Fuel Problem 2001 21i

[jchurch6713]

I have seen a few threads on this but I would like to make sure that you guys agree with my assessment before I purchase any parts. I have had a myriad of problems this year but the newest is that when I take the boat out it will run great all day and then I will sit and float for a while and when I start back up it will die after a few seconds and even backfire a little. After this happens it will turn over and crank but dies again immediately. I think it is vapor locking because yesterday we ran the blower for a while and opened the engine hatch and finally she started up and got us back to the ramp. Also, when I took the fuel filter off it was not full, the level was about an inch below the top of the filter. The fuel pump kicks on each time that you turn the key on so that does not seem to be the problem. I have the Merc 350 Mag MPI. I do not understand why it would begin to vapor lock unless I have a fuel pressure problem or a fuel cooling problem. I will check the water line to the fuel cooler but I think I will have to replace the fuel pressure regulator. What do you think? Is there any electrical problem that would cause this that I am overlooking?

Second, I noticed that when I was running once the rpm gauge seemed to be jumping around quite a bit although the engine was running great and holding a steady rpm. What could cause this?

Thanks.

[H20SKIER14]

I have been having the same problem on my '01 21i and I got it figured out this weekend. Yes it is vapor locking, to get the air out of your line there is a stem at the end of your fuel rail with a black cap on it. If you take the cap off and turn the ignition to on so the fuel pump runs and use a screw driver to push the stem in it will blow out the air. I usually turn the ignition on and off two or three times to cycle the pump and get all the air out. Hope this helps!!

[chpthril]

I have been having the same problem on my '01 21i and I got it figured out this weekend. Yes it is vapor locking, to get the air out of your line there is a stem at the end of your fuel rail with a black cap on it. If you take the cap off and turn the ignition to on so the fuel pump runs and use a screw driver to push the stem in it will blow out the air. I usually turn the ignition on and off two or three times to cycle the pump and get all the air out. Hope this helps!!

This is a great way to start a fire and or explosion.......dont do it. The "air" you are purging is gas vapor, not h20 or some other non-flammable gas, but something that goes BOOM real easy, especially when it hits a hot manifold or spark from an ignition source.

Vapor lock is an effect, or symptom of problem in the fuel system, you need to treat the cause, not the effect and find out what is causing the vapor lock. IMPO.

[dogbert]

This is a great way to start a fire and or explosion.......dont do it. The "air" you are purging is gas vapor, not h20 or some other non-flammable gas, but something that goes BOOM real easy, especially when it hits a hot manifold or spark from an ignition source.

Vapor lock is an effect, or symptom of problem in the fuel system, you need to treat the cause, not the effect and find out what is causing the vapor lock. IMPO.

I'm with you on this one, especially after my fuel system leaked gasoline into my engine compartment after they replaced the fuel pressure regulator. It's a sickening feeling when you're driving to the boat ramp and you know that you're leaking gas into the bilge

[dogbert]

I have seen a few threads on this but I would like to make sure that you guys agree with my assessment before I purchase any parts. I have had a myriad of problems this year but the newest is that when I take the boat out it will run great all day and then I will sit and float for a while and when I start back up it will die after a few seconds and even backfire a little. After this happens it will turn over and crank but dies again immediately. I think it is vapor locking because yesterday we ran the blower for a while and opened the engine hatch and finally she started up and got us back to the ramp. Also, when I took the fuel filter off it was not full, the level was about an inch below the top of the filter. The fuel pump kicks on each time that you turn the key on so that does not seem to be the problem. I have the Merc 350 Mag MPI. I do not understand why it would begin to vapor lock unless I have a fuel pressure problem or a fuel cooling problem. I will check the water line to the fuel cooler but I think I will have to replace the fuel pressure regulator. What do you think? Is there any electrical problem that would cause this that I am overlooking?

Second, I noticed that when I was running once the rpm gauge seemed to be jumping around quite a bit although the engine was running great and holding a steady rpm. What could cause this?

