Fuel Problem! help
 

I have a 502 mpi, which I'm having a problem with to much fuel going onto the plugs. The regulator was set on 40 psi, then i redused it to 38 psi but the problem remained there, then I redused it to 34 psi but still the problem remained. Can someone please help me cause I don't have a clue what is going on.
Harry

Are you refering to the plugs meaning spark plugs? I would think you need to keep the pressure the same but have the computer adjusted to reduce fuel at certain rpms..... (but please get more advice before following mine!!!)

you don't fix a problem in the mpi system by screwing with the factory settings... you fix what's broken. if the motor has gone rich and you believe its the fuel system you hook up your scanner and see what it says. then you fix that or those things.

on the mpi there are several things that will make the system go rich:

water temp too cold.... someone took the thermostat out

coolant temp sensor bad... temps ok but system THINKS its cold
or any or all of the rest of the sensor array connections...

also.... you refer to changing the fuel pressure.... if you have changed the factory non adjustable regulator to something else and screwed up the return line or return system it will overpressure the sytem and the fuel/pulse width ratio will be wrong comprehensively

OR a common failure is really dirty or failed injectors. the bottom line is that the mpi is not a carburettor that you just bash w/ a hammer and hope the floats unstick... it is a system that diagnosis and repairs VERY quickly and simply if you simply approach it with the correct tool and a calm and rational method. and the factory (not aftermarket) workshop manual will make it really really easy.

Stevesxm: thanks for your reply, but I forgot to tell you that the engine is no longer a standard engine. it has some mods made to it like 741 cam, upgrade Ecm, upgrade exhaust etc. The problem is that the engine is having a very rough idle and it hunts as well. When put on foward it still hunts till about 2K revs, then it's like it clears up and it runs ok although it's rich on fuel that you can actually smell it. I check the aftermarket fuel regulator and I found it block, cleaned it but the problem is still there. So now I'm out of ideas.

If the mods are just completed then the computer MUST be re-mapped to acount for the new engine. (I'm just getting new engines installled and having the motors dyno'ed and tuned to run.

I remapped the ECM according to the new mods. The problem is that here in Malta there isn't a dyno for a V8 engine and my only solution to solve this problem is to ship the engine to the US.

Do you have a scan tool? Checked for Trouble Codes?

Dave, I'm trying to get a DDT scan tool.

at a wild guess, tradidionally when people screw with the motors they put too much cam in it... that changes the manifold vacuum substantially and makes the MAP sensor berserk... and the rest is history. if you are going to run the injection you have to put it on a dyno and map both the fuel and the ignition at this point... no one... and i mean no one at all is going to be able to sell you and ecu that is " remapped" that will be correct without seeing your motor.

If you cannot send the motor to be dyno/tuned then you need to send someone who can all the info they would collect during that process. Contact on of the people here in the states (I use Precision Marine) and find out what info he needs to get your computer straight.

(Confirm with who you pick but, they'll need you to run a fuel pressure gauge, vacuum gauge and an O2 (oxygen) sensor and pull readings every 200 rpm throughout the rpm range. With that info he can get your computer dam near perfect)

BTW: If you don't think all this is needed, I'm rebuilding a motor that lasted 2 hours after not following every little step

Since I bought everything from Tyler crockett, I would prefer to send it to him since he knows every part I bought and even so, he had done my re mapping of the ECM.
After talking to him, I found out that the adjustable fuel regulator was block, so I cleaned it up. Now I see what happens, although after going through this forum I noticed that alot of people had the some problem which it turned out to be IAC. Hopefully I managed to get a hold of a DDT and by tomorrow may be we find the problem.

Thanks everyone, I'll keep you posted.

If I was guessing (and thats all I'm doing here without seeing whats really going on) I would say your map sensor isn't plugged all the way in or is bad. You could still use a merc scan tool even though you have modified things to get readings to find out if your basic components are even working,good luck,Smitty

Thanks Smitty,

I will check that as well.
It has to be some sort of sensor cause the engine works well at high revs, it's from idle to 2k it's were the problem is.

I managed to get a DDT scanner and it showed no trouble codes, So I changed the Msd dist cap and the rotor but I'm still with the same problem, a hunting idle, it idles at 1000 rpm, and it's like loosing timing. if anyone can come up with an idea please help.

Put a vaccum pump on the Map sensor and see if more vaccum at idle cleans up the idle. If so that will tell you that is the problem. I have done this on another type of computer when it was self tunning and it makes the computer go to a leaner part of the fuel map.
At least it might indicate where the problem lies.

Another solution to your problem might be an after market computer.. I am using a Megasquirt on my boat and have managed to make it work pretty good, so far, still in the evolution and tuning stages. http://www.bgsoflex.com/megasquirt.html
http://www.msefi.com/index.php?c=2
They dont like to talk about other systems on this site, and they dont like to answer questions until you have read the manual, but there is a wealth of info, that may help you out.

Hope this helps..
D*ck

[QUOTE=Mr Gadgets;2164155]Put a vaccum pump on the Map sensor and see if more vaccum at idle cleans up the idle.

Thanks Mr gadgets, thats another option.

Harry