Fellow Members, let me throw this fuel pressure concern by you.

I have a 99 2500 RAM with the diesel engine. Two years ago the lift pump on the side of the engine fails which then killed the injector pump. Took it to the dealer and $3800 later, a rebuilt injector pump and a new fuel pump relocated in the fuel tank were installed.

My mechanic friend suggested a that I should install a fuel pressure gauge which I promptly did. He told me if the pressure gets below 5 lbs, something is going wrong.

The pressure usually runs about 7 pounds when the engine is working hard and runs around 9 pounds at idle.

A month ago, I was on the road with the truck and about 3 hours into the trip, the pressure dropped and when the foot feet was pressed down, the pressure would drop down to about 3 lbs. I backed off and nursed it home so the pressure would stay above 5 pounds.

I took it into the shop 4 days later and the pressure was back to 8 to 10 pounds. They plugged in the computer and everything is supposedly OK. I talked the mechanic and he said as long as the pressure is above 0, it is OK. I asked if he would put that in writing with a guarantee to replace the injector at no charge but he declined.

I took it out on the road again this past weekend and once again after 2 hours on the road, the pressure dropped down and if I pushed the engine, the pressure would drop down to 2 to 3 pounds. Once again, I backed off and nursed it home trying to keep the pressure above 5 pounds.

It is going back to the shop on Thursday. Is it possible that the lift pump is shot after 10,000 miles? I don't want to spend another $4000 for a new lift and injector pump. Should I go ahead and have the pump replaced? and is there a better after market pump I should install verses using the standard Dodge pump?

Your assistance is appreciated!

Dave in Pierre, SD

 

whens the last time you replaced your fuel filter?

 

like brett said, check the filter, and put on a new one if its been any length of time, if that doesnt change anything, go to a fass or air dig fuel system, probably wont be much of a difference in price over a factory pump, the factory pumps are nothing but problems, and i have seen them fail in way less than 10,000 miles, 3-5psi is about the minimum you want to run, anything less and you will need a new injection pump very fast

 

I change fuel filters every 5,000 miles. This particular filter has 2,000 miles on it and when I change them, there is no discoloration or dirt in them.

I think its the factory pump going to hell already. At least the one that came with the truck that was mounted to the engine lasted 85,000 miles. This one didn't even make it 10,000. Guess I'll see if the shop can verify anything with their computer tomorrow. They tried to blame it on the electric fuel pressure gauge when they looked at it last time.

I'll let you know what they say tomorrow.

Dave in Pierre, SD

 

would be interesting to know how much volume that puts out in about thirty seconds. think the spec is 750 ml in like 20 seconds ... the intake pump produces pressure but is not diagnosed using pressure but volume. have on on my 99 and when pulling it runs appx 0 but know it still flows so check that and see what happens i know pressure helps fill the chamber fast for more power or full fuel but if there is fuel there the vp44 makes its own if there is fuel there have alot of miles on my current vp and no problems so far

 

The lift pump needs to flow more fuel than the injector pump can use, so that the extra is used to cool the injector pump and then gets dumped back into the fuel tank. When the lift pump starts failing, it doesn't flow enough and even when it is still working, the injector pump is starting to get cooked. So theoretically, yeah, you could have 0psi on the low pressure side and still drive the thing (or even vacuum!) but you're going to be damaging the expensive injector pump.

I didn't want to take a chance with the stock in-tank lift pump on mine, so I swapped it out for an Air Dog external filter/pump. It also filters better than the stock setup, so you don't get nearly as much crap through the injector pump.

 

 

I took the truck to the shop and that was a waste of time. They hooked up the computer and said everything is OK. They also said my electronic fuel gauge may not be accurate and not to trust it. Then he said as long as I have pressure greater than 0, everything would be OK. I asked if the dealership would put that in writing and pay for repairs if that was the case but they would not.

Screw them. I ordered the Air Dog 150 last night and will install it next weekend. I would rather give the after market folks $499 than to give that dealership $900 to replace an inferior pump with the same thing.

I will have to drop the tank since this truck now has the in tank pump and the Air Dog needs its own intake. I also understand that I will need to remove the stock fuel filter since the Air Dog has its own filter. That is fine.

Hopefully this will take care of my fuel pressure issues and I can again drive without worrying about ruining another injector pump. Heck, at 97,000 miles, the truck is just getting broke in.

Thanks

Dave in Pierre, SD

 

I just got a call from the dealership and they claimed to do some research on my fuel pressure issue and found a service bulletin that said that pressure gauges don't work with this 'new' 2006 and later in tank pump. They said the GPH, not pressure is what determines if the pump is working correctly.

She then went on to tell me that the reason the pressure goes down is because the injector is using more fuel capacity than the lift pump is delivering to the fuel filter housing. DUH, that is the problem!!!!! She can't seem to understand this is a problem. She said they would be glad to replace the intake pump with the same in kind, <but not at their expense>.

I'm done with them. The Air Dog was shipped this morning and by next weekend, my fuel supply problems will be history.

Dave in Pierre, SD

 

You'll be happy with the air dog. Apparently they (the diesel shop) had to cut my tranny cross member so I can replace the filter without unbolting the cross member, but with an older truck there might be room.

The only thing is that it's loud... you don't hear it much inside with the engine running, but the way mine's wired in it comes on with the key on ACC and doesn't turn off until I open the door with the key off. Plus it's easier to drain the water off than the stock location - no more reaching around dirty tires, just reach under the cab.

My stock filter is still bolted up, it's just completely bypassed. The other thing to note is that since the stock filter is bypassed, you need to check for water instead of relying on the idiot light on the dash.