Fuel Pump/Pressure Problem Or Something Else? TIGE Mercruiser Magnum 454 EFI

[Mike B3]

Hello, new to a boat forum but spend too many hours on a jet ski forum. Hopefully soon spend too many hours on here too, not in the same boat that I am in currently though. I have a 1994 Tige ski boat with a 454 EFI magnum MerCruiser motor and velvet drive. I bought the boat not running, needed a starter. Starter spun but not engaged. Lifted the motor slightly, replaced the starter. Had some issue with the switch and old connections but finally got the boat to turn over and start after running a new positive line off off of the solenoid to the relay in the fuse box that seemed to have a dead spot in there somewhere. I pulled out the fuel from the tank with a siphon pump (didn't see the fuel plug at back of the boat). Boat fired right up and was doing well. Testing out the transmission because I was wondering why it spun when in neutral. Neutral safety switch was connected, sadly I stepped on it so till I replace it I just have it jumped together. Never ran it on the hose, only a handful of quick starts for like 5-10 seconds. Was about to connect to hose or take to the lake was really the plan. I ran the boat one or two times and about 10-15 seconds at idle the alarm went off. I noticed the oil gauge wasn't registering so I figured no pressure and it was an alarm for that. I cleaned the oil sender, installed a brass T and installed a mechanical gauge just to verify I was getting pressure while keeping the original sender connected too. The mechanical gauge registered with something like 40-50PSI. Still nothing on the dash but the gauge tested with 12.4V. So i was happy to see I had oil pressure at the least. Don't need to see it on the dash.

The day following I had my girlfriend start up the boat (I had disconnected the drive cable and was attempting to make an adjustment if cable was off since prop was spinning with decent speed) boat ran for a few seconds and shut off. Ever since then it would fire up and then die a second or two later. Cycle the key and fuel pump a few times and it would fire up. Had to cycle key otherwise it would just crank over and cough. This was about two weeks ago. Today I went out, cycled the key a few times over a short period of time and it was only a quick cough. Never would fire up and go to idle for a second or two like it was.

I have done a bit of research but see a lot of stuff about MPI motor, however this is an EFI. I can get model or serial number if needed. I do not want to take it to a shop yet if at all, I have worked on jet skis for a few years now and trying to get more familiar with boats. To me it sounds like either some old fuel was in the system and some debris somewhere or that the fuel pump needs to be replaced. The boat hadn't been running for like two years and not sure what the previous owner did for storage. I don't believe they did anything as the fuel was discolored and they stopped using it when the starter went out. So my guess is it had some old fuel and I got a large majority of it but not all.

To sum up my short novel, is there anywhere to start by looking for debris? That is free and easy to do if I know where it would get trapped and cause issues delivering fuel. I have a fuel pressure gauge T'd into the fuel line, was there when I got the boat. I bought a new gauge because the old one rusted up and didn't trust it. I haven't seen the gauge move yet when cycling the key or cranking over the motor. The gauge that came out and the one replaced were both 0-100PSI. I didn't know what pressure should be so I just kept it the same. I wouldn't suspect fuel pressure was too high for the 0-15 gauges but I didn't want to chance it and change anything up. When I replaced the gauge I did hear a hissing sound and fuel bubbling out when unscrewing the old one last week. Will test that tomorrow and get some pictures too.

 

[GA_Boater]

Welcome aboard.

No expert, but;

Since the old gas was grungy, did you replace the fuel filter?

Do you hear the fuel pump run when cranking the motor?

 

[Mike B3]

Welcome aboard.

No expert, but;

Since the old gas was grungy, did you replace the fuel filter?

Do you hear the fuel pump run when cranking the motor?

I don't remember hearing the fuel pump when I would turn the key when I wasn't having fuel issues. I remember hearing the alarm go off when first turning the key for a few seconds and then when it would stop I would try and start the motor. Now that I think about it i might have heard a sound of the fuel pump before these issues, but I can't remember for sure or if I am just putting that in my mind.

I do not know where the fuel filter is. So that is a no on replacing that yet lol. That is what i was planning to check but not sure where to look. Is this in the tank or mounted on the motor or in line? I am used to them in line but didn't see anything jump out at me that was obviously the filter

EDIT: Just looked up fuel filter and have seen that before. I will start there. Usually on the jet skis I have worked on they stand out and you can look through. Sorry I am a noob to boats, plan to get better and with this boat I know I will learn a lot more than I planned lol.

