MFI Pump - Open Heart Surgery

[dicklague]

Doug Robinson the owner of Bursch told me the MFI system is slightly smaller in diameter than the regular and makes a big difference. I have had one on mine 73 MFI for 10 or 11 years and love it.

Does Innovate do the repairs on their units?

[fbarrett]

Folks:

This is a great thread! As the former owner of a '70 911E, it's great to know that so many people are putting such effort into preserving and improving the MFI system. I still recall the amazingly crisp throttle response...

Some of you here might be interested in the recent book by Michael Burgess, Porsche 911 Mechanical Fuel Injection Pump. 1069-1973, A DIY Step-By-Step Guide, Repair and Calibration of the PED 6 KL.. Mechanical Fuel Injection Pump (possibly the world's longest book title), now available at Toad Hall MotorBooks, specializing in Fine Books on Mercedes Benz & Porsche since 1980; Welcome..




Frank

[kenikh]

I've sent Michael a few emails to see if he'd consider making this available as an e-book. Makes purchase MUCH easier for those of us across the pond. Haven't heard anything since a conversation months ago. He was going to look into it.

[dicklague]

that would be good. Maybe not enough $ in it. I would buy one but too steep for me.

[kenikh]

The numbers prove out that there's more profit and reach in ebooks than hardcopy, except in some very niche areas.

[philippeF]

I don't know in the US, but Bosch AG do not allow (I mean firmly) to sell his proprietary docs ...

[dicklague]

Originally Posted by philippeF

I don't know in the US, but Bosch AG do not allow (I mean firmly) to sell his proprietary docs ...

I think we are talking about making this thread into a book. or and e book.

[356RS]

Yes this thread ended up providing lots of information. I would like to contribute along with others to put together an e-book or something.

[Gav P]

Hi all, I've been following this thread on and off over the years, and it's been a fantastic source of ideas and inspiration. This is my first contribution to it, albeit in the form of a question/ request

But first some background: my '73E - originally a Dallas TX car, but brought here to the UK 12 years ago - has always suffered from rough running in the 1000-3000rpm range in my 9 years of ownership. Over the years, I have been through everything in CMA, as well as getting throttle bodies rebuit, renewing the injectors, reconditioning the distributor, fitting pertronix contactless ignition etc. etc. I have also done quite a bit of seat-of-pants tinkering with the pump racks. To cut a long story short, nothing really helped the rough running situation, so I suspected this may have been down to non-MFI-related issues - i.e. high mileage, maybe badly set cam timing, cylinder leakage etc.

Anyway, this year I finally got around to doing an engine project: I acquired a '74 CIS motor and have rebuilt it with my original E-cams, my original E MFI system and higher compression JE pistons giving CR of 9.8:1. It's now fully run in, and is a cracking motor for all-round street driving - 214bhp, 205ft-lbs torque. My original matching-numbers 2.4 crankcase sits safely in my loft at home.

However, this new motor suffers from exactly the same rough running issues in the 1000-3000 rpm range, as the old 2.4 did. The MFI pump itself has not been rebuilt during my ownership, but I have had it calibrated twice over the years. Both times it performed well, delivering the factory specified volumes.

Since running on the dyno for the new engine power tests, it was clear from the A/F plots that there were some anomalous mixture fluctuations in the lower rev ranges. At this stage however, I do not have A/F data related to throttle position.

Still, the above was enough to tempt me to take a look inside the pump and get to know my space cam. So I took the governor cover off, wiped the oil off of the space cam surface and this is what I have found:



- comparing this to some of the images posted on page 11 of this thread, I would say my space cam looks pretty badly tracked out. There are some very sharp edges just off of the idle area (lower RHS of the cam surface) - corresponding to the small throttle opening/low RPM part of the map.

I rotated the cam to the WOT position, and it looks like this -



Not as bad as the other side, but there is a rutted score mark on the first (low RPM) lobe which can't be helping.

So, my question is, does the above cam look excessively worn/damaged? Does anyone have a picture of a 2.4E space cam in known good condition, for comparison?

Finally, if my space cam is questionable, i would like to buy a good replacement 2.4E space cam - anyone have one available?

Thanks
Gavin

[210bhp]

First question is Gav, is it the correct cam? What's the number engraved on the side?

Regards
Mike

[philippeF]

A 2.4E spacecam has a deep and high profile ...
It seems rather normal to me ...
I don't believe that it's available from Bosch.

