Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Technical BBS > 1- Porsche Technical Forums > Porsche 911 Technical Forum

Reply
 
LinkBack Thread Tools Rating: Thread Rating: 3 votes, 2.33 average.
Author
Thread Post New Thread    Reply
Registered User
 
Join Date: Mar 2004
Location: Higgs Field
Posts: 13,879
MFI Open Heart Surgery II - The Fuel Pump

I guess we all know how hard it is getting to find good MFI fuel pumps these days. "NLA" is the order of the day. Well, I found myself in need of one, and even with three on hand, none of them worked. Two didn't run at all, and one leaked out of the electrical connector base. I figured it was time to dig in and see what these are all about. After all, I had two chances to ruin non-working pumps before I had to figure this out and make one work. With nothing to lose, I went to work.

Here is a shot of the pump, even though most of you know what they look like:



The pump itself comes off of the motor with four screws. Here is what it looks like once off of the pump. Note the star wheel and little rollers. Those rollers are loose - don't lose them:



Take the rollers out and put them aside. The pump now looks like this. Note the tiny little hole at about 11:00; gas passes through that hole into the motor itself. The motor runs wet, i.e. it is full of gas and pressurized:



Next, the star wheel is removed from the shaft. The drive pin is pressed into the shaft, so there is no danger in losing it:



Now the fun starts. The endbell needs to be removed from the motor case. It is staked on in several places around the case. I inserted a screwdriver into the square notches on the endbell, and twisted to release the staking:



You will have to work at it, but the endbell will come out. With it will come the armature, commutator, brushes, and all of that.

Once it is all out, it will look like this. Note the thrust washer and shims - these go on the shaft end that slips into the bearing in the motor case. There should be two shims and a thrust washer:



Make sure you get all of the shims out of the motor housing. They are steel, and will want to fall off the shaft and stick to one of the magnets in the housing:

__________________
Jeff
'72 911T 3.0 MFI
At the track: http://www.youtube.com/watch?v=_YjzSZmGXZ8
'93 Ducati 900 Super Sport
"God invented whiskey so the Irish wouldn't rule the world"
Old 02-16-2009, 06:40 PM
  Pelican Parts Technical Article Directory    Reply With Quote #1 (permalink)
Registered User
 
Join Date: Mar 2004
Location: Higgs Field
Posts: 13,879
...con't:

The o-ring that fails is located in a groove where the endbell presses into the motor case. This one was so brittle it came off in two pieces:



This is a good time to take a look at the brushes and commutator. These weren't all that bad, but it would be easy enough to turn the commutator and put brushes in it. Clean everything (including the motor case) with some brake cleaner, electrical cleaner, or whatever.

The o-ring is removed in this photo. Put a new one in the big shiny groove, and it's ready to go back together:



Now it's ready to go back together. Slide the thrust washer and shims back on the shaft, and maybe put a blob of grease on them so the magnets in the motor case don't suck them off the shaft. Grease up the o-ring as well, and slide the whole works back into the motor case.

One the endbell is seated, stake the case back over it. I just used a punch and bent the tabs back in:



From here, all you have to do is reassemble the pump half. Don't forget to put a new o-ring in the groove on the endbell, around the pump mechanism.

That's it, that's all. Pretty darn easy, really. I hope this helps some of you in getting those old dried out MFI fuel pumps working again. God knows they ain't making any more of them.
__________________
Jeff
'72 911T 3.0 MFI
At the track: http://www.youtube.com/watch?v=_YjzSZmGXZ8
'93 Ducati 900 Super Sport
"God invented whiskey so the Irish wouldn't rule the world"
Old 02-16-2009, 06:51 PM
  Pelican Parts Technical Article Directory    Reply With Quote #2 (permalink)
Registered User
 
Join Date: Mar 2006
Location: WI
Posts: 198
fuel pumps

Great post!

Where did you find the o-rings?

Steve
Old 02-16-2009, 06:57 PM
  Pelican Parts Technical Article Directory    Reply With Quote #3 (permalink)
Registered User
 
jpahemi's Avatar
 
Join Date: Feb 2004
Location: Long Island, N.Y.
Posts: 1,798
Jeff:

How are the sparks from the brushes shielded from the gas vapors?

jp
Old 02-16-2009, 08:00 PM
  Pelican Parts Technical Article Directory    Reply With Quote #4 (permalink)
Registered User
 
Join Date: Mar 2004
Location: Higgs Field
Posts: 13,879
I found the o-rings at the local auto parts store. They are nothing special. I just brought the old ones in and matched them up with what they had.

