412 Variant LE

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TonyJ
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412 Variant LE

Post by TonyJ »

Hi Folks,
The electric fuel pump on my D-Jetronic FI system is kaput! Its the original 3-port type which now seems to be unobtainable. Any advice on a suitable replacement pump.
TIA


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Tony Z
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Re: 412 Variant LE

Post by Tony Z »

I had someone from JHB on the phone a few days ago asking the same thing.
No idea.
Your best option is to find out the pressure the system runs at and then find a pump and regulator to match
Dawie
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Re: 412 Variant LE

Post by Dawie »

D-Jetronic operates at 2 bar. Like most f.i. systems, it has a return line. The regulator at the back controls to a constant system pressure by simply returning excess volume to the tank.

I simply used an universal high pressure f.i. pump and re-arranged the plumbing. Newer metal fuel filter fitted after the pump. (Cleaned tank and retained the in-tank pre-filtering sieve which is not ideal because it could cause obstruction.)
Ideally one should increase the tank's fuel outlet diameter from 8mm to the same size as the pump's.

Newer f.i. systems use large diameter tank outlets to prevent pump cavitation at higher temps.

The pump i chose is a high pressure unit for K-jetronic 5 bar operation. I made a little switch-mode regulator which drops voltage to have just enough flow, same as original pump. (Had return line into a measuring container, then adjusted voltage till flow matces spec of original D-jet pump). That way i have a strong pump which just idles along in this application. Tested with full 13.8V and car still runs. So in an emergency if my regulator should fail, i could bypass and still get home. (This specific pump only requires 9.5V to match D-jet pump's flow).
Staying Aircooled is so much nicer.
Do'nt assume anything- (While doing fault-finding).
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sean
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Re: 412 Variant LE

Post by sean »

Merc's in the 70's use the same system. Just phone a Mercedes Benz agent, ask for a fuel pump for 1973 W116 350se.
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fig
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Re: 412 Variant LE

Post by fig »

Early 1970s Volvos also used D-Jet, and they were 4-cylinders, so parts may be more compatible than Merc V8 parts.
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Dawie
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Re: 412 Variant LE

Post by Dawie »

Staying Aircooled is so much nicer.
Do'nt assume anything- (While doing fault-finding).
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