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How do I eliminate the oil pressure shut off switch? 1993 454

E

East Coast Charters

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I have 1993 twin 454 xl crusaders and when coming in from off shore yesterday the low oil alarm went off and shut down port motor. Oil level was fine with no indication of leaks. Motor would crank but no fire was coming out of the coil. This was a shut down in the middle of a storm and I want to remove this option and rely on buzzers and a gage so this wont happen again. I have a brass tee coming out of block with a canister style sending unit with one wire on one end and smaller sending unit with one wire coming out of the other end of the tee. In your opinion, want can I do to fix this problem. Thanks.
 
Re: How do I eliminate the oil pressure shut off switch?

If you have an electric fuel pump then it's not a "problem" as you stated. It's actually a safety feature that is required to be there so that when the engine shuts down for some reason, fuel supply is stopped to prevent a possible explosive situation. I don't recommend changing this setup but it does help to know what to do with it if the fault is in fact a bad switch while out at sea.
 
Re: How do I eliminate the oil pressure shut off switch?

the larger oil canister sender is for gauge, the smaller is for alarm http://www.marinepartssource.com/crusaderpb/454xlikp25.asp

try removing the wire from the small sender, it should still start, the sender may be grounding the coil or an ignition circuit when low pressure is detected. you might have a relay in the circuit that controls that circuit so a cold start can occur. I would be curious on the low pressure, might just be a bad sender if the gauge still read ok
 
Re: How do I eliminate the oil pressure shut off switch?

Thanks, I am heading to the boat and I am going to clean all of my grounds, install a new sending unit and try the alarm wire. I will log on this evening at let you know what happens.
 
Re: How do I eliminate the oil pressure shut off switch?

I'd suspect the oil pressure switch is fine. The buzzer went off due to lack of oil pressure from the engine stopping (from lack of spark).

I'd look for no reference signal from the distributor; if absent, I'd start with the pickup coil inside the distributor.
 
You do not have an oil pressure shut off switch. The oil pressure alarm sender does not turn off the fuel pump or the ignition system. That engine has a separate oil pressure switch on the left side of the block near the front which prevents the fuel pump from running until pressure is present. Changing the alarm sender will not change anything. I agree with Mark, it sounds to me like you have other issues.
 
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Just came back and found out several things. First removed alarm wire and then sending unit wire and still no fire. Found that when turning motor with switch, pos side of coil is hot, but no spark is coming out of coil wire. Thought that coil was bad, replace w/ new coil but with the same out come, no fire coming out of coil. Can this be grounded out threw some other safety device? I will go back tomorrow and track wires to see if there is another pressure near the front of the motor and check back in. Thanks for your help
 
THERE ARE NO SAFETY SWITCHES THAT INTERRUPT THE IGNITION SYSTEM, DON'T WASTE YOUR TIME LOOKING FOR ONE. You have an ignition issue.
 
[THERE ARE NO SAFETY SWITCHES THAT INTERRUPT THE IGNITION SYSTEM, DON'T WASTE YOUR TIME LOOKING FOR ONE. You have an ignition issue.]

Not sure I agree with that statement. Both my present 454s and my prior 460s have/had low oil pressure shut down switches. No alarms. When I lost the oil in one engine (hole in pan), it shut down. Would crank, but not start, due to low or actually, no oil pressure. When installed 454s, included switches but experienced long cranking periods until oil pressure built up. Installed continuous duty solenoids (normally closed) in line with the switches. Solved the starting problem. Wire runs to coil and grounds coil when pressure drops. Switch is teed with oil pressure sending unit.
If it doesn't interrupt the ignition circuit, what does it do?

East Coast may have both an alarm and a low pressure shut down-separate sending units.

Gene
 
OK, so should I start by tracking the alarm and sending unit wires to see if the is some sort of shut down switch (toward left front of motor)? Also, I have four wires coming off of my coil. + & - go to the dist.(mallory prestolite w/ new cap & rotor), and the other + & - goes into a large group of wires in a cover. Should i track these wires and see if the have a cause behind the fire out of the coil? Or , are those wires just coming from the ignition? I just don't get how there is fire into the coil, but no fire coming out of the coil wire. Unless it's grounded out or shut down somehow. Tell me what you think.
 
I forgot to add this, after puting the alarm & sending unit wires back on, I cranked the motor. While cranking, I did build up oil pressure, approx. 25 lbs. Another q, if I do have an auto shut down, or something that grounds out the coil, how do i reset it?
 
The setup comogene describes is a modification from the factory configuration.

As far as troubleshooting the ignition system, it would be best to figure out if you have a mallory or a prestolite (there isn't a "mallory prestolite") and figure out if it is the older point type or the newer 'breakerless' style.

Generically, you need to have B+ to the positive post on the coil, from the ignition switch, and the negative post gets grounded, either thru the points or the breakerless unit. You may have a ballast resistor that has burnt out. A bad tachometer is another possibility (usually connects to the negative post on the coil-grey wire); you can just leave it disconnected. If the distributor has points, check their contacts to make sure they aren't burnt and check the gap, too.

Another valuable tool to have is the factory manual. Andrew, our web site host, offers these and can be reached via the 800 # at the top of the page.
 
Is this a carb or throttle body engine, also is your coil round or square, 93 454xl shows delco distributer and is electronic. Did I miss some where you have an older model?
 
