Carbed 5.0L stalls at idle. Oil pressure safety switch? How to replace?

[Maxumillion]

Can anyone advise on how to test & replace an oil pump safety switch?
3000SCR's port side 5.0L is stalling at idle. Runs very well above 2000 rpms. As soon as I drop the throttle down it stalls out. The yard mechanic serviced the carb (float, etc) for $100.00 but no change. I've read a lot about it possibly being the oil pressure safety switch cutting power to the fuel pump if the switch is shot. Oil pressure is ok & normal on the guage when running. Upon finding what I think is the switch near the oil filter, I pulled the 2 purplish wires off & put them back on to ensure good contact. No change. Cant seem figure out how it comes off the engine in order to replace it... (Also checked th safety lanyard which is also in tact & correctly in place.) Though it may be an easy & cheap next step to check out the op switch.
Anyone experience this issue & is it an easy DIY fix to test or replace it?

[mmwjr]

Max you can pull te 2 wires off the OP switch and jumper them together. Make a short jumper of the same guage wire and put blade connectors on it same as on switch. If this allows the engine to run then replace switch.

Just to verify your engine does have an electric fuel pump, correct?

The switch screws onto the engine. There should be a flat spot on it for a open end wrench. If not use channel locks.

Let us know what you find.

[jrsick]

If you don't have one already, this is good time to get a multimeter and learn how to do a continuity check. Easy to do and well worth your time to learn. The OP switch is particularly simple to check and you will save yourself time, money, and aggravation.

[Maxumillion]

[QUOTE=mmwjr;30225]Max you can pull te 2 wires off the OP switch and jumper them together. Make a short jumper of the same guage wire and put blade connectors on it same as on switch. If this allows the engine to run then replace switch.

Just to verify your engine does have an electric fuel pump, correct?

The switch screws onto the engine. There should be a flat spot on it for a open end wrench. If not use channel locks.

Let us know what you find.[

re Wires: I wanted to jump but wasn't sure how do to the blade connectors as you mention. I checked for corrosion to but seemed ok from what I could tell. Would it be easier to check with a volt meter?

re Fuel Pump: I'm actually not sure if its an electric fuel pump or not. How can I verify this?
Thanks-

[Maxumillion]

Sounds like a good idea. I'm assuming I'd need to have the ignition just turned to start/on, doesn't need to be cranking over while checking, & then check the wires correct?

Thanks-

[mmwjr]

O to make the jumper you need a wire crimper tha came be bought at any home store (lowes, home depot, ...) or marine store (westmarine, ...). The crimper has color dots that tell you what crimp slot to use depending on the lug size in this case blades. You can buy a kit at any of the places I mentioned that included lugs and the tool. See link for an example

http://www.westmarine.com/webapp/wcs...classNum=50569

[mmwjr]

A mechanical fuel pump will be mounted on the starboard side of engine near fuel filter. An electric fuel pump will be mounted on the front of the engine just behind the pullies. It will be about the height of a soda can and 1/2 the diameter.

To test the switch no power is required. Pull the 2 wire off it set the meter to ohms. Touch each terminal on the switch with one of the meter's leads. Should be zero ohms. If it is the switch based on what you told us I would assume it has a weak spring and is open ( no reading on meter) at low rpms and closes ( zero ohms) at higher rpm.

[mmwjr]

Here is what amechancial pumps looks like

http://www.westmarine.com/webapp/wcs...classNum=61533

Here is what an electric pump looks like

http://www.westmarine.com/webapp/wcs...classNum=61533

[pascavone]

I would believe a gasket or vacuum leak.

Since the engine run at 2000 rpm, its not a fuel issues, nor a oil pressure related.

But, if your sucking more air then fuel, then its a vacuum or air leak thru the carburetor base gasket, or some other hose.

If the floats where done, and not a full carburetor rebuild, then the gasket will need to be changed.

2000 rpm is pretty forgiving with the engine vacuum, idling on a leak fuel mixture would kill your engine, which s idling at 800 rpm.

