Motor break in with MFI - Page 2

Grady Clay · 01:49 PM

”I managed to get the right and left working in sync by lengthening
the left push rod slightly. The differential between left and right
is 3mm. I suspect this was affected by me rebuilding the throttle
bodies. I actually had all the butterflies and shafts out. The
shafts and bushing were all really tight so it was just a very
thorough clean and lube and reassemble. From what I can see
through the stacks, at full throttle all the butterflies seem to be
straight up and down.”

The issue isn’t full throttle. The critical points are at idle, just
coming off idle and cruising at part throttle (3800 in 2nd, 3200
in 3rd.)

”Also replaced all the fuel lines on the engine today with OEM
style braided line and proper clamps, nice crimp clamps on the
cold start lines.”

Good

”I replaced the MFI belt but not the gears, they looked to
be in good shape.”

Keep an eye on this. Long term you will benefit from having
all three start out new.

”New SSIs are currently on order and I do have new
heat exchanger tubing.”

Good

”What I have not gotten yet is the smaller diameter tube that
runs to the MFI pump. from the engine tin. Do I get this at the
dealer? As wel,l is that what goes on the underside of the
engine tin? Mine was missing and how long is this piece?”

Here is the diagram:

© Dr. Ing. h.c. F. Porsche A.G.

The small tube from the tin to the thermostat is actually two
concentric tubes: #28 (green 901.110.295.00) & #29 (blue
901.110.296.00). These are normal service items and should
be replaced regularly. If they get damaged and restrict the air
flow to the thermostat then the warm-up is slow and the engine
runs rich too long.

The #27 (red 999.181.212.50) is 25 mm ID and 440 mm long.
This hose usually lasts longer than the chassis. You should
be able to find a good used one.

The reason it is important to use the original hoses is their
warm-up characteristics are matched to the thermostat and
engine warm-up characteristics. If you find you want to have
the thermostat turn off sooner, you can use better, light weight
(low thermal mass) insulation. We did this on MFI 911s that
lived outside in the mountains. Start with the OE setup, you
shouldn’t need other.

”I don't believe this case was ever apart, although it may have
had some minor head work done at one time. Evidence was one
of the cam sprockets was on backwards. The chain was rubbing
pretty badly on the inside of one of the cam boxes (see photo).
Makes me wonder how critical chain alignment is when this car
ran in this state for so long.”

That is why you replace chains. How did the sprockets and
jack-shaft fare? I trust you didn’t reuse those chain ramps
(Hehe); they were responsible for much damage to 911 engines.

”The car was an original 80K car but I believe the motor's
premature wear was due to lack of proper maintenance and
poorly functioning MFI. I believe the car was running in rich mode
the last 10-20 years.
The previous owner who had the car the last 25 years got the car
as a debt repayment from a bankrupt brother in law. He wasn't
much of a car guy and basically changed the oil once a year
drove the car a few times and threw it back in the barn.”

Too bad, these cars are meant to be driven. What did
the rod bearings look like? How did the pistons & cylinders
measure?

”- the fuel filter I got has a different (much smaller) spigot on
the bottom than the original. Do I have the wrong one? My parts
guy tell me this is the only one available.”

Post an image. I have never seen a different filter.

”- 2 of the fuel lines off the electric pump that go
rubber/metal/rubber, the ones that go through the
chassis. How do you feel about one solid rubber line.
I don't like the look of my metal sections. Is the main
reason the risk of abrasion through the chassis?”

Check THIS thread. Most think reusing the metal pipes (if serviceable)
and replacing the hoses (using new clamps) is best. You are
charged with the responsibility to see if you have a flow
restrictor in the return “T” hose/pipe assembly.

One of the real benefits of DIY is you don’t have a deadline.
Don’t get in a hurry. Don’t set a deadline that forces you to
skip something important. It appears you have done an
excellent job, keep up the good work.

