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Fuel pump relayor wiring problem

J

John Train

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4.3 L OMC with high mounted fu

4.3 L OMC with high mounted fuel pump/filter. I have 12 v to the 6 amp breaker and thru the breaker to the relay contact. I have continuity thru the pumpwires(12v and ground) but I dont get 12 v to the pump. I have tried a new relay to no avail. I removed the relay and jumped the 12v directly from the relay block to the 12v wire in the block leading to the pump. This started the pump and I was getting fuel to the carb. I put the relay back in and started the engine but it only ran until the carb emptied. All fuses under the dash are ok and connections there are tight. Is there another relay/inline fuse that may be gone and I cant see the energises the relay?
1998 Four Winns
 
"Look at the relay plug and ma

"Look at the relay plug and make note of the wire colors and their positions. The relay has a diagram on the side with numbers like 85, 86, 87, 87a and 30 and the relay tabs are marked. 30 probably goes to the pump + lead, 85 or 86 will go to ground, the other of these two will have 12V on it when the key is on, and the center terminal in the plug is empty. 87 gas 12V on it at all times and is fused. Plug the relay in so you can still probe the tabs to check for voltage and ground. You may just have a bad ground on the relay or pump, too.

You may also have a sensor for oil pressure (if it's like a Mercruiser) and if this is bad or there's insufficient oil pressure, it won't run,"
 
"There are 2 wires that energi

"There are 2 wires that energize the relay, there is an orange wire that comes from the assist solenoid and provides 12v while cranking, after starting there is a green wire that comes from the alternator that provides the 12v. Both of these wires have diodes in them to prevent back circuits but it's hard to believe that both of these could be bad. See if you can put a meter on the orange wire and see if you 12v when the key is turned to start, this comes from the S terminal of the solenoid which also has the red/yellow wire from the ignition switch. The green wire from the alt won't have any power on it unless the alt is turning (safety feature)"
 
"The oil pump switch may be ba

"The oil pump switch may be bad. If you can get her running, and oil pressure is up, see if the switch has closed.

Jeff"
 
Where do I find this oip pump

Where do I find this oip pump switch?

Thanks
 
"There is no oil pump switch f

"There is no oil pump switch for your fuel pump, as I said above there is a green wire coming from the alternator that keeps the relay working when the engine is running, this is a safety feature to kill the pump if the motor stalls instead of the oil switch that Mercs might have. You can measure for 12v on the orange wire while starting and then measure 12v on the green if the motor is running"
 
"I am going to the lake today

"I am going to the lake today and will check for voltage on the orange wire. This seems most likely to be the suspect as it did not pump gas with the key on. All worked well once it was started and running so the green wire works from the alternator.
Could the orange wire just be loose or a poor connection. The boat was not run for 2-3 weeks before this happened and then we got a lot of rain, The engine was quite saturated with moisture.
The orange wire is in a taped cable. If the diode is shot where is it located and can it be replaced by itself.
Could I just replace the orange wire with another and cable tie it to the original? Do I need to have the diode?

Thanks for any info

John"
 
""The engine was quite sat

""The engine was quite saturated with moisture. "

Why didn't you say this in the first place?

Not saying water was sitting on it is like you going to the DR and telling him that your back hurts but leaving out the fact that you dug a 1000' ditch. You have to realize that electronics and water don't get along very well. Neither do most mechanical things and water.

If you have access to an air compressor, fire it up and blow out all of the plugs on each end of every harness and if it just slides on, remove them one-by-one and reinsert them. Inspect all terminals and connectors for corrosion, loosen the battery clamps and inspect the battery posts, the connections on the alternator, starter, etc. If your cover doesn't have any vents in it, get one that does. You can't have water sitting on an engine and not have problems afterward. If you had water in the bilge for the whole time, expect your starter and/or alternator to fail. If you remove the starter and lube the Bendix shaft and gear, you may be able to save it.

I'm not trying to dump on you or make boating a bad experience but you need to find out how to keep your boat in a way that it will be an enjoyable experience- water affects everything and you need to make sure it can't get into places it shouldn't. Get some dielectric grease (silicone grease- you can get it at auto parts stores and they sometimes call it "Tune Up grease") and coat the terminals on every plug you can find, before puttting them back on. If you see obvious corrosion, you'll need to either clean the terminals or replace them (If you didn't already know, the difference between a terminal and connector is that a terminal is on an individual wire and a connector is a holder with a group of terminals). Crimping and soldering is the best way to do this and if you see any green crust at the wire where is goes into the terminal, you need to cut it back to clean wire and replace the terminal, using the correct ones.

If you have a cover with vents and you need to leave the boat unused for long periods, keep the motor box open a bit. It can't breathe if it's not open and the condensation won't sit on the motor as long."
 
"John....don't try and run

"John....don't try and run a another wire with no diode for testing, the orange and green are tied together internally, the diode is to prevent a back circuit to the assist solenoid when the engine is running (green wire live), the diode in the green wire is to prevent a back circuit to the alternator when cranking (orange wire live) You need to test the orange wire and diode, see if you can remove it from the relay and the other end from the assist solenoid. If you have a multimeter with a diode tester great, if not you can use a plain ohm meter, put the leads at each end of the orange wire and check for resistance, one way you should no continuity, then reverse the meter leads and should have around 50 ohms (I think, it's been awhile) if you have no continuity either way then your diode is blown causing an open circuit. This is an image of your wiring harness, you'll see they actually list a diode kit # 28 PN 3852258 (0583898 sub up)if you prove your diode is open then you may want to try and order this from a dealer, doesn't look too expensive on Doug Russell site
28 3852258 0583898 Use 0583898 1 $10.99


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1998 Wire Harness
 
"I went to the lake yesterday

"I went to the lake yesterday (16-17 degrees C, and sunny) and the engine fired up the first time and ran normally. The engine was not very wet as it is 2 weeks ago so I think that advice of JimN is correct. Thanks very much for your input. I also want to thak Bob Hill as well for your input.
I now have the boat in my driveway and will apply these ideas when I winterize as well as check for loose /corroded terminals etc.
One other question if you please? If the battery was low due to sitting unused for a couple of weeks would this prevent 12v from reaching the fuel pump through the orange wire as the starter would draw most of the load.

Thanks John/ Northern Ontario"
 
"If the voltage drops low enou

"If the voltage drops low enough during cranking, the relay may not latch and you would have no fuel pump operation. You may hear a buzzing sound from the relay, though. Also, if you ever hear a relay buzzing continuously, it's usually an indication that tabs 85 and 86 both have positive voltage."
 
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