502 MPI wont start!!!
 

Just mounted the motor in the boat and it ran fine on the hose.

From the beginning it wouldn't rev more than 1800rpm under load, but now it wont start or ignite at all...

I have spark and the plugs gets wet so I know I have fuel.

I have topped off the fuel filter and put the tank hose in a bottle and the fuel pump sucks fuel and returns to the filter.

I will try to get my hands on a scan tool, but it seems hard to find any.


Does anyone have any ideas how to get it running???

Can a air pocket in the fuel rail cause this?!

Can a faulty tach cause this?

Can a fualty wiring harness cause this?

We need to know a little bit more about your setup- what year 502MPI do you have? If it is a mid 90's VST system- there are a couple of things you can check really easily. Fuel pressure would be a first thing I would check- there should be a schrader valve at the end of the fuel rail if I remember correctly. On my old Rinker we had lots of problems with the fuel system, it had the old cool fuel setup that ran off of the seawater pump, and it never seemed to work that well. I bought a block off plate for the seawater pump, and ran a Aeromotive Marine A1000. That seemed to solve all my issues.
Let me know if I can give you any other ideas- good luck:cool:

I believe it's a 2000, it has the short and narrow injectors.

What I can't understand is that the plugs get's wet and the spark is strong but it doesn't ignite what so ever.:hitfan:

my guess would be a bad water temp sensor or air temp switch. if the water temp sensor is bad or the wire is off, the motor starts wildly rich and stays that way and washes the plugs out nearly instantly. you need a scan tool ( which you should own if you are going to keep the motor) and the factory workshop manual ( not the aftermarket)

you didn't leave the tstat out did you ? because that will do this as well.

Is the distributor set correctly? How did you set the timing?

Also I had a 502 EFI that acted like that after a rebuild. There is a magnet on the distributor shaft that had cracked and the motor would spit and sputter and would not run well if at all.

I haven't touched it at all. It ran flawless on the hose but if something is loose in the distributor it would definately be acting up, I will check!

Thanks!

Fuel pres at just above 40PSI and it cough's once when it has been sitting for a while and then nothing.

A friend of mine has been trying to get it running since I'm out of town and he has checked all wiring, fuses etc and everything looks good.

The spark plugs still gets wet immediately so I'm guessing the temp sensors or something else that wahes out the plugs.

I will have it tested with a scan tool next week.

It's a silly suggestion but have you verified the kill switch isn't flipped.