 

[Mike B3]

Sorry for the spam

 

[Mike B3]

Okay so tried to upload pictures and it created nothing but numbers and wingdings lol. If any kinda would Upload them for me I could email them over. Something my phone and laptop must not be liking on here. Even tried to copy and paste. No luck.

I'm the boat I tried to remove filter and didn't budge. I disconnected the line going to the pump and hooked up to siphon and was able to draw fuel. Wasn't impressed by the color so will drain and clean tank out one more time.

I know there is something about if oil sender is not working not the computer will not allow fuel in because of low or no pressure. I am not sure if it is the gauge or the sender that is not working or even the blue wire that has the issue. Is there anyway to bypass this system, safety mode in computer, to test and see if this is where my issue is or if it is actually the fuel system itself?

 

[GA_Boater]

Numbers and wingdings are from the wrong format. It happens to all of us.

Click on the Forum Help link in my sig and look at the photo posting thread. Don't use Photobucket unless you have $400 bucks to waste.

When the key is in Start and the starter is turning the motor over, the fuel pump should be receiving power. Once the motor starts and is making oil pressure, the oil pressure switch, not the oil pressure sender, supplies power to the fuel pump. The oil pressure sender only supplies a reference voltage to the gauge for the pressure indication.

Neither the oil pressure gauge or oil pressure sender will stop the pump from working. Only the Start position on the key switch before the motor is making oil pressure or the oil pressure switch after oil pressure is developed, controls the fuel pump.

As I said earlier, I'm no expert on these, so I'm only spouting generalities. A serial number will help ID exactly what you have for the guys who do know. I'm going to change the thread title slightly to hopefully draw attention.

 

[alldodge]

Never ran it on the hose, only a handful of quick starts for like 5-10 seconds.

Even one of your quick starts without water going into the seawater pump can burn the impeller. Suggest your going to replace it before going boating. If you want to run for a short time without water you need to remove the belt off the pump

This is probably your motor but serial numbers are needed o verify
http://www.mercruiserparts.com/350-mag-efi-ski-tbi-gm-350-v-8-1994-1-1

You should have a block mounted low pressure pump (4 to 7 PSI) and filter should be item 14
http://www.mercruiserparts.com/bam/subassembly/31412/1612/90

Should have a Vapor Separation Tank (VST) mounted on top the motor which supply's 30 PSI pressure to the injectors
http://www.mercruiserparts.com/bam/subassembly/31412/1612/120

You can run your motor from a gas can by putting the intake fuel line going to the filter.

Check the fuses if the VST is not coming ON

 

[Mike B3]

No Title

Don't mind the rust and crust. These will be addressed when I have all the important things working

 

[Mike B3]

Even one of your quick starts without water going into the seawater pump can burn the impeller. Suggest your going to replace it before going boating. If you want to run for a short time without water you need to remove the belt off the pump

This is probably your motor but serial numbers are needed o verify
http://www.mercruiserparts.com/350-mag-efi-ski-tbi-gm-350-v-8-1994-1-1

You should have a block mounted low pressure pump (4 to 7 PSI) and filter should be item 14
http://www.mercruiserparts.com/bam/subassembly/31412/1612/90

Should have a Vapor Separation Tank (VST) mounted on top the motor which supply's 30 PSI pressure to the injectors
http://www.mercruiserparts.com/bam/subassembly/31412/1612/120

You can run your motor from a gas can by putting the intake fuel line going to the filter.

Check the fuses if the VST is not coming ON

Thanks for the info from both of you. Included some pictures. I do not see both parts of that low pressure pump but have something running off the belt which i am thinking takes place of it. I didn't see anything mounted on the block. I will get a serial number for the motor and post that tomorrow.

 

[alldodge]

The motor says EFI but this is an MPI motor. The air intake plenum is only used on MPI. The EFI uses a Throttle Body Injection and sits on the intake where the carb would be, looks like this



Here is the connections to the VST.


In this case your mechanical fuel pump may be mounted on top of the seawater pump

 

[Mike B3]

The motor says EFI but this is an MPI motor. The air intake plenum is only used on MPI. The EFI uses a Throttle Body Injection and sits on the intake where the carb would be, looks like this



Here is the connections to the VST.


In this case your mechanical fuel pump may be mounted on top of the seawater pump

Should I be testing the return and high pressure lines? Also the the low pressure line gauge is up to 100. Should I change this out to say a 15psi gauge to keep mounted and use the larger gauge for the high pressure line or not needed.

I do have the fuel pump on the water sea pump. Does it make sense to take this apart and clean it out or do they typically just need to be replaced?

