Weekend from hell...Need a fuel pump

[jleger98]

J,

Is your engine carb'ed or F/Injected?

EFI

[jleger98]

Is it very hot out when this is happening? Is it running fine when the temps are lower? It sounds like too much fuel when the temps are high. Check a spark plug when it's running good and again when it's not. Is your engine "throttle body injected"? Our 2000 350 Mag MPI is distributed injection. Our sends a vacuum signal to the fuel pressure regulator which I think causes it to bleed off fuel when the RPMs are low and allows max pressure at higher RPMs. One reference I read stated it is connected to "manifold vacuum" which is high at idle and low at WOT. I need to test it find out for sure. A leaking hose may give you max pressure all the time. "Wet" plugs will tell you if there's too much fuel.

Yes it is connected to the throttle body by vacuum line. I didn't think to check if plugs were wet.

when regulators go bad, do they go gradually, or all at once?

[spharis]

Yep, run it wide open down the lake, stop it kill it, and pull a plug fairly quickly. Also check the plug coloring. There was a really good website somewhere with this info, I'll see if I can find it when I get a chance.

[jleger98]

It was not particularly hot out when this happened. high 80's maybe.

SP, I'll try that....maybe I can go out for a test run tonight.

For what its worth, the plugs only have about 20 hours on them....they were brand new this spring.

[R&T Babich]

The picture I just saw of our regulator at Go2Marine, #77382, $96 http://www.go2marine.com/product.do?no=77381F, shows a vacuum can on the side similar to those that control car heater doors. If it's like yours it would have a rubber diaphragm in there that may have issues with heat. Mine is in a plastic housing out of sight. Our engine has fuel rails and a port to measure fuel pressure. If you could hook up a fuel pressure gauge and a brake bleeder vacuum pump to the regulator vacuum line you should see changes in the fuel pressure at idle. Just pulling the vacuum line on/off at idle might work, too. I'll have to try this on ours sometime to see what happens.

[jleger98]

Yep, thats the bad boy right there. I wish I had a pic, but the vacuum line on mine runs directly from that regulator to the base of the throttle body. No canister. If I can get out to the lake tonight, I'll try to run it with and without that vacuum line connected. Although, I'm not entirely sure what that will tell me.

[chpthril]

Is it very hot out when this is happening? Is it running fine when the temps are lower? It sounds like too much fuel when the temps are high. Check a spark plug when it's running good and again when it's not. Is your engine "throttle body injected"? Our 2000 350 Mag MPI is distributed injection. Our sends a vacuum signal to the fuel pressure regulator which I think causes it to bleed off fuel when the RPMs are low and allows max pressure at higher RPMs. One reference I read stated it is connected to "manifold vacuum" which is high at idle and low at WOT. I need to test it find out for sure. A leaking hose may give you max pressure all the time. "Wet" plugs will tell you if there's too much fuel.

You are correct, the fuel pressure reg is controlled by engine vacuum. It's function is to increase the fuel pressure to compensate for the drop in manifold vacuum.

The usual increase is about 7 to 10 psi. I dont know that this would be enough to cause any extreme symptoms. May run a little rougher at Idle but not to the point of stalling and/or not starting

EFI

I should have asked all at once, sorry but, is it T/body or port injected.

Throttle body - if it has a regulator, it may be part of the t/body and makes diagnosis harder.

Port injected - the regulator will be at the end of fuel rail right before the return line and will have a vacuum hose attached to it.

First, pull off the vacuum hose and check for raw fuel inside. This is an indicator that the diaphragm has split and the reg need replaced.

Next, with a fuel gauge attached, start and idle engine. Pull off vacuum hose and look for the pressure to increase and then drop back when the hose is reinstalled.

Yes it is connected to the throttle body by vacuum line. I didn't think to check if plugs were wet.

when regulators go bad, do they go gradually, or all at once?

The most common failure is a split diaphragm which will result in an extreme rich condition and stall the engine at idle and make it hard to start.

Your problem does sound fuel related.

[jleger98]

You are correct, the fuel pressure reg is controlled by engine vacuum. It's function is to increase the fuel pressure to compensate for the drop in manifold vacuum.

The usual increase is about 7 to 10 psi. I dont know that this would be enough to cause any extreme symptoms. May run a little rougher at Idle but not to the point of stalling and/or not starting

I should have asked all at once, sorry but, is it T/body or port injected.

It has the vacuum coming off the regulator and the regulator is down by the fuel pump/cooler, so I guess that makes it port injected.

Throttle body - if it has a regulator, it may be part of the t/body and makes diagnosis harder.

Port injected - the regulator will be at the end of fuel rail right before the return line and will have a vacuum hose attached to it.

First, pull off the vacuum hose and check for raw fuel inside. This is an indicator that the diaphragm has split and the reg need replaced.

Next, with a fuel gauge attached, start and idle engine. Pull off vacuum hose and look for the pressure to increase and then drop back when the hose is reinstalled.

Where can I get one, where do I hook it up etc?

The most common failure is a split diaphragm which will result in an extreme rich condition and stall the engine at idle and make it hard to start.

Your problem does sound fuel related.

[R&T Babich]

chpthril - in one of jleer98's earlier posts he mentions a hesitation at 2000 RPM. Ours runs great and usually we'll run the RPMs up to 3000-3200 when pulling up a skier. If I don't get the throttle set right and start pulling at 2000-2200 RPM there is a loss of power. Any thoughts? Is there some switch-over point around that RPM? On carbs there's a transition from idle circuit to primary.

[jleger98]

This weekend, with the additional ballast we were pulling at about 2900 and having the same issue.

The thing that puzzles me is that it eventually went away.

Is it possible that if you get too much water in the bilge that it starts steaming off the oil pan and then that moist air gets sucked into the air intake essentially creating water in the gas mixture?? It seems like when we load up the rear port corner, the bilge cannot pump because the hole it comes out is then below the water line.....and maybe water even comes in.

The first time this happened, at least this weekend, was when we were riding on that side. Once we emptied the bags, I flipped the pump on and it ran for a good 3-4 mins.. when I opened the engine cover, there was condensation everywhere except for the warm parts of the engine.

My engine cover does not have a vent like my old boat did. The other thing I thought of is if the blower hose gets water in it, that makes the blower that much less effective at removing that moist air.

[R&T Babich]

I have this gauge from Harbor Freight - http://www.harborfreight.com/cpi/cta...emnumber=92699.
I haven't had to use it, but my friend borrowed it to check his Wakesetter.
There should be a valve on the fuel rail that looks like a tire valve to hook it up.

[jleger98]

ok, so I should be able to just get one at a local auto parts store, right? Nothing really marinized about it?

[R&T Babich]

Right, nothing "marine" about it. I bought for testing my cars. I thought about finding just a gauge I could screw into the pipe thread fitting at the ends of the fuel rails, but it's hard finding one for gas, most are for air/water.

[jleger98]

I don't think I have fuel rails. I'm assuming there is something that I can attach in to.

[jleger98]

So after a lot of digging and some help from Anhaney, we discovered that MercCruiser recommends that if you replace the fuel pump and cooler, you should replace the fuel regulator too. Thats where I'll start and see if it fixes the problem.