Jump to content

Welcome to TheMalibuCrew!

As a guest, you are welcome to poke around and view the majority of the content that we have to offer, but in order to post, search, contact members, and get full use out of the website you will need to Register for an Account. It's free and it's easy, so don't hesitate to join the TheMalibuCrew Family today!

Engine Bogs Down at High RPM - Monsoon 325


Recommended Posts

Hey guys,

After 7 years of ownership of a 20+ year old boat, I think I'm finally having my first "major" issue.  I took the boat ('99 Sunsetter VLX) out a few weeks ago for the first time in several months.  It took a little longer to start than normal (maybe 4+ seconds of cranking), but nothing to be concerned about with a cold engine.  However, the transition from idle to into gear was extremely rough and would practically kill the engine unless I gave it a decent amount of throttle.  This has never happened before, but it eventually went away once the engine was warm, so I thought little of it.  Fast forward to the very end of the day (after 6+ hours of normal use with no other issues), and my wife is surfing (5 passengers, ~2000 lbs. ballast), and the boat won't accelerate over 10 mph.  The engine bogs down, surging back and forth at low speed, the throttle has no response past a certain point, and we even got a couple backfires and a little smoke.  Immediately trailer it and go home.

The symptoms seem like a much more severe version of a problem that I had a few years ago with water in the fuel, so I swap the low pressure fuel filter (high pressure was replaced a couple of years ago), and add a bunch of water removing chemicals.

Took it out yesterday, and it started right up and ran normally up to 30 mph, then the same bogging down/surging/no throttle response issues emerged.  Topped out at 35 mph (normal top speed is 45 mph).  Weighed the boat down with the same 2000 pounds of ballast (only 3 passengers this time), and it was fine at surf and wakeboard speeds, but still bogged down over 30 mph.

The only thing that I can think of is a failing fuel pump and cylinders not firing under heavy load.  Does that seem likely?  Thanks in advance for any insight you can provide!

Unrelated: Are these the correct spark plug wires for my engine? 

https://www.skidim.com/prodinfo.asp?number=RK120017

Link to comment

The best way to isolate your problem is with a fuel pressure gauge.  Check the pressure with key on, engine off, then at idle, then at cruise, then at wide open throttle.  If your pressure stays in the neighborhood of 42 PSI the whole time, it isn't fuel delivery.

Those wires should work.  You can also get them from your local auto parts house.  Change the cap and rotor while you are at it.  I bought a cap a few years ago that had an extra tab at the bottom that I filed away to make it fit properly.  Get one with brass points instead of aluminum.

Link to comment

my thoughts are check fuel pump and also plug wires and distributor like mentioned.     As for the correct wires, just email SkiDim - they will respond that day with the correct part number

Link to comment

Thanks guys! I forgot to mention that I swapped the cap and rotor when I replaced the LP filter just for the heck of it. 

I'll see if maybe there's some build up in the HP filter, then do a fuel pressure check. I feel like the fuel pump squeals have gotten louder and longer at key turn recently (may be psychosomatic) so seems like a likely culprit.

Link to comment

Yeah, there should be no fuel pump squeal/ high pitch noise when the engine is running. You should hear it prime when you turn on the key, but that's it. We had that issue a while back, turned out to be the inside of the fuel line collapsed restricting flow. New fuel line from the tank to the filter to the pump and the she stopped squealing. We had similar performance issues that you do, but worse.

Link to comment

I had a similar issue end of last year. I had been through this before as well. I replaced fuel pump again as well as fuel line between pump outlet and high pressure filter. I found the hose had a bubble inside it but I replaced the fuel pump anyway so not sure which one cured issue. Ran like a champ all this past season. 

Link to comment
  • 1 month later...

Well, now I'm perplexed.  I finally had a chance to work on the boat today, and I think I managed to cause another issue.

I figured that I would swap out the HP filter, spark plugs, and plug wires, and clean out the filter screen within the fuel pump while I was at it.  But first I wanted to get a baseline reading of the fuel pressure.  Tested at key on - 44psi (after a few key turns) and held steady.  Tested at idle - bounced around between 36-40psi.  Right at Indmar's specifications.  Cool, maybe I don't need a new pump.

Figured I would do all the maintenance I had planned anyway since the wires are 20+ years old, the HP pump hadn't been replaced in about 3 years, and I had never cleaned the filter screen (which ended up looking pretty clean).

