Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

[guushuntr]

I have a 1986 Johnson 150 outboard with the VRO system on a 1986 18' Cimmaron center console. Soon after purchasing the boat I had an alarm buzzer start to come on at various times. The boat mechanic I took it to told me that it was the fuel pressure warning buzzer. The way the boat is designed, the built in tank is in the front of the boat with the fuel line entrance in the front of the tank (away from the motor) and it is roughly 18 feet from fuel pick up to motor. The mechanic says the motor isn't capable of pumping the fuel that far and that there wasn't anything I could do. If you hook the boat up to a 6 gallon tank next to the motor, it runs awesome with no buzzer. The motor runs well until you get past about 3/4 throttle when the it will start to cut back from lack of fuel and the buzzer begins to go off. Because I just didn't believe the mechanic that a boat new from the factory wouldn't have been designed to operate properly, I began replacing parts. I've replaced every fitting, all the fuel lines from tank to motor, cleaned the fuel tank completely, fuel filter, VRO pump, all 3 carburators have been rebuilt, basically every part from fuel pickup to the motor has been replaced with no change in how the motor reacts. Sometimes the warning buzzer sounds at startup, but the motor idles fine, and other times it only cuts back and warns me at high speed. I'm stumped and need any advise someone might have. I've been told that I might help my issue if I lower the pitch on my prop since I"m running a little low on RPM's at max throttle (when I can get to max throttle). ???

 

[ezeke]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

You still have a restriction between the fuel supply and the vacuum switch at the engine, probably the anti-siphon valve, if everything else is new.

You should have 3/8 ID hose for that long a run, and all of the fittings should be that large including the primer bulb. If you have other than a full-sized water separating fuel filter you should replace it with one. Avoid sharp turns in trhe fuel fittings whenever possible.

 

[guushuntr]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

Can you explain to me what this anti siphon valve is and where it may be located?

 

[ezeke]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

Anti-siphon valves are USCG required fitting to prevent fuel from being siphoned from built-in tanks in the event of a break in the fuel line.

They are usually located at the top of the pickup tube on the outgoing fuel fitting and generally consist of a spring-loaded steel ball inside the fitting. If none of the the fuel line system is below the level of the top of the tank, they can legally be removed.

Because of their design they are easily clogged. Also, older ones were not designed for ethanol.

 

[surrender]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

Fuel pressure warning on an older carburated two stroke? Doesn't make sense. May want to find another wrench turner.

 

[clanton]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

How bout an update.

Engine run fine on 6 gal tank?
Horn self test, when key first turned on?
VRO wiring harness connected? 4 wire or 3 wire VRO harness?
Oil tank wiring harness connected? Oil tank ever serviced, including the filter? Is filter foam or mesh?

 

[Faztbullet]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

Ezeke 100% correct and dump the small filter under the cowling and plumb direct.

 

[guushuntr]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

Engine runs great on a 6 gallon tank. The horn self tests when the key is turned except when the warning buzzer has been activated. Once it comes on the warning buzzer keeps going off continuously when the key is turned even when the engine isn't running. Eventually it stops on it's own and i get the normal start up test tone when I turn the key. The VRO Wiring harness is connected and I think it's the 4 wire harness. The oil tank wiring harness is connected and the tank was emptied and cleaned. I did not see a filter on the end of the pickup when I took it apart. If it was not getting enough oil, then shouldn't the warning horn sound intermittently? According to the manual the continuous horn is engine overheat (I know that is not the case because i've checked the temp with a heat gun while running and the horn goes off at idle or even when the engine hasn't been running) or low fuel pressure.

 

[ezeke]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

Fuel pressure warning on an older carburated two stroke? Doesn't make sense. May want to find another wrench turner.

No reason for the 1986 150 parts catalog to show the vacuum switch if it does not have one - check your facts. I'm fairly confident that you will find his wrench is correct.

The fuel obstruction alarm from the vacuum switch is a constant horn.

 

[clanton]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

The temp sensors and fuel vacuum sensor will set a continuous alarm. Fuel pressure gauge from sears has a pressure side and a vacuum side. This gauge with a T from an auto parts store will allow you to tap into the fuel lines on the intake side of the fuel pump. Vacuum should not be over 4 in. hg. If over 4 in. hg. you have a fuel restriction. Just like the other posters said, you have to check everything back to the tank. Fuel line from pump to tank must be 3/8 no bends or kinks. Fittings must have minimum inside diameter of 9/32. You should check all after market fittings and filter housings for correct inside diameter. Anti-siphon valve or after market filter most likely problem. Not part of the problem, but VRO tank should have pickup hose filter.

 

[Joe Reeves]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

The 1986 V6 does have a fuel restriction vaccum valve.

Having the fuel tank where you mentioned is fine, no problem.

(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.

(Fuel Anti Siphon Valve)
(J. Reeves)

Many of the later OMC V/6 engines incorporate a fuel restriction warning via a vacuum device attached to the powerhead. If the engine overheats, or if you have a fuel restriction, the warning is the same.... a steady constant beep.

