hp500efi

Rewind, was out on Saturday boat up to dock (both motors running fine), 1/2hr later go to leave and port motor cranks, no start...limp home.

Once boat is back at home, I determined that there is no fuel getting into the motor since after cranking and checking the plugs, the plugs were bone dry.

Last night go out to check for fuel flows. Boost pump was removed, checked for any clogging, signs indicate all clear and re-install.

Remove fuel rail from intake and remove a few injectors. Injectors all look clear. I left off (3) injectors and proceeded to turn key to allow boost pump to flow fuel to fuel rail. Cycle key a few times and there is plently of fuel coming out of the fuel rail (where the injectors were removed).

Go to re-install the (3) injectors. Now, with the fuel rail and injectors OUT of the intake, I proceed to turn key again to cycle boost pump to see if I can notice fuel squirting out of the injectors....guess what....NOTHING. I put paper towel under each injector and the paper was dry as a bone.

Something electrical tells the injector to open right? I am now suspecting that something electrical is causing my problem and that now makes more sense since the motor was running fine until I turned off the motor and it would not re-start 1/2hr later. I do not know what to look for now.

Since my starboard motor runs fine, is it OK to remove the ECM and relay pack from the running motor and flop that over to the port motor to see if it will run? I could at least see if that is what is causing the problem and then go from there.

Is there a fuse somewhere? or something else to look for or test that is the gadjit that signals the injector to cycle?

Thanks

Reckless32

Last year I went thru a boost pump on each engine. Best way to tell is to put a fuel injectionpressure gauge (a gauge that connects to the needle valve on the stbd side of the fuel rail) and make sure your getting and maintaining 38-43 psi. If not, then in all likelihood, your boost pump is toast.

http://www.mercruiserparts.com/Show_...and+Boost+Pump

I believe based on all I've read, that mine gulped some pure water during a period when my tank was contaminated and the Ethanol brought o light. The boost needs fuel as a lubricant. Mine basically burnt out as a result of water injestion. Samples of my separator fuel proved mine was trash.

The "boost" supplements the main pump located on the port side amongst the cool fuel area next to the oil pan. Without the boost, you'll only see maybe 32 psi engine off, and a drop to 15-25 when at idle if it will start. Mine started, but idled like crap and would die if placed in gear.

Bottom line, check PSI. Then proceed to more complicated thought.

BTW, the fule pump relays are located next to the ECM. They're those black plasitc things. Amongst them, is a longer thinner one containing small 20 amp fuses. Check those too.

hp500efi

Thanks Rick.

I just purchased a fuel injection pressure gauge kit so I will check it tonight or tomorrow. Hopefully that is the problem as that pump is easy to change.

I will keep you posted .

hp500efi

Port Motor (the one not starting) = 44PSI rail pressure (key on only) settles down to 36PSI

Starboard motor (the one that runs = 44PSI rail pressure (key on only) settles down to 40PSI

Switched ECM modules for giggles and both work so that is not the problem.

Tomorrow I will be switching boost pumps to see if that is my problem.

Oh, checked fuses and those are all good.

superwrench0166

cam and crankshaft sensors. you may want to buy a noid light.
it plugs in your injector wires and flashes when cranked if they getting the corect signal.

hp500efi

Well, I found my problem. Thanks for all the remarks as they helped.

Also helps to have a running motor next to the one that isn't

Switched cam position sensor with running motor...same result.

Switched crankshaft position sensor with running motor and WHALLA, it runs. Here is a picture of the beast. Removing this part is a PITA. Very difficult to get to the bolt, very difficult to get the sensor loose and then very difficult to remove. After a few choice words, I was able to do the swap. Now I have to wait rill Monday to get a new sensor.

RonS

wish I would have seen this earlier Jeff, I had the same problem with my truck when I first bought it, took the dealer 4 tries to get it figured out because mine was intermittent.

Any plans on the fourth, we will probably be heading out somewhere, it will be the first time I get it in the water this summer.

hp500efi

Ron, nothing planned yet...might just stay home and watch the fireworks from my house . We might be off to the river this weekend...just don't know yet.

This part is hard to find, I tried NAPA and they have one that crosses over but after comparing the two, the Mercury one is different enough for me to get one direct from Merc. I will have the part tomorrow and installed tomorrow night.

RonS

If you decide to go somewhere on the 4th let me know, maybe we can hook up.

Reckless32

Congrats on the fix. The learning curve on these 496's has been real steep lately.

The 36psi has me wandering though. Run your PSI test again once you have it started to be sure you're in the 38-43 range, otherwise could be a sign of things to come.