Best,
Grady

TargaT · 10-16-2005, 05:41 PM

Grady, thanks for the words of encouragement. Unfotunately I do feel under a bit of a time crunch. The weather here is starting to get cool quick and I really want to know if this baby is going to run properly. If there are any issues I'll use the time over the winter to sort them out. The other project planned for this winter is to drop the front suspension and give it the same treatment as the rear.

"How did the sprockets and
jack-shaft fare? I trust you didn’t reuse those chain ramps
(Hehe); they were responsible for much damage to 911 engines."

Sprockets on the offending side were obviously worn due to misalignment. I installed new chains and ramps and was able to source some good used sprockets

"Too bad, these cars are meant to be driven. What did
the rod bearings look like? How did the pistons & cylinders
measure?"

All the bearings were in pretty good shape. I replaced the rod bearings and I'm about to open a whole can of worms but here it goes- I reused the mains. My journals measured slightly out of round and the bearings had conformed to this condition while maintaining good oil pressure. They had minimal wear with no scuffing. This came on the advice on my machinist who has rebuilt numerous 911 engines and I'm hoping I haven't made a crucial error.
The pistons and cylinders were still within spec although near the outer limits. I had them honed and installed fresh Goetz rings.

"Check THIS thread. Most think reusing the metal pipes (if serviceable)
and replacing the hoses (using new clamps) is best. You are
charged with the responsibility to see if you have a flow
restrictor in the return “T” hose/pipe assembly."

Thanks, I have already bookmarked this thread. Don't have my camera at this point I will post some current photos and the fuel filter in the next couple of days.

BTW which part of Colorado is Arapahoe county in?

I occasionaly travel to Colorado. I'm with a Company called Agilent Technologies, used to be part of HP. We have facilities in the Springs, Englewood, Loveland and Fort Collins. Beautiful part of the country. I'm hoping they send me this winter so I can take in a little bit of that Vail skiiing.

Best Regards, Joe Dren

.

TargaT · 10-18-2005, 07:58 PM

Grady and/or others,
Still chugging along, waiting for a few MFI hoses, SSIs and trying to finalize my rear brakes. In the mean time I do have a couple more questions:
- my electric pump has a bolt where I believe there should be a pressure relief valve? It's obvious this doesn't belong there. Any idea why or how this might affect things? Is this part available stand alone?
- At the rear of the air filter housing is a metal spigot pointing straight down. It appears there should be a hose there. Mine never had one. what is the function and where does it go?
- I'm starting to get a pretty good handle on some of the MFI concepts and operation but what gives the signal for the enrichment nozzles. I know it is the wire at the top of the fuel console but what triggers this ? Is it on with voltage or off?
- where the TEE is on the enrichment lines, it seems the line wants to droop and pretty much drag on the top of the MFI belt. Was there some specific way of routing this line?
- the hot air exit off the MFI pump, Is there supposed to be a hose off of it?

Thanks, Joe

TargaT · 10-18-2005, 08:03 PM

BTW, I thought I'd change whatever tranny seals are practical while out. I got a bit of a surprise on the input shaft. After doing some research here it appears I have the dreaded install from the inside only version. I don't believe it was leaking so I'm just going to cross my fingers on this one and see what happens.

joe

304065 · 10-19-2005, 04:31 AM

Yes, the electric pump is available standalone. The system pressure is 1 bar, relief valve opens at 2 bar.

That metal spigot, the brass looking one? You should be able to rotate it so the bead is facing the starboard side of the car. A large-diameter braided hose connects between this and the identical fitting on the side of the oil filler neck.

The solenoid on the fuel filter console is triggered by the engine cranking AND the thermo-time switch. According to CMA p.5 the "Thermo Time Switch operates above +113F down to minus temperatures (below +32F). Which I don't understand.

No hose off the hot air exit from the thermostat.

Grady Clay · 10-19-2005, 05:52 AM

Joe,

If that spigot on the air cleaner assembly is about 11 mm then it is the oil/condensation drain. There should be a hose to the metal drain piece that goes through the tin behind (to the front of the car) the oil cooler. That drain should have a rubber one-way piece on the bottom of it.

