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williemon

Fuel pump vapor lock issue (long)

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williemon

Short version: replaced fuel pump. Now have metal dust in fuel even after 5 tankfulls, new pump acts like it vapor locks and sometimes stumbles when running good. Swapped regular filter for water seperator filter. Now acts like a full vapor lock after sitting hot an hour but not stumbling while running good. 

Long version: 

I had a rough time this weekend. 01 sunsetter with monsoon efi. I have replaced everyhing already like plugs, wires and all. Cleaned injectors, replaced pressure regulator. The fuel pump whined all last year but ran well. No issues. This spring i took the boat out and could not get power up past 2800 or so rpm. This prompted me to do full tune up, check connectors, pull and clean injectors. Nothing helped so i decided to replace fuel pump, pressure regulator, fuel hose and filter. Now it ran well and had power up to 5000 rpm and i was pleased. But, then I noticed that when we stopped for a swim for 30 min, when i went to start the boat, it would run but id have to goose the throttle for a few min to get it to run smooth otherwise it would quit. Id hear the fuel pump whine get loud prior to it stumbleing and then it would quiet up a bit and the it would Get loud again, stumble, spit, finally after a few min it would smooth out and away we would go. 

Then i also started noticing that while running good, every so often it would stumble. Id start to bump the throttle but it seemed to pick back up by itself. Thinking i may have water in fuel, or a not so good filter, i removed the filter and in its place added a water seperator filter. 

Went out yesterday and this time i never felt a stumble while running, but, when we shut it off for about an hour, it would not run good and then after quitting, it would not start at all. the engine cranked good and solid but just would not start running. Every so often it would run for a brief sputter and cough but that was it.

I then opened the hatch and felt the fuel pump. It was very hot down at its bottom inlet. I got a rag and put the cooler lake water on it hoping to cool it. After a moment, i also hit the shrader valve to see if i got fuel or vapor and got a good fuel spray. I then cranked the engine and it ran this time. It still was coughing and i had to goose the throttle a few times but then with a backfire, it smoothed out and ran well. while cranking, i could smell fuel i think. It was not a strong smell though. I only use non ethanol though so it may not smell strong, so i could not be sure that there was too much fuel. 

I dont know why this fuel pump acts this way. The old pump nver had issues like this, it just started whining and eventually would not supply  pressure. I also keep getting metal particles or dust in the fuel now since i replaced the pump. The old pump never caused this metal dust. I keep finding it now on the fuel sender since it has a magnet on it.  

 

 

 

 

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williemon

Figured it out. I broke don and took it to a local mechanic and he found a small leak in the fuel connection from tank to pump.  Nothing that put fuel anywhere, just enough to allow it to loose pressure while sitting for an hour or so. This he concluded contributed to the vapor lock. He redid the connection and i tested it this week. No issues that i could find. We also checked the fuel sender magnet for metal and we did not find any this time. Guess it must have got in there from filling up at a new place a few months ago. I have not been back there since. Seems that  particular station with no ethanol gas uses a pump and tank that had be used for diesel prior. 

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williemon

Well batts!!! The issue is back. I will be calling skidim this week to look at getting another replacement. 

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formulaben

You've dumped a ton of money at this so far...I'd add the secondary fuel pump before you do anything else, but that's just me.  Bakes sells a kit if you're not handy with splicing a couple wires, but it is spendy.  I added the pump and no problems since.

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williemon

I called skidim and they will warrantee the pump if it is bad. I need to send it to them for testing. The way i look at it is this... Old pump had no vapor lock issues. New pump does. Pump must not be any good. Id rather take that pump back off, install a single pump as it should have and run it. Im wondering if the quality is off on these later year made pumps. They do not make that pump now. There is another pump that has been retroed to take its place. You can also buy different pumps with the same specs and plumb your own with custom hoses. I guess once i get the pump to skidim, if it tests good for them, im just out of luck. Im wondering if the metal i found in the tank came from the new pump. 

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Steve B.

Before I'd throw money at it, I'd make a habit change first. Sounds like you have typical vapor lock that so many have posted about over the years. The one thing you haven't changed is your sitting for an hour thing. Next time, as your sitting, raise the engine cover enough to let the ambient heat out. That, AND or run the blower the entire time you sit.