[Maxumillion]

Thanks Mike.. Very helpful.. I have find out which one I have. If my fuel pump is manual I'm assuming it will eliminate the OP as a possible cause for stalling, right?

[Maxumillion]

Thanks Pascavone.. Makes sense as its starving for fuel at low rpms.. I'll have to hand it back over to the yard if its an air leak/gasket.. I'll see if I can rule out the OP 1st & go from there..

[mmwjr]

Max if it has a manual fuel pump then it shouldn't have an OP switch. What Pas said could also be true.

[ss3964spd]

Just curious, if it dies at idle how do you get it started and keep it running? How do you get it in gear if it won't idle?

It would be helpful to know the full scenario and symptoms. Do you have any trouble starting it when the engine is cold? Will it idle when you first start it cold? Or does this happen only once the engine is warm and you are throttling down from cruise speed?

Since there is no electric fuel pump does the oil pressure saftey switch kill the ignition instead of the FP?

[mmwjr]

Max as ss3694spd stated more info would help. You said it's a 5.0L which means it has a carb and not a TBI (throttle body inject) a lot of folks can't tell the difference. If carb does it have TKS (turn key starting)? Will it idle when cold, when hot?

You initial description says you can use the boat as the engine will die whenever it's brought to idle therefore you could never get into gear, is this correct?

ss3964spd, I don't think Max has yet determined what fuel pump he has.

[ss3964spd]

Originally Posted by mmwjr

ss3964spd, I don't think Max has yet determined what fuel pump he has.

Ah, you're right, Mike, somehow I concluded that he had a manual pump.

Dan

[Maxumillion]

SS, I can start her up with the throttle up near 3/4 & a few pumps to get fuel in the bowl, & she'll run all day @ 2000 rpms but as soon as I budge the throttle down below 2k she conks out. It's poss to catch it before she quits by pumping the throttle & kicking it up past 2k, but it'll die way before you can put her into neutral or in gear.. Still have to determine fuel pump type, but was advised that if I have a op safety switch then I'd have to have an elec fuel pump. I took a pic of what I think is the switch right near the oil filter, I'll try to upload it..
Thx-

[Maxumillion]

Mike, no, I don't think this year/models was TKS...I believe it's standard 5.0L 2bbl carb..won't seem to idle cold or hot, therefore can't put into gear or even in neutral w/out it stalling. If I start her up with throttle up to 3/4 she'll start high & if I keep throttle up there she'll hold a higher rpm idle but not a low 650 - 2000 rpm type idle, as she'll just conk out even if she's been idling at temp above 2k for sev mins & all is warmed up she'll still die when you try to reduce the idle below 2k...thx-

[mmwjr]

Max you did mention a device with 2 purple wire that should be the OP switch. I don't think you mentioned what year the boat and or engine is but from what I recall 1998 and up use the electric fuel pump.

With that said the OP switch usually fails open and the engine won't run for more than a few seconds, however it is possible that the spring is getting weak and the conditions you are experienceing is possible. Another thought is that you really do have low oil pressure at idle and the Op is protecting the engine. The jumper test I told you about will rule out both but if the pressure is low be ready to shut her down quickly.

The next likely thing is a vacumn leak at the base of the carb (gasket between carb and intake manifold) also could be leak from intake to heads or within the carb itself. Using some carb cleaner (sparingly it's flammable) lightly spray around the gasket and see if idle improves for a moment. If it does you have found the leak.

Since the condition exists when either cold or warm I am assuming the choke is working properly.

[Maxumillion]

Mike, The boat & twin engines are all year 2000... (Mod 3000SCR)... Question on the jumper since I'm a hot wiring novice: I would cut the flat terminal ends off, strip the ends & just twist together? Should I cap them as we'll? Any other hazards to be aware of while doing this? I have a pic of what i think is the op switch but it wont upload onto this site for some reason.. Thx-

[mmwjr]

Max no no no. Never cut up wiring harness.

Get a 6 inch piece of 20 guage wire. Strip 1/4 inch off each end. Crimp on blade lug as should in attached picture. Remove both wires from OP switch and connect one to each end of jumper.