Fuel Filter light - what does is measure?

derjackistweg

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I recently got my truck running after years! :peelout

But I noticed now that the fuel filter light comes of. Mostly when accelerating, and when WOT. When idleing is goes off, or only slightly blinking.

What is the gauge measuring? Pressure before and after the fuel filter or what else?

PS: Truck/ engine runs great! easy 80 mp/h, wich is allowed in good old Germany :)



btw almost everything is new:
- first fuel filter, main fuel filter < 600 km, 450 mils
- diesel in the tank is new
- IP rebuild
- GP new, + relais
- lift pump new, an electric one from hardi (marine high quality)
 
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The Warden

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I know you said you replaced the fuel filter and the injector pump, but did you replace the lift pump? If the filter's definitely happy, that'd be where I'd look next. What's the fuel pressure at the Schrader valve on the filter housing?
 

derjackistweg

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I know you said you replaced the fuel filter and the injector pump, but did you replace the lift pump? If the filter's definitely happy, that'd be where I'd look next. What's the fuel pressure at the Schrader valve on the filter housing?
I edited the 1rst post. Don´t have any failures.

This is why I wanted to know what this sensor measures, where it sits or whatever.

PS: Have not measured the schrader valve yet, what should it read?
 

79jasper

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If there's air in the filter, it's coming from somewhere else.
Dies it run like it's pulling air?

Sent from my SAMSUNG-SM-G890A using Tapatalk
 

derjackistweg

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If there's air in the filter, it's coming from somewhere else.
Dies it run like it's pulling air?

Sent from my SAMSUNG-SM-G890A using Tapatalk
Nope, like mentioned above no failure noticeable and easy going 80mph.

So there is a pressure sensor inside the filter?
 

Black dawg

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if there is vac between the filter and injection pump (fuel supply not keeping up with what the injection pump is pulling) the light will come on.
 

FORDF250HDXLT

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Typically the reason for the fuel filter light,is due to a fuel filter in need of a change.If it's still on after a filter change,then the next likely issue would be the lift pump.If it's still on after those are changed,then you've got something wrong with the fuel lines,like blockage or the the fuel tank selector valve is plugged up.If the truck has been sitting for a long time,I suppose one might suspect algae plugging up things like the fuel screen on the pickup.

This light doesn't become triggered by air though.........I don't think.I don't seem to ever recall seeing it during a late change of the fuel tank switch or during a re-prime of the system after an ip swap.
Odds are high,a fresh fuel filter resolves the issue.
 

icanfixall

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as already posted. The light tells you the fuel pressure has dropped and now you have a vacuum on the filter and fuel system. Very ******* the injection pump too. Check the fuel pressure at idle. It must show bout 5 or 6 lbs to be correct. You might need a new lift pump at a new rubber hose from the frame to the lift pump. Those lines wear out too.
 

derjackistweg

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Update:
The vacuum light from the fuel filter still comes on. AND its is actually a vacuum in the filter incurring. I dove like that 1000 miles with no problem, starting, power was ok, high speed easy over 80 mph.

BUT recently after I drove my truck 10 miles. (changed coolant) started and run 15 seconds - and then died. After some try and error. finally the main fuel filter was only half full. Hardi Pump -ok.

It´s a 1993 7.3 N/A, 100k. Most parts new [IP redone Advance piston, Injectors redone, GP new, GP relais new, GP "Computer" new, Electric fuel pump new, fuel lines from frame to top, no air leaks].

After all air was out of the system, truck ran as good as usual. But light comes on again and again.

I spoke with the German manufacturer [Hardi el. fuel pump] and the pump is fitted and installed correct.

The "original" pump the truck was equipped when bought is an facet:
You must be registered for see images attach

The facet was shot, once. It produces ~ 5- 7 PSI - a facet posi flow EFP -3. I don´t know how much flow. Should be a very old one.
As I live in Germany I don´t want to rely on simple parts that can NOT be purchased locally, if possible. As far as I can remember (in early 2015) this facet is a simple ~ 50$ pump w/o an amazing flow.

So I bought this pump: This manufacturer has a very good reputation in Germany:
https://www.hardi-automotive.com/produkt/kraftstoffpumpe-10012-6v-12v-ab-100ps/
HARDI fuel pump 10012-6V [product name]
Delivery rate: 100-130 / h
Pressure in bar: 0.28-0.35 [- 5 PSI]
Starting voltage: 8.5-9.5V
Rated voltage: 12V
Current consumption: 1.5-1.9A
Suction height: approx. 1,5mtr.
Weight: 1000g
Neck: 10mm
splash-proof, suitable for motors over 100hp

this should be suffisant flow at least for no load on the IP. But it isn´t.

The pump is - like the old facet - electrically connected to the GP relais. It is the small red wire at the left lower corner:
You must be registered for see images attach

This plug has power as soon as the GP system starts. So from right before start. And also while running, as far as I have [multimeter] testet after the recent failure. The Hardi pump starts already at low voltage from ~9 volt onwards.


I really don´t want a mechanical pump again. Having had so many problems with the system in total I want the easy way to transmit fuel w/o engine running. And also it is impossible to get one cheap. Shipping form the US is always + ~ 100$.
We all know that fuel translates into power in a diesel engine. So I don´t want to give this up of course. But I doubt that this is - at least the only - issue.

I once med a Canadian Mechanic (actually an engineer) who repaired my pump in no time (40 minutes). Before, he did a diagnostic via telephone! and was right. An amazing guy - but I think he moved back to Canada :-(
He gave me a lot of advises. One was something like put this 10 mm steel ball inside a return line. It is 10 months ago and I had other issues at the time, so I am not 100% on that.
This could make sense to me if it is the return line from the filter - which I guess he meant. This return line is supposed to send back fuel if the pumps get´s more than it needs. This is obviously NOT the case but could cause issues IF and in the long run.
  1. Doesn´t the DB2 by itself has an return line for that? I´ll check the Stanadyne document for that....
  2. Is there something like a valve opening the return line at the filter housing for overflowing? IF this is permanently open, pressure cannot be enough, eventually.
 
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Thewespaul

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Try hooking the fuel pump directly to the battery terminal to eliminate it as an electrical issue
 

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