Thanks.

If you had a fuel pressure problem, you'd be getting some intermittent alarms, usually at higher RPMs. I'm guessing vapor lock caused by a combination of newer fuel mixtures (including Ethanol) and the heat.

As for the RPMs jumping, that's most certainly a grounding issue. I'd check the wires in your dash to make sure you have proper ground on all of them.

[jchurch6713]

I have been getting a double beeping alarm at some higher rpms usually directly out of the hole. So you may be right but I do not really have a dealership nearby to check the alarm.

[illiniboarder88]

I'm having the exact same problem. Dog, what did you do to correct the leaking pressure regulator?

[dogbert]

I had to have the fuel pressure regulator replaced. The part had to be ordered. It's a bitch to get to on a V-Drive, but should be easier on a direct drive. It's on the back end of the fuel cooler, port side (for direct drive). The fuel cooler is inline to the transmission from the water pump.

Be careful not to pinch the gaskets from the fuel pump. My dealer did that and I ended up having gas streaming into my bilge while running

If you're not a DIYer, I'd have the dealer do this job.

[illiniboarder88]

Do you mean the gaskets coming out of the fuel pump that are kind of go up in a U shape into the cooler?

[dogbert]

Yes.

[jchurch6713]

I have seen some mention that they have totally redesigned the fuel pump, cooling assembly and that the entire assembly should be replaced if you have this problem. Have any of you heard this? I saw a service bulletin on how they no longer provide the fuel pump as a single component and that you must purchase the entire system so this adds some relevance to this idea.

[chpthril]

I know there was a retro kit for the VP prob on the closed cooling system.

[dogbert]

I'm having the exact same problem. Dog, what did you do to correct the leaking pressure regulator?

Just to be clear hear, my fuel pressure regulator started acting up and the symptom was a double beep at higher RPMs. It's a diaphragm that deteriorates after a while.

The fuel leak was introduced by the service tech when he accidentally pinched the gasket on the fuel intake into the fuel cooler.

2 different problems, the scary one was caused by the service tech, but it's apparently easy to do on a V-Drive where the fuel cooler is a PITA to get to. I agreed to leave the plastic cover off of it so they wouldn't have to remove the muffler to get to it the next time. The plastic cover really serves no purpose.

I asked about the fuel pressure regulator and was told that at first it will only alarm at higher RPMs, but will eventually fail altogether and your engine will just shut down due to lack of fuel.

I do not think they replaced the entire pump assembly, but I could be wrong. It was about a $280 repair all told. Most of that was labor.

[teachercop]

I experienced similar symptoms last year on my 99 22i with MerCruiser 5.7L 315MPI. We were at Lake Havasu boarding and such where we would ski then stop and swim,,,no problems with the ambient temp 125 degrees (July 4th 2007). Previous posts of this discussion.

We then went to Lake Powell, would board and then shut down swim or eat lunch, 30-60 min later go to fire up and experience a vapor lock condition. Put a fuel pressure gauge on in the lake when it did this and was getting 3 psi (Should be 30psi’ish) During this Powell trip, when it acted up, I took the kids water rifle, sucked some ice chest water, fired the water stream at the fuel pump and problem solved. I felt like M.r Goodwrench on the water to a huge applause. We even went to Havasu and Parker (Tige ReUnion) after and never reproduced problem.

I self determined the fuel pump cooler was no longer cooling the fuel. Soooo not wanting to mess with this, never had any on lake problem in 9 years, I replaced fuel pump and pressure regulator. Currently at Lake Powell, day one, no problem however it has been cooler temps so far.

What I think contributed to my problems (I hope);

• Aged fuel pump (450 hours) weakened at the Lake Powell elevation approx 4000 feet.
• Accumulated debris inline contaminating cooler over the years.
• MerCruiser did redesign fuel pump, no more drain plug (I bummed) and cooler appears slightly different.
• Replacement parts come with directions plus I have the workshop manual which details the R&R, easy swap on DD.