PCM wont read codes

[kevinsatterfield]

I have unhooked the MAP sensor and the PCM wont read any codes.I inplug the Idle Air Control valve and it reads a code.Try'n to understand why it reads one and not the other.The truck wont run at all.

[nickle989]

On my Ford or Chev truck .. the engine will not run at all if you unhook the MAP sensor or if it is faulty.

What is your vehicle ?

[kevinsatterfield]

98 dodge ram 1500

Me and Leon got some codes on the MAP sensor when the plug in the PCM was dissconnected by the wire'n harness tonight.We thinks its come down to a faulty PCM but it still wont read start.Ive replaced the cap,rotor,plugs,wires,ignition pik up coil,MAP sensor and time'n chain.Its flood'n itself out and cant find a way to lean er out.

[AlaskaStar]

CHECK EVERY GROUND. Also check the wires that run the back of the block and top edge of bell-housing for the transmission. also check relays, just because it clicks means NOTHING. remove horn relay and put in place of ecm (if they are same type like some fords), also do what is called a "Wiggle" test. in whatever mode required to check codes, have someone keep scanning (pressing read button-don't know what type of scanner you have), and while they are doing that, grab wires, and harnesses, and connectors all over the place under the hood, and wiggle them. keep on doing this until you get something. once you have located the general area, you have a good place to start. if the relays are fault, try turning the key on, and "banging" the relays with a screwdriver handle or to the same effect.

Make sure all fuses are in place and not blown, and fusible links as well. count the computer as last on the list for failure, until you absolutely must.

I have seen people put new computers in, and cured NOTHING. where like on a chevy that won't start, they replace everything, and computer, fuel pumps, injectors, sensors....etc....etc....and finally, they give up. I put a $7.00 OIL PRESSURE SWITCH in it, and it works just fine. the Oil Pressure Switch on most EFI GM products is tied to the Fuel pump for safety reasons, when oil pressure is lost in a collision, the fuel pump shuts down. also if the bearings in the motor have too much slop, same effect.

Dodge is #1 in triple redundant technology, followed in a tie between ford and chevy.

I hope this sheds light on your situation.

AlaskaStar

[kevinsatterfield]

No luk tonight. I stil have things to do on yer list Alaska.Tonight I find that the PCM has 3 plugs and from the first plug being disconnected no fire seems to be happening.the second plug discconnected and no noticable change in engine behavoir when all 3 plugs are connected.( It floods itself out and chokes on a spit ,let set for a few minutes and it tries to run for 3 seconds)The third plug disconnected the fuel pump doesnt cut off .

I have done a few of the "wiggle tests Alaska mentioned and loosened and retightened most grounds.
'
The scan tool im usen is an Actron pocket scan.Is there a scan tool better than this as im not get'n a code when the MAP sensor is unpluged again.

Also tonight ..when the fuel pump relay is taken out after being flooded on a try start it tries to run for about 3 seconds.Its basicaly flood'n out.I dont understand why its so hard to find the problem on a simple flood out.Its operate'n on an OB2 system .

Has anyone converted an OB2 system to a carburator?

[Art]

i dont know if a dodge has one but a frein has a f150 and we had the problem of it flooding thru certin rpm and found that even though the fuel control modgel under the hood showed it was good when the tps would give it signel for more paulse to the injectors it would send this 1 11 1 11 instead of this 1 1 1 1 1 1 the scan tool did not show any thing wrong and it took the dealer 3 days to find that the paulse signel was wrong just a thought but you could also have a differnt problem


keep on keeping on

[nickle989]

Here is a link for what looks like a very cool scan tool .. DIY with software or you can buy the hardware. Software is free

http://www.obddiagnostics.com

[kevinsatterfield]

[kevinsatterfield]

[AlaskaStar]

[kevinsatterfield]

Alaska, tried the flood mode rutein again and it all happens up to the part where the engine starts, that doesnt happen.
I wish i culd use my oscilloscope to test the injector pulse width but im as lost on how to use the scope as i am try'n to fix this dern truck.
Im gonna try to find someone with a decent scan tool and pay em to come over and try that.
I appreciate all the help.....thanks a bunch!!!!!
there is one thing i havent got around to doing that i prolly shulda done did.Thats to make sure EVERY plug is get'n fire .I have tested plug 1 and it was get'n fire but i havent made sure all of em are get'n it yet.If ther all get'n fire i'll just pay someone with a dern decent scan tool to come over.I still need to know a simple way to lean er out tho...am hope'n the fix on the problem will help with that problem too.

