MFI: Did I get a good deal--or ripped off?

[Andy Ring]

I have a 72 911T that needs a little work. It runs rich, doesn't cold start well and my mechanic says that he thinks the MFI is tired on my car (throttle bodies are worn?). I hope to soon be able to make my own diagnosis, but at the moment I'm not even book smart about MFI. I'm just beginning to come up to speed on MFI thanks to the advice of Grady, Early S Man, etc.

Anyway, I've downloaded CMA and lots of other MFI stuff and am wading in. Right after a session digesting some of this written material, I check in to Ebay with the key words "Porsche 911 MFI" and find someone selling pretty much an entire set-up for a 2.4 911 T at buy it now price of $450. Knowing how expensive parts are and how quickly having someone else tinker with your MFI adds up , I figured I really couldn't go wrong. For $450 I get a pump, the throttle bodies, etc. So, any opinions?

Here's the link to the listing: http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2475765473&category=46098&sspagename=STRK%3AMEBWN%3AIT&rd=1

If the link doesn't work, search for item 2475765473. Any opinions would be appreciated--even if I'm closing the barn door after the horses are out. Thanks...

[Paul Thomas]

I would spend my $450 on a better diagnosis than "tired" and possibly on a throttle body rebuild. These systems are so often set incorrectly, people think that they are messed up or broken.

$450 goes a long way towards a very nice rebuild that is probably over due.

Paul

[techweenie]

If the throttle bodies are tight on the injection you bought, you did well.

I think the pump is worth about $300 as a core. Some of the injectors are probably good...

You really can't go wrong. You might have gotten some componenets better than those you now have. And the seller gave you a money-back guarantee!

[Zeke]

How do you know the thing on Ebay isn't "tired?" I'll say this, I bet my MFI is pretty tired, too. But, by fooling with it for 2-3 days and ddoing all the CMA stuff, it runs pretty well. The seroius stuff is the linkage adjustments and the butterfly adj's. A little tweaking on the mixture can dial it right in and I mean a LITTLE. Plugs, wires and timing are big in this business. Try tuning a litte before you leap. For $450, I think you are buying someone else's same problems, maybe worse. I could be wrong, but I wouldn't buy it w/o seeing it in person. One enemy of MFI is sitting around. Yours is working.

Enough. I've stated my case.

[Andy Ring]

One clarification: I'm not giving up on my current MFI or expecting to do a swap with the ebay unit. I want to learn about MFI and will start by trying to do CMA on my current system. I guess I figured having a spare set-up at my disposal would:

1) let me check both set-ups to see if one matches what is described in the literature. For instance with the thermostat there's lots of talk about the disks or washers or whatever--now I'll have two sets to look at to see if one comforms to what is described.

2) when something does wear out or perhaps is already worn out maybe I'll be able to have a replacement already in hand. At least I'll have something I can send into be rebuilt without disabling my car. After my mechanic told me my MFI was tired, I asked him how much it would cost to fix--he said he didn't know but it would be well over $1000.

This was my thinking in buying the set-up, but I must admit that something like Milt's take was lingering in my mind. Great, now I have two tired MFI set-ups. Not sure why I'm asking the board this question, but I guess I got second thoughts after clicking the buy it now button and now I'm wondering whether I made a mistake. I can live with it if I did, so no hard feelings at all if you say I did.

[Zeke]

You put it in a different perspective with your last post. I see it your way more now. I bought one a year ago for $500 here. It had every last screw. I sold it only because I wanted to raise some money for the now gone race car. Luckily, I found a whole motor, MFI and all, for similar money 2 months ago. Yes, having a spare setup is a good plan.

Sorry, if I seemed harsh. I tend to have that problem.

[Grady Clay]

Andy,

I agree with what you have done and the reasons you posted. That “…lingering in my mind….” is just normal “buyer’s remorse.” You can always get out of it at $450, give or take a hundred, no big deal.

Swap the parts back and forth to your engine and see the results. You may get better (less worn) parts on your engine and then have demonstrated good parts as spares.

When the parts show up at your door, inventory everything. Your first chore should be to remove the MFI pump side cover and inspect for any rust. Rinse out the old oil and fill with fresh oil and Marvel Mystery Oil, including the fuel circuit. Make sure everything moves freely. In addition to CMA, the early Factory 911 Workshop Manual has great diagrams and theoretical operations explanations. This will teach you a lot about MFI pumps and the system.

The MFI system you are getting isn’t complete, over the long term I would work (inexpensively) to make it absolutely complete. Lot’s of value there for you.

If you don’t have access to the MFI nozzle tester, just swap the injectors (one-at-a-time) onto your engine and see how they run.

Farther down the line, as you gain knowledge, experience, and tools, you can swap on the throttle bodies and eventually the pump. Fun and useful projects. You may end up with an entire spare system worth significantly more than you paid and have served your purposes at the same time.