The commutator and brushes are not shielded at all from the gas; they don't have to be. D.C. electric motors actually run quite well underwater, or in this case, under gasoline. When my son was younger (the son I'm building this car with) we used to race radio control cars. It was common practice to break in their motors by running them underwater. Kind of counter-intuitive, for sure.
__________________
Jeff
'72 911T 3.0 MFI
At the track: http://www.youtube.com/watch?v=_YjzSZmGXZ8
'93 Ducati 900 Super Sport
"God invented whiskey so the Irish wouldn't rule the world"
Old 02-16-2009, 08:28 PM
  Pelican Parts Technical Article Directory    Reply With Quote #5 (permalink)
Registered User
 
jpahemi's Avatar
 
Join Date: Feb 2004
Location: Long Island, N.Y.
Posts: 1,798
Jeff:

Never knew that, always thought electric motors had sparks when running; I remember seeing some kind of spark when looking in the vent area??

jp
Old 02-16-2009, 08:38 PM
  Pelican Parts Technical Article Directory    Reply With Quote #6 (permalink)
Registered User
 
sc_rufctr's Avatar
 
Join Date: Feb 2009
Location: Adelaide South Australia
Posts: 15,097
Send a message via MSN to sc_rufctr
Modern cars with fuel pumps either inside the gas tank or external run "wet"...
(The fuel acts as a coolant for the pump)

Kinda weird when you think about it...lol...
Old 02-16-2009, 09:01 PM
  Pelican Parts Technical Article Directory    Reply With Quote #7 (permalink)
Senior Member
 
Ron,K's Avatar
 
Join Date: Nov 2000
Location: Chandler, Az.
Posts: 174
Jeff,

I just went through this exercise but had trouble getting the pump to run. I suspect that the O-rings I used on either side of the impeller were to small. If I loosened the the screws holding the impeller it would run, but would not seal. I'll have to try some larger O-rings. I was not aware that gas entered into the motor casing. I actually need to have some work done on the commutator but I was reluctant to pull the shaft out for fear of not being able to seal it when it was reassembled.
__________________
Ron

69 911T
Old 02-16-2009, 09:05 PM
  Pelican Parts Technical Article Directory    Reply With Quote #8 (permalink)
I would rather be driving
 
jpnovak's Avatar
 
Join Date: Apr 2000
Location: Austin, TX
Posts: 7,121
Jeff, Great post. I have a siezed one on the bench that I have wanted to tear into but have not had the time. btw, this procedure will work for the carb version of the fuel pump that is also NLA. These rotary vane pumps run quiet and will deliver a lot of volume.
__________________
Jamie - I can explain it to you. But I can not understand it for you.
71 911T SWT - Sun and Fun Mobile
72 911T project car. "Minne" - A tangy version of tangerine
classicautowerks.com - EFI conversion parts
Old 02-16-2009, 09:06 PM
  Pelican Parts Technical Article Directory    Reply With Quote #9 (permalink)
Registered User
 
Join Date: Jan 2001
Location: So. Cal.
Posts: 5,687
Thanks Jeff,
Now I won't be tearing mine apart blindly when the time comes.
__________________
Marv Evans
'69 911E
Old 02-16-2009, 09:22 PM
  Pelican Parts Technical Article Directory    Reply With Quote #10 (permalink)
Max Sluiter
 
Flieger's Avatar
 
Join Date: Mar 2006
Location: So Cal
Posts: 19,579
Garage
Wow, great timing. Mine failed this Saturday.

Great photos and informative procedure.

Thanks
__________________
911S
1971 chassis, 2.7RS spec MFI engine, suspension mods, lightened

Suspension by Rebel Racing, Serviced by TLG Auto, Brakes by PMB Performance
http://www.flickr.com/photos/max_911_fahrer/
Old 02-16-2009, 09:49 PM
  Pelican Parts Technical Article Directory    Reply With Quote #11 (permalink)
Registered User
 
Join Date: Oct 2004
Location: S California
Posts: 5,793
Hi Jeff ... Great Post.

Did you do anything with the pump head? There is a pressure relief valve with a piston and spring behind that little aluminum cap. I pulled one apart awhile back and that valve was stuck from old fuel. I ended up sending it out to have rebuilt and they replaced a part in there and installed a new cap.
__________________
1971 911T Sunroof Coupe
1973 911E RS Clone (project)
1973 911E RSR Clone (3.5 MFI Project)
1974 911 Getty 959 Cab Conversion
http://www.campster.com
Old 02-16-2009, 10:49 PM
  Pelican Parts Technical Article Directory    Reply With Quote #12 (permalink)
 
Now Available for Ordering:   101 Projects For Your BMW 3 Series 1982-2000  [more info]
Registered User
 
pwd72s's Avatar
 
Join Date: Apr 2001
Location: Linn County, Oregon
Posts: 34,531
Great thread...a link going off to Istanbul!
__________________
"Now, to put a water-cooled engine in the rear and to have a radiator in the front, that's not very intelligent."
-Ferry Porsche (PANO, Oct. '73) (I, Paul D. have loved this quote since 1973. It will remain as long as I post here.)
Old 02-17-2009, 12:13 AM
  Pelican Parts Technical Article Directory    Reply With Quote #13 (permalink)
Registered User
 