After I did all that, I went back and tested the fuel pressure again, and, for whatever reason, the fuel line no longer holds pressure.  The pressure jumps up at key turn (as high as 46 psi), but then immediately drops below 10psi.  I checked all the nuts that I had to loosen to swap the HP filter and gain access to the filter screen...no leaks or bubbling.  My next thought is there's not enough fuel in the line after disconnecting and reconnecting hoses, so I run the engine.  Starts right up, and fuel pressure holds steady at 40-42psi.  After a minute or two, I turn off the engine, and try another key turn...still won't hold pressure (one of the key turns actually did hold pressure at 45psi, but that was 1 out of 30).  At this point I figure it's a bad gauge, but when I press the pressure release valve, it's clear that there's little to no pressure.   What gives?

Edited by aggie08
Link to comment
6 hours ago, aggie08 said:

Well, now I'm perplexed.  I finally had a chance to work on the boat today, and I think I managed to cause another issue.

I figured that I would swap out the HP filter, spark plugs, and plug wires, and clean out the filter screen within the fuel pump while I was at it.  But first I wanted to get a baseline reading of the fuel pressure.  Tested at key on - 44psi (after a few key turns) and held steady.  Tested at idle - bounced around between 36-40psi.  Right at Indmar's specifications.  Cool, maybe I don't need a new pump.

Figured I would do all the maintenance I had planned anyway since the wires are 20+ years old, the HP pump hadn't been replaced in about 3 years, and I had never cleaned the filter screen (which ended up looking pretty clean).

After I did all that, I went back and tested the fuel pressure again, and, for whatever reason, the fuel line no longer holds pressure.  The pressure jumps up at key turn (as high as 46 psi), but then immediately drops below 10psi.  I checked all the nuts that I had to loosen to swap the HP filter and gain access to the filter screen...no leaks or bubbling.  My next thought is there's not enough fuel in the line after disconnecting and reconnecting hoses, so I run the engine.  Starts right up, and fuel pressure holds steady at 40-42psi.  After a minute or two, I turn off the engine, and try another key turn...still won't hold pressure (one of the key turns actually did hold pressure at 45psi, but that was 1 out of 30).  At this point I figure it's a bad gauge, but when I press the pressure release valve, it's clear that there's little to no pressure.   What gives?

At key on, without the engine running, the fuel pump only runs briefly.  So it pumps up to >40psi then is leaking back down.  It could be leaking through the regulator, any of the injectors or back through the pump itself.

Link to comment
2 hours ago, MadMan said:

At key on, without the engine running, the fuel pump only runs briefly.  So it pumps up to >40psi then is leaking back down.  It could be leaking through the regulator, any of the injectors or back through the pump itself.

Isn't their a check valve within the pump that is supposed to prevent this? The fuel line held pressure before I swapped everything out, so I just don't understand what changed.

Link to comment
1 hour ago, aggie08 said:

Isn't their a check valve within the pump that is supposed to prevent this? The fuel line held pressure before I swapped everything out, so I just don't understand what changed.

Possible explanations include:

- You got some crud in the fuel rail when you pulled the HP screen and diddled with it.  This could hold any check valve (if it even has one), the regulator, or an injector open.

- Your regulator is bad.

- You have a bad injector.

- You have a bad pump.

If things changed like you say, my vote is on crud in the fuel rail.  I think I'd change the regulator first, or at least pull it and take a look, clean it, and attempt a separate pressure test on it.

Link to comment
36 minutes ago, justgary said:

Possible explanations include:

- You got some crud in the fuel rail when you pulled the HP screen and diddled with it.  This could hold any check valve (if it even has one), the regulator, or an injector open.

- Your regulator is bad.

- You have a bad injector.

- You have a bad pump.

If things changed like you say, my vote is on crud in the fuel rail.  I think I'd change the regulator first, or at least pull it and take a look, clean it, and attempt a separate pressure test on it.

I'll give the regulator a look tonight.  

If the check valve in the fuel pump is shot, I suppose I could always add a check valve in the fuel line, but it would have to be before the pump, not after, so not sure how useful that would be.

What confuses me is that, after key turn, I can watch the pressure drop to basically zero, but still have the engine snap right on when I put it in ignition.  Nothing makes me think it's starved for fuel.

Link to comment

Try using an inline shut off valve between the fuel pump and the fuel rail to determine where you are losing pressure.  This is a common hose/valve setup found in larger (or master) fuel pressure testing kits, but you can make your own with a trip to the automotive store for fuel quick connects, hose, clamps and a ball valve from the hardware store.  After key on, quickly shut off the valve to see if the pressure on your test gauge continues to drop, indicating loss of pressure through the injectors.  Otherwise, if the pressure does not drop with the valve closed, you are likely losing pressure through the fuel pump.  I think this only works on port fuel injected motors, because throttle body injection motors will always have a pressure loss.

If the pressure is intermittent, see if there is a wiring or connection issue on the pump or relay preventing the pump from consistently running correctly.

