vacuum gauge on diesel engine

simonfraser

simonfraser

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Simon, if you want to monitor the pressure you need a pressure gauge and not a vacuum gauge as this assumes the fuel lift pump is located in or near the tanks to provide pressure to deliver the fuel.

If the pump is on the engine it is a vacuum gauge as it is sucking the fuel to the engine from the tanks.

In either case a correctly installed system of either kind should cause no problems.
 
Tnx, that's a good point, KAD 44, the lift pump is on the diesel engine, so recon it sucks

guess it was my brain thinking about the fuel filters, higher pressure on one side, lower on the other
no real 'vacuum' as its the air pressure above the air intake of the tank pushing the fuel through
which is due to the air mass and gravity ;)
 
simonfraser said:
not had any problems, but can see the merit in keeping and eye on the fuel pressure

so, leave it well alone or

https://www.ebay.co.uk/itm/DRAPER-59075-VACUUM-AND-FUEL-PUMP-TESTER-BARGAIN-10-44-/272384841270
or do you know of a more reliable one ?

install it in between the primary and secondary filter ?

if the gauge fails it can leak and air will get into the fuel, how likely is that ?
Click to expand...

You install the vacuum gauge between the primary filter and the inlet to the lift pump. It will show you when the primary filter is getting blocked and needs changing.

A pressure between the lift pump outlet and secondary fliter will not tell you a lot as moat lift pumps try to maintain a constant pressure on the outlet.
 
Hi. If your particular diesel VP looses any fuel pressure, you woul soon know about it. I wouldn’t think it was nesessary at all. With mechanical fuel pump it either works or doesn’t.
The engine would be noticeably down on power will sound different on too with the last cylinder in the line suffering most. You’ll loose boost etc etc. Will be so obvious an likely white smoke will be evident from exhaust initially.
All that said, I always admire this type of thinking and if you were fussy you could put a differential gauge in line fed from before and after the primary filter. This would most often indicate when or if the filter is suffering. As we know, the most common cause of fuel deprivation.
 
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