Join Date: Mar 2004
Location: Higgs Field
Posts: 13,879
Nope, I didn't do anything with the pressure relief. I was lucky in that one of mine was quite clean inside, so that's the one I used. One of the other ones leaks, so I assume the thing is stuck, but that's a project for another day. We have lots of other things to do on my son's car to get it on the road. When that is all done, I'm going to have a peek under that leaky pressure relief cap. I bet there is another dried out o-ring under it.
__________________
Jeff
'72 911T 3.0 MFI
At the track: http://www.youtube.com/watch?v=_YjzSZmGXZ8
'93 Ducati 900 Super Sport
"God invented whiskey so the Irish wouldn't rule the world"
Old 02-17-2009, 06:23 AM
  Pelican Parts Technical Article Directory    Reply With Quote #14 (permalink)
Warren Hall Student
 
Bobboloo's Avatar
 
Join Date: Aug 2000
Location: Los Angeles Ca.USA
Posts: 3,959
Garage
Great stuff Jeff! Sent a recommendation to put it in the Wiki.
__________________
Bobby

Warren Hall 1950 - 2008
_____"Early_S_Man"_____
Old 02-17-2009, 08:58 AM
  Pelican Parts Technical Article Directory    Reply With Quote #15 (permalink)
Max Sluiter
 
Flieger's Avatar
 
Join Date: Mar 2006
Location: So Cal
Posts: 19,579
Garage
What size O-rings are needed to do a full rebuild on the pump? I am going to tackle this project very soon and want to get a parts list together?

Thanks for any tips
__________________
911S
1971 chassis, 2.7RS spec MFI engine, suspension mods, lightened

Suspension by Rebel Racing, Serviced by TLG Auto, Brakes by PMB Performance
http://www.flickr.com/photos/max_911_fahrer/
Old 02-19-2009, 12:35 PM
  Pelican Parts Technical Article Directory    Reply With Quote #16 (permalink)
Max Sluiter
 
Flieger's Avatar
 
Join Date: Mar 2006
Location: So Cal
Posts: 19,579
Garage
How much fuel came out of your lines when you removed the fuel pump?

I am curious to how much is contained in the lines between the fuel pump (on the rear sway bar mount) and the MFI pump. Also, the lines running forward to the tank.

How do you cap the fuel lines? I may need to have the pump off the car for a while so I hope to keep debris out of the fuel circuit and fuel pump while the pump is on the bench and disassembled.
__________________
911S
1971 chassis, 2.7RS spec MFI engine, suspension mods, lightened

Suspension by Rebel Racing, Serviced by TLG Auto, Brakes by PMB Performance
http://www.flickr.com/photos/max_911_fahrer/
Old 02-19-2009, 10:42 PM
  Pelican Parts Technical Article Directory    Reply With Quote #17 (permalink)
Registered User
 
Join Date: Dec 2007
Location: Strasbourg, France
Posts: 396
Quote:
Originally Posted by jpahemi View Post
Jeff:

Never knew that, always thought electric motors had sparks when running;

jp
Even if there were sparks, there's no air. Liquid gasoline does not burn - the vapors do. A tank half full is a dangerous thing to keep around when your playing with fire - a completely full tank is not.

There was a link to an aircraft site a while back (in one of the efi-conversion threads I believe) where the author talked about fuel mixture. In explaining the above scenario, he even said something along the lines of: light a match, throw it on the ground, and pour gasoline on it. It will go out.
Old 02-20-2009, 01:54 AM
  Pelican Parts Technical Article Directory    Reply With Quote #18 (permalink)
Registered User
 
al lkosmal's Avatar
 
Join Date: Jul 2001
Location: mt. vernon Wa. USA
Posts: 6,588
Pump rebuild

Jeff,
Very nice job. I love to rebuild rather than replace. Have you ever rebuilt one of these? I have four of them. One works. I have yet to figure out a good way to remove the top cap to get at the innards.


__________________
[B]Current projects: 69-911.5, Previous:73 911X (off to SanFrancisco/racing in Germany).77 911S (NY), 71E (France/Corsica), 66-912 ( France), 1970 914X (Wisconsin) 76 911S roller..off to Florida/Germany
RGruppe #669,
http://www.x-faktory.com/
Old 02-20-2009, 08:11 AM
  Pelican Parts Technical Article Directory    Reply With Quote #19 (permalink)
Registered User
 
tharbert's Avatar
 
Join Date: Jun 2008
Location: So. Illinois
Posts: 1,739
Garage
You could use a Dremel to make slits in the bell that fits over the lip and gently pry each newly made tab out. It might be an academic endeavor as I think you would be hard pressed to find a way to seal it back up especially if it's under pressure. And the cap looks like steel while the body looks to be aluminum. Tricky!

As for the MFI pump, I had just the pumping portion apart on mine. Fortunately, my pump was gummed and the brushes were stuck. As soon and I had it apart and turned the shaft a few times by hand, I hit it with a trickle charger and it spun up right away. 37 years old! I'm always amazed by this car. I cleaned up the star and rollers, slapped it all back together, and it works great. I still wish I had a spare on the shelf!

Last edited by tharbert; 02-20-2009 at 08:40 AM..
Old 02-20-2009, 08:24 AM
  Pelican Parts Technical Article Directory    Reply With Quote #20 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 07:15 PM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2017 Pelican Parts LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.