vacuum switch

N

Newell

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Nov 6, 2001
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1988 Erude 70hp.<br />Clymer's shows a vacuum switch n/o to ground<br />on line "C" of the commector.<br />What is the purpose of this switch?<br /><br />Newell
 
clanton

clanton

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Re: vacuum switch

I dont that engine has a vacumn switch. What manual number, page number are you looking at.
 
clanton

clanton

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Re: vacuum switch

I cant match that diaghram to the OMC diaghrams.<br />Does your engine have the switch? May find this on on older commerical engines. Trent and DHadley what do you say.
 
R

rwise

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Re: vacuum switch

Newell<br />It is my understanding the purpose of the switch was to prevent engine "run away" in the event it over rpm'd the switch would shut it down or shut down one cylider dropping the rpm's.<br /><br />Richard
 
D

Dhadley

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Feb 4, 2001
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16,978
Re: vacuum switch

I don't recall a vacuum switch on the 3 cyl motors. V6's and V8's have one that is used to sense a fuel restriction and sound the alarm. <br /><br />Like Clanton asked, does your engine have the switch? What's the model number?<br /><br />Good luck!
 
N

Newell

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Re: vacuum switch

Clarification: my boat is 150 miles away, close to the Chesapeake Bay and I forgot to record the model number. Am going there this weekend. Not sure if it has a vacuum switch but since Clymers shows one I thought it might be part of my problem, which is- motor starts and will idle OK for about 2 minutes then dies as if fuel starved.<br />Have disconnected VRO and using 50:1 premix.<br />Suspect fuel pump but want to explore all possibilities before laying out the cash.<br />Plan to disconnect the fuel line at the carb, squeeze primer bulb and verify gas flow. If OK will turn engine over 10-12 and check flow.<br />I am open to any and all suggestions.<br /><br />Newell
 
oldboat1

oldboat1

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Re: vacuum switch

don't mean to make it too simple, but I had similar symptoms a couple of weeks ago. It was the gas -- first experience with "bad gas". I filled a trolling motor tank with fresh gas and oil, and used that. The motor ran fine.<br /><br />regards,<br /><br /> Curt
 
D

Dhadley

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16,978
Re: vacuum switch

Good point Oldboat1. Newell, if the fuel is more than 30 days old it's gotta go. Start over with FRESH 87 octane and make sure you are using Champion plugs.<br /><br />Good luck!
 
N

Newell

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Re: vacuum switch

Gas is pushing 30 days. Will put new in this weekend.<br /><br />Newell
 
N

Newell

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Re: vacuum switch

Weekend update:<br />Re-connected VRO, squeeze primer bulb(muffs on), ran for about 1-2 minutes and shut down as if out of gas,restarted and intermittently squeezed primer bulb, ran for more than 5 minutes OK,stopped squeezing bulb and motor shut down in about a minute,removed drain screw in float chambers, no gas escaped, squeezed bulb and removed float chamber screws, gas flowed out.<br />Logic tells me that by manually pumping gas into the float chambers, fuel is reaching the plugs and the only thing not working properly is the fuel pump.However,since I have been quoted $250 for a new pump by an OMC dealer, I just want to explore anything I might have overlooked.<br />Opinions welcomed.<br /><br />Newell
 
P

petryshyn

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2,851
Re: vacuum switch

before buying a pump, disconnect the fuel inlet line from the pump. (careful, don't break fittings) Connect a hose directly from the pump to a primer to the fuel in the tank (no fittings inbetween) try again. Also make sure the crankcase pulser hose isn't cracked, split or kinked.<br />*I'd hate to see you replace a fuel pump cause you were sucking air or had a restriction!
 
N

Newell

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Re: vacuum switch

Schemo, good point!<br />I removed the pump and did not see any hose problems.<br />Question: since the motor runs OK as long as I manually supply gas with the primer bulb, wouldn't that indicate that the crankcase pulse line is working ok as far as putting fuel to the carbs?<br />Please understand that this question comes from a guy who repairs computers and monitors and knows absolutely nothing about motors.<br /><br />Newell
 
J

jegervais

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Jan 18, 2002
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Re: vacuum switch

To add one thing here, from the pulse limiter fitting (on the block) a hose runs to the air motor section of the pump. If that hose were cracked or split, the crankcase vacuum and pressure pulses would not reach the air motor, therefore the pump would not work. Also, the engine would run poorly because the crankcase for #3 would be venting to the atmosphere.<br /><br />I suspect your issue is with the pump, but verify it as schematic suggests. Since you already run pre-mix, replace the VRO with a p/n 438402 Premix Conversion Kit. It looks like and mounts up the same as your VRO. It just doesn't have the oil pump or alarm module - it's also about $100 cheaper than a VRO.<br /><br />-John
 
N

Newell

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Re: vacuum switch

John, good idea on the Premix Kit. Seems like postings on VRO run about 50/50 disconnect or not.<br />What's your viewpoint?<br />I have the pump on my bench and just opened it up.<br />The large diaphram (that connects to the crankcase) looks ok. What is the air motor, the one in the center of the pump assembly?<br /><br />Newell
 
J

jegervais

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Messages
646
Re: vacuum switch

I've owned a couple of VRO equipped outboards - no problems. At the last dealership I worked for we replaced 2 or 3 defective VRO's in 5 years. Only one of those pumps failed the powerhead. In the other one(s), the engine wouldn't run. Based on my experience I'm an advocate for keeping it, I respect anyone's freedom to choose disconnecting it, just don't bash the pump. <br /><br />To answer your last question: The air motor is the large end (connect to crankcase/pulse limiter), the fuel pump is in the middle, the oil of course is pumped by a piston on the smaller end of the pump.<br /><br />-John
 
N

Newell

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Re: vacuum switch

John,<br />Found the problem, the plunger that operates the fuel pump has broken off from the air motor(black plastic around the 1/4x20).<br />Have a new VRO pump on the way!<br />Just pissed on the fence.<br /><br />Newell
 
N

Newell

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Re: vacuum switch

John,I will be installing the new VRO pump this weekend. Old pump is a three wire harness, new is 4 wire. Instructions say to remove pins from Amphenol connector and insert in new one.I don't have a pin extractor tool yet.Is there another way to remove them?<br />Also, it looks like the sole purpose of this harness is to sound the oil/heat alarm and if so,I should be able to test the motor with the harness not connected and bring it on line later.<br />What's your opinion?<br /><br />Newell
 
J

jegervais

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Messages
646
Re: vacuum switch

That harness controls your "no oil" warning. The removal and insertion tool is pretty much a necessity, I've never been able to remove or install pins with out the tool (I usually break something or add a scar to one of my hand when I don't use the correct tool ;) ). You should run a tank or two of premix until you verify oil consumption from the oil reservoir (draw a line at the oil level with a magic marker) - I would suggest running premix until you get the alarm system functional.<br /><br />-John
 
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