Fuel pump check

[akilkenny]

Firstly, great forum as I've been able to change water pump by just reading many people's comments on here. A great help.

I have a fuel pump problem and just want to be sure of the problem before ordering parts.

I've taken off the VRO fuel pump and was wondering if you should be able to suck air through the impulse nipple?

My boat won't suck fuel and I've run manually via a new fuel line (gravity fed) and all ok. Once I lower it below the fuel pump (no gravity) it cuts out. Works fine of the original line when bulb priming but kids starting to look like Arnold Schwarzenegger which all sounds good but their boyfriends are not impressed

 

[F_R]

Re: Fuel pump check

No you should not be able to suck air through the pulse fitting. Should not be able to blow through it either. OOPS!!, which nipple are we talking about anyway? I'm talking about the one in the fuel pump. If you are talking about the one in the engine block, yes air should flow freely through it, in both directions. Well, that isn't exactly true either. Depends on the position of the piston in the cylinder. If at the bottom of the stroke, unrestricted airflow. If not at or near bottom of stroke, it will have free airflow, but will build up pressure in the crankcase if you blow into it.

 

[akilkenny]

Re: Fuel pump check

Thanks F_R.

Was talking about the fuel pump impulse nipple not the engine block.

I can't blow or suck air through the nipple ( VRO fuel pump removed from boat) but I thought I should have been able to suck air given it should suck fuel.

Any easy way to see if my problem is with the fuel pump or from pressure from crankcase? I've done compression check and around 120 on all 4 cylinders.

 

[F_R]

Re: Fuel pump check

If the motor has compression on all 4 cylinders, and runs on all four, it is not a crankcase pressure problem. It can't run on the associated cylinder without pulses in the crankcase. The pulses happen as a result of the way that a two-stroke pulls fuel and air from the carburetor and sends it on to the cylinder.

The pulses are transmitted to the diaphragm inside the fuel pump, which moves it back and forth, which pumps fuel as it strokes. If you could suck and blow through the pulse fitting, it would indicate a ruptured diaphragm. The diaphragm sucks and pushes the fuel through one-way check valves and pushes it on toward the carburetors.

 

[akilkenny]

Re: Fuel pump check

Thanks F_R. Makes sense what you say about how the fuel pump works and that I should not be able to blow/suck air. Thanks.

Should have made it a bit clearer that I assumed the crankcase was all good given that I had 120 in all 4. I was more concerned about the pulse getting to the fuel pump from the crankcase.

Bit the bullet and am going to order a new non VRO fuel pump (cheaper).

Cheers

 

[racerone]

Re: Fuel pump check

The fitting on the block is called a " pulse limiter " --It not a check valve.---------------The air motor on the VRO pump has check valves and send the + pulse to one side of the diaphragm and the - pulse to the other side.---------The VRO is elegantly simple and easy to repair.------Repair parts and kits are available.--------Please note that the cylinder compression is not related to the crankcase compression !---------You can have good compression in the cylinder and poor compression in the crankcase that drives the fuel pump !

 

[FLAlien]

Re: Fuel pump check

Hey is have a 6hp johnson seahorse 1970 and it's runs good but when I go to accelerate it hardly revs up it seems like I'm still on the slow setting could this be a fuel pump issue?

 

[Bosunsmate]

Re: Fuel pump check

Hey is have a 6hp johnson seahorse 1970 and it's runs good but when I go to accelerate it hardly revs up it seems like I'm still on the slow setting could this be a fuel pump issue?

Yep it could be, try priming the ball while running and see if that fixes it temporarily.
You will need to start a new post if you want to ask more questions as hijacking another thread is against the rules as it makes it hard to follow whats being said

 

[FLAlien]

Re: Fuel pump check

I'm sorry about the hijacking I said that right after I posted it I'm going to make a new thread I hope to hear more from you guys I need help bad

 

[akilkenny]

Re: Fuel pump check

The fitting on the block is called a " pulse limiter " --It not a check valve.---------------The air motor on the VRO pump has check valves and send the + pulse to one side of the diaphragm and the - pulse to the other side.---------The VRO is elegantly simple and easy to repair.------Repair parts and kits are available.--------Please note that the cylinder compression is not related to the crankcase compression !---------You can have good compression in the cylinder and poor compression in the crankcase that drives the fuel pump !

