02 ram stalls shortly after fuel cap is opened

hello everyone I have a 02 dodge ram 1500 4x4 quad cab with 5.9l. it will stall and will not crank back up till I unplug the computer.. I have noticed it does it shortly after I gas the truck up or take the fuel cap off and then reinstall the cap.. I need help this is my daily drive.. I have replace the pickup in distributor, cap and rotor, and camshaft position sensor. any help will be greatly appreciated..

Any codes?

no codes. just stalls and then it will turn over but wont start. unplug all three plugs to the computer and then plug it back up it will start up.. its also hard to start all the time..

went to move it this morning and it stalled without touching the fuel cap. and wont start.. still turns over. I guess its time to take to a shop..
Steve

You might check the fuel pressure to be sure the fuel pump is working.
Here's some info,
https://www.youtube.com/watch?v=Ow9FXFZxi9w

I did got 45 psi.

How about a re-boot?
Disconnect the battery for 20 minutes, re-connect, turn the keyswitch On, slowly mash the throttle to the floor then slowly release.
Turn the keyswitch Off.
Now try to start the engine.

I will try that tomorrow. I tried cranking it today and it threw p0351 which is the coil, replaced and still nothing.. code just comes back after I erase.. I read somewhere that same code could be a bad computer. is that true? I got half the plugs changed before a storm blew up.

This is all I can see in the '01 FSM with a P0351,

P0351 Ignition Coil # 1 Primary Circuit.
Peak primary circuit current not achieved with maximum dwell time.

ok I replace the coil and reset everything. it comes back.. so I have no clue what's going on.. my code reader is where I read the possible problems and ecm is one listed..

Without engaging the starter, turn the keyswitch On, Off,On, Off,On then look at your odometer for codes.

without engaging the starter, turn the keyswitch on, off,on, off,on then look at your odometer for codes.

p0351.

From the 2001 FSM,
SPECIFICATIONS - FUEL SYSTEM PRESSURE -
GAS ENGINES
All Gasoline Powered Engines: (49.2 psi + or - 5 psi)

Does the fuel pressure stay in range while you're trying to start the engine?

yes the fuel pressure stays at 42-43 psi. they disconnect battery wait 20 minutes connect battery turn switch on slowly press the gas pedal to floor and then turn off key did nothing.. replace all plugs coil and wires. disconnected computer and blew it out the best I could.. it started 2 times.. left it running came inside and it shut off on its own and now will not start..

and the 0351 code has not come back.

don't have a clue why but the engine light is flashing 12 times then stays on.. no codes

Here's something to see,

https://www.cargurus.com/Cars/Discussion-c5432_ds480382

On the Pre OBDII vehicles, 95 and earlier. 12 flashes or code 12 meant: Battery disconnect. Battery input to PCM disconnected during last 50 key starts.

Is it possible it means the same on OBDII vehicles? Time to start counting starts? lol

On a side note, I would also check for Pending codes. Just because there are no tripped codes or hard codes, doesn't mean there aren't any pending ones.

I'm trying to get thru all the advice.. replace the iac and tps. no change. I don't have the cash for a battery right now so as soon as I can ill get it replaced.. the only thing that hasn't been replaced is the ignition switch. its cheaper than battery do yall think its a possibility? there are no vacuum issues that I can find.

If the vehicle cranks... and radio and accessories work (which can only work if key is on), then I wouldn't pick up an ignition switch yet. Battery checks are for free at the local parts store. Don't spend $$ when you don't have to... I highly doubt the battery is the issue too, but if you can get it checked, why not? Before removing the battery, Check for PENDING codes.... Don't skip steps. I know it's frustrating, but you don't have the $$ to be throwing at it aimlessly either.
What code reader are you using BTW?

Have you gone through all your fuses and checked them with a meter? NOT by eye.
From the Battery, Make sure you have a good Body ground (somewhere on the frame or firewall) and a Block ground. Must be corrosion free & tight. Check any grounds you spot along the front by the radiator, sides (fender), & firewall... these are grounds BESIDES the main battery cable.

