Ok I need a little help with this--
if I were to install a fuel pressure gage (or have someone do it for me!) and the filter started to plug up would the gage show it?

If it did, would it show a lower fuel pressure or higher pressure.

Sorry to be so dumb about this but we spent a rather unpleasant 3 or 4 hours stuck on the side of the road till the tow truck showed up and then found out(the next day) it was a plugged filter,one with only 5k miles on it.
Trying to avoid that happening again,and my thought is that if a gage would show it starting to plug then I could chose my place to pull out of traffic and change it out

Ok I need a little help with this--
if I were to install a fuel pressure gage (or have someone do it for me!) and the filter started to plug up would the gage show it?

If it did, would it show a lower fuel pressure or higher pressure.

Sorry to be so dumb about this but we spent a rather unpleasant 3 or 4 hours stuck on the side of the road till the tow truck showed up and then found out(the next day) it was a plugged filter,one with only 5k miles on it.
Trying to avoid that happening again,and my thought is that if a gage would show it starting to plug then I could chose my place to pull out of traffic and change it out

All the way from Fremont NE question... You guys still a #5 on the license plate?

This is a good question. To be honest I bet a vaccuum guage or switch better yet would be a better solution. As if your truck is stock your CP3 has to suck the fuel through the fuel filter. I bet that dumb plastic vent screw would be a good place for it. I also think that setting the switch to go off at anything more negative than -3 psi would be a good starting point. Then you could have it turn on a light in the cab for indication. Next week if I get some time I may have to check into this simple idea of mine. As from what I have read several people change there filters to often just to be on the safe side.

FWIW when I lived there my plate started with a 1.

Unless you're got biomatter in your diesel (OLD fuel sitting for a long time)

Your filter should last for 15k at least... Your truck would stumble at the top end and not want to shift at WOT either, with a failing filter. I'd call it fluke your filter plugged at 5k. Dump a bunch of additive in your tank, change your filter again and don't fill up at the farm diesel station unless you have to.

depending on where you tapped for the fuel reading it could read high or low. It's low coming out of the tank and then gets bumped up before it hits the rails. You'd have to put it on the low side because I don't think there are guages that measure 25k psi.

I would suspect that if you did have a guage that it would have erratic readings from clogging and/or trash in the fuel and quite possibly the pressure would not be as high or take longer to raise the pressure.

depending on where you tapped for the fuel reading it could read high or low. It's low coming out of the tank and then gets bumped up before it hits the rails. You'd have to put it on the low side because I don't think there are guages that measure 25k psi.

I would suspect that if you did have a guage that it would have erratic readings from clogging and/or trash in the fuel and quite possibly the pressure would not be as high or take longer to raise the pressure.

We have different mind sets on this one. I have concoured the dirty filter issue before.

In a positive fed filter when the pressure prefilter varies more than the postfilter more than 2 pounds than when the filter new was recorded at then its time to change the filter.

In a negative system like our Dmax's if you record the max negative pressure post filter at wot and set a vaccuum switch to go off if it exceeds that vaccuum and once again had it power a light or in some peoples case and electroshock device they would know if they really need to change your filter at 15000 miles or 40000 miles or even a couple hundred if you where to get some really really bad fuel.

Braino am I missing something? If the vaccuum switch was post filter the amount of fuel in the tank wouldn't be a factor worth considering in my view. I haven't proven this yet but it seems like a pretty simple solution.
And a pretty cheap one too.

All the way from Fremont NE question... You guys still a #5 on the license plate?

This is a good question. To be honest I bet a vaccuum guage or switch better yet would be a better solution. As if your truck is stock your CP3 has to suck the fuel through the fuel filter. I bet that dumb plastic vent screw would be a good place for it. I also think that setting the switch to go off at anything more negative than -3 psi would be a good starting point. Then you could have it turn on a light in the cab for indication. Next week if I get some time I may have to check into this simple idea of mine. As from what I have read several people change there filters to often just to be on the safe side.

