MFI problem???

[oldautoradio]

Hello all,

at last, after a year and a half my 1969 911S 2.0 MFI has returned from mechanic were they have completely body restored and repainted to original color (tangerine).

I have mechanical problems now. The car does smoke a lot and seems to run rich. Also it does not rev up correctly and stalls after 2500/3000 rpm. Sometimes it runs ok over it. I have not been able to do more than 10 miles as the car runs really bad and it even stops.

Theorically the MFI system has been adjusted by the mechanic but I think that he just messed it up. I have checked and connecting rods seem to be at correct specs.

Any help? have someone suffered the same??

Thanks all,

Josep

[spydr32000]

Does the engine run rich or lean? If it is rich, then check to be sure the thermostat on the MFI pump is not sticky, or the hot air hose is not blocked. These problems are not unusual for any car, but especially one that has been in storage for a period of time.

[oldautoradio]

Hi,

hot air arrives to thermostat and is not siticky as I took it off, cleaned (was already clean) and mounted again.

Josep

[Jeff Higgins]

Since it sat for so long, I would suspect the fuel system upstream of the actual injection. The screen in the gas tank, the electric fuel pump, and the filter might be contaminated. Today's gas, if left to sit without one of the gas stabilizers, forms a really hard reddish "sand" for a lack of a better description. Essentially a sediment that will collect in the bottom of whatever is holding gas, not just the tank. I would bet that if you did not drain the whole system, the remaining fuel in these three components degraded a bit and deposited this sediment. Clean the tank screen, flush the fuel pump, replace the filter, blow out all the lines, and see where that gets you. If that doesn't help, then start working your way through the MFI system itself. Don't start fiddling with it until you have verified everything upstream is clean and flowing fuel.

[Grady Clay]

Josep,

Jeff is right on. Don’t adjust the MFI, look for outside issues first. Follow CMA!

Search Pelican on my name and MFI. You will find details of this issue there.

Best,
Grady

[oldautoradio]

Hi,

I have been checking some issues, I took all injectors off and three of them look like this:


I was quite worried as I saw the rust in the inside part. Does that mean something very dramatic? is it normal?

I have cleaned and re-mounted the injectors and the car seems to run the same, too much white smoke and quite faulty. I will take the MFI fuel lines out and see what is inside.

Where is the screen in the gas tank located?

Josep

[spydr32000]

Josep, have you checked to make sure the valves are operating correctly? Also have you checked the MFI pump timing?
Looking at the pics of your injectors the engine must have been quite wet, so check to be sure all the linkages and accessories are moving freely and as they should. This is what makes me think your valves might be sticking, if they have been wet and are rusty they will stick.

[oldautoradio]

Hi,

the valves has been checked and adjusted by the mechanic and the engine runs, the problem is that is not reliable as it stops after a short run (about 5 miles).
I haven't tried to go out again after the injectors were cleaned, I just fired it and leaved running at idle for about an hour, the engine didn't stop.

Can it be a fuel pump problem?

Thanks,

Josep

[cmcfaul]

I suspect the screen in the bottom of the gas tank is gummed up. Easy to fix. take the fuel level sensor off the of the top of the gas tank. There is a screen at the very bottom where gas is drawn from. I used a long dril bit and just made a hole in the screen. Many years later the car runs great and does not have the issue of fuel starvation after a few miles of agressive driving (in my case).

Definitly where I would start. A full tank of super unleded with some injection cleaner could not hurt either.

Chris

73 911 E

[spydr32000]

It could be a fuel pump problem. Do you know if the pump and system have been sitting dry for any period? They don't like that! Also have you checked all the electrical contacts for the pump?