Was wondering if anyone has ever installed a fuel flow meter to monitor how much fuel the engine pulls while driving.

Of course placement of the sensor is an issue.
Correct me if i'm wrong; depending on which car you apply this to, some cars having a closed loop fuel system and some have an open loop fuel system? One with a return fuel line would be an open loop fuel system? And a closed loop would be like an engine that just drew fuel as needed.

An open loop fuel system, the sensor could not go on the main fuel line from the tank because excess is always going back to the tank. Maybe if you put it inline to one of the injectors?

Also you would have to have the correct senor (ie sensitivity, max flow, min flow, no interactions with diesel or gasoline depending on what car you put it on).

Then you would have a gauge in the cockpit and as you drive, you see how fast you can go, while drawing the least amount of fuel. Is thier any fallacy in my logic?

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'80 240D (sold) wish I didn't.
'85 300D (240K miles)

Don't forget that diesels return a fair amount of fuel back to the tank. Your idea might work if you had two flow meters, one in the return line to subtract that fuel from the amount measured by the flow meter in the supply line.

Alot more fuel travels back to the tank via the return line than is burned by the operation of the car. I'm not aware of ANY MB cars that have a "closed loop" fuel system, I think all the cars have the setup with the return line.

Exactly. I would think a carburetor engine is a closed loop system, maybe? Anyways, then the sensor would have to go inline with the fuel system, after the return line. Doesn't matter. Seems like I am just going to have to find some flow sensor somewhere. Will have to do some research. I gave it a try.

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'80 240D (sold) wish I didn't.
'85 300D (240K miles)

I haven't used one yet, but I just assumed that there were two flow meters, one incoming and one outgoing & the gauge or whatever calculated the difference. As far as I know all engines, diesel and gas, have both lines, to prevent vapor lock. I found one over at JC Whitney, but they don't have an installation diagram or anything.

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Michael Roth

1982 300TDT Wagon
1982 240D Euro!, 4spd manual-Parts car now, dead engine
88 Jeep Grand Wagoneer-fixing up for offroading
1989 Ford F150 (rust bucket) For Sale!
1953 Dodge B-4F, 1 1/2 ton Stake Bed (new restoration project)