Once all cleaned up, you can store your spare MFI as a “coffee table.” 911 Engine Coffee Table


Best,
Grady

[RarlyL8]

Just as a data point -
I gave away my functioning '73 2.4T MFI a couple of years back to a Pelicanhead looking to get into MFI from scratch. I had switched to Webers for simplicity and asthetics. There are many of these systems sitting on shelves. You too can find someone like me who doesn't value the old 2.4T system.

[304065]

Dear Andy,

Years of listening to the gurus have convinced me that most problems that people think are the MFI pump are actually the setup. CMA is invaluable in getting you comfortable that something actually needs to be changed. But the only way to tell is to baseline the setup.

Money wasted? No way. I have a spare '71E setup, I consider it a soul wating for a body. . .

[Early_S_Man]

Andy,

You did OK, so don't worry!

Clean off the injectors with Berryman's B-12 Chemtool. Soak them for a day or two in B-12 in an ultrasonic cleaner -- in a HD aluminum 'boat' if the tank is plastic! After cleaning, tape up both ends of the injectors with duct tape!

You can build a simple nozzle tester from a new/used VW Bus single master cylinder with integral fluid reservoir ... doesn't even need to have a pressure gauge, initially, though it would be nice. Use kerosene as the test fluid, and have large fire extinguisher on hand for all testing!!! Or, you can use Marvel Mystery Oil as test fluid.

Cap the injector pipe outlet fittings, ASAP, on the injection pump! If you got the six hard injector lines, clean them off and spray B-12 and compressed air through them, them tape up the ends with duct tape.

Clean off the injection pump externally. Put a pint or so of B-12 in the pump lower end after draining out all oil, thoroughly ... soak for a couple of days. Fill fuel plenum with Marvel Mystery Oil or kerosene, and assemble hard lines and injectors to pump in what I call the "butterfly configuration" on the workbench ... and turn over the pump by hand until all six lines are bled of air and all six injectors are 'chirping' and spraying ... and examine the spray patterns. Disassemble, drain B-12 from lower sump, allow to air out, then fill with favorite 20W-50 motor oil, seal/tape and store everything away until you need the parts!

Good luck!

[304065]

Warren,

The "Blue Book" recommends storing the pump full of a certain oil, your thoughts?

[Early_S_Man]

Yes, that elusive 'test fluid' ...

I have asked about it at dealerships, and nobody ever knew what it was, or had any ... I assume it is similar to kerosene, or Marvel Mystery Oil.

Forgot to mention draining out the B-12 Chemtool after testing ... airing out for at least eight hours, and then replacing with fresh SAE 20W-50 oil of your choice!

[Andy Ring]

Thanks for all the info. I plan to keep my 72 for many years and thus am reading up on MFI so I can do my own repairs and also assembly as many spare parts as I can if the price is right.

I may have more questions about storing away the parts once they arrive. I do have an immediate question concerning taping up the openings for storage. Are you guys suggesting cleaning out the various bits with B-12, then filling with Marvel Mystery or SAE 20W-50 and then taping up? Or do I just drain out the B-12, let dry and tape up? I suspect that some parts are to be stored with oil and other dry, but I'm not quite clear on it. Thanks again, Andy

[Grady Clay]

Andy,

For whatever reasons that I don’t know, Marvel Mystery Oil seems to be a good preservative. It has worked well for me in both engines and fuel systems for more than 30 years. My lame 2c worth.

I don’t like duct tape to seal things. The adhesive can get into places you don’t want. The high pressure fittings can use a ball bearing and the screw nut off some old pipes to seal. Same with the nozzles. Use some fuel hose between the inlet and outlet fuel circuit. Figure a way to connect the oil supply pressure line to the oil return line. If nothing else keep the pump, pipes, and nozzles connected and full of oil. CMA p.43 has some good guidelines.

I just went out and rooted around my garage and found my MFI Bosch injection nozzle tester. Somewhere I have part of a 5-gal container of the Bosch test fluid. I’ll bet someone in Bosch-USA can find all that stuff. This is part of what you pay for when you send your stuff to a reputable rebuilder.

Best,
Grady

[Early_S_Man]

Andy,

Kerosene or Marvel Mystery Oil in pump fuel plenum, lines, and injectors wouldn't need draining after testing ... just tape or cap off everything to prevent dust/dirt entry.

The pump lower sump is what I was referring to that would need draining, and airing out prior to filling with SAE 20W-50 engine oil.

The only caveat I would add about the duct tape is that you need to use a shop rag and B-12 or other carb. cleaner to remove all traces of adhesive when cleaning up parts to do diagnostics or put them in service ...

If an aircraft supply store is handy, you could try them to find 'Caplugs' of the appropriate size to fit over injector ends, lines, and various pump outlets and supply fittings.