I have an issue with a 2005 ram 1500 with a random fuel issue. I was having no issues than about a week ago I came out from work to head home and the truck would not start. Had it towed home and started diagnostic a day later. Turned over but "no fuel" type issue. Ran fuel pressure test and had zero pressure at fuel rail. In lieu of running electrical diagnostics of relay just replaced it ($12 to save time) came home and installed and got no start. came home the next day to work more and it started right up ran pressure test and it was at 54lbs. (good). Turned off and on a couple times and everything was fine. Had some other work to do that day so left it assuming it was the relay and had been resolved. Next day came into the shop and went to turn on started but had no pressure at the fuel rail. Was running just fine so I assumed it was likely the guage or leaking shrader valve. I returned the borrowed fuel pressure guage assuming everything was fine. Came home again no start. Could not hear the relay click or the fuel pump start up. Tapped on the fuel tank and it started no issue. Came back later that day and no start. Pulled cables from Battery waited attached and everything worked. It has gone back and forth though and still having random issues starting. When it does not start I am hearing no pop from relay and no pump.

Any specifc areas to look at electrical system?

I assume that the random nature and fact it was at full pressure when I first got it working points to it NOT being the fuel pump. Could this still be a fual pump issue?

Going through connection to connection with test light and dialectric grease today.

 

OK I am now thinking that the pump is failing but I really want to know why it is intermitent? Does anyone know why it would be that tapping on a gas tank would make the pump work at start up and run just fine with good pressure? It seams that this is an electrical issue possibly in the pump and not an actual pump failure. What am I missing? FRUSTRATED!~!

Though this truck has 300K and the only major repair was a tranny rebuild at 260K. Mostly just want to know how this failure is happening.

 

When it doesn't start, you need to find out if there is voltage through the relay to the pump, or, is it possibly the computer output voltage that fires the relay. Pumps are a PIA to change, check the electrical first----maybe save some time and money narrowing it down. I had a fuel pump on an older dakota 5.2 did that for nearly a year, I put it off just long enough for it to strand me and my wife on a trip out west in Northeast Oklahoma.

 

I got power from the relay. It is live at the orange/ red wire from the Relay to the pump. All three other wires are dead. Assuming the Black orange is ground fpr pump (traced it back to a bolt at the frame next to battery). Assume that the Two blue wires are for the Fuel guage and measure resistance only so they wont show voltage when not running.

At this point I am fairly confident it is the pump. I just wonder why tappingthe tank would make it work. To me that says it is resistance (corosion)in either the motor itself or a wire connection in the pump. Looking for clarification on this???

 

Yep,

Wiring Diagrams say you are on the right track. I'd be planning on a pump replacement

Probably a simple wire connection, or commutator brush connection in the pump, unfortunately, I believe the entire module, pump, regulator, filter has to be replaced. Sooner or later, it will die for the last time.

Good Job on the wiring diagnostics, Rockauto.com has prices around $200

BTW-----You can get the full FSM for your truck as a free download from Weedahoe in his sig.

 

right from the start i could told you it was the pump. the pump is a sling type pump. the roller sling bearings get worn out and get jam up in the pump. after a while the pump will unjam and work again un till it jams up again.

 

Had a similar issue on my sister in-laws 96 Lincoln. Replaced the pump, it ran a fer days and did it again. Turned out to be a bad crank sensor. No signal, no fuel pump. buy if you are actually getting 12v to the pump, then you need a pump.

 

Which is why smacking the tank gets the pump to run. It allows the pump to un-bind and work. Agree w/Lxman. I would check a your powers/Grounds to the pump. If thats good replace the pump.

 

I could be wrong but it sounds like you have no clue what you are talking about. A sling pump is used in irrigation not your fuel tank. I was under the impression that it was the pump from the beginning and looked at the electrical because it was a random issue. My question was why wrapping on the tank would trigger the pump to work. I am pulling the pump in a day or two and will do the Sherlock Holmes myself. I assume that it is corrosion in the brushes similar to most electric motors.