FWIW when I lived there my plate started with a 1.

Hi Opie!
They changed Douglas,Sarpy,Lancaster, counties from the first number system to numbers and letters---sorry but no more number 1, the rest of the state still has the numbers.

If you get around to checking into your idea let us know what happends:grd:

Thanks

We have different mind sets on this one. I have concoured the dirty filter issue before.

In a positive fed filter when the pressure prefilter varies more than the postfilter more than 2 pounds than when the filter new was recorded at then its time to change the filter.

In a negative system like our Dmax's if you record the max negative pressure post filter at wot and set a vaccuum switch to go off if it exceeds that vaccuum and once again had it power a light or in some peoples case and electroshock device they would know if they really need to change your filter at 15000 miles or 40000 miles or even a couple hundred if you where to get some really really bad fuel.

Braino am I missing something? If the vaccuum switch was post filter the amount of fuel in the tank wouldn't be a factor worth considering in my view. I haven't proven this yet but it seems like a pretty simple solution.
And a pretty cheap one too.

Nope, your logic makes perfect sense and I agree with it

The filter head vent is on the intake or "dirty" side of the filter cartridge. It will not properly indicate a clogged filter because the pressure drop is after the vent on the "clean" side of the filter. There is already a pressure tap on the clean side of the fuel system, between the filter and the injection pump. It's the large black plastic cap covering a tire-stem looking (woodruff?) valve just below the alternator. The vacuum swings through some pretty large numbers, varies with fuel level as well as whether the truck is sitting on level ground. It is mostly dependent upon rpm as vacuum is produced by the low pressure section of the injection pump driven by the cam gear. Kennedy www.kennedydiesel.com sells a vacuum/pressure gauge that clips onto the test valve - but it's not useful for "full time readings" since you need a consistent testing condition (like at idle). Perhaps installing a pressure switch with a "maximum" might be good for alerting to a clogged filter, but you could probably trip that maximum value repeatedly just by hitting WOT.

The filter head vent is on the intake or "dirty" side of the filter cartridge. It will not properly indicate a clogged filter because the pressure drop is after the vent on the "clean" side of the filter. There is already a pressure tap on the clean side of the fuel system, between the filter and the injection pump. It's the large black plastic cap covering a tire-stem looking (woodruff?) valve just below the alternator. The vacuum swings through some pretty large numbers, varies with fuel level as well as whether the truck is sitting on level ground. It is mostly dependent upon rpm as vacuum is produced by the low pressure section of the injection pump driven by the cam gear. Kennedy www.kennedydiesel.com (http://www.kennedydiesel.com) sells a vacuum/pressure gauge that clips onto the test valve - but it's not useful for "full time readings" since you need a consistent testing condition (like at idle). Perhaps installing a pressure switch with a "maximum" might be good for alerting to a clogged filter, but you could probably trip that maximum value repeatedly just by hitting WOT.

Idle_Chatter thanks for the input, I have been swamped and haven't had the time to look into this yet.
That being the case I think the next easy/right answer now would probably to be installing a Tee fitting in the line that leaves the Fuel Filter. The extra open port in the Tee would have the negative pressure switch in it. I will talk with my pressure switch vendor tomarrow. After I test it out I will post the part numbers and settings on this thread.
Zoom I guess after 22 years things do change in Nebr. :lol:

Keep in touch with this thread as I have real good follow through history.

The filter head vent is on the intake or "dirty" side of the filter cartridge. It will not properly indicate a clogged filter because the pressure drop is after the vent on the "clean" side of the filter. There is already a pressure tap on the clean side of the fuel system, between the filter and the injection pump. It's the large black plastic cap covering a tire-stem looking (woodruff?) valve just below the alternator. The vacuum swings through some pretty large numbers, varies with fuel level as well as whether the truck is sitting on level ground. It is mostly dependent upon rpm as vacuum is produced by the low pressure section of the injection pump driven by the cam gear. Kennedy www.kennedydiesel.com (http://www.kennedydiesel.com) sells a vacuum/pressure gauge that clips onto the test valve - but it's not useful for "full time readings" since you need a consistent testing condition (like at idle). Perhaps installing a pressure switch with a "maximum" might be good for alerting to a clogged filter, but you could probably trip that maximum value repeatedly just by hitting WOT.

