Very technical MFI question....

Zeke · 10:03 AM

I have opened up two MFI pumps to find the same situation, namely a pin that appears to want to be in the hole in the adjacent arm.

Look to the top there and see the pin or small shaft resting on the top of the arm. Logically, it would seem to go in the arm. But two in a row makes me want to ask.

BTW, this is a 2.4 T pump that is frozen (rack won't move) and Berryman's doesn't seem to help so far. It is for sale as a core if anyone needs it. I will post as such after I figure out what's up on the rod or shaft, or whatever you want to call iit.

304065 · 07-07-2006, 10:49 AM

Milt,

You are inside the forbidden temple!

I don't think that hole goes on the arm. But I don't have the pump in my hands.

Jays72T · 07-07-2006, 11:09 AM

Interesting, I've have never seen the inside of a pump. It does seem like the pin would belong in the hole on the arm but I don't know what they do.

I do have another 2.4T pump but don't really want to crack it open.

Zeke · 07-07-2006, 12:12 PM

Quote:

Originally posted by john_cramer
Milt,

You are inside the forbidden temple!

Nah, I have half a mind to tear this thing down completely and see all there is to see. People talk about how sensitive these things are and they are made hell for stout. The pin, shaft, rod, whatever lines up with and fits the hole perfectly. I have the CMA and the Repair Manual downloaded from our host. It didn't give me a clear indication on this (same as above scan). Also, if there is a spring that belongs on the other end of this shaft, it's missing. That seems to be what they are saying, unhook the spring. There are so many damn springs and levers and gizmos in here that it's hard to figure out what they are referring to.

What happened to this pump is it sat on top of a motor that spun a rod bearing. It sat outside in the weather, but the internals look terrific. Me thinks the fact that it is frozen is due to the varnish left over from the fuel and bearing frazz that undoubtedly went thru the oil system and ended up in the pump. However, I didn't see the usual bearing material in the oil that came out of the pump, just some black oil that indicated that the owner didn't care too much about maintenance. It's probably not worth much in this condition.

HawgRyder · HawgRyder's Garage

I have had my pump apart before...I believe you are correct, the pin goes in the slot or hole as the case is in your pump.
Don't worry about the others saying not to take it apart, go for it, become an expert, then answer questions of others when they get stuck.
Bob

Bobboloo · Bobboloo's Garage

Looking at picture #14 that John posted you can see that the shaft doesn't belong in the hole. The shaft appears to be a stop for the lever which is in the away position in #14.

304065 · 07-07-2006, 12:44 PM

Milt,

You wanted a river to cross, this is it. As far as I know, nobody has prepared a concise set of instructions for actually opening one of these up, fixing it, and putting it back together.

The tools to do this fit your need for the unobtainium, too!

As far as them being robust I offer the below. . .

jkarolyi · 07-07-2006, 03:38 PM

Milt, had my MFI pump apart on a '73 911E and it looked just like that. Soaked mine in Berrymans (soak it for a week!) and if finally roared to life. So I'm pretty certain it doesn't belong in the hole.

Jay

boxster03 · 07-07-2006, 06:46 PM

Like a Swiss watch, ever tried taking one of those apart and putting it back together.

Zeke · 07-07-2006, 08:05 PM

Quote:

Originally posted by Bobboloo
Looking at picture #14 that John posted you can see that the shaft doesn't belong in the hole. The shaft appears to be a stop for the lever which is in the away position in #14.

I won't disagree because I don't know anything. However, I have to point out that if not in the hole, then the shaft flops around and does nothing. As a "stop," it just rests on the roof of the pump. In the hole it makes a teeter-tottor out of the top bar balancing between the altitude compensator and the air thermostat. As such, it has an influence on the next bar down which, in turn, has an influence on the rack. I'll wait and see until everyone has had his say.

69911e · 05:46 AM

The pin belongs in the hole. That pin provides the input for barometric pressure compensation.

ED

69911e · 07-08-2006, 05:59 AM

Milt: I am glad to see you are still playing with Porsches. I have admired your attitude of having fun with the cars without concern for going along with the crowd.

Here is a picture of the inside of my pump.

.

