swordfish

Glad to hear you got it running. It can be very frustrating working on a truck and not seeing results for a while, but the minute everything comes together and the job is complete, its very satisfying. Way to go. Glad your up and running again.

swordfish

patdaly

FWIW, My low fuel light is on at about 7 gallons remaining, and the needle is at 0.

You might add 5-7 gallons to make sure............

robinlh

Thanks Swordfish, I have to get her registered but was at least able to drive her around the pasture. omg ... what a difference in Trucks (and even in her before she broke down).

Brownie ... I have DTE (distance to empty) that says 0 as well. I am wondering if my fiance forgot to plug the connector into the top of the module. lol

Hey .. do any of you know either where the motor number is on a FASS DDRP 02 or what the number might look like? We were able to get the Serial number, but I'm not sure what the motor number looks like and I need that too for the warranty.

robinlh

On the motor number. Some of the warranty registration cards (like mine) ask for a motor #, there isn't one on the DDRP (they have since changed the cards), so all they need is the serial number. Just an FYI

robinlh

Ok so the truck is running like a champ. Haven't taken her out on the open road yet as I still have registration to contend with. I have taken her on some backroads by my house though and have some questions regarding fuel pressure (or at least what is showing on the gauge at any rate).

I should mention that the gauge is pre filter at this point I have the same gauge as duster75 which is a mechanical gauge . I am going to add a second gauge at the vp44 in the next week or so (before she hits the highway for normal driving) these are just test drives. I should also mention that the idle is steady and strong and doesn't faulter throughout this.

At idle when I start the truck, the gauge is reading 15psi, while driving it fluctuates between about 15 and 18psi. When I stop however, the gauge will drop to 0 and as you accelerate pressure comes back within a few seconds.

We are going to check all lines for any leaks, etc, but do you guys have any suggestions?

Thanks.

Robin

KATOOM

Well I cant confirm it unless I was there but it sounds to me like the fuel pump is doing the typical FASS DDRP thing. Even though they're marketed to be a direct replacement for the OEM lift pump which is supposed to be reliable, they too can suck. Your fuel pressures going from 15 to 18 to 0 is a sure sign that the fuel pump or the fuel pressure gauge is bad. Checking with another fuel pressure gauge will reveal which ones the culprit. Since you're reading pre fuel filter your pressures shouldn't fluctuate at all. Although, I'd change the location you're reading from to post filter ASAP, and DONT tap right in at the VP. Its to harsh on the gauges. Instead tap in at the outlet of the filter housing. And lastly, I would highly suggest that you stop driving it until you resolve the fluctuating fuel pressure issue or plan on going through this whole ordeal again in the near future.

robinlh

I am not driving it right now other then this particular test drive so I could take some notes. I should also mention that there are only a few gallons of fuel in then tank (not sure if that makes a difference, I had read someone having this problem with low fuel). I have hard lines coming from my filter cannister, what is the best way to put a gauge there?

One question, if there were truly 0 pressure after a stop would the truck continue to "sound" normal? I am just curious ... and frustrated of course.

KATOOM

No, low fuel level in the tank should have zero affect on fuel pressure readings. Well.....except for heat reasons but I wont go into that and it wouldn't do anything you're experiencing.

Yes, the truck would still sound normal with 0 fuel pressure but if its truly getting 0 fuel pressure then the VP's diaphragm is forced to pull its own fuel supply which eventually causes the diaphragm to tear. Also the lack of fuel supply will cause the fuel to get unnecessarily hot which causes the lead free solder in the VP's computer to deteriorate, which is also bad. And the VP has a fuel temperature sender which will cut power if the fuel gets to hot. The VP is a positive pressure pump and must have head pressure to function properly.

If you plan on keeping the 5/16" hard fuel lines then to read fuel pressure from the output side of the fuel filter canister, you will need one of these: http://www.vulcanperformance.com/ban...cess-p/tbb.htm Other vendors have this part too if you so choose.

robinlh

Ok, I tried this. I bumped the starter this morning and the results were pretty irratic on the gauge. (I had someone listen to the DDRP while I was in the cab watching the gauge. Each time I bumped the starter the ddrp motor running sounded exactly the same, however, the first bump the needle bounced at 0psi like it was trying to move, the second time it did move and the third time it was at zero again.,

I removed the gauge and put the fuel line in an empty gas can and tried another 3 times, the flow was exactly the same each time, consistently full flow (of course I don't know the exact psi as the gauge was off).

I am thinking this is possibly a gauge issue and not a ddrp issue, of course I won't know for sure until I get a new gauge. I imagine it could be a "pressure" issue with the ddrp as there was no flow restriction with the gauge off, although the ddrp motor doesn't sound any different in any of these scenarios.

Comments?

KATOOM

I commend your efforts but no matter, I would wait until you can confirm the fuel pressure before you run it anymore. There is tester gauges you can buy which temporarily connects to the banjo bolt shrader valves on the fuel filter housing or on the VP, for pre and post readings. It has a longer rubber hose so you can even run it out from the hood and in the open drivers window for road testing. Although I cant remember where to get one. I think they're about $50 too.

robinlh

I don't plan on driving it until I get this resolved. I just ask a lot of questions lol

KATOOM

Thats OK by me.

Junk Man

Perhaps the fuel is sloshing in the tank to the point where the pick up is sucking air. With low fuel, mine drops to 0 if I stop suddenly or go around a corner sharply. Refueling a t1/2 tank takes care of this.

I've also read where the tank will be pushed up from the bottom when installing a draw straw with the tank sitting on the ground. Which makes proper pickup hieght difficult to determine. AND is a good reason to lift the bed instead.

For comparison, AirDog operation: mine kicks to its max pressure with key to start then drops to 0. It goes back to 15 as son as the engine starts. Fluctuates between 15 & 13# while driving.

KATOOM

If I remember right, the OP doesn't have a drawstraw which means that any low fuel issues wouldn't be because of sucking air. The OEM fuel pickup canister has a cup built in the bottom of it which stops that from happening. Also your Airdog fuel pressures are totally normal.

duster75

Robin,Fill the tank with fuel and see what happens..... I will get a 0 reading if i.m down to a 1/8 of a tank and stop hard or leave a stop sign hard. The canister in tank can get full of crap and "plug up" causing problems also. Yours has not been gutted so it could be a issue. I pull my fuel pressure at the V.P with no problems, other then fluctuating gauge witch hopfully is a bad pump have a "new' 1 coming under warranty. Nate