NOTE... Only the V/6 & V/8 engines have the above "Fuel Restriction Warning". The warning horn will not sound on the other models.

The fact that a engine is not overheating, but the warning horn sounds off with a constant steady beep, and that the rpms drop drastically would indicate that the engine is starving for fuel due to a fuel restriction. Check the built in fuel tank where the rubber fuel line attaches to the tank fitting. That fitting is in all probability a "Anti Siphon" valve which is notorious for sticking in a semi closed position. It will be aluminum, about 2" long, and the insides of it will consist of a spring, a ball, and a ball seat. If this valve exists, remove it, knock out those inner components which will convert it to a straight through fitting, then re-install it. Hopefully that cures the problem.

The above procedure will cure a restriction problem with the anti siphon valve as stated. BUT, it may also allow fuel to drain backwards to the fuel tank when the engine is not running (siphoning backwards) due to the fact that the carburetors/fuel pump etc are higher than the fuel tank. This condition is not an absolute as the valves in the fuel primer bulb usually prevent this backwards siphoning problem. However.... if this does take place, the cure would be to install a new anti siphon valve.

 

[clanton]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

Part number 1986 V6 150 vacuum switch 0394937 Located on BRP web site. V4 carb models do not have vacuum switch. Only V6 and V8.

 

[guushuntr]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

Thanks for all the advice on this. I will get the test gauge from sears, install as you instructed and check to see what it says. I will check the anti siphon valve tonight and see if that could be part of the problem. I was checking some other posts and someone had a similar problem when the the tank vent was stopped up, so I'm going to double check that tonight as well. I will respond back with what I find out.

 

[guushuntr]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

Well, I checked the gas tank vent and it is clear. I checked on the anti siphon valve and there isn't one, it is a plain fitting going from the tank to the line. I had the old one from where I replaced everything the first time and it was not an anti siphon either. All fittings are 9/32 with 3/8 ID lines from pickup in tank to where gas enters motor. All lines, fittings and primer ball are new factory equipment. I replaced the fuel filter again, even though it had only a few specs of black in it. This all didn't change the alarm buzzer, it still goes off continuously. I had the fuel line disconnected to change out the filter and I checked the alarm by turning the key. Even with the fuel line disconnected it still went off continuously (Hadn't even started the engine yet)?? If that was caused by more than 7 HG at the fuel sensor, when I disconnected the fuel line shouldn't it have turned the warning buzzer off because I released the pressure in the line?? I will get the pressure gauge and check that this weekend, but in the meantime, can anyone tell me why that darned buzzer wouldn't go off when i broke the vacuum on the fuel line?

 

[Joe Reeves]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

The horn sounding constantly indicates either a fuel restriction OR a overheating problem, BUT....................

It's always possible that the horn is faulty. When it's sounding off, remove the TAN wire from the horn. If the horn continues to sound, it is faulty and requires replacing.

Also......... there have been times when someone wires the horn wrong. The TAN wire must be connected to the terminal closest to the built in black ground wire. If connected to the other terminal, weird things will happen.

 

[cdoliver]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

what does the primer bulb look like when you get the alarm?

 

[clanton]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

Horn probley bad, connections are marked on horn. You said engine run up to 3/4 throttle then begins to cut back due to fuel, and alarm goes off. You also said runs fine on 6 gal tank. Correct?

 

[emdsapmgr]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

You might want to pull the gas tank pickup out of the boat and check to be sure it is clear. I found a bandaid stuck in a fuel tank pickup once, causing a fuel restriction. Agree that it is good to make sure the tank vent is clear. It is always possible the vacuum switch is bad, however any time the engine starves for fuel at top end, disastrous things can happen. Good thing you are tackling this issue now. I had this same high speed fuel starvation issue on my boat and found a couple of small pcs of sand/grit in the anti-siphon valve. They were enough to prevent normal movement of the ball. Runs great without the valve now.

 

[guushuntr]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

I pulled the fuel pickup out of the tank last night and no crud on the screen. (I've cleaned it not long ago when I replaced all these parts, but I thought I would double check). There is a connection point on the tan wire below the vacuum sensor (it goes from the sensor down through a bundle of wires and out to the buzzer I think) that if you dissconnect it, the warning horn stops sounding. With this dissconnected the test horn still works when I first turn the key, but the continuous buzzer does not sound. It acts so weird because motor will go up to 3/4 throttle then begin to cut back and fall off plane, but if I keep it just below 3/4 throttle it runs pretty well. Buzzer doesn't necessarily go off all the time. One time I idled to the dock and cut the boat off, everything fine. Started it back up 30 min. later and buzzer started immediately?

 

[clanton]

Re: Johnson 150 Fuel Pressure Problem....Out of ideas, please help!

Tell me one more time. Does the motor run OK on 6 gal tank?