2000 mercruiser 7.4 fuel pump issue...

[thegoat86]

I have a 2000 Reinell with 7.4 mercruiser. Got it out after sitting for a few months. Would not start, checked for problems. Found good spark, no fuel pressure. Hooked up my pressure gauge, not even a whisp of pressure. Replaced the water/fuel filter, no change. Hooked up my hand vacuum pump and primed fully at shrader valve on engine. Still no pressure. I located the electric fuel pump and checked voltage, 8 volts. I will start looking for connection issues or loose/corroded wiring. Does anyone know where the positive wire goes before it gets to the pump? I would love to check there first. Strange, I feel the pump should work at that voltage. Just be sluggish.

 

[thumpar]

Did it work after the fuel pump replacement? If you go electric you will need to add an oil pressure switch. I would also put a blockoff plate where the mechanical pump is.

 

[Bt Doctur]

sound like a fuel injected motor mentionin a :shrader valve.depending on your particulatr setup, there are some creative options available.
for the wiring, that depends on the computer or the pressure switch. A engine serial number would be most helpful.

 

[alldodge]

I would remove fuel filter housing and other stuff to get at it over pulling the motor, unless pulling the motor is real easy. Can't say it would be easy to pull since you are unable to get at the fuel pump. Prior to rebuilt I had to hang upside down to get at it on my Formula.

On another note, you need to remove the pump and clean out the seawater pump housing. My guess if the low pressure pump is gone, then fuel has leaked into the housing. The housing is filled with gear lube and when the pump leaks internally fuel mixes with the lube. After enough time the gas will damage the pump seals and then it needs replaced or rebuilt.

See link in my sig about the pump maintenance

 

[thegoat86]

The pump is on the underside of the block next to the motor mount. It is a cooler setup. I found the relay, jumped it out, pump works fine. I am not getting a ground from the green/white wire going to the ECM. What sensor would tell the ECM to not ground the pump relay circuit? Wire has continuity between the ECM harness and the relay block.

 

[thegoat86]

on the motor cover it does not have a serial number, just a transom number. The other spots are blank.

 

[alldodge]

The pump is on the underside of the block next to the motor mount. It is a cooler setup. I found the relay, jumped it out, pump works fine. I am not getting a ground from the green/white wire going to the ECM. What sensor would tell the ECM to not ground the pump relay circuit? Wire has continuity between the ECM harness and the relay block.

OK, you have cool fuel module under the port side and between engine and motor mount.

So you can jump the relay connection, pump runs and the engine will start, correct? Or the pump runs but there is no start?

Are you getting 2 beeps when you turn key to ON?

 

[thegoat86]

Boat is running now. I found the green/white wire was not pushed all the way into the ECM connector. I got it to go in all the way then plugged back in. Started right up after I bled the air out of the system. But now I have a water pump issue. When I put the suction cup over the outdrive pump holes, the water does not make it up to the motor. Just sprays everywhere. It used to suck right on when the engine was idling. I pulled the hoses off the motor and when the motor is running, the water does not come up the feed side like it should. Is there an impeller in the drive? and how hard is it to change? I can shove the hose down the feed line where the motor is and the water comes out the drive, so I know its not plugged.

 

[Bt Doctur]

7.4`s did not have an impeller in the drive .Only Alpha drives use an impeller, the rest use a engine mounted pump

 

[thegoat86]

yeah, so..... I guess my boat has the raw water pump mounted to the bottom starboard side of the motor. I removed the belt and tried to spin it. It feels like there are rubber paddles flapping against each other inside and does not move smoothly either way. Is this normal? The pump has too much corrosion on it to rebuild. I believe I will break bolts off trying to get it out. Advice? As I stated above, the water hose suction cups used to suck themselves to the drive at full blast when the boat was idling.

 

[Bt Doctur]

If that was true then you have a vac leak in the hose connections preventing the pump from drawing the water. Could also just have a worn impeller.
that pump is mounted buy 2 bolts or a bolt and a stud.

"I can shove the hose down the feed line where the motor is and the water comes out the drive, so I know its not plugged."
Exactly where are you doing this?

