496mag no start issue.

[paulswagelock]

So if you fill the fuel filter and it runs for a while and dies, open the fuel canister back up. If empty, then that points to the low pressure side that draws fuel from the tank. That could be the pump, a crack in a fuel line, blocked or faulty anti siphon, blocked screen on the pick up, etc. If it is still full, that points to the high pressure side that pressurizes the fuel rail.

 

[QBhoy]

Hi. As said. Definitely bleed that fuel rail

 

[wjs1820]

So I bled the fuel rail and hooked the cool fuel up to a external tank and it will still only run for 2-3 seconds. I disconnected the hose from the regulator and I got about 6-8 seconds but it ran like crap. This points me at the cool fuel box. I had rebuilt the CF3 last year and it ran great for a while but obviously not running these engines for a few months has caused me more grief.

 

[alldodge]

Need to go back to looking at the 5V reading. If its not seeing exact 5V then nothing going to work right or run.

 

[QBhoy]

Hi. I remember having similar issues working on a 350 mpi. Went through a load of things. Eventually got it running after messing with a few things. One or a combination of them got it going. Not entirely sure which.
I messed with the distributor position (even though you should t have to if it’s between the lines setting). Turned it a mm or two made a difference to it for sure. Made sure it had the right iridium plugs (it didn’t). New battery in it. Cleaned out the fuel delivery system to make sure there was no black paint in it. And I seem to remember something about the fuel pressure regulator too. Perhaps also messed with the relay boxes on top of the engine at the back also.
Oh and I’m quite sure I might have replaced a temperature sensor too. Thinking it was causing it to run too rich or too lean on start up. Can’t quite remember.

 

[wjs1820]

So, a summary of where I am today.
New Battery, New Sierra MAP Sensor, new Mercury MAT sensor. New Iridium spark plugs & New spark plug wires, from last year. Rebuilt cool fuel with new filters and Walbro pumps (low & hi). New box and a new top (pump cover with regulator) sent to me by mercury (post paint issue). Torqued to 100 in/lbs. as per spec. Replaced fuel line flat o-ring with new at cool fuel. Removed and cleaned fuel line then. Confirmed injector pulse with noid light, primed fuel rail. Regulator confirmed works, as removing hose increases fuel pressure. (40 at key on drops to 35 after rail pressurized. Drops to 32 after no start and stays there until I give up). Only runs on starting fluid. (confirmation of spark). DTS wont allow me to spray continuously and I dont want to. I'm in fresh water SC ICW. Exhaust manifolds 3 years old. I have a Rhinda tool and a fuel rail pressure gage. I have 5v on Sensor 1 & Sensor 2. 13.6v on battery, MAP and MAT sensors are reading properly. (500 hours on the engine). No codes other than lake temp and pitot, which are BS codes). All connections to computer and grounds are checked and clean. Fuel isn't fresh but I drained the tank last year, when I replaced the fuel pick up and cleaned ASV (confirmed proper function). Same non-ethanol Fuel runs the kohler EFI generator with no issue. The only thing I haven't done is remove the fuel rail and injectors but how on earth would all the injectors fail at the same time? Keep in mind this engine ran perfect in June last year with an ACDelco MAP sensor. The IAC is built into the throttle body and I swapped it from the other motor that runs fine with no change to either motor. Also to note, I swapped out the Quantum fuel pumps that were in the CF3 from my first rebuild. Using a new low pressure and a good used hi pressure. I'm hearing fuel pull from the tanks, which I wasnt hearing before (Progress?). Unless anyone has a better idea, I'm leaning towards cleaning out the fuel rail, more or less to scratch that off the list. Probably check fuel injectors too while I'm in there.

 

[alldodge]

You bleed the fuel rail
Fuel pressure is good enough to start
NOID light shows injectors (assuming more then one injector checked} are firing.
You have spark (will hit with starting fluid)

Need spark, fuel and compression to run

So either your loosing spark or fuel

Seeing 0-degrees would indicate ECM isn't seeing pulse from Crankshaft sensor (rear of motor) and/or Cam sensor (front of motor). Do you see the Tach increase in RPM when cranking?