Thanks for the headsup about the cylinder/crankcase compression racerone.

Tried to order a new non VRO pump but the guy said it was for a 110hp and may not suit. He was going to find out and get back to me but didn't. And it seems you can't get repair parts for VRO fuel pump in Australia by the looks of it.

Does anyone know of the non VRO 3 hose fuel pump that should fit an 88 120 TLCCA? I see on Maxrules they have one but not rated for 120 to 140 V4's

 

[racerone]

Re: Fuel pump check

Your dealer may not be familiar with getting the VRO repair part #'s -------I am sure if you took it apart for inspection and repair you could get those parts.----Find the repair part #'s on the web and present them to your dealer !

 

[akilkenny]

Re: Fuel pump check

Will do racerone but it will take time. Trying to do a quick fix for some kids skiing this weekend. Forget what I said about Maxrules as it's the wrong pump by the looks of it (2 hose).

Do you know if part 8555 at JOHNSON EVINRUDE FUEL AND VRO PUMPS and REPAIR KITS. REPAIR YOUR VRO OR FUEL PUMP! -- MASTERTECH MARINE should do the trick?

Happy to have a temporary setup so we don't have to pump while I try to order the repair kit for the VRO which I would rather fix properly.

 

[racerone]

Re: Fuel pump check

My approach is to take apart / inspect / repair as needed.-----Others may differ !---------I was given a VRO pump after dealer recommended owner install a new one.-----Took 10 minutes to inspect to find nothing wrong.-----Cost the owner plenty of money to say the least.-----Some shops / techs can only say ------" you need a new one "

 

[akilkenny]

Re: Fuel pump check

My approach is to take apart / inspect / repair as needed.-----Others may differ !---------I was given a VRO pump after dealer recommended owner install a new one.-----Took 10 minutes to inspect to find nothing wrong.-----Cost the owner plenty of money to say the least.-----Some shops / techs can only say ------" you need a new one "

Took your advice racerone (i'm the beginner).

Took impulse hose off the fuel pump and started engine. I could feel a vacuum source from the pipe with engine running but don't have a pressure guague to confirm the strength.

Took apart the fuel pump and all looks OK visually. With the vacuum/air part removed I can pull/push on the center piece and it moves reasonable freely and pulls air through. Question, if I put my finger over the port for the line to the carbs should I still be able to pull/push the center piece (because I can't and I thought I should be able to)?

Appreciate the advice.

Cheers

 

[akilkenny]

Re: Fuel pump check

After studying the pump further just realised it needs to blow out the carb port at the same time as pulling in from fuel port. Please ignore last post.

 

[akilkenny]

Re: Fuel pump check

Been busy and finally got back to the problem. Bought a vacuum and fuel pressure tester and T'd it up the vacuum hose to the fuel pump and the guage. Started the boat and let run for a few minutes but the needle keeps bouncing around very fast between engine vacuum and fuel pump pressure. Can't read it at all. Anyone know what could cause this or how to get a good reading on vacuum?

 

[racerone]

Re: Fuel pump check

It is NOT a vacuum port , it is a pulse port !------If it bounces around then all appears to be as it should be.--------Air is sucked into the crankcase ( - pulse to the pump ) then that air is compressed in the crankcase ( + pulse ) to pump air motor.---------The check valves on the air motor portion of the pump direct these pulses , + to one side of piston and negative to other side.

 

[akilkenny]

Re: Fuel pump check

Quick update because I hate reading threads that have no ending. Installed a loaned 2nd hand 3 port non VRO pump and all seems to work fine on idle. Am off for the weekend skiiing so hopefully it will work on full throttle too. I'll update when back. Thanks again for the help guys.