having engine issues.. need a little help, Fuel or ignition. 350 mag mpi

[DirtNasty]

yes im pretty sure its in time... I went ahead and hooked up timing light and it was around 8 degrees at idle of 600 rpm. Moved the the distributor both ways and it never changed a bit. It revs up just fine and will get to max rpm under load fine as well just loses power after running there for a few seconds. Im pretty sure the issue is fuel...as I was in the beginning. Now just what part... lol that is the question. boost pump should be here soon.

[boatwakes]

Glad to hear about the timing. Again, the computer takes care of everything as long as the distributor is mechanically timed within about a 30* range. Boost pump failures cause a surging symptom above about 2800rpm, the engine will surge between 3000 and 2600 or so. Anti-siphon sounds likely especially since you had crappy gas. To rule out fuel pump(s) use a small outboard style fuel tank connected to the fuel filter and see if the symptoms resolve. If so, it's most likely the anti-siphon. Keep us posted.

[DirtNasty]

Update. So I made a few mistakes wording some of my other posts. I did not buy the boost pump I bought the high pressure pump that is located on the cool fuel system. Not the boost pump near the water sep filter. Anyway. Took it out today after installing new pump and same system. Beyond frustrated right now. No only the engine issues but have had issues with a guys who is painting my speakers and tower. I guess next I will do is get a fuel pressure gauge tomorrow and take it back out and check it and see if maybe the boost pump is bad.

[DirtNasty]

Also installed new anti siphon valve

[boatwakes]

Also something I forgot to mention before, those distributor caps are referred to as "crab caps" from the wire orientation and have had internal cracking problems due to heat. Change the cap and rotor and try again.

[whitlock87]

I had the exact same issue on my Marine power engine and my problem tuned out to be a lose wire going to the high pressure fuel pump ( the marine power engines have two fuel pumps in line with each other. One draws from the tank and the other pressurize the fuel injectors)

[DirtNasty]

well took the boat out today with the fuel pressure gauge hooked up and sure enough im losing fuel pressure after a run at high rpm. I am ordering a boost pump (low pressure) that should fix it.

[TeamAllen]

Are you going to order the Mercruiser kit or figure it out yourself with a generic pump?

[IDBoating]

Seems a high pressure fuel pump problem could cause that too, by not being able to keep up with demand on the fuel rail. The more demand from the injectors, the more flow at pressure is required, and if the HPFP can't keep up you'd get exactly this symptom.

I mention this because I am in the middle of helping a friend solve this EXACT problem, and tests show the LPFP is working perfectly with plenty of flow. In his case the effect is most dramatic when hitting maximum acceleration, i.e. trying to pull up a skier from a full stop to ~30MPH. If you accelerate slowly the boat will hit and hold 30 MPH while a HP fuel gauge shows steady pressure, but hit it hard - which requires maximum fuel flow - and the engine sputters and coughs while a HP fuel gauge shows pressure dropping.

In his case the HPFP is driven by the ECU, and its drive circuit isn't pulling the ground side down as far as the manual says it should (likely that the ECU driver is starting to fail). That means the HPFP isn't seeing the voltage it should. We've crafted up an external drive circuit controlled by the ECU which guarantees the pump motor will see full voltage, and the next test drive will reveal if he's done or if a HPFP is needed.

Moral of the story: It may still be the HPFP.

[boatwakes]

For all who have the boost pump and high pressure pump set up: when the boost pump fails, the engine will surge between 2600-3000rpm. When the high pressure fails, the rail will lose pressure and the engine will lose power but not surge.

[DirtNasty]

went with an airtex pump low pressure. runs like a top.

[Ruger761]

Good deal, glad to hear you got it figured out.