The brass piece John is talking about is a flame arrester (guess why needed) in the main breather connection to the air filter assembly. You should take the flame arrester out and clean it.

You have the plastic air filter assembly. Earlier (up through ’71) have metal assemblies. The metal can rust in the double wall area of the breather. This spreads rust chards to the intake. The usual symptom there is with flakes getting in carburetor jets.

When you go through your front suspension, you might consider moving the fuel pump back up there. There are nice Factory brackets from ’69-’71 MFI you can use. The pressure relief on the pump is a safety not a regulator. I wonder why someone defeated it’s purpose?

John is right on with the operation of the cold start solenoid valve. It is supposed to either off or on. The problem comes when it leaks or shuts off slowly. When Checking & Measuring MFI; it is worthwhile to disconnect the hose from the solenoid valve. This circuit gets power from the yellow wire at the starter to operate the “Auxiliary Starting Relay” and to heat the element in the “Thermo-time switch.” Power from fuse 2 at the electric relay panel is switched to the solenoid valve by the relay. The circuit can only operate the solenoid valve while cranking. If the engine is warm or the cranking has heated the Thermo-time switch sufficiently, then the circuit is disabled by the Thermo-time switch. Above 113F it is always disabled. The clever part of this is it’s time of operation is limited by both temperature and how long you have been cranking.

Best,
Grady

TargaT · 10-19-2005, 06:23 AM

Thanks guys, as far as the pump goes my guess is the the pressure relief was defective and leaking or maybe there was a fuel pressure issue that the last wrench decided to solve by simply capping it off with a bolt. I dont want to buy a new pump simply for this reason but it seems this valve is not available a as a stand alone part. The only option would be to find an old defective pump and remove it. My guess it that is threaded in, maybe an M10 or so. I will try to locate an old pump somewhere.
Understand the flame arrestor. and I will digest the info regarding the enrichment nozzles.
Regarding the the other spigot on the air cleaner I believe I understand the function. When I first got the car I overfilled the oil and it ended up in the air cleaner housing out the spigot and all over the engine. Didn't know where it was coming from and the volume of spillage caused me to think there was a crack in the block. This is what deterred one buyer when I had the car up for sale. Thank god I didn't sell it based on this mistake.
I'm still not sure I understand the routing because it looks like my pieces are missing. Once I have them in hand maybe I'll figure it out.
From my parts diagram it seems I'm missing:
- 285 mm of hose
- 911 108 021 02 (tube)
- 901 108 297 00 (valve)

Thanks, Joe

TargaT · 11-04-2005, 10:49 AM

Hello Gentlemen,
Finally almost time for a marriage.
Wish I had my camera to post some pictures but will do so in a few days. I took Grady's advice and did not rush at the end.

The motor is fully complete. All soft fuel lines have been replaced and the fuel tank drained and rinsed. The fuel tank screen has been thoroughly cleaned and a new fuel filter installed. I bench tested the pump first then installed and checked all fuel connections for leaks by powering the pump with and independent supply. No leaks and a steady supply from the bottom of the fuel filter.
I believe this is correct? I have every thing connected according to Gradys "corrected" diagram.
I will double check Grady's check list and hope for an install tonight/tomorrow.
Wish me luck.

Joe
Joe

Jays72T · 11-04-2005, 02:17 PM

Cannot beleive I missed this thread, what great information.

Good luck Joe, can't wait to hear how it turns out.

TargaT · 11-06-2005, 05:33 PM

Well, she didn't fire. Cranking over fine. Looks like there is oil pressure (how much should I see at cranking?). Gas all the way up to the MFI pump inlet (inlet on the right side looking from the back?). No gas at the injectors. All I can think is I've got the in and out reversed or the pump is not functioning. I just had it tested and calibrated. Any ideas?

Thanks, Joe

Grady Clay · 11-06-2005, 06:39 PM

Joe,

It takes a lot to refill the metal MFI high pressure lines. You can screw a small (M5?) bolt in the forward end of the MFI rack and pull it forward to make the pump go full rich. When I have done this, I left the connections at the nozzles loose until they peed gas.