Also, the high and low pressure lines are both needed to fire up and get motor to idle or is this typically one of the two. Guessing low pressure line. Without having a gauge in line I know I can get a gauge at AutoZone to test pressure. How would I test the high pressure line. Can key just be turned to the "run" position or do I have to crank motor over?

Any need to test return line or would this only be an issue if motor was flooding?

 

[alldodge]

Should I be testing the return and high pressure lines? Also the the low pressure line gauge is up to 100. Should I change this out to say a 15psi gauge to keep mounted and use the larger gauge for the high pressure line or not needed.

The low pressure line has been replaced and rerouted. The original line was routed up and cross the front of the motor and down the port side. The 100 psi gauge is to large and should be able to read 3-7 psi. Gauges are always nice to have but most the time they are only needed when things are not working correctly.

I do have the fuel pump on the water sea pump. Does it make sense to take this apart and clean it out or do they typically just need to be replaced?

Need to find out if the pump is putting out the pressure needed (4-7 psi).

Next there is 1 or 2 screws on the side of the seawater pump housing. If it only has one screw remove it and see if anything but a few drops of gear lube come out. If it has two screws remove the top one. If a lot of thin lube comes out then the fuel pump diaphragm is leaking and pump needs to be replaced.

Also, the high and low pressure lines are both needed to fire up and get motor to idle or is this typically one of the two. Guessing low pressure line. Without having a gauge in line I know I can get a gauge at AutoZone to test pressure. How would I test the high pressure line. Can key just be turned to the "run" position or do I have to crank motor over?

For a fuel injected motor to run it needs high pressure at the injectors. Being your motor is an MPI the pressure should be 43 psi. The VST pumps the pressure around 60 psi but the fuel pressure regulator keeps it at 43 psi. The regulator is under the fuel rail behind the thermostat housing and also under the intake plenum. There is a shrader valve at the end of the fuel rail where fuel pressure is measured

Need your motor serial number. Its located on the box with the yellow label.

Any need to test return line or would this only be an issue if motor was flooding?

Don't see any reason to test it at this point.

 

[Mike B3]

The low pressure line has been replaced and rerouted. The original line was routed up and cross the front of the motor and down the port side. The 100 psi gauge is to large and should be able to read 3-7 psi. Gauges are always nice to have but most the time they are only needed when things are not working correctly.



Need to find out if the pump is putting out the pressure needed (4-7 psi).

Next there is 1 or 2 screws on the side of the seawater pump housing. If it only has one screw remove it and see if anything but a few drops of gear lube come out. If it has two screws remove the top one. If a lot of thin lube comes out then the fuel pump diaphragm is leaking and pump needs to be replaced.



For a fuel injected motor to run it needs high pressure at the injectors. Being your motor is an MPI the pressure should be 43 psi. The VST pumps the pressure around 60 psi but the fuel pressure regulator keeps it at 43 psi. The regulator is under the fuel rail behind the thermostat housing and also under the intake plenum. There is a shrader valve at the end of the fuel rail where fuel pressure is measured

Need your motor serial number. Its located on the box with the yellow label.



Don't see any reason to test it at this point.

Does the high pressure only come on for higher RPM or even used during idle?

Also, pulled out the one screw on the water/fuel pump and had more than just a few small drops come out. Wasn't shooting out but very fast dripping. Could this also be cause by previous owner over filling this port? And when you talked about pump being replaced are you saying the entire pump or just the fuel pump half?

Serial # on the motor is 0F349631


I will try and get a smaller gauge to test

 

[alldodge]

Does the high pressure only come on for higher RPM or even used during idle?

No, the high pressure pump inside the VST comes on when the key is turned to ON, and pump should run for 2 to 3 seconds. When the motor start cranking over the pump comes back on.

Also, pulled out the one screw on the water/fuel pump and had more than just a few small drops come out. Wasn't shooting out but very fast dripping. Could this also be cause by previous owner over filling this port?

Doubt it was over filled. If it only has the one screw, this is the fill hole, and gear oil is filled to the top of the hole. The pumps do fail and start leaking gas unto th pump area. If not changed out with fresh lube the gas will eat away the seal and the water pump will start leaking.

I would remove the entire sea water pump and fuel pump. Once removed, remove the fuel pump and clean out the lube housing of all lube. Replace the water pump impeller and inspect the housing. If the fuel pump is good, refill the housing with outdrive gear lube to the top screw.

And when you talked about pump being replaced are you saying the entire pump or just the fuel pump half?

Just the fuel pump, not the whole thing.

