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View Full Version : 2001 350 MAG MPI Half of cylinders not firing, no fuel?


PolarBear
06-21-2011, 11:12 PM
Looking for help on my inboard engine. It appears half of my cylinders are not getting gas (starboard side). Barely made it to the landing last fall to put boat away and didn't look at it all winter.

Here is what I've tried:

Cleaned off cap and rotors before I even started it up (Had to take off a lot of corrosion on the cap wouldn't come off with emory cloth, needed a dremel sanding tool). I'm going to replace the cap, but haven't yet.


Started engine and friend pulled off 3 or 4 plugs from the distributor and engine didn't change a sound. They were all from the same side of engine. I was getting a spark to those wire, shocked my buddy a couple times pretty nice. :)


Sprayed some starting fluid into air intake on top, and cylinders appeared to kick in and fire


Read somewhere that there are 2 drivers for the fuel for each side. Checked the wiring harness and computer to see if any pins were bent or pushed back, could see none.

Are there fuses somewhere for these drivers that would go bad? Are there any other simple checks? Any other thoughts or threads that already covered this? Thanks!

Jerseydave
06-22-2011, 07:07 PM
Looking for help on my inboard engine. It appears half of my cylinders are not getting gas (starboard side). Barely made it to the landing last fall to put boat away and didn't look at it all winter.

Here is what I've tried:

Cleaned off cap and rotors before I even started it up (Had to take off a lot of corrosion on the cap wouldn't come off with emory cloth, needed a dremel sanding tool). I'm going to replace the cap, but haven't yet.


Started engine and friend pulled off 3 or 4 plugs from the distributor and engine didn't change a sound. They were all from the same side of engine. I was getting a spark to those wire, shocked my buddy a couple times pretty nice. :)


Sprayed some starting fluid into air intake on top, and cylinders appeared to kick in and fire


Read somewhere that there are 2 drivers for the fuel for each side. Checked the wiring harness and computer to see if any pins were bent or pushed back, could see none.

Are there fuses somewhere for these drivers that would go bad? Are there any other simple checks? Any other thoughts or threads that already covered this? Thanks!

Look inside the dist cap.....do you see any carbon trails? (black lines in the plastic going from one post to another)
If you have coil pack ignition instead of a distributor, you may have a bad coil pack.

JimN
06-22-2011, 07:20 PM
Looking for help on my inboard engine. It appears half of my cylinders are not getting gas (starboard side). Barely made it to the landing last fall to put boat away and didn't look at it all winter.

Here is what I've tried:

Cleaned off cap and rotors before I even started it up (Had to take off a lot of corrosion on the cap wouldn't come off with emory cloth, needed a dremel sanding tool). I'm going to replace the cap, but haven't yet.


Started engine and friend pulled off 3 or 4 plugs from the distributor and engine didn't change a sound. They were all from the same side of engine. I was getting a spark to those wire, shocked my buddy a couple times pretty nice. :)


Sprayed some starting fluid into air intake on top, and cylinders appeared to kick in and fire


Read somewhere that there are 2 drivers for the fuel for each side. Checked the wiring harness and computer to see if any pins were bent or pushed back, could see none.

Are there fuses somewhere for these drivers that would go bad? Are there any other simple checks? Any other thoughts or threads that already covered this? Thanks!

That's TBI, right? If so, go to AutoZone and borrow a set of noid lights. They snap into the injector wire clips and will flash when the ECM tells them to fire. Have you looked at the injectors when the engine is running? If the fuel spray alternates from one side to the other all the time, I would bet that the ECT (Engine Coolant Temperature) sensor is telling the ECM that the engine is overheating.

Table Rocker
06-22-2011, 07:47 PM
I think you have multi-port injection (MPI), I would guess the first thing you should do is check the fuel pressure at the service valve located on the fuel rail crossover. You will need a fuel pressure test gauge (http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_Fuel-Pressure-Tester-Kit-Actron_9030328-P_N3065_A%7CGRP2020A___) which is available at your parts store.

PolarBear
06-22-2011, 09:32 PM
Thanks a bunch for the replies. However, you confuse me when you ask me questions that I think I already put down (350 mag MPI engine, cleaned distributor cap). Can you have a TBI on a MPI engine? Jersey said look at my cap then said if you have a coil pack ignition, can you have both?

I loaned a set of noid lights, but not sure if they are going to work on MPI? Do auto stores loan fuel pressure gauges? I see the service valve and know exactly what you are talking about. I'm guessing if it's good on the one side, the pressure is equal on both sides of the fuel rail?

Thanks again everyone.

JimN
06-22-2011, 09:52 PM
Thanks a bunch for the replies. However, you confuse me when you ask me questions that I think I already put down (350 mag MPI engine, cleaned distributor cap). Can you have a TBI on a MPI engine? Jersey said look at my cap then said if you have a coil pack ignition, can you have both?

I loaned a set of noid lights, but not sure if they are going to work on MPI? Do auto stores loan fuel pressure gauges? I see the service valve and know exactly what you are talking about. I'm guessing if it's good on the one side, the pressure is equal on both sides of the fuel rail?

Thanks again everyone.

The coil packs don't have anything to do with how the fuel is delivered but direct injection tends to like hotter spark for complete combustion.

