JLANE

I need some help. I have a Fountain with twin 502's. These engines have fuel injected B&M 250 Blowers. The starboard engine runs great very little blower surge and idles around 7-800....I can live with that, the port engine can only idle at 1200-1300 and has alot of blower surge anything under that. Under load they they both idle great. One other thing both engines seem to run a little fat which I don't understand because the fuel injection should compensate for altitude,air density, and temperature should it not???

Any ideas would be greatly appreciated????

JLANE

I'd like to think I can fix anything but I think I'm over my head.
The B&M system uses the port injection from the 502 MPI. It has a B&M adjustable fuel regulator mounted in the manifold under the blower and purple B&M something or other that plugs into the wiring harness or maybe thats the ECU. It uses the stock fuel system.... Total timing is 30.

As this is my first fuel injected anything my knowledge would fit in a thimble but shouldn't the ECU adjust itself. For like temp, alt, air/fuel mix.... stuff like that.

Any help/advise would e greatly appreciated.


Jason

JLANE

Lean is like my last 2 wifes they both cost me nothing but money.

To check for a vacuum leak where and how do you recommend I start. I started sprayed carb clean around the manifold but I didn't notice a difference in the way it ran. And unfortunetly no one up here has any experience with boating anything. So I'm kind of on my own.

Any advise would be great.

Jason

WETTE VETTE

I believe blower surge is attributed to a lean idle condition. Maybe you can tweak your fuel pressure up a bit and see what happens. Make sure you have fresh plugs in the motor as well. I just helped out a buddy with a stock 502 EFI and couldn't even set the timing the thing ran so bad. Installed fresh plugs and it ran like a ***** cat! His plugs were the original plugs in a 1999 motor.

WETTE VETTE

I guess Sutphen beat me to it!

JLANE

Thanks Guys I really appreciate the help.... although I'm a little baffled. How does adjusting the fuel presure change the richness of the motor???

Thanx

Finding a sharp corner to bang my head on

Griff

The ECU is preset and does not adjust with conditions. It does not monitor conditions. It has a programmed fuel curve that will remain constant.

That is, if it merc one or similar.

tssteph

Are their fuel pressure gauges for each motor? If not get some..... Boost gauges will also help. That is the first set of information needed. I have been doing a ton of reading on this topic as I have been chasing my own fuel related issues myself. I now think I have a good handle on what my problems are.

Important things to know:
Fuel pressure at idle
Fuel pressure under boost check this when everything else if correct
Timing, inital and total
Boost at WOT check this when everything else if correct
Vacumn at idle

All of this information with a comparison between motors and you will figure out what is going on.

JLANE

Thanks a bunch... Let me get this information and I'll let you know...

Jason

meckmotion

i also have a 1990 35 fountain lightning with 502s. How old is your boat and how fast are you running?