F552

For the last week my truck has been exhibiting erratic fuel pressure readings (especially in the morning). At idle I am getting 12 psi (Westach gauge) but when I touch the throttle, I immediatley lose pressure down to zero (or less!!). As soon as I let up on the throttle, fuel pressure recovers to 10 psi. Stop the truck and bump the starter to see 12 psi. Later in the afternoon, the same idle pressure but upon throttle pressure drops to 8 psi. I changed the filter yesterday and the lift pump sounds OK and had no problem pushing fuel. How do I diagnoss a faulty lift pump or possibly a bad sending unit??

F552

I would also like to know the consensus best transfer pump (ie: FASS, Airdog, etc...) to install if my lift pump should indeed be replaced. I would be willing to install a pump that mounts to the rail or firewall (in other words I am not desiring an in-tank installation).

Lt.B

Id take it in and have the pressure ckd with an alternative guage. Auto Meter warns that without a special restrictor that they sell you over and above the outrageous price for the **** kit that the senders will be damaged on the dodge ram w vp44 pumps. Id like to smack that Auto Meter guy in the eye but I think thats the best guage money can buy, so a sender is a real good possibility.
Oh I just went thru this. I went with the Airdog FP 100. I have a stock truck and have no intention of mucking it up with a bunch of block busting hot rod mods. The FP 150 costs the same but requires a new pickup straw be installed in the tank. To me the Airdog offered an easy to change spin on filter and an easy to drain separator with a nice quiet pump all in one unit. I wrench for a living and I installed it myself in an afternoon without a bunch of high tech tools. Some allen wrenches a 10 adjustable wrench and a 3/8 socket set. A straight slot screwdriver and a sharp knife for cutting hose. It didnt require dropping the tank. I was able to remove the left rear fender liner and work the fuel neck and tank top mods from there. The instructions were pretty close and there were no issues. The gauge port is provided in the Airdog fitting block. Id recommend it to my friends. I give it a 87....good beat and easy to dance to....uh oh... there goes that senior moment stuff again. Oh 18 psi at hot idle.

F552

Thanks for the great advice!! Testing with a mechanical guage will probably be my next step to diagnose a possible bad sending unit. It is hard to believe that my lift pump gushes fuel when I bleed it after filter change only to plummet to zero with the lightest tap on the throttle. strange...

Fishin2Deep4U

This is a typical description of a failing stock pump.

What's best for a replacement? Pick your favorite. I really like the Raptor pumps as they have a very easy install.

As always a DrawStraw I for stock modules or a DrawStraw V should be used with all fuel pump upgrades.

Dave

F552

Just spent the last two days driving around with a mechanical test gauge. The verdict is.....Bad fuel pressure gauge sending unit!!! Got a new one (at discounted price, Thank You Brandon!!) coming from Geno's garage. The first sending unit lasted three years and two weeks.

Karl

sheriffav8r

Grounding is pretty important for the electrical sending units. Also, try to isolate the VP pulsing by putting in a cheap needle valve, if you can....

ldornak

I have the same Westach electric gauge. The 1st time it started fluctuating, I could not figure it out. After replacing my 6 year old batteries, the fluctuation went away. Not sure if it was coincidink or if the dying batteries had something to do with it. Since then, my gauge will sometimes fluctuate when it's cold out. I found that if I open up my needle valve and then adjust it back down to barely open, it stops fluctuating. My fluctuation is different than what you are describing. Mine would bounce from 18 to 0 at idle and would jump to 18 at acceleration.

Nor_Cal_Angler

I'll second the Raptor....VERY EASY install....I love the fact that I can adjust my PSI with a wrench and flathead screwdriver....but right out of the box they have them set at Factory spec's 16psi idle and 14 psi crusing...I have a hard time pulling it down to 12 at WOT...pluse they are designed to compinsate...after the shortest period of time (almost undetectable) the pump will build pressure...what I mean is it will drop to 12 psi right away when I hammer on the "go" pedel but it will almost right away begin to rise to 14 psi even while the pedel is still hammered....

plus with 2nd gen trucks we dont require the "over the top" filtration that say a common rail will....stock fuel filter will do the job just fine...(just use a station that has a good turn over of diesel fuel)

I went with the raptor 100 because all said and done I probally make around 400 give or take (when the wire is taped) and a 100 will fuel to about 600...

My previous truck had a GDP walbro with the big line....which was good as well but it isnt an option as a package anymore...you can purchase a big line kit and get a walbro on ebay and that in my opinion is another good set up....

NCA