I really think it's something silly, so we're going to double check all the little things. KISS... Keep It Simple Stupid! ;) Not that I'm calling you that...just a saying

I believe its the ecm. it no longer communicates with my plug in scanner.. all but one grounds are clean.. will be having my battery tested this week. if it jumped time it wouldn't have cranked and ran ten minutes before right?

Verify that all your fuses are still good, that none are blown. Use a meter. If all the fuses check out good & still can't communicate then we can take another course of action, not necessarily ECM still.

If it jumped time, if could have run, but very poorly, and if it jumped a tooth or 2 only. It still would communicate with the scanner too. Don't jump the gun assuming things yet. Remember to Keep It Simple.

all fuses are good. and after I changed the spark plugs it cranked and ran normal for around ten minutes.

Ok... at the DLC check for the basics (12v, good ground)
If you have a good electrical schematic for your truck, even better. Can even use the $20. common Haynes manual from the chain part stores. I have a pinout for the DLC to PCM, but I'm not sure if it's your truck specific. Here's the link
https://www.dropbox.com/s/c2m2rd8712oqs47/2016-08-15%2015.17.52.jpg?dl=0


Also, how did you check the fuses? With a meter only? I can't tell you how many times I saw what looked to be a good fuse, but somehow the tabs were corroded not making contact in their slot. Especially verify those that have to do with PCM. Can even make sure PCM connections are dry. Unplug & inspect. Sometimes leaks can be wicked to other locations.

I checked with a meter. Ill have to go out after the rain to pull all and check for corrosion. I pulled all the ones that have the see thru cover and tested with meter. all plugs on ecm look clean and are firmly connected.. the battery in it needs to be charged from trying to crank after everything has been tried.. I will be taking it Wednesday to get it tested. and if it fails I will purchase a new one.

Good, good. Checking the battery is also a great idea. Many Chrylser/Dodge/Plymouths can be quite finicky when the battery is on the way out. Usually you'll have other issues like dummy lights going off & on or flickers, gauges fluctuating... but not always.

I also forgot to ask, has anything else acted up since all the issues started? Like the radio, accessories, anything else you can think of? The PCMs on these are all looped together... a failing head unit can contribute to failed PCM communications... newer stuff & their "networks" are such a PITA!

no other issues, after all this started I replace the resistor that controls the speeds of the blower, but it was confirmed bad, it was burnt like the common resistor problems with these truck.. the pcm will show on dash a code like the P0351 but my scanner wont see it. but I can watch live data like rpms cause I thought maybe I got a bad out the box crankshaft position sensor. but at this time there is no codes. I read on another forum that pcm was the problem..

ahhh... yes, I'm now leaning that way too. PCM. After reading your last post. Please post an update. I'd love to hear a happy ending after such a frustrating issue. Good luck with everything!! I meant to get back here earlier, but I was setback with work.

oh I totally understand about the delays on timing of responses. thank you for your help. I'm going to take the battery today, and if it checks out I'm going to have to save up for a computer. everything has been replaced except map sensor, ignition switch and computer.. so if I get it back on the road I should get some awesome gas mileage for a bit..lol

ok battery passed test. so its the computer of ignition switch.. I don't have the money for a computer right now so I will update as I can.. thanks everyone

a dumb question.. after I buy this computer hopefully in the next 2 weeks, am I still going to have to have my truck programmed for the key?

If the key operates the keyswitch now, it shouldn't affect the computer except supply electricity to the system.

ok heres my update. the new computer finally got here.. installed it and the truck fired right up.. everything is good.. I did notice that when the key is on but engine not running the check engine light still flashes 12 time..

How come no one comes back and answers what the problem was? That is about the only complaint I have with a forum. thanks for the one come back.

I did in my situation it was the computer, the flashing light is alerting you that you have a problem with emissions system. my case was a bad catalytic converter, the down flow 02 sensor and a hose leaking by emission canister. I have no codes or check engine lights at the moment..

I had a chevy that would just quit going down the road. Believe it or not it was the temp sending unit went bad. Drove me nuts finding that one.