350 MPI suddenly Cut Out at 3700 rpm.

To change the fittings requires using a tap to cut threads into the housing. Others have done it with success.
I had a very similar situation this year, and it ended up my cool fuel module was failing - same symptoms but happened at 4400 rpm.
Put a pressure gauge on the fuel rail - no pressure. I decided to replace the whole unit rather than try to R&R the old one. $900 later the boat runs perfect.
Do you mean the high pressure pump failed - I think these units have both a high pressure and a low pressure pump. If so then would the engine still start at idle?
 
Without the proper tools it will be very difficult, not a lot of material there. Hand held drill isn't going to work, hole needs to be cut slightly off center. No bracket needed.

water in the fuel area indicates a breach in the wall
 
Update, I have repaired the cool fuel unit connections, much stronger than original and I will start another thread with pictures of what I did - it can be added to the many others.

Update - still will not fire, I have a spark at the coil, I have 43 psi at the Schrader valve on the rail, I see no fuses blown (tho not sure if I have checked all of them), I have no smart craft alarms except the Port engine Low Spd Data Loss - which I get when I try to crank for too long. Where do I go next?

My mechanic with his diagnostic is still out a ways, though he may feel bad and get here earlier.
 
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Did you have paint flakes in the system?
Did you clean the upstream filter?
Purge the system of air? It could be 43 psi of air
 
43 psi sound a little low I might be wrong but 65 psi. is the norm.If you have a bad crank sensor or out of time you will still get spark at the coil but it will not be in time.You can see if it will run on starter fluid spray but be careful when doing that have a fire extinguisher near by .If it fires right up on starter fluid and runs its a fuel problem.
 
Did you have paint flakes in the system?
Did you clean the upstream filter?
Purge the system of air? It could be 43 psi of air
It is Purg3d, my fuel gauge has a purging nipple. All three filters replaced.
 
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38-42psi is the norm operating range pressure that I have read and mine tests at 42psi (4.3l MPI) so it all sounds good. And I would assume if you're using a fuel pressure gauge, when you purge it, you'd see good fuel flow in the plastic purge line on the gauge, to know its not just air... Try a spark plug tester at the head of a plug...otherwise, has me stumped!
 
43 psi sound a little low I might be wrong but 65 psi. is the norm.If you have a bad crank sensor or out of time you will still get spark at the coil but it will not be in time.You can see if it will run on starter fluid spray but be careful when doing that have a fire extinguisher near by .If it fires right up on starter fluid and runs its a fuel problem.

39-43 psi is what I think I should have at the rail. If the crank sensor is gone usually you can tell on the gauge as it will not move when cranking, my gauge is alive at 7-100 rpm when I crank.

I am going to pour a cup of fuel directly into the engine as my next step to see if I can get it to crank from there.

Anyone know where the injectors fuse is?
 
BTW - for the hell of it changed the IAC and both relays over from starboard engine also, no change.
 
Anyone know where the fuse or relay is located for the injectors, I cannot find it in my manual.
 
someone on e-bay was making the fittings for the old style out of stainless with an o-ring but its still a flawed design - you can get just the new (updated) style housing with the threaded bosses for $200 or so and re use your pumps, filter housing, etc. You don't need the hose kit they try to sell you, there is enough hose if you bust the remainder of the plastic fittings out instead of cutting the hose. I have heard about numerous 320s having a problem with the wiring harness resulting in blown fuel pump relays (they are on top of the motor) usually, when one blows you can see evidence of it around the pins. When you click the ignition switch to the first position do you hear the lift pump energize? When your cranking it have you put a fuel gauge on it? Lastly, there are many threads about cool fuel III on here if you search. Good Luck
 
When you press on the schrader valve, gas comes out, correct?
 
someone on e-bay was making the fittings for the old style out of stainless with an o-ring but its still a flawed design - you can get just the new (updated) style housing with the threaded bosses for $200 or so and re use your pumps, filter housing, etc. You don't need the hose kit they try to sell you, there is enough hose if you bust the remainder of the plastic fittings out instead of cutting the hose. I have heard about numerous 320s having a problem with the wiring harness resulting in blown fuel pump relays (they are on top of the motor) usually, when one blows you can see evidence of it around the pins. When you click the ignition switch to the first position do you hear the lift pump energize? When your cranking it have you put a fuel gauge on it? Lastly, there are many threads about cool fuel III on here if you search. Good Luck


Thanks - you can see in earlier posts in this thread what I have done. I have repaired the cool fuel unit, a much more robust repair which I will post on a seperate thread once I get the engine fixed.

I get the pump energized on first switch, I have 39-43 psi at ten Schrader valve, I have bled all air out of the system. I have swapped out all relays and th fuses I am aware of, I have changed th IAC (yes I know should not have been an issue but I changed it anyway).
 
When you press on the schrader valve, gas comes out, correct?
Yes, also I have a fuel gauge on the Schrader right now. I have bled the air out of the system via the bleed on the gauge.
 
Are you Getting spark at the plugs?
Ignition module
Pickup coil
I get a spark at the coil, just in case I have swapped coils - no change.

When you say ignition module, what is that? This is the HT unit I changed over from other engine.

image.jpg
 
Have you tried spraying the intake with carb cleaner or some fuel, and seeing if it fires for a second or two. If yes, fuel issue, if no, spark issue.
 
I get a spark at the coil, just in case I have swapped coils - no change.

When you say ignition module, what is that? This is the HT unit I changed over from other engine.

View attachment 41452[/QU
https://www.mercruiserparts.com/Sho...=40&bdesc=Distributor+and+Ignition+Components
Number 6 in the picture.
You said the motor just shut down which sounds like an ignition problem.
If it was a fuel problem motor would have spit and sputtered before it shut down.
 
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Update - my mechanic got there. Zero, nada, nothing at all on the diagnostic.

Before he arived I squirted fuel in, and got a back flash so sparks are good.

He is also stumped - and this is a really good mechanic, well known in the area. I know I have pressure at the fuel pump but now I am going to change the pump and regulator tomorrow. Grasping at straws here.
 
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