 

[alldodge]

Boat is running now. I found the green/white wire was not pushed all the way into the ECM connector. I got it to go in all the way then plugged back in. Started right up after I bled the air out of the system.

I'm a bit suspect that one wire on the ECM was loose, it could happen, but very unusual. My thought is the relay is going bad or there is corrosion on the relay terminals. Either way glad you got it going

But now I have a water pump issue. When I put the suction cup over the outdrive pump holes, the water does not make it up to the motor. Just sprays everywhere. It used to suck right on when the engine was idling. I pulled the hoses off the motor and when the motor is running, the water does not come up the feed side like it should. Is there an impeller in the drive? and how hard is it to change? I can shove the hose down the feed line where the motor is and the water comes out the drive, so I know its not plugged.

Impeller should be changed out every 2 to 3 years and it's not that hard. Remove the two hoses, note the top comes from the drive (don't swap them upon reassembly). As BT mentioned there is three places which hold the pump and bracket. Remove the nut on top and bolt a bit lower, then remove the one long bolt which goes clear thru to the rear bracket.

Once off you can then remove the other bolts and get at the impeller. Use soap or glycerin to lube the impeller prior to reinstall, don't use oil or grease. Your housing may also be a one piece plastic type which many use instead of all the pieces shown in pic below.

If the pump has gone bad they can be rebuilt with items listed

 

[thegoat86]

bt; I did this at the t-stat housing hose on right facing front of motor. So essentially, I pushed the water through the fuel cooler, then through the raw water pump, and out the line of holes on either side of the drive. When I put the muff on, the water blows by the cups. IE; water does not go up into the motor even under me holding them tight kinda force. I also count four blots in the face of the pump holding it to the bracket. All of the bolt sleeves into the pump are split open with rust, and the bolts themselves are flaking rust off the hex heads. very corroded outside. The rest of the motor seems good. meaning not a lot of rust like that.

 

[thegoat86]

AllDodge; Thanks for the reply. Good to see you on here. Happy new year. I will have to buy the whole assembly or find one used. Like I stated above the bolts and housing where the bolts go in are corroded/rusted/split. Its good to know this will be something for me to look at every couple years. It would have been bad to overheat out in the intercoastal this spring.

 

[alldodge]

Before you write off the pump I would get it out of there and have a look. Your pump uses grease inside it, so the outside may be superficial. The rear pump hosing and impeller is cheap compared to the pump. Pump cost around $350, the housing and impeller are around $80 for the whole kit

 

[thegoat86]

ok, taking it out in the a.m. I will repost with my findings. If its still good would it have some resistance turning the pulley? When I turn the pulley it goes with some nominal resistance and feels like rubber flappers are pushing against something. It is really hard to spin the other way. And same to reverse direction. Wondering if I am chasing the right problem.

 

[thegoat86]

Am I chasing the right ghost? I tried to turn it and had the resistance and what felt like a rubber flapper brushing against something.

 

[alldodge]

ok, taking it out in the a.m. I will repost with my findings. If its still good would it have some resistance turning the pulley? When I turn the pulley it goes with some nominal resistance and feels like rubber flappers are pushing against something. It is really hard to spin the other way. And same to reverse direction. Wondering if I am chasing the right problem.

That's normal, the rotation should be hard to turn in one direction and real in the other. Basically when you try to turn it in the wrong direction the impeller blades are being rolled over on top them selves. Note when it comes apart if all the blades are there, and also makes sure to put the new impeller in the same way so the blades are bent over as before. The engine will flip it over if it is wrong but you don't want to damage the new impeller.

 

[alldodge]

Am I chasing the right ghost? I tried to turn it and had the resistance and what felt like a rubber flapper brushing against something.

You probably have some broken rubber impeller blades inside, it's normal

 

[thegoat86]

Got the rebuild kit for 80 at west marine. going to rebuild it. The case is plastic and split where the bolts go through. The original bolts were rusted to a point where they split the case. I was advised to put anti seize on the entire bolt to prevent this further.