 

[wjs1820]

You bleed the fuel rail
Fuel pressure is good enough to start
NOID light shows injectors (assuming more then one injector checked} are firing.
You have spark (will hit with starting fluid)

Need spark, fuel and compression to run

So either your loosing spark or fuel

Seeing 0-degrees would indicate ECM isn't seeing pulse from Crankshaft sensor (rear of motor) and/or Cam sensor (front of motor). Do you see the Tach increase in RPM when cranking?

Yes, it's cranking at 130 rpm

 

[alldodge]

Yes, it's cranking at 130 rpm

Not enough RPM to build compression high enough to fire so ECM even if it want to send spark, not much would happen. Should see at least 5 to 600

Measure voltage at starter post and then at engine breaker while cranking. Voltage may be dropping to low so ECM can not function

 

[dubs283]

Yes, it's cranking at 130 rpm

PCM needs to see 300 rpm at cranking to start/run the engine

I'd swap cps from good running engine to troubleshoot

 

[wjs1820]

PCM needs to see 300 rpm at cranking to start/run the engine

I'd swap cps from good running engine to troubleshoot

I've done the Cam sensors before. No change and the good motor (port) still ran with the cam sensor from the starboard side. I've changed the crank sensor on the port motor years ago and it was a bear! Really hoping it's not that. Is there a way to test it. I assumed that seeing rpm confirms it works but I do have a fluke, if there's a better way.

 

[QBhoy]

So my thinking is that it can start with fluid but not by injecting fuel, may mean that you are losing a defined or steady supply to injectors. Can’t remember if you said or not, have you tested injectors manually with a voltage to them ? You’d imagine that something I’d maybe not allowing them their 5v supply (think that’s what they meant to get)
Also wonder if something from the fuel supply system has found it’s way to the injector rail and blocking things up a little ? Think I’d be removing the injector rail for a look…if you haven’t already

 

[wjs1820]

So my thinking is that it can start with fluid but not by injecting fuel, may mean that you are losing a defined or steady supply to injectors. Can’t remember if you said or not, have you tested injectors manually with a voltage to them ? You’d imagine that something I’d maybe not allowing them their 5v supply (think that’s what they meant to get)
Also wonder if something from the fuel supply system has found it’s way to the injector rail and blocking things up a little ? Think I’d be removing the injector rail for a look…if you haven’t already

I'm starting on the rail now. I swapped cam sensors again to confirm. No change, starts fine on the good port motor.

 

[QBhoy]

I'm starting on the rail now. I swapped cam sensors again to confirm. No change, starts fine on the good port motor.

Ok. In that case…I’d be swapping over the pump relay from the other engine to try. If you haven’t already.

 

[wjs1820]

That's what came out of my fuel rail... if that's not the problem. It definitely needs to be cleaned and fuel injectors. I'm stunned!

 

[alldodge]

POST 1
Had an issue last year with the cool fuel 3, which I replaced that turned out to be multi layered. (Bad fuel- so I drained tank, replaced fresh but in April and all ethanol free). Replaced fuel tank pick up tube and everything was running perfect.

POST 26
Rebuilt cool fuel with new filters and Walbro pumps (low & hi). New box and a new top (pump cover with regulator) sent to me by mercury (post paint issue). Torqued to 100 in/lbs. as per spec. Replaced fuel line flat o-ring with new at cool fuel. Removed and cleaned fuel line then. Confirmed injector pulse with noid light, primed fuel rail

That is a lot of crud and dirty fuel
Will need to have injectors cleaned and flow tested

 

[wjs1820]

Any recommendations on who to send them to?

 

[alldodge]

Either
https://www.boatunlimited.com/marine-fuel-injector-flow-testing-cleaning/
or
https://www.mercruiserparts.com/filterSearch?q=injector cleaning

 

[QBhoy]

Think that crap is out the cool fuel module inners ?

 

[wjs1820]

I think so, I found quite a bit of paint chips, which corresponds with the cool fuel paint issue.
Current update: Cleaned all injectors in my ultrasonic jewelry cleaner 30 min bath followed by a second in clean fuel injector cleaner. Then cleaned inside to confirm flow with fuel injector pulse/ cleaning kit. Replaced all the O-rings. Confirmed internal screens were clean as crystal. The rail was more difficult. I needed to clean it with spray fuel injector cleaner and blew it out with compressed air a few times. I got alot of crap out of it. I'm reinstalling today. Wish me luck.