Link to comment

I tried to test the regulator as best I could without pulling it.  It seems to do its job.  Holds pressure steady at idle (@ 42psi...a little higher than Indmar's 35-38psi in the book, but not alarming).  Pressure jumps up to 50psi when I pull the vacuum line, immediately settles back to 42 when I reattach.

The pressure does something unique/different every time I turn the key on.  Sometimes it almost immediately drops back to zero; other times it takes a minute or two to drop and can even settle around 10 psi.  This leads me to believe that it's probably not the regulator or injector as it seems those would result in somewhat consistent pressure drops.  A failing, clogged check valve within the pump makes sense to me.

The weird thing is, no matter how long I let the pressure sit at zero after key turn, the engine always starts on first crank and sounds great.  Fuel pump whining at key turn has also decreased in loudness and pitch significantly since I changed out plugs, wires, and HP filter.  Might be one of those things that I test on the water, and, if everything seems fine, stop worrying about it?

On 11/27/2019 at 7:52 PM, csleaver said:

Try using an inline shut off valve between the fuel pump and the fuel rail to determine where you are losing pressure.  This is a common hose/valve setup found in larger (or master) fuel pressure testing kits, but you can make your own with a trip to the automotive store for fuel quick connects, hose, clamps and a ball valve from the hardware store.  After key on, quickly shut off the valve to see if the pressure on your test gauge continues to drop, indicating loss of pressure through the injectors.  Otherwise, if the pressure does not drop with the valve closed, you are likely losing pressure through the fuel pump.  I think this only works on port fuel injected motors, because throttle body injection motors will always have a pressure loss.

Any issue with just installing a permanent one-way check valve in the fuel line just before it reaches the fuel pump (or would it work better between the pump and filter?)?  If it holds pressure, then it's definitely the pump; if not, it's the regulator or an injector.  People do it on cars all the time, so I can't imagine that it would cause any issues.  Excess pressure can still be purged by the regulator and sent down the return line.   If nothing else, it will keep the pump submerged (if I install it in the fuel line before the pump).

Edited by aggie08
Link to comment

If you have your pressure drop issue tested and figured out, but still have running issues, try eliminating different systems in the boat as the culprit.  For example, using a small, separate and independent fuel source may eliminate the tank, lines and anti-siphon as the potential problem.  If you take a small fuel container, using new fuel supply and return lines going directly to the container and you can see if you have the same running issue.  If you still have the problem when using the alternate fuel source, concentrate on the engine compression, fuel or ignition systems.  If the problem goes away when using the portable fuel tank, look for issues with the boat fuel tank, lines, pickup, vent, or anti-siphon valve.

Link to comment
On 10/22/2019 at 5:31 PM, williemon said:

I had a similar issue end of last year. I had been through this before as well. I replaced fuel pump again as well as fuel line between pump outlet and high pressure filter. I found the hose had a bubble inside it but I replaced the fuel pump anyway so not sure which one cured issue. Ran like a champ all this past season. 

How did you replace the line between the pump and HP filter? Did you break the metal clamps and pry out the fittings and metal rails to reuse with the new hose, or did you buy a whole new assembly? What did you decide on for re-clamping? Just standard hose clamps, or something more substantial?

I cut the line to put in a check valve, and, wouldn't you know it, there was some deterioration inside.

Link to comment

Standard screw clamps and hose should not be used on any of the fuel lines that are under pressure.  It is fine to use clamps between the pump and the tank, but all lines after the pump should be crimped, threaded, or use high pressure push on connectors.

Link to comment

Found it:

https://www.skidim.com/prodinfo.asp?number=78-6013

Though Indmar said that I'd be perfectly fine with the updated pump to rail direct connection (linked below), but I think I'll keep the HP filter in the equation, even if it's redundant.

https://www.bakesonline.com/indmar-fuel-pump-to-rail-hose.html

 

Edited by aggie08
Link to comment
8 minutes ago, aggie08 said:

Though, if I do have to replace the fuel pump in the near future, I wonder if the direct option would allow for a more seamless conversion...

https://www.bakesonline.com/indmar-556014-fuel-pump-conversion-kit-to-pierburg.html

Thoughts?

I guess it depens how long your pump lasts.  BTW it is possible to piece together the same solution for far less then the Bakes kit if you are so inclined.

Link to comment
22 minutes ago, Eagleboy99 said:

I guess it depens how long your pump lasts.  BTW it is possible to piece together the same solution for far less then the Bakes kit if you are so inclined.

Yeah, I've got a good hydraulic shop down the road that I may check out first.

I was initially thinking that the direct line option attached to the fuel pump outlet via the large nut on the left, but I think I have it backwards: it's still the hard line that goes into the pump, just like my existing setup.  So the conversion to a new fuel pump would be nearly identical.  Now it's just a question of whether or not to keep the HP filter.

Edited by aggie08
Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...