Just got back from the boat and discovered a "oil pressure switch(fuel pump) #98220 that is located on the left side of the motor just in under the alternator. It has two purple wires and one yellow/red wire which plugs into a harness that runs from the sending unit and alarm along the block and into this switch that screws into to block. Now that I know that I have a shut down switch, my question is still. how do I by-pass this to keep the enigine from going into shut down mode. I would prefer to rely upon a buzzer and light system.
 
It is a 1993 454 XL. It has rochester quadjet carbs. The tap on the dist. says prestolite and when I ordered nes dist. caps they were mallory. The coil is round and like a ford coil and with two post and holr for the coil wire.
 
I don't know whether you're in the charter business, but I would tend to think that if anything bad happens and your insurer finds out you bypassed the engine safety shutdown.....just sayin.
 
East Coast Charters said:
Just got back from the boat and discovered a "oil pressure switch(fuel pump) #98220 that is located on the left side of the motor just in under the alternator. It has two purple wires and one yellow/red wire which plugs into a harness that runs from the sending unit and alarm along the block and into this switch that screws into to block. Now that I know that I have a shut down switch, my question is still. how do I by-pass this to keep the enigine from going into shut down mode. I would prefer to rely upon a buzzer and light system.
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That is an amazing discovery. That it the switch I described in the prior post. This is the last time I will repeat this: It does not interrupt the ignition, only the fuel pump. Here is the diagram. You have a 3 wire sender but the system is the same. Also, it does not run to the other senders, it only runs by them en route to the main engine harness. As a Crusader dealer I am not taking the liability of explaining to you how to bypass a safety system that will allow your electric pump to run constantly, any time the ignition switch is on. If you want to do that, you're on your own.

Classic Wiring.jpg
 
linesix said:
That is an amazing discovery. That it the switch I described in the prior post. This is the last time I will repeat this: It does not interrupt the ignition, only the fuel pump. Here is the diagram. You have a 3 wire sender but the system is the same. Also, it does not run to the other senders, it only runs by them en route to the main engine harness. As a Crusader dealer I am not taking the liability of explaining to you how to bypass a safety system that will allow your electric pump to run constantly, any time the ignition switch is on. If you want to do that, you're on your own.

View attachment 1497
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Linesix- I am trying to locate the exact switch described in your post above. I cannot seems to find the darn thing. :confused: Any other suggestion/instruction, or a reference to a great shop manual? I have 7.4L 454XLs.
 
You dug up an OLD thread....

look along the bottom of the block, about an inch or so above the oil pan flange....
 
It is cylindrical in shape and threads into the left side of the block kind of behind the alternator. A three wire bundle is potted into the switch which terminates to a connector. These switches are problematic and often cause start/run issues. The switch allows the fuel pump to run while cranking the engine to start. When oil pressure comes up, the switch directs battery/alternator power to the pump.
 
Mulletwagon said:
It is cylindrical in shape and threads into the left side of the block kind of behind the alternator. A three wire bundle is potted into the switch which terminates to a connector. These switches are problematic and often cause start/run issues. The switch allows the fuel pump to run while cranking the engine to start. When oil pressure comes up, the switch directs battery/alternator power to the pump.
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I appreciate the responses. I have 1997 454xl 7.4L, TBI. I am looking for the exact part you describe. Looking at the front of the engine, the alternator hangs off the bottom right hand side, there is really nothing behind it. As far as a location along the bottom of the block (above the oil pan), the only attachment/sensor I've found is the knock sensor (Left hand side of block, towards rear). It has been mentioned that the switch may be located near the coil- I may look there next.

This is becoming quite the treasure hunt, as I have not been able to locate any drawing/picture showing the location. My wiring diagrams indicate a "fuel pump pressure switch", but it is well hidden. I believe this is a simple fix to my electric fuel pump problem, but locating the switch is proving to be very difficult.
 
The pressure switch that controls the electric fuel pump is a needed part and should only be by-passed for emergency running. Being a big block motor it can be located in very few places. At the rear of the blocl to the right rear of the dist body or just above and to the left of the oil filter
 
MW hit the nail in post #23....TBI (1997) = MEFI controller = ECU control of the fuel pump.....this can be verified by listening for the pump turning on for ~ 2 seconds when the key is turned to RUN....

In other words, if you have a MEFI ECU on the engine, you won't have the switch in question.....however, you will have an oil pressure switch that the ECU monitors to control the fuel pump during the engine running condition.
 
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The pressure switch that controls the electric fuel pump is a needed part and should only be by-passed for emergency running. Being a big block motor it can be located in very few places. At the rear of the block to the right rear of the dist body or just above and to the left of the oil filter
 
makomark said:
MW hit the nail in post #23....TBI (1997) = MEFI controller = ECU control of the fuel pump.....this can be verified by listening for the pump turning on for ~ 2 seconds when the key is turned to RUN....

In other words, if you have a MEFI ECU on the engine, you won't have the switch in question.....however, you will have an oil pressure switch that the ECU monitors to control the fuel pump during the engine running condition.
Click to expand...

Verified! My port engine electric fuel pump turns on for ~2 sec when key turned to RUN. SB engine pump does not.

So, are you suggesting the ECU or oil pressure switch may be the problem?
 
Before you start with the big dollar items, start with loose/corroded wiring, ground wires, etc.
You may have to swap ecm`s to verify a ecm issue
 
The manual will help....so would a scan tool......

A clear statement of your problem would be good too.....you inferred an issue with the starboard(?) engine's fuel delivery....won't idle, won't start, dies under load, etc?
 
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