200xs

[rock]

I have no fuel pressure at rail. Can no pressure at low pressure electric pump result in no pressure at fuel rail? High pressure pump is new. Thanks.

Rock

[Jim Speros]

I can't speak to that engine specifically. Sure, fuel needs to be present. Electric pumps don't pull fuel very well. They push fuel.
If you had system open be sure system is full of fuel.

[rock]

I worded that wrong. What I am asking is the low pressure pump the only source of fuel to the high pressure pump or does it have access to the vst like a standard efi. I don't want to disassemble the vst to see the inner workings. I have seen the low pressure pump called the boost pump so I was not sure. It does make sense if that is the only source. Thanks.

Rock

[NICE PAIR]

I worded that wrong. What I am asking is the low pressure pump the only source of fuel to the high pressure pump or does it have access to the vst like a standard efi. I don't want to disassemble the vst to see the inner workings. I have seen the low pressure pump called the boost pump so I was not sure. It does make sense if that is the only source. Thanks.

Rock

As I remember all xs fuel injected mercury's have a vst (vapor canister of some type) low pressure diaphram pump fills the canister, High pressure pump draws from canister feeds motor. I believe the high pressure pump has 12v. when the ign. is turned on, computer dependent on signals supplies the ground. Seems like a check valve in the canister has been talked about. Good Luck!

[rock]

It actually has 3 fuel pumps. Diaphram transfers fuel from tank to separator filter then to vst then to low pressure electric then to high pressure electric. What I did not know was can the high pressure pump be supplied from only the boost pump or from the vst also. Did not want to take vst apart. Too old to learn any more. I'm full.

Rock

[NICE PAIR]

I am not seeing that, Ive got 3 litre pro maxes down pretty good, got the 3.2 xs's fair, You got pictures? as you suggested, I'm pretty full of it too. (the 2.5's are far enough back, all I remember is that beautiful screaming noise before the "POP")

[Jim Speros]

The boost directly feeds the second pump. The boost pump is submerged in fuel. If the vst is not full pumps cannot make pressure. AN easy way to see if it is in fact full is open a drain and check. You can also pump primer bulb while drain is open to see if flow is unobstructed.

[Jim Speros]

I think if one of the two pumps were not working you would still have some pressure. It would show an issue at hi demand.

[25two.stroke]

https://www.mercruiserparts.com/bam/...2451/13440/170

Link shows components of vst. The boost directly feeds the second pump. The boost pump is submerged in fuel. If the vst is not full pumps cannot make pressure. AN easy way to see if it is in fact full is open a drain and check. You can also pump primer bulb while drain is open to see if flow is unobstructed.

Link you sent is not for the correct vst on a 200XS. Post says its a 200xs not a 200 ProXS. Very different motors.

The question asked about if the high pressure pump can pull from the vst area or just gets fed from the mid pump...it gets fed just from the mid pump. You can follow the line around from the out of the mid pump (that makes about 35 psi if I remember) to the bottom of the high pressure pump area.

[rock]

Thanks for the replies. For clarification there are 3 pumps. The boost pump is external, not submerged. The boost pump is supposed to make 6-9 lbs. pressure. If the boost pump is the only source of supply to the high pressure pump I think I have found my issue. Today I will check for voltage at that pump and if present I will cough up the $500 and take a chance. I have worked on a lot more EFIs than Optis and I think the EFI vst set-up had me confused. Obviously the Opti vst is much different. Thanks again for the replies.

Rock

[Tcatrett]

I been using these pumps. Been good so far.
FPF Dual Fuel Pump For Mercury 75-90HP and 115HP to 250HP DFI High pre – Fuel Pump Factory

[rock]

I will try to contact them to get some specs. Part #s don't match but that don't mean they don't have what I need. Thanks for the lead.

Rock

[NICE PAIR]

Thanks for the replies. For clarification there are 3 pumps. The boost pump is external, not submerged. The boost pump is supposed to make 6-9 lbs. pressure. If the boost pump is the only source of supply to the high pressure pump I think I have found my issue. Today I will check for voltage at that pump and if present I will cough up the $500 and take a chance. I have worked on a lot more EFIs than Optis and I think the EFI vst set-up had me confused. Obviously the Opti vst is much different. Thanks again for the replies.



Rock

Rock, I am still trying to remember, but it seems I had an issue with a check valve inside the opti vst. The pisser was the swelled up o-ring/top gasket wouldn't fit back in. Had to make a trip to the boat store.

[25two.stroke]

Yeah I can't remember exactly what was wrong but I had a similar issue in one of these VSTs. The oring or grommet or something didn't fit or was all screwed up and it made zero pressure after installing a new high pressure pump. Took it back apart and found the problem. They are temperamental.

[kellytheaker]

Rock I had a 200 sx for a while - I did not experience a fuel issue but previous owner had and replaced a pump before my ownership .
What I learned was - one pump primes to a certain pressure and then another delivers . If sat for a period of time in between use - they can stick . He had mentioned to unplug the power to the pump and try and run it backwards to unstick .
If you have the means to hook up the fuel pumps to guages - they will show the 2 differant stages of pressure to check - I believe there are schrader valves .He had made a 2 lead pressure guage setup to ascertain which pump was not doing its usual and I believe the manual gave him the idea . Do you have a manual ! I do have one specific and a parts manual .
Injector services - a strong. Member here is well versed in opti and usually picks up the phone - he advertises here for the number . I would certainly call him and begin your thorough basic look and probably gain some knowledge or at least give you a solid base .