Does your engine have what looks a bit like a carb on it? Why not post some photos? It's not an engine MC has used in their boats and not all of us are familiar with it. I saw them in Malibu boats but don't remember the details.

AutoZone has tools for loan.

Table Rocker
06-22-2011, 09:54 PM
Do auto stores loan fuel pressure gauges? I see the service valve and know exactly what you are talking about. I'm guessing if it's good on the one side, the pressure is equal on both sides of the fuel rail?

Thanks again everyone.I don't know if they loan the gauges or not, but I would call them. The valve is on the crossover and should represent the pressure of the entire rail (both sides). There is a fuel pressure regulator near the valve that could be something to look at if you have fuel pressure problems. I think your fuel pressure should be in the neighborhood of 40 psi.

PolarBear
06-22-2011, 10:04 PM
No, there is no carb on the top. Just a big air intake. I would add a pic but I don't know how. It says to put the URL of the pic and I don't know how to do that yet.

PolarBear
06-23-2011, 10:10 PM
Guys, I put a fuel pressure gauge on my rail and at idle it only reads 24-26 psi. When it's cold and I turn the key, it temporarily goes up to 32, but then drops down once the fuel pump stops buzzing. I've read that this engine should be at least 37psi and I've seen people with psi at

Also, I put noids on my injectors and I got a good signal to all injectors. Am I dealing with a fatiguing fuel pump or do they either work or don't work at all.

mtajpa
06-23-2011, 10:26 PM
I would suggest you pull the plugs on the side you say is not getting fuel. If the injectors are plugged then the spark plugs will be bone dry. Also the exhaust manifold will not be warm as the is no combustion taking place. I am speaking from experience here not just guessing. I purchased my MC as a project and after replacing the frozen fuel pump I got the engine running not well mind you and what I actually found was there was carbon covering the tips of the injectors causing them to be plugged. Starboard 4 cylinders firing and port was completely cold. Injectors could be heard firing but spark plugs were bone dry.

The cure was to remove the injectors and fill them with carb cleaner let them set with the carb cleaner in them. then take compressed air and pressurize the injector. While your pressurizing the injectors apply 12 vdc (I used a car battery) and energize the injector. The first 1 or 2 times in energized the injector the spray pattern was a dribble after the third try the pattern was a perfect cone shape.

reinstalled the injectors and presto all 8 cylinders firing and both exhaust manifold even temp.

This fixed mine hope my idea helps.

Table Rocker
06-23-2011, 10:58 PM
Guys, I put a fuel pressure gauge on my rail and at idle it only reads 24-26 psi. When it's cold and I turn the key, it temporarily goes up to 32, but then drops down once the fuel pump stops buzzing. I've read that this engine should be at least 37psi and I've seen people with psi at

Also, I put noids on my injectors and I got a good signal to all injectors. Am I dealing with a fatiguing fuel pump or do they either work or don't work at all.
It might be your fuel pressure regulator. It is on the starboard side of the crossover, near the pressure valve.

It is part #13 on the diagram here (http://www.boats.net/parts/search/Merc2/Mercruiser/350%20MAG%20MPI%20SKI/0W690000%20THRU%201A089999/Intake%20Manifold%20And%20Fuel%20Rail/parts.html). It is about $100 for the part.

The first thing I would do is change the fuel filter(s). Then I would look at the condition of the injectors and look into the fuel pressure regulator.

Table Rocker
06-23-2011, 11:13 PM
You can download a service manual here:
http://www.4shared.com/document/Pss92fbC/Service_Manual_24.html

It is supposed to have a troubleshooting section. Good luck!

PolarBear
06-23-2011, 11:15 PM
Oh, I should have mentioned, I fired it up tonight and it sounds like all cylinders were firing. Only thing I really did was pull some fuses and look at them and put them back in, and also removed one relay looked at it and put it back together. Both manifolds felt warm, although there was a time when one was cold and the other was warm, but that went away. The thermostat was really opening and closing a lot for the first 3-4 minutes. Temp was going to 150 then down to 125, then back up to 150. After 7-8 min it settled at 175. Maybe the fake a lake doesn't supply enough water so I don't know how much that could play with it.

Idling definitely does not sound smooth however. RPM was at 600 but it's not a nice hum. Also, should I be smelling a light gas smell out of the exhaust? Maybe that's normal, I don't usually have my car sitting in my garage running with the doors open for that long (10 min).

JimN
06-24-2011, 08:27 AM
Oh, I should have mentioned, I fired it up tonight and it sounds like all cylinders were firing. Only thing I really did was pull some fuses and look at them and put them back in, and also removed one relay looked at it and put it back together. Both manifolds felt warm, although there was a time when one was cold and the other was warm, but that went away. The thermostat was really opening and closing a lot for the first 3-4 minutes. Temp was going to 150 then down to 125, then back up to 150. After 7-8 min it settled at 175. Maybe the fake a lake doesn't supply enough water so I don't know how much that could play with it.

Idling definitely does not sound smooth however. RPM was at 600 but it's not a nice hum. Also, should I be smelling a light gas smell out of the exhaust? Maybe that's normal, I don't usually have my car sitting in my garage running with the doors open for that long (10 min).

A boat won't run as lean as a car and live for long because boats are run at higher RPM, so they run a bit rich. However, you might want to do a compression test (at normal operating temperature, without fuel- remove the fuel pump fuse). Did you look at the spark plugs after running it the last time?