Mechanical FP gauge story and ??'s

[JPLB22]

Two weeks ago I measured my fuel pressure with a hand held gauge at the schrader valve FP = 12 psi. at idle.



This morning I had the full time Dipricol FP gauge isnstalled. It is the new white face made to match '03 gauges ( it looks good even though I have a 2nd gen ), it also has the new billet aluminum isolater. I had it installed on the steering column. When truck was first started after install the FP = 9 psi. at idle. It was an hour drive home at 80 mph and FP stayed rock solid at 9 psi even when under WOT. I shut truck off at work and FP gauge falls to 5psi when truck is off. Three hours later I go out to truck and gauge is sitting at 6 psi with truck off. I start truck up and gauge goes to 7 psi and stays there solid for entire trip ( about half hour ) will not budge off 7 psi at WOT either. And I had a stainless steel line used from the schrader to the isolater, the line seems to be giving off some sort of vibrating noise ( very annoying ).



My questions are this...



Why the difference in fuel pressure from one trip to the next ?



Why did the fuel pressure only go up 1 psi after second start ?



Is my LP dying ?



What would a remedy for the noisy steel line be ?



Sorry for being so long winded any replies are greatly appreciated!!

 

[nickleinonen]

And I had a stainless steel line used from the schrader to the isolater

is the core still inside the schrader valve?

 

[JPLB22]

I don't know if the core is still in there.



I went to someone who comes quite highly recomended by this website for diesel work in my area. But I guess anyone can make a mistake at any time. Would there be any problems with unscrewing the S. S. line from the schrader ?? Would the S. S. line need to be purged is I unhooked it ??



P. S. I had this gentleman do the fuel line kit for the line from LP to filter at the same time.

 

[JPLB22]

Well I took care of the stainless steel line vibration. I got some 3/8 rubber fuel line and cut it down the middle and wrapped it around the S. S. line and took a ride. It was as quite as it was before, nothin but pure cummins music.



As for the FP it is still at 7 psi, but this time after shut down the gauge fell to 4 psi instead of 6 psi.

 

[SEmerson]

Bad guage or isalator or the value is still there. I pulled the seal off my valve and put it back in. It worked well as a snubber.

 

[overfueled]

I run 2 Autometer / Mechanical Fuel Pressure Gage's with the Isolator, no banjo’s, #6AN SS 3/8 Lines, tank to VP-44.



1 isolator I have on the intake side of the fuel filter and it reads 5-7 lbs all the time. 0-20 Lb gauge. I run the dual carter replacement pumps (P4600HP 7 psi, P4601HP 15 psi)



The other isolator I put right at the VP-44 using a T #6AN metric connection with the 3/8 lines this (0-100Lb gauge) reads 15-20 lbs most of the time. When the filter needs to be changed it will drop to 10 Lbs. I keep an eye on this.



JPLP22 I also had that stainless steel line vibration. At the gauge in the cab. I keep the lines the same. I remounted the front pump with the rubber bushings that came with the pump this also took care of the noise in the cab.



Also I had to fill, refill, refill again the isolator with antifreeze, it would read "funny" but I was able to get this right as well. I have had this setup in for over a year, it works well. This could be your problem as well. I run the autometer gauge and isolator I don't know if your Dipricol FP is the same, this is my best guess. OverFueled

 

[JPLB22]

overfueled... I saw some air bubbles in the isolater line this morning. I was thinking that since air can be compressed that this may give me an inaccurate reading on psi. What do you think ??



On the way to work the pressure was down to 4. 5 psi. The gauge fell to 2. 5 psi overnight while truck was off. The gauge is consistent in the fact that it will only increase 1 - 2 psi when the motor is started. So if the gauge was at 5 psi before starting I would only see 6 - 7 psi after start or 2 psi before start would = 3 - 4 psi after start ect. ect...

 

[overfueled]

JPLP22 The air indicates that a fitting is not tight or that you did not fill it all the way.



I would guess, that it's the latter, this happened to mine.



That was what I was talking about when I said that I had to fill, refill and refill again until it was right. I should have said until I got all the air out. It now works GREAT.



