help...blower surge
 

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????

Re: help...blower surge
 

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

Re: help...blower surge
 

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

Re: help...blower surge
 

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.

Re: help...blower surge
 

I guess Sutphen beat me to it! :drink:

Re: help...blower surge
 

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

Re: help...blower surge
 

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.

Re: help...blower surge
 

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.

Re: help...blower surge
 

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

Jason

Re: help...blower surge
 

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

Re: help...blower surge
 

As persistence over comes Resistance here are the results

Starboard motor

Runs fine, fuel pressure was low at 35 at idle.... I cranked it to 42 psi still runs great. Vacuum is 11 pounds

Port motor still runs the same. Fuel pressure was 42 at 1300 rpm as thats the only place I can get it to run without surging. The full pressure also stayed constant up to 4000 rpm. Vacuum is at the 10 to 11 mark.

I reinstalled the the fittings and vacuum line to the regulator as well as to the gauge thinking maybe that was the leak.... no difference. Although when I pulled the vacuum line from the regulator the surging got worse.

So... now I'm at a loss...

Re: help...blower surge
 

I used a Merc scan tool and this is what I got...???

PORT

Engine RPM 850-1400
Coolant Temp 85
Manifold Air Temp 92
TPS Volts .50
Trottle tps 0
Map Volts .72
Manifold Pressure 7
Baro Volts 2.09
Battery Volts 14.1
Spark Advance 3.1 deg
IAC position 41
Base IAC 21
IAC follower 20
Injector on time 2.7
Fuel flow rate 5.5



2nd run for port engine

Engine RPM 1400
Coolant Temp 115
Manifold Air Temp 107
TPS Volts .50
Trottle tps 0
Map Volts .70
Manifold Pressure 6.9
Baro Volts 2.09
Battery Volts 14
Spark Advance 9.8 deg
IAC position 77
Base IAC 77
IAC follower 0
Injector on time 2.8
Fuel flow rate 7



STARBOARD

Engine RPM 830
Idle speed 837
Coolant Temp 81
Manifold Air Temp 70
TPS Volts .52
Trottle tps 0
Map Volts 1.01
Manifold Pressure 8.5
Baro Volts 2.09
Battery Volts 14.2
Spark Advance -.03 (all over the board)
IAC Position 9
Base IAC 9
IAC follower 0
Injector on time 2.4
Fuel flow rate 3.3

I took both throttle bodies off and adjusted the port side to match the starboard side and then swapped them. I swapped one peice at a time and then ran the motors. The starboard motor runs fine and it has all the port sensors, ECU, MAP, IAC, TPS, and trottle body, yet I still have a surge problem. I'm at a loss???

Re: help...blower surge
 

Theres only 82 hours on it. Wouldn't the scan tool pick up something if that were the problem?

Re: help...blower surge
 

[QUOTE=JLANE]I used a Merc scan tool and this is what I got...???

PORT

Engine RPM 850-1400
IAC position 41
Base IAC 21
IAC follower 20


2nd run for port engine

Engine RPM 1400
IAC position 77
Base IAC 77
IAC follower 0



STARBOARD

Engine RPM 830
IAC Position 9
Base IAC 9
IAC follower 0

QUOTE]

I noticed your IAC (idle air control) readings, they're all over. Is the motor making a loud air sucking sound at idle?

Re: help...blower surge
 

You may have a bad IAC and the motor is compesating by dumping extra fuel?

Someone mentioned that surge is from a lean condition? I always thought it was a rich condition from fuel puddling in the intake....

Re: help...blower surge
 

I agree but I swapped throttle bodies and the starboard engine ran fine. The port engine has all the starboard sensors and it still surges.

Re: help...blower surge
 

Try swapping the ECM from one motor to another. You have the benefit of two motors, so swap away.

Re: help...blower surge
 

I always understood that the surge was caused by uneven fuel feed. My idles were adjusted up to approx 11-1200 and surge when first fired up. Aftyer running a minute they calm down to a low surge if any at all.

Re: help...blower surge
 

I swapped the ECM as well... no difference. I've run this thing ever evening on the driveway for the past 10 days I really have to wonder what my neighbours must think. lol

Anyway.... I really appreciate everyones input I'm sure will figure it out soon.

Jason

Re: help...blower surge
 

Your surge is caused by an over-rich condition. You verified that yourself when you pulled the vacuum line from your fuel pressure regulator and the condition worsened. IF the calibration is correct and this surging was not present before, and since you have swapped all the sensors and ecu.... I'd have your injectors cleaned and flowed, sounds like you got one that is leaking.

Re: help...blower surge
 

OK...I'll look into that. Question though....if you have a leaky injector would that cause the fuel pressure to drop when the engines not running???

Re: help...blower surge
 

Surge is from over rich idle conditions

update
 

One should always look at the simple things first....I guess.

It turns out the distributor had moved and the timing was out by a couple of degrees causing the motor to surge. Re timed motor @12' base timing and I'm dilemma free.

Thanks for everyones input it was GREATLY appreciated.


Jason

Re: help...blower surge
 

I wasn't aware B&M made a blower that bolts on the stock lower intake of a 502 mpi,thats coool,glad you found the problem,Smitty