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

Ed, pull that pump off the engine already. Your back will thank me.

Ed, Doesn't look as bad as I thought it would. Cylinder/plunger tops of the ones I can see in the picture look good. There is some evidence of dirt/corrosion on the pressure valves. Wash and clean in solvent then with something like a wooden cotton swab stick, check to make sure the ball & spring move. Spring is in the threaded section and ball is in the flat sealing end. Push ball in toward the spring gently a few times and make sure it clean inside and returns to the seated position.

Thanks Mark, done that as well. Also thought the pistons looked okay (although didn't understand the little dent in the piston). Well, hopefully the drive tomorrow will clear some last dirt. Otherwise I'm out of ideas and will it be over to the pro's.

http://forums.pelicanparts.com/uploa...1259869238.jpg

To complete the picture, the HC values are extremely high.

Ed

Bad news... Today tried the car on the road. Lots of (blue) smoke and lack of power. Puller the injectors one by one, no spray just some (minor) dripping.
Pump is next.
Ed

Ed, I know I asked before, what have you gotten regarding fuel flow and pressure to the MFI pump. Trying to remember if there is a system pressure valve on the return from the pump.
Again, there is on the BMW, kugelfischer pump.
you may be able to borrow a pump from one of your Porsche mates just to isolate.
Good luck with getting her screaming again

Looks good also given the fact that 2 of the injectors have a nice spray!
Ed

Sorry to hear that Ed. You said that you pulled the injectors one by one and checked for spray. I assume the engine was idling when you did the spray check?

That's correct, the engine was idle. BTW, replaced all the injectors, no change...
Strange enough motor kept idle when removing one of 4, with 2 it stopped.

Mark, send you an email as well.

Ed

Can it be the pressure of the fuel pump? It works but will it loose pressure when broken (the fuel lines are all renewed as the solenoid and filter)

Ed, I thought you checked the electric fuel pump pressure? If not, you should. If you have the Porsche P233 pressure test gauge or equivalent, install it at the filter console where the MFI pump return line (left side of MFI pump) is connected to the upper side (closest to the rear of the car, easiest one to get to) of the fuel console (has an arrow pointing inward). You should have about 1 bar of pressure with the engine at idle. You should also check the fuel pump delivery. With that same fuel line coming from the MFI pump and a 1000 cc or more measuring beaker, engine off, but ign. switch on, the electric fuel pump should deliver 900 to 1000 cc of fuel into the beaker in 30 seconds.

Thanks, will check just to be sure. Isn't it strange that 2 of the injectors have a good spray? When the fuel pump is not good, one would expect all the injectors to have a limited or no spray at all.
Ed

Ed, I worked with a Czech in Sweden when I was with Volvo. He always referred to himself as the cancelled czech.
Back to the electric fuel pump, you can take them apart and clean all the little rollers and check valves and give it a whirl. Keep us posted.

Your right Ed. I'm not saying the electric fuel pump is the reason some of the injectors are not working, but it just makes sense to check all the related components of the MFI system. Might as well make sure everything else is working properly before you install another pump. Your doing a great job.

Thanks all. Mark will send a calibrated and checked pump, confident the pump will solve the problem.
Still puzzled by the smoke when driving (not so much at idle or at higher revs when not driving). Is that related to the not proper working fuel intake? Remember, leakage test was good and no oil spills.

Could it be the valve seals? Can remove those without removing the cylinder heads right?

Just checked the electrical fuel pump. Pressure is 1.1 Bar, fuel delivery is (after 2 checks) 600cc/30 sec. Filter already renewed.

What does this mean? New pump or should the engine also work fine at 600cc. At idel the engine runs fine, lot's of smoke when reving up.

Ed

Check inside your fuel tank for any sediments that could be on the bottom around the tank filter screen. If the screen is obstructed this would cause the low fuel delivery. The engine will still run at low to mid rpm's but could cause the MFI pump to run out of enough fuel at high loads and rpm's while driving.

Thanks, will check tomorrow. Looking forward to the MFI pump!
Ed

Hello, a quick update.
Received the pump from Mark. Installed and must say, what a difference!
The engine runs smoothly and strong!
Went for a short test drive (first time since 1992 that this 72 was back on the road). The engine still smokes but a bit less then before. Smoke mainly when aggressively accelerating. Nevertheless is was still at an embarrassing level, hopefully it goes away after a longer drive.
Had to abandon the test drive because changing gears was really difficult. Turned out the shift coupler to be completely worn and broken. Ordered a new one, next attempt this Friday!
Keep you posted.
Ed