Erratic Fuel Pressure

[woodtrucker]

I may have posted here before. I have had this issue for sometime and have read that is a concern and also read that it's not a problem unless fp drops. 

My fuel pressure mostly runs at around 18ps and down to 14 psi at WOT when towing a heavy load. 

I noticed yesterday that while unloaded, I drove to round trip 5 hours and let truck sit for about 4 hours. Then when I got in it to leave to go home from work, my fuel pressure was bouncing up a lot. It will run at 18 psi or and it just so happen when cruising in 5th gear, the fp would drift up and down from about 24-25psi back down to 18psi. It did this a bunch of times and slowly settled out the longer truck ran but never completely cleared up. didn't do it at all on the trip. 

very strange. It's a ddrp-02 pump. thoughts?

Sounds like it might be a return spring issue. Can this be replaced easily or should eat it and upgrade lift pumps?

This lift pump probably has 40k on it.

[dripley]

You might want to run that by FASS. It seems to me that most folks have a drop in pressure when that pring gives them trouble. Are you running a mechanical pressure gauge or an electric. The brain on the electrical ones can go out and give some whacky readings.

[woodtrucker]

isspro ev2 gauge. I have snubber on it too. 

[Me78569]

I would chat with FASS also.  

[notlimah]

Does the DDRP have a return ball and spring?

 

If so then I feel you'll just be wasting your time calling FASS. All they'll do is send you a new ball and spring and the same problem will come back eventually. Or want you to send your pump in all together for them to check it.

 

I ran into almost exactly the same issue with me FASS 150 except with a LOT less miles on it, and swapped multiple ball and springs out supplied from FASS and nothing worked. 

 

It wasnt until I called up Eric and Vulcan and got a 17lb spring and ball from him that this issue went away. The main reason seems to be that they use a Buna ball and Vulcan (read Airdog) uses a Viton ball which is a strong, more robust material. 

 

If you search for my thread titled longer cranking, you can read through what I found out.

[woodtrucker]

I called FASS and they said it could possibly be the return line check valve on vp-44 or that the DDRP02 is not keeping up and overpressuring. Then he went on to tell me the ddrp-02 is not going to last long on my setup and I needed to go to titanium 150 for a cool $600. 

What is strange to me is that if it couldn't keep up, I could see fp's going low but fuel pressure spikes just don't make sense. 

Especially considering I am not in a hevy throttle condition when this happens. It's usually happening at idle or cruising throttle positions. I run an Edge EZ and 40 hp sticks and even when towing/or not sometimes fp runs textbook and sometimes it's spikey. I do think the ddrp02 has a return ball and spring but usually folks replace that when the spring doesn't have a high enough constant to keep fp UP to where it should be. FASS guy says that a lp that can't keep up can go low or go high as symptoms but I'm not sure I believe that. 

 

[crf450ish]

I too am interested in the return line spring deal. I stretched mine out to 1 1/2" from the 1" it was. Went up to 16 psi steady from 13-14 steady psi. I'd like 20 steady psi, seeing as how I'll be going to larger injectors later this year. Almost about to remove the spring completely and go buy a new stiffer one. Theres a place in Spokane valley called Tacoma screw that will make custom springs based on poundage.  

Edited March 3, 2017 by crf450ish

[notlimah]

2 hours ago, woodtrucker said:

I called FASS and they said it could possibly be the return line check valve on vp-44 or that the DDRP02 is not keeping up and overpressuring. Then he went on to tell me the ddrp-02 is not going to last long on my setup and I needed to go to titanium 150 for a cool $600. 

What is strange to me is that if it couldn't keep up, I could see fp's going low but fuel pressure spikes just don't make sense. 

Especially considering I am not in a hevy throttle condition when this happens. It's usually happening at idle or cruising throttle positions. I run an Edge EZ and 40 hp sticks and even when towing/or not sometimes fp runs textbook and sometimes it's spikey. I do think the ddrp02 has a return ball and spring but usually folks replace that when the spring doesn't have a high enough constant to keep fp UP to where it should be. FASS guy says that a lp that can't keep up can go low or go high as symptoms but I'm not sure I believe that. 