[AlaskaStar]

The plug may fire, but is the plug WET? if so, it will not fire, regardless of the amount of spark. you have to pull the plug out, and I find it faster to simply replace it. Also, I suggest getting a "Spark Tester" it is simple to make, as it is nothing more than a regular spark plug, with the ground strap removed, and an alligator clip attached to one side.

The ignition voltage should be high enough to jump that gap. affix the clip to a good ground, and attach plug wire, or coil wire. if no spark at plug wire, go to the coil, if good a coil, and not at plug, then replace cap and rotor.

the color of the spark also denotes importance. if the color is RED, ORANGE or YELLOW, replace the coil. if it is WHITE, PURPLE, or BLUE, the coil is good, and move on to other things, also make sure plugs are dry and clean.

Simple, Simple, Simple. this is what you need to think. Air? Fuel? Spark? Compression? Timing?

As for the timing, remove distributor cap, grab rotor and try to rotate it by hand. if you can rotate the rotor (with slight dragging) into a complete circle, the problem is that the roll pin in the base of the distributor that holds the gear to the distributor shaft is sheared. replace with new pin and gear, and check shaft for bending, excess shaft play, or other signs of wear.

Does the rotor even rotate when cranking? if the rotor does NOT turn by hand, and the rotor does NOT turn while cranking, check for broken TIMING CHAINS, or BROKEN TIMING GEARS. All 3 of the "big boys" have started using (against everyone's better judgement) PLASTIC TIMING GEARS, like on the camshaft....even the GM products have had these, as the timing sprocket on the camshaft will have all the teeth fall off, and upon removal, you think to yourself, why in the F*** WOULD THEY DO THIS????? Ford did this all the way back in 1987 on the 300 cube inline 6. the gear looked like metal, but was actually FIBERGLASS. That one "oops'd" at highway speeds in the middle of nowhere in the middle of winter in the middle of the night on my neighbor in his Bronco, 4 weeks after we rebuilt the engine together. He "Upgraded" to a STEEL (made certain with a MAGNET!) CAM GEAR. truck still runs, and it's been at least 3 years.

When in doubt, ask questions, or get a visual. remove the valve cover, and validate that the rocker arms and valves/pushrods are actuating while the engine is cranking.

Check for fuel pressure. Do you have any? on the fuel rail that connects to all the injectors, there should be a small plastic cap, similar to that of a bicycle tire cap. remove it. you will see a valve that looks like a tire valve. push this in with a pencil. Gasoline should spray like a fountain out of this. if it doesn't check fuses and relays, or possibly the pump itself.

Validate fuel pump is working. TURN KEY OFF. TURN RADIO OFF. TURN HEATER/AC BLOWER OFF. TURN CELL PHONE OFF. REMOVE ALL EXTRA NOISE FROM VICINITY. REMOVE JABBERING NEIGHBOR. TURN KEY TO "ON" POSITION-***IMPORTANT***-DO NOT CRANK ENGINE!!!***LISTEN WHEN KEY IS IN "ON" POSITION, IF DOOR OR "ANNOYANCE BUZZER/DINGING" NOISE IS TOO LOUD, FIND IT, AND REMOVE IT.
NOW LISTEN FOR SOUND OF PUMP FOR 2 SECONDS AFTER TURNING KEY TO "ON" POSITION.

If no noise, proceed to find friend with long broom handle, or rubber mallet. have friend under vehicle, gently "Thumping" on the bottom of fuel tank directly under the position of fuel pump. *NOTE: hit hard, but do not dent tank, and keep thumping repeatedly. turn key to "on" position, and listen for fuel pump noise, if now heard, have friend keep thumping, and start engine. engine should stay running. purchase new fuel pump and install as per manufacturer specification.

Hope this helps some more.

AlaskaStar