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Patrick Francis
Frequent User
Username: jackpot

Post Number: 73
Registered: 11-2016
Posted on Saturday, 15 April, 2017 - 23:44:   Edit PostDelete PostView Post/Check IP

Hi guys
I have a 1972 Aston Martin DBS V8 that is an early fuel injected version. It uses the Bosch mechanicai MFI system that was used by Porsche and Mercedes at the time.
My problem is that there is no calibration information for the injection pump this car, and no replacement cams.
Not many of those cars produced before they went to carbs.
Anyone by any chance know any info that might help please?
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Patrick Lockyer.
Grand Master
Username: pat_lockyer

Post Number: 1251
Registered: 9-2004
Posted on Sunday, 16 April, 2017 - 04:24:   Edit PostDelete PostView Post/Check IP

Hi Patrick F, looking for my more detailed book.

Don't know if this will help on injection timing.
should be set at end of stroke at 60 deg ATDC.
Injector pump type should be Bosch 0408028007.
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Omar M. Shams
Grand Master
Username: omar

Post Number: 1173
Registered: 4-2009
Posted on Sunday, 16 April, 2017 - 04:24:   Edit PostDelete PostView Post/Check IP

Dear Patrick,
I had the same problem when I owned a 1968 Mercedes 300SEL 6.3. There was a specialist in London who did those at that time (late 80s). I cant remember who they are now but they used to advertise in the Exchange and Mart. If you are unable to trace them the Mercedes Benz Club UK will certainly be able to help.
Good luck.
Omar
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Patrick Lockyer.
Grand Master
Username: pat_lockyer

Post Number: 1252
Registered: 9-2004
Posted on Sunday, 16 April, 2017 - 04:43:   Edit PostDelete PostView Post/Check IP

Hi Omar, yes I have had a few probs with Mercs mainly over fueling through sensors and diaphrams letting go.
The Aston may be the same system but different settings imo.
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Patrick Lockyer.
Grand Master
Username: pat_lockyer

Post Number: 1254
Registered: 9-2004
Posted on Sunday, 16 April, 2017 - 07:31:   Edit PostDelete PostView Post/Check IP

Patrick F.
Set distributor contacts to 15 thou, set the dwell to 27+-1
Set static timing to 10 deg BTDC on damper.
Then check, strobe at 30 deg BTDC.
Then set injector timing as stated before ; end of stroke to be 60deg ATDC.
Hope this helps.
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Patrick Francis
Frequent User
Username: jackpot

Post Number: 74
Registered: 11-2016
Posted on Sunday, 16 April, 2017 - 07:32:   Edit PostDelete PostView Post/Check IP

Thanks guys for your sggestions and advice. I once had a 1969 Porsche 911s with the same Bosch pump, whicjh I managed to calibrate on a diesel pump calibrating rig.
Omar you are right, the Mercedes V8 aldo had it.
The problem seems to be obtaining the calibration stats for the Aston, which is different to the rest. Also they have a 3d cam in them that is particular to each car make. Fortunately mine seems OK, but they do wear also, and are as rare as rocking horse sh!.
I'll keep searching....
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Patrick Lockyer.
Grand Master
Username: pat_lockyer

Post Number: 1255
Registered: 9-2004
Posted on Sunday, 16 April, 2017 - 17:53:   Edit PostDelete PostView Post/Check IP

Ok looked up the Bosch part no for the Aston pump,
found this link.
https://www.scribd.com/doc/40080565/Bosch-MFI-Repair-Manual
If it is this pump I will look for the Mercedes work shop manual but I think the data is all different.
Have you checked the service injection setting I gave you first.
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John Beech
Grand Master
Username: jbeech

Post Number: 329
Registered: 10-2016
Posted on Monday, 17 April, 2017 - 10:56:   Edit PostDelete PostView Post/Check IP

I believe I had that same Bosch pump on my 1966 Maserati Sebring. Never gave me any trouble so I didn't mess with it.
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Patrick Lockyer.
Grand Master
Username: pat_lockyer

Post Number: 1258
Registered: 9-2004
Posted on Monday, 17 April, 2017 - 17:54:   Edit PostDelete PostView Post/Check IP

Wow! John that was some car.
Pic of the car under Maserati Part 3.
http://www.velocetoday.com/cars/cars_73.php
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Patrick Francis
Frequent User
Username: jackpot

Post Number: 75
Registered: 11-2016
Posted on Tuesday, 18 April, 2017 - 05:30:   Edit PostDelete PostView Post/Check IP

Hi Patrick L
Thanks for the info and your helpful input.
I have managed to time the pump to the engine. The car runs quite well apart from when it is cold.
To do this I used an Aston Workshop manual which I am lucky to have - also using it to set the timing etc, taking into account modern fuel octane. Also my car has electronic ignition BTW.
I would like to give the pump a complete overhaul, but since it is running OK I am loathe to touch it until I am sure that I have the data spec that I require to set these pumps up.
They are very complicated and I remember it was a long drawn out process setting up the Porsche one. The problem is that each adjustment affects all the other adjustments, so it is a matter of going over and over with small adjustments until you obtain the optimum.
The data that I seek is a large array of fuel volume produced at incrementing revs and varying throttle settings. These are calculated according to engine cc, valve timing for each particular engine. That is why the mercedes settings are (probably) different to the Aston's even though they are both V8s (as you rightly say).
Thanks again for what you have sent, which is informative, please don't stop throwing any other info in my direction, no matter how trivial it might seem.