Hello, I have maybe a year on my isspro gauges and my fuel pressure gauge seems to be acting up. Is the sender an often replaced item? I have a needle valve, snubber, fuel hose plumbed to my sender. My hose is 6 ft long to my sender. At idle it is fluctuating from 11 psi and at idle revving to 2k it is at 18 psi.  Just trouble shooting on where to start. 

9 hours ago, 01cummins4ever said:

Not quite sure on the Hobbs switch but I can see the potential for issues, I think @IBMobileruns that set up and keeps it deactivated, He can probably fill you in on that,

 

I just run straight mechanical, and an old school draw straw in the tank outside the basket and no needle valve, just a snubber, fuel pressure jumps to 16 the second engine fires, been going strong for several years 

So you arent running the hobbs switch? My pressure has been great the last few years, up until recently. The Hobbs switch was just something I thought to maybe isolate to verify if it could possibly be causing the issues. I am doubtful, but who knows. As a last resort I can clean/replace fuel hose to make sure there isnt some blockage in my system. I do have a new fuel sending unit, but I ran a tank of fuel through it and had good fuel pressure 16+ at all times. 

Here is a video of my fuel pressure doing what it does. Sorry for the unsteady hand. Under acceleration it tanks pretty quick, but as soon as I start to go downhill the pressure rebounds. 

 

 

 

Edited June 3, 20213 yr by Red Rambler

No, I'm not running the hobbs switch or even a secondary lift pump, I would try and bypass the hobbs system and see if that tells you something, here is a diagram of my set up, It seems to me if you have a failure in the hobbs switch you will force fuel to run through your stock lift pump, although your fuel pressure seem to be acceptable it shouldn't be dropping on acceleration

 

 

I think I will give that a go, try to eliminate the hobbs switch and see what results I get. I am going to get new fuel hose today as I am making a shorter run of hose for my pressure gauge. I had it running in the cab before(mechanical gauge) and used the same hose(electric gauge), so it is too long currently and I have to make a loop. I am going to get some extra hose as well in case its needed to bypass the stock lift pump entirely. Unsure if I can simply unplug the hobbs switch or if it will throw a code? Slowly but surely, going to get this lined out. 

Stupid question, what is the purpose of the Hobbs switch?

Also, are you sucking through an electric, rotary vane pump?

9 minutes ago, LorenS said:

Stupid question, what is the purpose of the Hobbs switch?

Also, are you sucking through an electric, rotary vane pump?

The Hobbs switch controls the stock lift pump and turns the stock lift pump off once a certain preset pressure is reached, the preset pressure is set within the Hobbs switch. So, once your fuel PSI reaches say 6 PSI, it commands the stock lift pump not be used. No, the only pump I have is the mechanical pump that is driven by a pulley on the harmonic balancer, and the pump itself attaches at the lip of the oil pan. Not my picture, but how it works. 

 

your truck does not know the hobbs switch is there to throw a code.

 

As an update. I ordered a few 1/4 JIC fittings, barbed, that took a few days to arrive. The truck fired after putting my new fuel hose on the fuel pressure fittings, and to the gauge. PSI reads low again, 10 PSI now. So in testing I unplugged my lift pump wiring so it would be running 100% mechanical. Fuel pressure kept falling and it finally sputtered so I shut it off. Plugged my stock lift pump back in, bump the starter to cycle the lift pump. And she fired. PSI is at 10. So this tells me that possibly my mechanical pump possibly isn’t working. I take it off, check it, appears to be no blockage. I tried calling glacier to see if there is anything else to check on their pump, but no answer. At a loss at this point. 

Edit***
So, after taking my pump off and cleaning it, making sure it was spinning fine. I did notice my belt looked a little worn, so I decided to swap it out for the new one in my glove box. Fire it back up, and BOOM 17 psi. My worn belt was causing the issue the whole time. Long circle to find the solution, but glad I figured it out. User error on my part for sure. Now I need to figure out the best way to adjust belt tension and ensure the problem is fixed. 

