...hello all...first time poster here...

...help please...

....1999 ram 2500 4X4 gasoline automatic trans...

....truck cranks but will not start...

....replaced the fuel pump in tank...no joy...tested old pump with jump wires, and it will pump...

...changed the PCM...

...changed the fuel pump relay...

...can use a jumper wire with the fuel relay out....to send hot to fuel pump...the fuel pump will run...and truck will start but wont idle...you have to keep foot on accelerator just a little to keep it running...if you put the AC on it will idle....

...what do yall think the problem is?...

...i've been reading the forum before registering and posting, and see that the PCM signals the fuel pump relay...but i have replaced the PCM...

...i also read that the PCM also gets a signal from the CPS before it will send signal to the fuel pump relay?...did i read this correct?...do you think its bad?...

...was thinking of replacing the ignition switch behind the key...but got online and tried to some "online troubleshooting" first...do you think it can be bad?...

...back to the fuel pump relay....so the key switch send a hot to the relay when key is on?...and then PCM sends a negative...to complete the magnet and make contact between main power in and wire to the fuel pump?....am i understanding this correct?...

...thanks in advance for any help...

...redzone....

 

Could be IAC or cat.

 

asd relay, camshaft position sensor (throws a code), iac, plugged cat all won't let it idle very well.

you could check your battery cables also, i know it sounds unrelated but my sister was having trouble getting hers to start and the battery wire that goes to the fuse box in the engine was blistered all the way down it and i changed that wire and it fired right up.

 

+1 IAC or Cat.

 

...the iac will keep the pcm from activative the fuel relay to kick in the fuel pump?

...sheriff...i redid the battery terminals....and you can crank the engine over good...but wont start unless you use a jumper across the fuel relay...

...i only talked about the idle, to let yall know that i belive there is more of a problem than the fuel relay...

...but i will check the iac...

...redzone...

 

check the starter fuse under the hood, i had a starter relay put in , kinda had the smae prob, kept changing fuses and they would blow all the time, check all fuses under the hood

 

http://dodgeram.info/tsb/2000/08-24-00.htm
check your door lock fuse.

http://dodgeram.info/tsb/1998/18-36-98.htm
has the new pcm been flashed with the newest software?

also, did you check the fuel pump with it plugged in before you installed it, it could be going out or working half assed.

 

What about the ignition switch? Maybe it isn't allowing the circuit to the relay for the fuel pump stay completed curing the crank and run positions. Just a thought.

 

I'm not sure why you're checking some of the things you are checking with the way you described this. It cranks, so the ignition switch is fine. It turns over so your starter is fine. And the fuses and relays for both are fine. You said that it will run if you keep your foot on it so, you are getting fuel and all relays and fuses for the pump are fine.

You said it will not idle. So at idle, it is not getting enough air in, or not getting enough fuel at idle, or it is not getting enough exhaust out. So not enough air in at idle means you have a rag stuffed in the TB or your IAC is not working properly. Not enough fuel means your injectors are trashed or you have the wrong or a bad pump. Not enough exhaust going out means you have a banana in your tailpipe our your cat is trashed.

Pull your air box off and make sure nothing is in the TB and then see if it still does it. If it does, then disconnect the y-pipe from your exhaust manifolds and see if it still does it. If it does, I bet your IAC is crudded over.

 

...maybe i wrote the post in a confussing way...

...it will only run with a jumper wire across the fuel relay female pins...by taking the fuel relay out and using a jump wire...

...and then after doing this it wont idle...only run with foot on throttle...

...the key switch give a hot to the far right pin (smaller ones) on top....

...but the PCM will not send a ground to complete the relay switch...

...i have check the relay...it is good....

...i only brought up the idle issue to ask if yall thought there was more of a problem than no PCM negative signal to the fuel relay. and what could cause it...

...ok...todays update...

...i gave up on fixxing it right...and cut the negative side of the relay from underneath the fuse box under hood...and wired a ground to the mounting bolt on fender well where the fuse box is attached...

..the relay is on full time now with key on and key in start...

..solved the idle problem, by doing the TPS step i read about on this forum, by turning key on and waiting 5 secs then pushing throttle to floor and hold 2 secs and then let it up and then start...i only had to do this once to solve the no idle...and after anytime i take the negative off the battery to work on wiring...

...the truck runs great now...at start up...at idle...at normal operative temp...will run 100mph easy...

...but now a new question....by doing the "poor boy fix" of taking the PCM out of the equation, and being fuel pump pumping all time while key is on, have i created a new problem that anyone knows of?...i mean it cant over pressure, with a pressure regulator bypass in the tank can it?...am i understanding how the regulator works correctly?...

...thanks in advance...

..oh and PS...still no codes or warning light...during, before or now...

...redzone...