 

[Mike B3]

Okay so before I remove anything I wanted to test the low pressure line. Rented a gauge at auto zone to use for testing. Removing the old gauge I did not hear a hissing sound of pressure like I have in the past. Pulled the old gauge off and no pressure but the line was full of fuel. Installed new gauge and when cycling the key no pressure. I figure that is normal since that is off the pulley and nothing electrical. I go to crank the motor and some fuel was in the line so boat fired for a split second. Then had to just crank over for pressure. The gauge read near 8psi I think and held there for a bit and slowly moved to zero.

I had removed the fuel filter finally and emptied the fuel. Not only was the filter disgusting but so was some of the fuel. I am kicking myself that I even ran the boat on this. So filter is empty, reinstalled to test to see if any fuel was being pulled from the tank. After the quick cranking and quick fire of the motor I removed filter to find no fuel in there. Going to order a new filter, clean the holder that it mounts too so I can feel better there when and if the boat fires up. I am wondering if the fuel pump on the pulley could just be clogged with debris? Before I take anything off I figured I would ask if taking apart the fuel pump while on the sea pump (so just the round piece on one side with like 8 little screws) if there could be debris there causing the issue. I figure it I remove the whole pump I need to get at least a new gasket. I don't mind doing this but while testing figured I test things while not having to wait on parts to arrive. I assume the round window/plate is where the gaskets and diaphragms are? Before running the boat I plan to address these small things but wanting to see fuel get drawn to the filter will make time pass a bit smoother knowing there is some progress while I sit and wait.

 

[alldodge]

just the round piece on one side with like 8 little screws

This sounds like you want to take the lower half of the fuel pump apart, I would not do that without removing it from the sea pump. This is where the rubber diaphragm is located. You can disassemble at this point and see what it looks like. All the crud in the filter leads me that the fuel in the tank may be an issue. There is an anti siphon valve on the tank where the rubber fuel line connects, this can also get clogged up.

 

[Mike B3]

This sounds like you want to take the lower half of the fuel pump apart, I would not do that without removing it from the sea pump. This is where the rubber diaphragm is located. You can disassemble at this point and see what it looks like. All the crud in the filter leads me that the fuel in the tank may be an issue. There is an anti siphon valve on the tank where the rubber fuel line connects, this can also get clogged up.

I am thinking and hoping it's a debris issue more than anything. I will take the fuel pump off and apart, clean it and the filter piece and see if this changes anything. With the filter not filling up I would think this debris would cause something in the pump where one way it builds pressure and the other way is blocked off. It doesn't make sense that the pump would build pressure and not pull fuel from the tank unless a blockage somewhere or an air leak.

When taking the gas cap off the 5-10 gallon jet ski tanks I have there is always a hiss or release sound. This boat does not seem to have that. Any ways to leak test a tank. I don't think there is a leak because no fuel smell. However maybe a gasket or fill hose with a small crack that would affect pressure? I know this can cause affects from a system drawing fueling not sealed. Or does this not affect boats as much as PWCs?

What does this anti siphon piece look like. I was looking at the tank the other day and saw one or two 90? brass fittings at the top and an electronic device (fuel gauge I would have to assume).

 

[alldodge]

The anti siphon valve in screwed into the tank fitting and has a spring and ball inside which keeps fuel from siphoning out if the fuel line has a leak. They can get stuck from crud easy

http://www.iboats.com/ANTI-SYPHON-V...3555661--session_id.255603003--view_id.927961

 

[Mike B3]

The anti siphon valve in screwed into the tank fitting and has a spring and ball inside which keeps fuel from siphoning out if the fuel line has a leak. They can get stuck from crud easy

http://www.iboats.com/ANTI-SYPHON-V...3555661--**********.255603003--view_id.927961

Besides removing the tank because that looks like a PITA. Can I get in there with a wrench to remove it and check. Also how work i go eith checking. I assume this is similar to a one way check valve? Also helps eith tank not imploding or is there a different device for this? Is it worth pressure checking the tank and fill hose system up to the cap to see if any big leaking going on

 

[Mike B3]

No Title

So I removed the fuel pump. Liquid up to the top so obviously a leak. Pump had so much debris in. Not sure if this is an item to rebuild or just replace. The arm at the bottom of the fuel pump doesnt move very much. The diaphragm looking piece on the inside still moves when pushing by hand but not sure how much it is supposed to move the arm. Any way to clean this? The roller on the sea pump pulley has a slight movement to it like a cam. I have seen the cam is how the fuel pump actually pumps and sends the fuel. Not sure on the mechanism how much movement there is supposed to be. I would have figured more of a rise and drop but at least I see movement so happy that isn't shot (from lack of knowledge and at quick glance).