Let us know,

Steve B.

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williemon

I dont mean to be disrespectful, but The old pump never vapor locked. Why should the new one? That is just an unacceptable solution to have to prop open the cover. Thanks for the thoughts though. I know that habit can make a difference, its just not for me though. The mastercraft site has a good discussion about using the carter p5000 pump. Its less than 100.00 just needs some modification to the plumbing like the new pump kits have. That may be my ultimate route. Replumb and use a different pump, use a 5 or 8 micron filter on the high pressure side of the pump as well as a 10 on the low pressure supply side and mount the pump off the engine block or use a better insulator. Im also now convinced that the metal i found in the tank and fuel rails after i installed this new pump came from this pump. It will be a good winter project since i want to pull the injectors again and do a ultrasonic cleaning and rebuild of them. 

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williemon

Ive contacted skidim and they will check the pump if i send it in. I will do the that next week but they seem to want to blame ethanol fuel. I know thats bunk but maybe they will see an issue if i send the pump in.

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dalt1

I tried every trick in the book on my old 06 VLX. It never vapor locked the first 2 years then did it consistently. After chasing it and trying every fix short of secondary pump, I finally gave in. Installed secondary Carter low pressure pump and solved it for good.

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formulaben
4 hours ago, dalt1 said:

I tried every trick in the book on my old 06 VLX. It never vapor locked the first 2 years then did it consistently. After chasing it and trying every fix short of secondary pump, I finally gave in. Installed secondary Carter low pressure pump and solved it for good.

Same for me.  Didn't seem to be an issue then it progressively got worse and worse...maybe it was the primary pump getting just a touch weak?  Who knows, I tried different fuels but adding the Carter fixed it for good.

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dalt1

I replaced the primary at one point, didn't help. Did I say I tried every trick in the book? Yep!:whistle:

 

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williemon

I did some reading and found myself on several racing forums and some boat forums. Seems many folks have funky issues with these 2 stage pumps in a pulling pushing situation. They are just so sensitive on the primary inlet pull side and really is setup in a bad config for our boats. Now im wondering even if I send it to skidim would they actually find a problem with it. Might have to try a larger antisiphon and feed hose along with a free flow filter prior to the pump inlet unless a second pimary pump is cheaper. I also learned that not having a 10 micron to 5 micron filter just before the injector rail   Is a bad idea. 

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formulaben

Just to be clear, after adding my 10 micron fuel filter/water separator that is upstream of the primary fuel pump is when my problems REALLY started.  I had an occasional issue but after that installation it was really bad.  The fuel filter/water separator is downstream of the Carter secondary fuel pump, and I SAY AGAIN, this solved all of my problems, and at a cost of only $80 and some basic installation time/skill. 

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MadMan
7 hours ago, williemon said:

I did some reading and found myself on several racing forums and some boat forums. Seems many folks have funky issues with these 2 stage pumps in a pulling pushing situation. They are just so sensitive on the primary inlet pull side and really is setup in a bad config for our boats. Now im wondering even if I send it to skidim would they actually find a problem with it. Might have to try a larger antisiphon and feed hose along with a free flow filter prior to the pump inlet unless a second pimary pump is cheaper. I also learned that not having a 10 micron to 5 micron filter just before the injector rail   Is a bad idea. 

The stock pump in my boat ('00 Monsoon) has a bypass and fuel return built into the inlet side of the pump to support a separate low pressure pump at the tank.

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williemon

Yes. Im going to price it out with a small second pump prior to the 2 stage primary pump. Might put a water sep filter just before the small pump or just after. I was against all that beforehand but after a lot of reading I see now that these pumps just arnt ment to pull much and every little thing that could alter flow while it pulls from the tank could upset its sensitive nature. For sure though the racers say to always put a filter in the high pressure side just prior to the fuel rail. That will protect the injector screen baskets from getting junk in them and leaning the cylinder out and trashing the engine. My injectors did have junk clogging them this past spring and one spark plug insulator was white. Dont need no trashed engine. 

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