Where do I look up the fuel presure spec for a 1985 300sd? It now runs 16 lbs idle and same at load. It will go to 40 lbs if I pinch the return hose for a few seconds.

Thanks, Dave in Mesa,Az.

... why would you pinch the return line?
afaik, the fuel pressure is just above atmo, enough to supply full load of fuel at speed through the three filters... the IP does all the work of compressing the fuel. about 3000psi at the injectors...

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My drivers:
1987 190D 2.5Turbo
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1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

wondering if you could put a pressure gauge on that and determine when filters needed changing or riggin one those flow meters inline sounds like a good project for someone.

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2004 Infiniti G35 3.5L 6mt Coupe 73K miles 25.6mpg ytd
2001 Green Audi TT 225 AWD Roadster 71K 6sp 30.9mpg >>STOLEN<<
1982 300D Turbo 231K 120hp? 28.1mpg YTD

Why a pressure gauge? why not a vac gauge just before the IP as is done in other applications?

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83 300SD Dark Silver Dark brown inside

Because the filter is on the pressure side of the lift pump.

You would need two gauges. 1 before the filter and 1 after.

I am one of those horrible people who convert diesels to run on veggie. I like to have a baseline of the car before conversion. I check fuel pressure before conversion on Dodge..Chevy..Ford and even now Mercedes. I want to know if the lift pump is up to snuff before putting 160 degree oil thru it.

I run two tank systems and do not run on veggie until engine is up to temp and oil is hot. When the fuel pressure drops on veggie and not on diesel my cleints will know several hundred miles before the filter clogs that there is a problem.

I so far am having trouble finding the factory spec for mechanically injected Mercedes Diesels. I would like to know pressure specs and volume specs for these cars. And how to perform these tests to factory standards.

I am in the middle of trying to design a new way to plumb the older cars for veggie. I want to have the diesel run thru just the stock pump and have a seperate electric pump for just veggie. Stock pump will recirculate diesel back to tank while on veggie so as not to deadhead stock lift pump.I would like to match the fuel pressure of the veggie pump to within a few pounds of the stock pump specs. To do this I would like to have the stock specs to match.

I was hoping not to have to explain all this.... just get the spec.

Pinching off the return line for a few seconds is another way of checking max pressure of the lift pump. I have built a gauge adapter to replace the banjo bolt going into the injection pump so I could monitor fuel pressure on diesel and veggie.

Dave www.veggiegarage.com