Fuel pump doesnt pump when key is on start

[kaw550]

I have a 98 bayliner capri with a 4.3 Mercruiser I/O.
After the boat sits for a week it will start for a second and then die. I can always get it started by borrowing the feed from the choke and jumping the fuel pump. Here is where it gets interesting...

It always runs once I get it going. I assume that means the power feed through the oil pressure sendor is good.
That lead me to the second power source throught the iginition. I connected a test light to the starter solenoid and found there is power from the solenoid with the key in the start position (purple/yellow wire).

I also removed the plug at the fuel pump and confirmed there is power there but the fuel pump will not start on it's own. If I reconnect the power to the pump and jumpstart I can get the pump going. As I said before. Once it gets going it is fine.

This started at the end of last season but I found the wire was loose at the solenoid, so I assumed it fixed the issue. I was wrong.

So, Can a fuel pump stick? Any thoughts why the pump would only start after I jump it when it already has power going to it?
I am going to check to ake sure I am getting full 12 volts from the starter.

 

[Don S]

Re: Fuel pump doesnt pump when key is on start

The fuel pump does not run just by putting the key in the run position. Only while cranking and running. Try cranking the engine for a couple of seconds, then pump the throttle a time or two and see how it starts.

 

[kaw550]

Re: Fuel pump doesnt pump when key is on start

The fuel pump does not run just by putting the key in the run position. Only while cranking and running. Try cranking the engine for a couple of seconds, then pump the throttle a time or two and see how it starts.

I actually tested for power while cranking. It is there but the pump does not run.

 

[CoffeeHound]

Re: Fuel pump doesnt pump when key is on start

I would be checking the fuel pump ground /ground wire first because i am suspecting your boosting the pump from a booster cable,,thereby , bypassing the ground wire completely .

 

[Don S]

Re: Fuel pump doesnt pump when key is on start

I actually tested for power while cranking. It is there but the pump does not run.

Where and how did you test for power? On the pump connector itself?

 

[kaw550]

Re: Fuel pump doesnt pump when key is on start

I disconnected the connector at the pump with a test light on the terminal and had someon crank the engine
I also tested the wire post on the solenoid while cranking,
It has been a few weeks but I swear the light came on when cranking and stayed on for a few seconds after I cranked the engine and left the key on ithe on position.


I almost forgot. Someone cut ofs a small slice of the insulation on the purple/yellow wire just before the connector. I have only had the boat in the shop once and bought it when it was two years old. No sure how, why or when it was done. When I jump start the pump with the choke power source, I use a jumper wire from the choke to the exposed section of wire. I hace also used the exposed wire to check for power when connected and cranking.

 

[kaw550]

Re: Fuel pump doesnt pump when key is on start

How is the pump grounded? Is it the second wither on the connector? I was not sure if that was the ground or the second power source for when the engine is running.
The boat is an hour away so I would like to get as much information as possible before I go out there.

 

[dingdongs]

Re: Fuel pump doesnt pump when key is on start

oil pressure switch has probably failed not the sender.join the two wires together.if it runs,replace switch.

 

[kaw550]

Re: Fuel pump doesnt pump when key is on start

I will do that bfore I get it running. Once it is running it ways starts right up.
Manual is with the boat....I am not....Where to find the oil pressue swith? Is it on the block? Below the manifolds? Above the starter?

 

[Maclin]

Re: Fuel pump doesnt pump when key is on start

If it runs ok after starting, i.e. does not run out of gas in the carb once engine is running, then the oil pressure switch is ok. If the oil pressure switch fails (or there is a wiring problem there) the fuel pump will not run unless the engine is cranking (key in START).

 

[Pete104]

Re: Fuel pump doesnt pump when key is on start

The "oil pressure switch" is down by the oil filter.

 

[Panu]

Re: Fuel pump doesnt pump when key is on start

Why using electric fuel pump?
Doesnt that engine have mechanical pump also?
mech is more reliable than electric one.

 

[kaw550]

Re: Fuel pump doesnt pump when key is on start

The electric pump is factory.

I went out yesterday and had the same problem.
So I tested the voltage to the pump. With the pump connected I put my meter to the slice in the wire insulation and the ground.

When cranking I measured 8.8 volts. When I stopped cranking it jumped to about 11 for about 5 seconds then shut off.
I tested the power to the chole wire and that measured 11.99.

Looking back I am not I should have tested with the pump connected. In case it is the pump motor.

When I went to jump the pump I notcied it wouldt start right up. Is took 6 or 7 tries to get it going.
It comes out of the water next week. I may just replace the pump and hace the solenoid an the starte checked unless you guys can think of anythig else.

I dont want to go through this again next year.

 

[dingdongs]

Re: Fuel pump doesnt pump when key is on start

jump the switch as stated then measure your volts.make sure the ground connections are good too.the fault is not your pump as its just like having a torch with flat batteries.you should be looking at volts on the +side of 12.7v not 8's or 11's then the pump stands a chance of working.

 

[kaw550]

Re: Fuel pump doesnt pump when key is on start

I now have the boat at home in the garage. I connected the meter to the post on the starter solenoid that feeds the pump (purple/yellow wire)and cranked the engine. While cranking it measures 8 and jumps up to 11.9 when I stop.

When in the water the pump would not start at all. In the garage it starts pumping when I stop cranking and the voltage jumps to 11.9.

I then disconneceted the purple/yellow wire from the starter and tested the voltage. It still measures 8 when cranking and 11.9 when I stop
Could it be a bad solenoid on the starter? Could the wiring on the starter solenoid be wrong? I would think it wouldn't crank at all if the small wires were reversed.

 

[dingdongs]

Re: Fuel pump doesnt pump when key is on start

there are 2 circuits the cranking and the running cicuit.what voltage do you have across your batteries,if its about 12,7 that is what is required on the pump.i would go around checking all the grounds first or run a new ground wire directly off the battery when checking voltage as your wiring sounds as if its faulty,even changing the ground and main cable may be an option.
this post may be helpful too but voltage is your problem; http://forums.iboats.com/showthread.php?t=310760&highlight=oil+pressure+switch