I do recall that I would get an inaccurate reading when I had air in the system. Slowly it would drop. It would start out high but in time it would go down, that is when I would refill. One week it would say 25 lbs and the next it would say 20 lbs, then another it would read 12 lbs but like you said what ever it would read it would not move much.



On mine when I shut off the key it drops right to zero. When I bump the key it will jump up to seven and then back to three, the main will jump to twenty then down to ten.



When I start they go to twenty for one and seven for the other.



Until the smoke comes on then I will drop as much as 5-7 lbs on the main and 2-3 on the pusher. OverFueled

 

[HoleshotHolset]

Let's imagine that someone hooked up an Auto Meter mechanical FP gauge (with isolater)..... without filling it with coolant.....



I ruined my very nice liquid filled Pro-Comp gauge, didn't I... ?



It has recently ceased to operate... . after only about 1. 5hrs total runtime.



I didn't have any instructions for the gauge setup - it was something I had in my basement for over 5 years since I bought it used with a bunch of other stuff.



Matt

 

[illflem]

I don't see how running one without antifreeze could hurt it. All of my Ag sprayers use an isolator to keep caustic chemicals from eating the gauges, none have antifreeze, just air, and have worked for years.

For something as safe as diesel an isolator just seems like an unnecessary hassle and expense, I run diesel straight to the gauge.

 

[HeberRam]

Jplb22... The problem you are having is the isolator!!!! The plunger inside is stuck, and needs to be replaced. If you purchased from Ken Jones, let him know ASAP, and he'll replace. The same thing happened to me with the "new" purple billet one just yesterday.



Steve

 

[HoleshotHolset]

Should I be able to blow through the isolator? What are the innards composed of inside these things?



I really hope I didn't wax my gauge... . it was a nice one.



Matt

 

[illflem]

You shouldn't be able to blow though the isolator. All they are is a plunger that moves when pushed on by diesel pressure to provide the same pressure on the dieselless side. I've seen some that are just rubber diaphragms.

 

[HoleshotHolset]

So... I guess my isolator ate itself... way before it ended up in my truck.



The gauge was getting POUNDED by fuel pulsations from the lift pump... . I was sorta wondering if this was normal. It was pretty loud.....



Now I get to figure out if the gauge itself has gone to the "great gilded cage in the sky"... .



Matt

 

[CFAR]

Matt talk to Scott at MASSDIESEL he has the braided SS lines from the schrader to the back of the gauge.

 

[CFAR]

Matt talk to Scott at MASSDIESEL he has the braided SS lines from the schrader to the back of the gauge.



Its where I got mine. My isolator (which I don't use) instructions said to put the isolator and gauge on the same level as close as possible, for the best accuracy.

 

[HoleshotHolset]

If I decide to get rid of it..... I'll just eliminate the isolator with some fittings... . no need to buy a whole new SS braided line... . when my SS braided lines are perfectly fine.



As much as I love talking to Scott on the phone ... . there is another fix for this issue. Besides, if I go down to the shop I'll end up working on something!



Matt

 

[illflem]

Matt I doubt if you ran the gauge long enough to ruin it if you didn't use a snubber. On a 12 valve without snubber the gauge is so loud and wild that few people could stand it for more than a few seconds. An isolator is no substitute for a snubber on a 12, you must always use a snubber.

 

[MrFixit]

As for my Diprocol, I used the genos tapped banjo, 18" grease gun hose and no problems. I spilled a little fluid while installig my gauge thus leaving 3 inches of air. Does not seem to affect performance at all, even though air compresses. I see a solid 15 at idle and the needdle drops to zero, the minute I shut the truck off. I get a slight pulse on the gauge when I turn the ignition on as the LP cycles. Does sound ike the isolator might be bad. Did you make sure it was in the down position when you installed it???

 

[HoleshotHolset]

Bill: I know what you mean... . that thing was obscene in the cab. It sounded like I had a VW diesel running behind the dashboard... .



Okay - who sells snubbers - hopefully with 1/4" flare fittings... .



Matt