Edited June 11, 20213 yr by Red Rambler

Does look a bit worn. Happy found that problem.

I can’t see the pic, it won’t show up on my phone, but here is the belt adjustment instructions from fuel boss 

 

) Setting Belt Tension: Slide pump to center under the harmonic balancer. Install the timing belt around small pulley then around large pulley. Adjust the pump so that there is JUST ENOUGH tension to keep the belt teeth engaged. Proper tension for the belt is LOOSE. While this may seem odd, this is a cogged timing belt and requires zero tension to stay engaged. Grab the pulley on the pump and rotate it to place tension on one side of the belt. There should be a loose bow to the non-tension side of the belt. If in doubt, looser is better!
Any tension on the belt will cause early pump wear and seal failure. Pumps that show shaft wear from over tension will not be covered under warranty.

Cant see the photo either.

 

The belt tension is definitely loose on the GDP Fuel Boss pumps. Never had a belt thrown in 4 years/18k miles.

 

GDP also says their belts should go like 50-75k between changes.

 

Speaking of.. I need to check where a fuel leak is coming from around the fuel pump.. might be the hoses, might be fittings, don't think is the pump halves seal. Especially since I have my first pull of the year tomorrow..   

37 minutes ago, 01cummins4ever said:

I can’t see the pic, it won’t show up on my phone, but here is the belt adjustment instructions from fuel boss

One side of the the teeth on the belt is very noticeably rounded off.

Could it have been too loose? If the belt was rounded off on one side only, could that have meant that the belt was skipping over the pulley teeth?

1 hour ago, Silverwolf2691 said:

Cant see the photo either.

 

The belt tension is definitely loose on the GDP Fuel Boss pumps. Never had a belt thrown in 4 years/18k miles.

 

GDP also says their belts should go like 50-75k between changes.

 

Speaking of.. I need to check where a fuel leak is coming from around the fuel pump.. might be the hoses, might be fittings, don't think is the pump halves seal. Especially since I have my first pull of the year tomorrow..   

I am thinking mine may have been a touch loose as I’m at roughly 35k on my old belt. Good luck on your leak. 

 

If any of you get time, you care to snap a picture of your belt, turn your bottom pulley so one side is tight so I can see the bow in the opposite side that the instructions speak of? I uploaded the picture of my belt from my PC, instead of my phone, so maybe now it is visible. I am having issues seeing a few pictures in other threads as well. It just has the picture icon of mountains I think it is, but not an actual picture.

Edited June 11, 20213 yr by Red Rambler

Large pictures might be filter out... Server software being weird. 

1 hour ago, Red Rambler said:

I am thinking mine may have been a touch loose as I’m at roughly 35k on my old belt. Good luck on your leak. 

 

If any of you get time, you care to snap a picture of your belt, turn your bottom pulley so one side is tight so I can see the bow in the opposite side that the instructions speak of? I uploaded the picture of my belt from my PC, instead of my phone, so maybe now it is visible. I am having issues seeing a few pictures in other threads as well. It just has the picture icon of mountains I think it is, but not an actual picture.

No pic at the moment, but I have 3/4 inch deflection in the belt on both sides with it in the relaxed position,  I’ll try and check it later the way the directions state 

3/4 inch to half inch is what i have too. Cant seem to upload a photo from my phone. Possibly too big? Server error -200.. 

 

I think one of the fittings is loose for the fuel leak. And an oil leak from my vacuum pump.. 

Yes. Photo is too big. Needs cake back your camera or use a resize app. Most cellphone create monster huge photos. I've had to scale back the allowed size so we do run out of hard drive.

Been pissed about fuel related items on my truck lately. Didn’t touch it much, but she was due for a bath and I am now sitting at a happy 17 psi fuel pressure. So she got a bath. 

Edited June 12, 20213 yr by Red Rambler

 Mine needs a good scraping and a bath in blue paint. Yours looks very nice.