:confused: Shrader???

That's it! Schraeder!! Thanks Blackmax. I knew it was a "name" but just spaced on it at the time I was typing! It's hell getting old!

I will still be going with the Tee idea as I run a mechanical lift pump. However I can still get some part numbers/adapters for the guys who don't. Does anyone know what thread the Schraeder valve uses?

This is how I do it:

http://www.kennedydiesel.com/images/Dmax-fuel-filter-rest1.gif


What you will find is that the gauge will swing around a lot as flow rate, load/rpm and inertia affect the readings on the std suction based system. Having this tool on board to periodically check filter restriction can be priceless. I got bit by a plugged filter myself while on the road and having this gauge to verify the issue was priceless...

Nice pics. My intention on this thread is to try to change the exsisting logic of changeing the fuel filter at a set amount of miles, instead change it when it actually needs to be changed. I very well maybe off my rocker, if not this may prove to be good for peace of mind.

Your pic above on the right is what I thought I would see with a stock truck truck at idle. My experience is if the filter has 10 psi of neg pressure or more it is time to change the filter. There are some guages available that are modified vacuum guages that use a different backround that back me up on this as well.

If a guy wanted an idiot light to come on when it was time Hobbs sells adjustable vacuum switches that would do this. P/N 78813 (Single terminal, the ground is taken from what it's 1/8"npt male threads is threaded into ) and 77432(2 terminal. One of the terminals has to be routed to ground.)
I haven't gotten any prices yet and it very well maybe cheaper just to use a vacuum guage for indication. But I feel knowing the health of the factory fuel filter is worth having another guage for, if need be.
Again I haven't had the time to check out what threads are being used for the shrader but I will find some time to guage them if need be and it will be easy to find or make an adapter that goes from the shrader to female 1/8 npt. But before I can mention any "what should be the max numbers" we do need to monitor the trucks in all operations with a vacuum guage.

Being that I am running a pump that increases negative pressure I got a responsability to have some real world answers for that set up as well.
I will be installing a vacuum guage and two pressure guages. That way I will be able to obtain some numbers on both the stock filter and on the Permacool filter added as well.

If I were running a positive pressure pump like I do on my dodge I measure the difference in pressure on both sides of the filter when new. When the difference in that number climbs over 2 psi from what I recorded when new this is when I changed the filter. I use two senders one switch and one guage to do this.

I believe that this is best tested periodically at a set fuel level rather than watching it. The readings swing around a lot under normal driving. All I do is slip off the switched power to my pumps and I can see with great resolution, the amount of restriction in the filter(s)

I believe that this is best tested periodically at a set fuel level rather than watching it. The readings swing around a lot under normal driving. All I do is slip off the switched power to my pumps and I can see with great resolution, the amount of restriction in the filter(s)

Thats cool, but whether the readings are swinging around some or not as the filter life is going the pressure would be getting that much more negative. Like I mentioned earlier I have a different view than most. After I am done I too will only periodically check my guages the main diffrence is I will only have to look down to do so. :cool:

if interested the black plastic scew is a 10mm o-ring fitting
i ordered 2 from a hydrolic hose shop took a couple weeks to get i have a kd fuel pump and a inline fuel filter mounted under the frame i just need another gauge to fill my pod so i got 0-15psi gauge it will let me know if my inline is dirty
i get the filter through work so change them way to often to notice any difference in pressures ussaly around 3-5 psi
i ordered a 10mmoring x 1/8" npt and then a 2' steel braided hose to the sending unit of the gauge looks good