Fuel Pressure

[chucksram]

I have a 98 12v auto. Is it as important to monitor fuel pressure with this engine as it is on the 24v engines?

Also, I would like some input as to where to tap into for fuel pressure guage.



Thanks



Chuck

 

[Jim Fulmer]

Hey again chuck, I bought a fitting from TST so I could tap into the bleed screws at the filter housing and use the boost guage to check it (only) so I came up with 14-15 lbs at idle and 22 lbs max RPM and if you under a load at max RPM it drops just a bit say to 20 so I replace the overflow valve via Piers and the pressures stayed the same but it starts just a little easier now.



Jim

 

[John_P]

Chuck:



"JFulmer" has already given you good advice on the

fuel pressure gauge etc.



IMO, I think it is important to monitor the fuel pressure

on our 12 valvers. Although the 24 valve trucks have

more pump failures etc. , it can still happen on the 12

valve engines and being able to "watch" the pressure

can avert many engine problems.



I have an electrical fuel pressure gauge on my 96'

12 valve. My pressure stays around 27-28lbs. under

constant RPM and around 17-20 @ idle. I have a "Prime-

Loc" System on my truck and I hooked the "sending unit"

to the NPT plug for that purpose on the mount which

takes the fuel filter.



I do not recommend using a "mechanical" gauge though!!

They are cheaper than the electrical gauge, but they have

diesel fuel flowing through a hollow line (rubber or plastic)

into your truck and up to the gauge! If that line ever

breaks or come loose... ... ... ..... what a mess that would be!



Good luck!



----------

John_P

 

[illflem]

Originally posted by John_P



I do not recommend using a "mechanical" gauge though!!

They are cheaper than the electrical gauge, but they have

diesel fuel flowing through a hollow line (rubber or plastic)

into your truck and up to the gauge! If that line ever

breaks or come loose... ... ... ..... what a mess that would be!

John_P

Not really a problem since you need a gauge snubber if you use a mechanical gauge(should really have one for electric gauge also). With a snubber the fuel flow is restricted to less than a pin hole, in the event you did have a leak it would take an hour just to fill a cup. If you use a needle valve instead of a snubber you have the option of shutting it down in case of a leak. After 40 years driving rigs with mechanical oil pressure gauges I have never had one leak motor oil in the cab. Motor oil is at higher pressure and hotter, more prone to leak. I wouldn't worry about bringing diesel into the cab. My mechanical fp gauge has been leak free almost three years and cost under $30 for the full setup. A fp gauge is not really necessary but very handy to diagnose any problems.

 

[LarryB]

I got to thinking about my fuel pressure and like everyone else, The more I thought about it, the more I worried. I decided to just make a quickie gauge to check my overflow valve. I found a pressure gauge, internally dampened, liquid filled, stainless case, vibration proof, that was only 1-1/2" in dia. I made a double banjo bolt that includes the origional bleed screw on my lathe. I also turned and tapped a ring for the gauge. It mounts firmly right on top of my fuel filter housing.



It's probably not as good as a gauge mounted in the cab because you cannot see it while under load. But it took me all of about 5 min to install it. Total cost, about 35$ I can make up some more if anyone is interested.



My idle press is about 17 and 2500rpm is about 30. Does this seem about right?? I posted this on the Acc. forum but got no answers.



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[Jim Fulmer]

Larry, you come up with all kinds of cools stuff! I want to mount an electric type fuel pressure guage like the 24 Valvers do and use the sterring wheel type pod for it cause my triple pod is full and I don't like the dash ones, then I thought that same location would be cool for a second boost guage to monitor the big turbo boost pryor to entering the little one... ... ... . did I mention twins again



Jim

 

[LarryB]

Jim

You might consider using a solenoid valve to switch your existing boost gauge between turbos. I use one now for switching between boost and E-brake back pressure. It works great. You could use a little pushbutton or mini toggle switch right next to the gauge you have now. Mount the solenoid under the hood. Maybe save you some money and hassle. It would be another gizmo to play with too!



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[illflem]

Why not do the same thing to toggle between fuel pressure and boost with one gauge?

 

[LarryB]

Bill, Good idea! Unfortunately I cannot find a solenoid for a decent price that will hold up to diesel. The ones I'm using have a rubber seal.





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Well, maybe it's time to tear into one and make it "diesel proof"

 

[LarryB]

WRONG!



Those seals are tiny, rubber and very intricate. Guess I'll have to keep looking for one with hardened steel seats. #ad

 

[BillGotthelf]

My 96 had two lift pumps go. The first at 30,000 miles and dodge replaced it locally. The second died at (60,000) 10 pm on I-95 15 miles south of Savannah, Ga and the Cummins dealer in Sav (cannot remember the name) replaced the lift pump ( which dodge reimbursed me for for-nice of them-I had a 100,000 mile extended warranty). That one is still holding up. I use double filtered fuel-always do- and change primloc filter often. My 99 has not died yet (68,000) miles. I doubt if the dealer will replace lift pump unless its way out of spec-at least thats the attitude at dodge down here. So I have gauges on everything else (including one to tell me when my wifes cat has farted) but no fuel pressure gauges yet. Oo.

 

[illflem]

Seems like a solenoid valve designed to switch between main and aux fuel tanks would work.

 

[Jim Fulmer]

Larry B, that twins comment was a joke, it's just something I want but can't afford nor do I need right now, but never the less a heck of an Idea to use the solenoid and an A/B switch.



Jim

 

[pwknapp]

Well guess I havta' get a fuel pressure guage also. Have over 400k on the original pump and need to know what the pressure is. Picked up a spare and tossed it under the seat just in case.

 

[LarryB]

Originally posted by illflem

Seems like a solenoid valve designed to switch between main and aux fuel tanks would work.

Duh! Hello, Of course it would. Why didn't I think of that? I happen to have a couple left over from when I converted to the diesel fuel system with return lines. Now, if they will hold up to 40psi boost pressure. Awww man! All that work to figure out the pressure gauge thing.



Thanks Bill, sometimes the things right in front of your face are the hardest to see. Oh well, back to the shop I go.