There is not much to worry about if you want to take apart the pump to fix or modify. As long as you have 2 pumps, one can be used (as you have done) to verify how it is assembled. The only adjustment which I wouldn't touch is the adjustment for each piston to change the correlation between individual cylinder fuel delivery. I think you would need a special setup to calibrate this.
ED

Zeke · 07-08-2006, 06:32 AM

Quote:

Originally posted by 69911e
The only adjustment which I wouldn't touch is the adjustment for each piston to change the correlation between individual cylinder fuel delivery. I think you would need a special setup to calibrate this.
ED

The one pump I have (the T) has been worked on before. There is a spring missing, that I have verified. Probably ran poorly, I don't know. AFA the individual correlations, I noticed that the previous intruder made witness marks with a scratch awl to get them back to where they were. The special tool you talk about is a bench tester where the pump is run and the output is measured precisely and calibrated. I would enjoy this sort of work but I'm not buying a bunch of testing equipment. I have enough stuff as it is.

Thanks for your answer about the rod. After looking at it for a long time, I couldn't imagine it being loose and having any function. I have already inserted the rod into the lever/arm on my E pump which I am planning to run.

(What do you mean you're "glad to see you are still playing with Porsches"? Wa'd you think I was playing with?)

Early_S_Man · 07-08-2006, 11:04 AM

Milt,

That pin & lever seems to be part of the baro-cell and warmup thermostat linkage. As you surmised, it seems to need the pin in the slot of the lever ... according to the diagram below:

Zeke · 12:39 PM

Thank you, sir! I didn't get as far as my factory manuals, so thank you for looking that up. I guess I'm lazy nowadays, but I do have the resources.

Don't you (everyone) think it's weird that I opened 2 of these things and they were both apparently reassembled wrong? Makes you wonder about whom you take these to. And, for the record, I have no idea where these pumps have been. That's why I'm skeptical and examining every small detail. I might even understand them before I'm through!

Also, it looks like the T pump is going to be somewhat sacrificed for a couple of small parts. I'll chronicle the disassembly on a new thread for the curious just as I did when I disassembled an MFI fuel injector that was beyond repair.

See the injector here:
Ever wonder what's inside an MFI fuel injector?

edited for spelling

jkarolyi · 08:26 AM

Weird. My car seemed to run just fine after re-assembly. I remember seeing a picture in Check, Measure, Adjust that showed the pin as being out of the hole. I'll see if I can track it down.

Edit: Not in CMA...it must have been some other publication that describes how the MFI system works.

Zeke · 09:30 AM

No, it's not in the CMA. You might also have the download "Repair" where the above pics from JC came from. However, there are dark areas and shadow that prevent one from clearly seeing the shaft. What's more, the sequence has one taking out the altitude compensator early on in the disassembly process. AFAICS, they don't show how to remove the shaft which is on a pivot held by a dinky circlip.

I'll go with what Warren says (who wouldn't?

) and also my own observation that the arm will not influence the next operation if not anchored at each end. AFA your MFI running good, I can see that, too. When one looks at the over all effects of this ass'y, I'll bet many racers don't have any of this stuff left in their pumps. It's just too fine of an adjustment to be worried about if you're on it hard all the time. This part of the unit is all about keeping the engine clean running at part load, to the best of my guess.

Thanks to all that replied. I have put the shaft in the hole on my E pump and that's where it will remain. Now, there may have been some info from the factory at some point to disconnect these, I don't know.

edit: Jeez, my spelling has really suffered lately

Wayne 962 · Wayne 962's Garage

Very swiss-watch like. I wouldn't mess around with a pump that you are actually planning on using in the near future...

-Wayne

304065 · 02-12-2007, 05:34 AM

Here is a photo of my spare pump that is now at Gus's.

When the pump gets back I will resolve this issue once and for all. Surely GUS knows how it goes.

Jeff Higgins · 02-12-2007, 05:47 AM

O.k., just out of curiosity, I pulled the cover off of three spare pumps that I have. Every one of them has the pin above the lever, out of the hole. I have a fourth that is on the car and running, so I really don't want to dig into it, but I guess just taking the cover off can't hurt anything. Two of my pumps have apparently never been appart; one looks like a fresh rebuild with all the lacquer seals on the screwheads and everything, but I don't know its history. The one in the car was rebuilt by Pacific about five years ago and runs great. Maybe I really should look at that one.