Following the Factory revised fuel circuit diagram should present no problem for fuel delivery at the pump, check again. Have you checked the fuel pressure at the fuel filter console fitting closest to the rear? If the fittings at the MFI pump are reversed it won’t cause a problem although I like them as Porsche installed them. One less thing ….

Do you have spark at the plugs? Are the plugs wired correctly? Is there a rotor in the distributor? You can clip the timing light sensor on the coil wire and see a good indication of cranking timing. It should start with static timing at Z1 or slightly retarded.

Is the MFI pump belt installed? Is the MFI pump timing correct?

Try manual operation of the cold start solenoid for very short squirts of raw fuel while cranking. Don’t use either “starting fluid.”

Best,
Grady

TargaT · 11-06-2005, 06:45 PM

Grady, plenty of fuel right up to the MFI pump. Bone dry at the injector connections. Spark is present. When you say it takes a lot to refill the lines what do you mean. I filled an inch of a coffee can with just a couple of cranks at the MFI pump inlet.

Joe

Grady Clay · 11-06-2005, 07:08 PM

Joe.

The MFI pump inlet is supplied by the electric fuel pump. The MFI pump has to have pressurized (1 bar) fuel at the inlet, be turning over and be rich to get fuel to fill empty pipes quickly and finally start squirting the nozzles.

The best test is to squirt a small amount of fuel while cranking. It should start and die until the metal pipes are full and the nozzles working.

The critical issue is to make sure you have ignition. If not, the unburned fuel will wash the assembly lube from the cylinders from repeated attempts with cold-start fuel.

As you can see from my last post, don’t discount the dumbest of omissions – we all make them. Systematically check everything. Assume nothing.

Best,
Grady

TargaT · 11-06-2005, 07:35 PM

Grady, I must be missing something here. Plenty of fuel reaching the MFI pump. Am I trying to prime the pump or something? The pump is definately turning. No matter how much I crank I can't seem to get gas to the injectors. Where is all that fuel going? Back through the return to the filter and recirculating.

BTW had a heck of a time figuring out why I couldn't get my spark plugs in on #1 and 6? First time for me installing 911 plugs. Got them started using a piece of rubber hose to thread them, but could not tighten down the plugs in these two cylinders. Wasted about 1.5 hours figuring out you need a thin wall socket to access them. No mention of this anywhere that I saw.

Joe

TargaT · 11-07-2005, 06:47 AM

Well, she's alive. After repeated cranking I couldn't get fuel to the injectors so I decided to reconnect the cold start circuit and see what happens. It fired immediately and ran for a couple seconds. Tried again same thing happened. On the 4th try it stuck and kept running. Oil pressure came up and even idled. Ran it up a few times and seems to be running pretty smooth. Two major oil leaks on each side. It appears they are coming from the upper rockers which are the original magnesium units. I replaced the lowers with the newer units. I will replace these uppers before I start it again.

So I believe the lesson is to try with cold start connected. If it doesn't kick after a couple of cranks disconnect it and leave it off until the problem is found. I don't know how long it would have taken to get fuel to the injectors on it's own without the help of the cold start.

Joe

Grady Clay · 11-07-2005, 07:49 AM

Joe,

Congratulations!

Nothing like the sweet smell of success – unburned hydrocarbons in the morning and oil on the heat exchangers. Hehe.

When you replace the intake valve covers, put a wrench on the rocker arm shafts in the off chance that some aren’t tight. That can cause a leak similar to a valve cover.

Once you have the leak fixed, go drive it.

Best,
Grady

TargaT · 11-07-2005, 06:26 PM

Finally, some pictures.

TargaT · 11-07-2005, 06:27 PM

TargaT · 11-07-2005, 06:31 PM

Jays72T · 11-07-2005, 08:47 PM

Joe,

Wow, looks beautiful and congratulations. Nice Job.