for Vacuum switch alarming.

 

[achris]

For those asking. I've done tons of tests..Usual compression...and I have all DVA peak readings on these motors compared to the charts.....All is in order except the System-Check "check engine" light coming on for Vacuum switch alarming.

Have you tried running on a 20litre remote fuel tank? That's a great way to isolate/eliminate problems.

Chris..........

 

[jakedaawg]

There were two different fuel restriction sensors. One is grey, the other black. They had two different alarm pressures. Sorry, I cant remeber which one is which. The manual states the specs in a very little blurb on one page only if i recall correctly. I believe it was a 150hp manual i noticed it in.

 

[rothfm]

Jakedaawg, Thank you.

I thought I saw that too, where a switch is closing around 4in.

Have to look into that.

now that ive tested that each will Alarm about 4in when i pinch the hoses....I will do my higher rpm load water test Saturday.

Im expecting to see the suspect motor approach that and alarm...

Does anyone know if that is too high? Particullarly if there is another Vac switch that sets off a bit higher? But maybe I dont want to see any higher than 4? Dunno.

 

[jakedaawg]

With all new lines I bet it's fixed. If it still sets off at 4 I bet it's supposed to. At that point I would run off a known good portable with 3/8 hoses and fittings and go from there.

 

[jakedaawg]

 

[jakedaawg]

Make sure you use the good fuel line. Not the two layer stuff by quicksilver or moeller or sierra. The pic above you can see the inner layer separates from the outer layer. This collapsed under suction creating a fuel restriction. I replaced this yesterday. It's one season old. Customer complained and argued with me till I showed him. Went for a ride and issue solved. Happy boater now. Dont use cheap fuel line.

 

[rothfm]

Yes, it did have those lined hoses, now gone.

My suspicion is something in one of my new pickups/screens.

I had a new tank modified by a shop to put ports where i needed them..

Will do Portable tank Saturday, and swap lines at motors...see if issue m9ves while monitoring gauges.

In doing that tank work, I could have alum bits/slag in that tube or screen.

Thanks for all input...should be able isolate it Saturday...if it says with that fuel line path, will pull both pickups.

Think I will remove my new screens, this will allow something to pass to the Racors at least I think...easier to change filters as needed.

 

[rothfm]

Update:

Possible Soved issue...More testing on the water tomorrow. Thunderstorms came through

I had placed T'd-in Vac gauges on each of the twin motors the other day. Went out today, verified same motor set off alarm (port) and truely the gauge showed 5 inches on dial. Good side just a tad obove zero, maybe 1".

Shut down, swapped motor feed lines. Restarted and got underway...Now Alarm on Starboard motor!!

NET RESULT: Issue moved to other motor after moving fuel lines.

So, for the 2nd time took that fuel line all apart--all Good. Then removed the tank pickup port which I put in this spring new.

Noticed it had 2 "curves" in it, like a slight "S" shape.....Seems it was 1.5-2" too long for the tank depth. I took off 1.5" with a 45 cut. And made sure when It went back in, it did not hit bottom of tank. Put it all back together.

It appears its 45 bevel cut, combined with the excessive length, forced it into the corner and the 45 bevel was pressing flat into the tank bottom....I BELIEVE.

So, I kept the guages in place for now....Swapped lines back to original locations and will test again tomorrow.
FINGERS CROSSED.

QUESTION: My clear test Hose when put on the good fuel path (no alarms) at 3500 RPM shows some VOIDS..Meaning
solid fuel in areas, and areas where fuel is moving, but alot of voids. Is this Normal fuel flow. I didnt have clear on
both motors just one, so cant really compare that flow.

The test gauge setup could have some air leak, as there are alot of temporary clamps in place. Maybe this is why one at idle stays just above "0", at idle, while the other shows about 1 inch. I'll have to take that other line apart looking for air leaks I guess.

 

[rothfm]

PS...That pickup tube in question, left the screen off this time, as it had some minor debis in it..The Racor filter and motor filter should suffice..

 

[rothfm]

Haha...Well that particular fuel path is fixed. It was the bent pickup tube for sure. However the other engine/line that was Ok, is now sounding.

IT has they gray lined old line in the the pic that Jakedaawg posted above. Forgot I only replaced one side. I know the liner wasnt attached well, I guess making my T connections with the test gauges, plugging and replugging in that fuel line, some of that liner is causing a block.

Hope to take care of that soon, and retest in hopes that both engines & Fuel paths are now Aok.

 

[jakedaawg]

So glad you got the issue sorted out. Thanks for posting back the results. Maybe it will help others. Great catch on the fuel pickup length.