I just recently purchased a 1998 Ram 1500 from a local a few weeks ago and now I have hit a brick wall. The truck drove fine on the test drive. I drove it home, drove it to work and back a few days and had no issues. I drove to the local feed and farm co-op a few days ago and parked out front. Walked back out and the truck wouldnt start. I cranked and cranked and cranked but nothing happened. I pushed it into the barn behind the co-op as I am friends with the owner and came back for it the next morning. It fired right up on the first crank and I drove it home and parked it. Went to start it up 15 minutes later and it did it again. Crank no start condition. I took it to my local garage and they said it was a fuel pump which I knew wasnt right as it drove fine. So I took it to my local dodge dealer where it waited on parts from the vintage chrysler parts department. They replaced the ICV and the MAP Sensor as well as replaced the throttle body which they did a good job of. Only problem was that when I took it home and parked it wouldnt start. Now here is what I have found. If I crank on it and mash the pedal to the floor it runs but wont idle at all. Also with the pedal mashed its only at 1000~1500 RPM. I am getting fuel at the fuel rail and I replaced all my spark plugs as they were pretty fouled up. All my wires too. I am getting good spark and compression is good between 150 and 175psi. The truck only has 136,815 miles on it. I hooked up my friends Snap On Scanner and there are no codes nor is there a check engine light. I looked on this forum and found many people having similar issues but those questions either are resolved by replacing simple parts and cleaning throttle bodies or they are just threads that have no answers. My Throttlebody is new, I have a new Idle Control Valve and new Manifold Absolute Pressure Sensor. I noticed that I can only keep the truck running if I either, A). Yank on the acclerator cable from inside the engine bay or B). Mash the acclerator pedal to the floor. Other than that nothing happens but dumping fuel, sucking air and throwin spark. I also saw my Cruise Control cable is seized but I unhooked it and ruled out that wasnt an issue. I am not the most mechanically inclined person. I am only 21 and this is my first pickup truck. Before this I had a 1985 Bronco II that I got for $200.00 from a salvage auction. I was thinking maybe my Throttle Position Sensor is bad or my acclerator cable was stretched ? Is this a feasible train of throught ? My ICV and MAP are getting power. No blown fuses, getting spark, air and fuel but wont run unless pedal is mashed to the floor. All parts placed on truck by Dodge were Genuine Mopar parts from the Vintage Chrysler Parts Department. The truck is a 1998 Ram 1500 5.2L V8, Auto Trans, 4x2 with A/C if that matters at all. I am thinking its gonna be my throttle position sensor but I wanted to come here and ask first. I love this truck and I need it running for my farm and for my job as I need the 8ft bed and the ability to tow my trailers. I got it for a good deal of only $700.00 and the previous owner had no issues besides replacing both front hubs, balljoints and driveshaft U joints as well as tie rod ends and a set of tires. Nothing major for a vehicle with 136,815 miles. Thanks to all who reply.

 

The new throttle body didn't come with a new sensor?

I'd almost wonder if the TPS was installed backwards (not sure if that's possible or not), or needs calibration. Usually to calibrate the TPS on fresh install you turn the key (don't crank) on slowly run the pedal full cycle and turn it off. On a truck that's already been used since install, you may have to disconnect the batteries and let it set overnight to clear the computer. Possibly disconnect both cables and touch them to discharge any capacitors.

 

Plug you scanner back in, have a look at the live data. You wanna know what the various sensors are reporting, first one *I* would check would be the engine coolant temp sensor. If it fails open, pcm thinks the engine is -40 degrees, and positively DUMPS fuel in order to get a burnable mixture.... Mashing the pedal to the floor, on the other hand, puts the computer into Clear Flood mode, and radically dials back fuel....

 

What psi and when was it tested? You should have 49 psi as soon as you turn the key to "on".
Did you ask why he thought it was the pump? It can be intermittent just like what you are describing will run one time and the next not. Could be the fuel pump relay also.