Fuel System Problem

[ghollow]

I own a 1998 PRE2200i with the a Mercruiser 350 MAG MPI engine. I am having a problem with air getting into the fuel line. It happens everytime that I have been running the boat for a while and shut it off for 30 minutes to an hour. When I go to restart, the first time I hit the throttle it bogs out. I then have to bleed the air off the fuel rails with the schrader valve. Once the air has been bled off, it runs great until the next time I shut it down. It does not do it on a cold start first thing in the morning, just after the engine has been warmed up and shutdown for a while.

I have checked for leaks. My fuel filter is tight. The fuel pump seems to work fine. One mechanic I talked to said that he thinks that the fuel is vaporizing in the line and causing a "vapor lock" situation.

Anyone else had this type of problem? If so, how did you solve it?

Thanks in advance for your help

[fleetpaint]

check to keep all fuel lines away from heat.(exaust manifolds,intake manifolds)

[dogbert]

Try running your blower for a bit before starting the engine. If it is vapor lock, then this should help cool the engine compartment so that you're not boiling your fuel. I've had to do this a few times this summer because of the heat.

One other potential issue is that your fuel pressure regulator is starting to go. It's attached to the outbound side of the fuel cooler. Mine went out last year. I did get intermittent alarms at higher speeds, but your engine is older so maybe it's not doing that. My dealer had to check the codes to determine if this was the problem. Is your engine an MPI?

[jchurch6713]

ghollow,

I strongly recommend that you do not bleed the shrader valve because that is not air but extremely flammable vaporized fuel. I am currently having the exact same problem and I have a fuel pressure regulator on the way. Once I get it installed, I will let you know if it eliminates the problem. If not, the next step is to replace the fuel pump and cooler. You have to buy these two parts as a unit. A temporary fix is to run the blower or open the engine compartment and allow it to cool. One owner has suggested carrying a cheap watergun and spraying the fuel pump with water from the ice chest when it happens. Let stay in touch and get this issue resolved on both our boats. I'll keep you updated but the pressure regulator did not seem to be in stock so it may take a while for me to get it.

[ghollow]

My engine is an MPI. I have removed the fuel pump on the side of the cooler. It appears to be working fine. It kicks on for a few seconds when you turn the key and runs continously while the engine is running. I always run my blower for a few minutes or lift the engine cowling before I start the engine. All of the fuel lines are in their original positions. I have never re-routed them. I have owned the boat for eight years. This is the only engine problem I have had with it. It just started doing this over the July 4th weekend. It has been running fine up to that point. I had probably already put 50 hours on it this summer prior to July 4th.
I may try changing the fuel filter also. I changed it at the end of last summer as part of my winterizing process. Maybe I got a load of dirty fuel and the filter is causing the problem.

[ghollow]

jchurch6713,

Did your boat just start doing this suddenly?
Is the cool fuel system supposed to keep this from happening?

Due to other things going on in my life I have not been able to spend any time investigating the problem. I do not keep my boat at my house, it is two hours away. I probably will not use my boat again until Labor Day weekend. My mechanic said that he would let me borrow a fuel pressure guage to see if the pump is keeping the fuel rails fully pressurized. He said that it should stay at around 30 psi. If not, he suggested that I replace it.

[R&T Babich]

... He said that it should stay at around 30 psi. If not, he suggested that I replace it.

Ours runs great at around 22 psi at idle and slow cruise.

[TeamAllen]

A lot of us went through this last year. There are a couple of extensive threads about this. Good luck. My fuel pump was working also, but since I replaced it with a new cooler assembly and new anti-siphon valve, the problem has not returned.

http://www.tigeowners.com/forum/show...ight=fuel+pump
http://www.tigeowners.com/forum/show...hlight=bad+day

[ghollow]

Thanks Everyone,

This gives me plenty of things to check out.

[jchurch6713]

jchurch6713,

Did your boat just start doing this suddenly?
Is the cool fuel system supposed to keep this from happening?

Due to other things going on in my life I have not been able to spend any time investigating the problem. I do not keep my boat at my house, it is two hours away. I probably will not use my boat again until Labor Day weekend. My mechanic said that he would let me borrow a fuel pressure guage to see if the pump is keeping the fuel rails fully pressurized. He said that it should stay at around 30 psi. If not, he suggested that I replace it.

Yes, I have never had this problem before until this year. I have had a similar problem in the past but it turned out to be water in my fuel. I siphoned the tank and changed the filter and had no more problems. I have read several of the older threads and I am pretty sure that it is vapor lock and your problem sounds exactly the same, especially if bleeding the air gets you back underway. The last time it happened to me we opened the engine compartment, I removed the fuel filter and it was no quite full (about 1" from top of filter.) We sat for a while hoping that we would not have to get towed (never fun although it is inevitable) and after running the blower, letting the engine cool, and cycling the key on and off to reprime the fuel filter we got back underway. The boat did sputter a few times at first then it ran flawlessly all the way back to the ramp. Like you I only have the problem when I run for a while, then sit for 30 min - 1 hr. My thinking is that the pressure regulator is allowing pressure to bleed off while sitting and allowing the fuel to vaporize, then the fuel pump can't get fuel to the injectors. I realize that I may have to replace the entire pump and cooler but I figured the pressure regulator was worth a try b/c it is only $90 versus $300+ for the pump and cooler. There was also another owner who had this problem and the dealer installed a new pressure regulator and he has not had a repeat episode. I hope the same is true for both of us.

[dogbert]

My thinking is that the pressure regulator is allowing pressure to bleed off while sitting and allowing the fuel to vaporize, then the fuel pump can't get fuel to the injectors.

You've nailed the issue on the head. The fuel pressure regulator has a diaphragm that's just a membrane and it will deteriorate after a while, usually 8-9 years. After a while it fails completely and no fuel gets to the injectors.

[ghollow]

It all sounds good guys.

Sounds like I may need a new pump/regulator. I do not see the need to replace the cooler system. It may need cleaning or flushing out, but unless it is leaking, I do not see the need in replacing it.

Thanks again for everyone's help

[illiniboarder88]

well guys, I was hoping it was the regulator, but that didn't take care of the problem. I just ordered a pump. Hopefully that does it. My pump is kicking out the right pressure intermittently. I'll get it running, and if I hold the pump, you actually feel it cycle off after a while. Kind of weird. Probably a short or something in it.