[356RS]

All space cams have the high and low profiles shaped into them for controlling the rack movement/fuel delivery. It's rare but some can start to pit and cause a uneven wear in certain areas on the space cam. The deeper the pitting/wear the richer the fuel flow will be in that area. The only way to see if the pump is performing to engine spec. is to have it flow tested. Attached are some photos of good working space cams.

[Gav P]

Thanks all for comments. Not sure my iphone has quite managed to capture the full character of my cam surface, but to my eye it certainly appears to show wear in a style that is not present on the cams Mark has posted there - scoring of the surface in line with some of the common motion directions of the stylus at low rpm/small throttle positions.

Currently the cam is still attached to the pump. I will need to get hold of the tools required for removing the flyweight assembly before i can remove it and study the surface more carefully. Mike - only then will i be able to verify that it is the correct cam for the pump...

Still, i would be very interested to get hold of another 2.4E space cam, and see how the car ran... I understand that very small changes/damages to the cam surface can have noticeable effects on the mixture.

[210bhp]

Gav

You can check the number without removing the cam with a little dentists mirror
inserted between the cam and the case. If you are going to extract it anyway then there's no point but useful if you are checking a possible replacement in situ.

Regards
Mike

[philippeF]

All space cams have the high and low profiles shaped into them for controlling the rack movement/fuel delivery. It's rare but some can start to pit and cause a uneven wear in certain areas on the space cam. The deeper the pitting/wear the richer the fuel flow will be in that area. The only way to see if the pump is performing to engine spec. is to have it flow tested. Attached are some photos of good working space cams.

Mike, your right about wide cams, but you' ve noticed that thin cams (2.0 and 2.2l engines) have a flat profile !
Philippe

[Peterfrans]

Originally Posted by Gav P

Thanks all for comments. Not sure my iphone has quite managed to capture the full character of my cam surface, but to my eye it certainly appears to show wear in a style that is not present on the cams Mark has posted there - scoring of the surface in line with some of the common motion directions of the stylus at low rpm/small throttle positions.

Currently the cam is still attached to the pump. I will need to get hold of the tools required for removing the flyweight assembly before i can remove it and study the surface more carefully. Mike - only then will i be able to verify that it is the correct cam for the pump...

Still, i would be very interested to get hold of another 2.4E space cam, and see how the car ran... I understand that very small changes/damages to the cam surface can have noticeable effects on the mixture.

There are a few companies in germany that can make you a new spacecam to factory spec. Look for mst-mechanik.de or eisenbrandt.eu There are probably some in the USA that can do the same

[Gav P]

Originally Posted by 210bhp

Gav

You can check the number without removing the cam with a little dentists mirror
Mike

Ahh - tricks of the trade Mike

I did wonder earlier whether the numbers might be visible using a mirror - dental instruments don't feature strongly in my toolbox, but maybe i should invest

Thanks for the leads there peterfrans - very interested. will check them out....

[A.T.]

Hey Guys

I've been meaning to post this for a while. Not sure how to embed it here but here's a vimeo link.



It's the MFI pump out of my RS replica being tested on a real mfi test bench. Pretty clear view of the business end of the pump with the cover off. You can clearly see the movement of the cam and the stylus as the rpm and throttle positions change. Also some footage of one of the fuel injectors being cleaned.

Get a load of how much fuel one of these things pumps when it's really cranking. Yikes!

A.T.

[philippeF]

Quote de Gav P

Thanks all for comments. Not sure my iphone has quite managed to capture the full character of my cam surface, but to my eye it certainly appears to show wear in a style that is not present on the cams Mark has posted there - scoring of the surface in line with some of the common motion directions of the stylus at low rpm/small throttle positions.



Currently the cam is still attached to the pump. I will need to get hold of the tools required for removing the flyweight assembly before i can remove it and study the surface more carefully. Mike - only then will i be able to verify that it is the correct cam for the pump...



Still, i would be very interested to get hold of another 2.4E space cam, and see how the car ran... I understand that very small changes/damages to the cam surface can have noticeable effects on the mixture.

There are a few companies in germany that can make you a new spacecam to factory spec. Look for mst-mechanik.de or eisenbrandt.eu There are probably some in the USA that can do the same

MST Mechanik believes he's the only one to "know" and makes crappy (sometimes) cams, thatīs said !
Philippe

[Peterfrans]

Originally Posted by philippeF

MST Mechanik believes he's the only one to "know" and makes crappy (sometimes) cams, thatīs said !
Philippe

Thanks for that feedback Philippe, I might want a new spacecam in the near future and mst is falling of the shortlist.