 

 

They're pretty quick to blame other things other then it possibly being the pump. It's a real shame how they do that and had I known that prior to buying I would've gone a different route, because they've given me the same type of responses.

 

I know it seems weird to replace the spring and ball since pressures are spiking but what is more the likely happening is the spring has twisted or contorted itself so it's not providing a even seal against the pump using the ball. Also, the ball has more than likely indented itself into the pump weakening that seal the spring and ball are trying to achieve.

 

1 hour ago, crf450ish said:

I too am interested in the return line spring deal. I stretched mine out to 1 1/2" from the 1" it was. Went up to 16 psi steady from 13-14 steady psi. I'd like 20 steady psi, seeing as how I'll be going to larger injectors later this year. Almost about to remove the spring completely and go buy a new stiffer one. Theres a place in Spokane valley called Tacoma screw that will make custom springs based on poundage.  

 

No need for a custom spring. Just call Eric at Vulcan Performance and get a 17lb spring and Viton ball. They're on his website as well. I had similar fuel pressure on my 150 setup and finally replaced it with what I just mentioned and now fuel pressure sits between 17-19psi all the time.

 

You guys should read my thread here

Basically starting from my post on August 15th should for the most part cover what you are experiencing @woodtrucker and what you're concerned about and how to possibly fix your concern @crf450ish

[woodtrucker]

Interesting read. I might as well give it a try. I think that's the problem. I would think I'd have bigger problems if it was something on the VP-44. So is this all I need? I saw on your other post you talk about fittings but do I need to swap out fittings too?

 

 

I assume that air dog spring will work on my ddrp02 correct?

Edited March 3, 2017 by woodtrucker

[tbo1450]

Mike told me too shim the spring. I had 10psi to 7 psi bouncing all over with my fass 95 ti. I put one brake line washer inline with the spring. I have steady 17psi. 

I don't rec to stretch the spring. It got worst when I stretch mine. 

[notlimah]

2 hours ago, woodtrucker said:

Interesting read. I might as well give it a try. I think that's the problem. I would think I'd have bigger problems if it was something on the VP-44. So is this all I need? I saw on your other post you talk about fittings but do I need to swap out fittings too?

 

 

I assume that air dog spring will work on my ddrp02 correct?

 

Yea that's all I got. I can't say 100% that it'll work on the DDRP. If it does have a return spring and ball then I would imagine it would. Remember I was using this on a FASS 150 so I'm unfamiliar with the DDRP. It's been working fine in my FASS 150, still in there as I'm typing this. As far as the fitting, I was only looking at another because mine was getting a little beat up from taking it on and off so much and I didn't want to use another FASS fitting. But it turns out that the Airdog fitting won't work on the FASS 150, it was compressing the spring too much and I couldn't get the fitting to completely seat, so I just kept the FASS fitting.

 

2 hours ago, tbo1450 said:

Mike told me too shim the spring. I had 10psi to 7 psi bouncing all over with my fass 95 ti. I put one brake line washer inline with the spring. I have steady 17psi. 

I don't rec to stretch the spring. It got worst when I stretch mine. 

 

This works well if you're having low fuel pressures. Problem is when the Buna ball becomes indented and the spring gets out of whack you start seeing the erratic stuff. That's when better materials are needed, hence the Viton ball and airdog spring. If pressures are just low then shim away!

[tbo1450]

Mine was erratic. All over the place. My sec ball and spring too. Even when I hit the brakes the fuel pressure would spike. Like the spring was weak. ???  Fass was being *** about sending me another ball and spring. So I shimed it. 

[notlimah]

Hmm, it would seem that the spring wasn't causing enough pressure onto the ball to keep fuel pressure happy. Glad you got it fixed!

[tbo1450]

I think ur right. The sec ball and spring I got lasted a few months before things started to get weird again. I also thought the ball was the problem. It's a steady 17 18 psi now. Been steady for months. Good to know that about the air dog spring. I'll def get one if it acts up again. Strange fass doesn't offer one. 

[notlimah]

They do offer a spring and ball replacement. I went through two replacements from FASS before I tried the Airdog spring and ball from Vulcan performance. Not sure what's different with the springs but the ball that FASS uses is a Buna ball and the one Airdog uses is a Viton ball and they're pretty different.