Running out of ideas MFI
 

I'm running out of ideas. Despite cleaning of the MFI pump (little plungers move freely) and cleaning the injectors (ultra-sound) still 3 of the fuel lines give only limited fuel. It get's better at higher revs but the difference between the 3 strong and the 3 weak ones is remarkable. Also checked all the MFI articles and threads but can't find any reference. Anybody have a thought / idea / tip what to do next?
VERY MUCH APPRECIATED because running out of ideas here....

I'd suggest that you send the pump to someone and have them calibrate it. There are a few people good at this.

JR

Did you check the hardlines for blockage?

Thanks, what does calibration exactly mean? Is this not only needed if all cylinders are not working properly?

Ed

Yep, checked that as one of the first things. Changed all the fuel lines and filter as well. The car hasn't run for quite a long time.

I would send the pump to Gus @ Pacific Injection in San Francisco and have the real pro go through it. Send the Throttle bodies to Matt Blast in Boston, they will be "works of art" when he's finished and buy new injectors. Then she'll make beautiful music.

Steve

73 Aubergine 911 T MFI Coupe, built back to E spec.

You want and even amount of fuel delivered to all six cylinders and you want the correct amount of fuel delivered...

Gus is the solution to your problem.

JR

If you are going to send it to gus, get ready to spend big bucks, and if the pump has not been rebuilt, you might as well have it done.

Contact Mark Jung (356RS) and ask for his advice. Mark calibrated my MFI pump recently and it works very well. Like you, I had my pump pistons etc. all working freely, but realized that the flow may not be correct and/or balanced properly. (I'm a total do-it-yourselfer, but occasionally I have to call in the big guns.) Mark has built a very nice flow/test bench and can cal your pump for you.

regards,
al

PS: search for posts by 356RS and you'll see pix of his tester and get an idea regarding the expertize required to cal these.

Send him a email, thanks.

Bit worried to send the pump to the US (from Europe) and back. Might end up paying import duties twice....


Ed

Fuel pressure and flow?

Ed, From what you are describing it sounds like those 3 pistons are damaged/worn. When this happens it's very hard for those pistons to produce an adequate flow at low RPM's but will come alive at the higher RPM's. The pistons (plungers) & cylinders have a very tight clearance that must be maintained to produce the pressure and flow required for the MFI system. Just a little moisture in the fuel head area over time (sitting on a shelf or on an engine not running) can cause the plungers to corrode very slightly, actually looks like the plunger has a stain on parts of it, and this is enough to alter the fuel pressure required for that injector. The only other thing that can cause what you have described is someone has played with the adjusting clamp on those particular low pressure plungers. The clamps provide a way to adjust each plunger for more or less fuel pressure/delivery. The adjustment is very sensitive in that a movement of .010" can put that particular injector out of spec. Too rich or too lean.
I hope this explains your IMHO problem.

Thanks.

So what you're saying it's either a rebuild or a calibration?
Is it possible to test what the problem is or do I need special tools for that?

Ed

Mark, do the MFI pumps have delivery valves? My 2002 tii had a fuel problem about 6 years ago and I pulled the delivery valves and cleaned them, pump working as should.

Ed, I am trying to get a little history on your T pump from reading back on your posts starting around 10/30/09. At that time you were asking if a T MFI pump will be OK on an E MFI engine. So my question is, do you know the history of this pump? I ask this question because if you got this pump from a recently know good working engine I wouldn't think the pump was the problem. But from what you have described in the last few posts, I do not think a recalibration will be enough. I think you have some plunger/cylinder damage. Tools needed to test this would be a MFI Flow Bench. And if you found that there are 1 or 2 low reading plungers and adjustments can't resolve the problem, you will need to replace the bad plunger/cylinder sets. This also takes special tools and manuals.
You have some options; Locate a know good working T or E pump (you said in one post your engine was an E) and install it. Used T pumps are not that expensive compared to a rebuilt pump if you want to save $. Or just send in your pump for a complete rebuild.
If you were closer, I would be glad to just test the pump and let you know what is really going on.

Thanks Mark, wished I was your neighbour!

The pump is on a car I bought not that long ago. The car didn't run for 17 years. By now I've fixed all "normal" issues ranging from new clutch, fuel filter, refurbished alternator to new wiring. Also did all the check, measure, adjust sequence. Last is the MFI because still not happy with how the engine runs (have a little movie clip if you're interested). Cleaned the pump, cleared the fuel lines and cleaned (and replaced) the injectors.

The engine is an E but all the components are T (distributor, MFI, engine cover, etc). Very strange and impossible to find the true history because the first owner is not longer with us.

Rusty, They have what is called a "Pressure Valve" that is on top of the plunger/cylinder. It has a ball and spring inside and keeps fuel from going passed it while the electric fuel pump is now, before you start the engine. The "Pressure Valve" is held down by the "Pressure Valve Holder" which is the connector/connectors (6) on top of the MFI pump. I have seen these get corroded and not seat which lets fuel pressure enter the metal fuel line when the engine is off but electric fuel pump on. You only notice this if you have all the metal lines off of the pump with ign. on. Now if one of these were corroded so bad it did not let the fuel pass through it, could be the problem Ed is having. I think that's what your getting at Rusty. Good call. I hope it's that simple.

Nope, all removed, cleaned and refit. Unfortunately not the problem....
Must be something with the little cylinders.
Tomorrow we take the car on the street, see if a little driving around (first time this millenium) improves the engine a bit. Other wise it will be plan B (not known yet ;-). Btw, CO value is pretty low.

Ed

Ed, I think Rusty has a good thought. Pictures of how to get to the Pressure Valve.

http://forums.pelicanparts.com/uploa...1259866589.jpg

http://forums.pelicanparts.com/uploa...1259866637.jpg

http://forums.pelicanparts.com/uploa...1259866651.jpg


http://forums.pelicanparts.com/uploa...1259866668.jpg

http://forums.pelicanparts.com/uploa...1259866646.jpg
http://forums.pelicanparts.com/uploa...1259866662.jpg
http://forums.pelicanparts.com/uploa...1259866676.jpg

And some pictures!
Ed