I have several questions about my 1994 3/4 automatic. Where is teh sensor for the outside air temperature dispaly. It reads 0 until I go through a car wash and then it will sometimes read 45 for a little while. Also, where is the rpm sensor located? Anybody have a tachometer that starts bouncing all over while at a steady speed? Last questions, any troubleshooting hints for alack of top end. Mine seems to top out under full throttle at about 60 mph. It will do a little better if I back off the throttle. I did not notice any excessive smoke. The tach was swinging all over at the time and not giving a true reading.

 

Outside air temp probe should be on the hood grill. The tach issue I would think would an issue with the crank sensor, located on engine block behind the starter.

 

how about your air filter and fuel filter, have they been serviced...

 

here is some links with info for some reading on common problems along with everything you want to know, the crank sensor is on the front of the engine on top of crank damper, should be set to .050 gap.

http://dodgeram.org/tech/dsl/trouble...p.htm#Overflow

http://dodgeram.org/tech/dsl/filter/pre-filt_clean.htm

 

The temp sensor on your '94 is almost behind the driver's side headlight.
Check and clean the connector for the engine speed sensor, you'll see it by folding back the upper radiator hose.

 

Thanks, Everything was right where you said it would be. Do you have a wiring diagram for the charging system? I changed the fuel filter and now the charging system is in-op.

 

Unless you some how blew the main fusible link in the fuse box under the hood the problem is likely the engine speed sensor. The ESS is telling the PCM that the engine isn't running. Do you also have no tach?

 

You are psychic. The tach does not work at all. It used to be intermittent, so I cleaned the speed sensor terminals. The connection fits very loose. Is there an updated connector?

 

Some of the connectors are loose, I've seen them from the factory held together with cable ties. Try squeezing the female connectors together with pliers to tighten them up.

 

I checked the connector and it wasn't very tight. I tightened the connections and ther is still no alt output and no tach. I hooked up test leads to bypass the connector and verify a good connection. I received 8 volts on one wire and 5 on one and about .2 on the third with the engine idling. Does that give you any other ideas of suggestions for me to try next? It is a 94 3/4t long bed automatic

 

It sounds normal except the signal (.2) some how isn't making it to the pcm or the pcm is faulty (not likely)
Trace the wire to the pcm and use a needle or paper clip down next to the wire at the pcm connector. The connector comes apart. If there is no voltage the problem is somewhere in-between the pcm connector and a ess connector. If the .2 is present at the pcm make sure the female connector at the pcm is making good contact with the pcm. Beware of sticking voltmeter probes in the female connectors, you can stretch them out making even worse contact.
I'm not sure if the .2 at idle is enough but will see if I can find out, if it's too low the ess might be bad.
Make sure the clearance between the dampener and sensor is about the thickness of a match book cover.

A friend and I took over a month to finally figure out that the reason he kept on losing electronic functions one by one was because of his probing with the voltmeter stretched out female connectors. Started out as cruise control problem. Besides a few sensor failures most electronic glitches I've run into were caused by something someone did while working on the rig. Retrace everything you did before it started acting up.

 

From the symptoms you describe for your 94, it would seem you have several areas that need to be checked.

The first thing to verify is that you have good common engine to battery, engine to frame, and engine to body grounds. Do not trust that because you see a wire that you have a ground. Be sure all the lugs and attachment points are clean and free of rust.

The temperature sensor can either be bad body ground, bad PCM ground, or a bum sensor. OR, you can have PCM pins that are not making contact with the socket. The most common problem is a bad sensor that picks up water over time and fails.

The tach bounce is common, and can generally traced to the sensor that is located above the front crankshaft damper. It is a hall effect switch that reads a magnetic field change, and needs to be set to the proper gap and tight to the block. It does not hurt to use a bit of blue loctite on the bolt to keep it from flopping around again in the future. Also, take the time to check the connector on the pigtail for the crankshaft sensor and make sure it is clean and tight. Trace the wires back from the sensor to locate the connector.

The power problem is likely in the fuel system. There are several things to watch on a 12 valve, and they include the fuel hoses that dry out and allow air infiltration (this is all of them, from the tank to the lines on the frame, the hoses from the lines to the engine, and pick-up hose in the tank), the filters, an air leak at the wire connection to the fuel heater, a plugged screen in the heater (9 out of 10 owners never replace that screen and then have power problems when it cruds up from water and rust), and a bad overflow valve (located on the inside of the injection pump, and is where excess fuel is returned to the overflow line that leads to the tank). If you are not having starting problems, I would replace the fuel filter, and screen in the heater first.

The power problem can also be slipped timing, but for it to be that bad from slipped timing you will probably also be blowing exhaust around the exhaust manifold to head mounting flanges, and the exhaust manifold will be warped and likely cracked from too much EGT over time. Since you do not describe any lousy fuel mileage, I would suspect that this is not a problem.

The charging problem most commonly is traced to someone bumping the hot lead on the alternator when they changed the oil filter, and may be a blown diode. Trace the hot wire from the alternator to the PDC and make sure it is still in-tact. If that does not locate the problem, then pull the first layer off the Power Distribution Center and reach under and tug the wires. Look for one that is spongy or elastic, that will be a blown fusible link. It can also be a bad battery power lead attached to the PDC that is corroded inside the lug and not making full contact. If it turns out that none of the wires or links are bad, then have the alternator checked by a shop that can determine the status of the diode pack.

 

Thanks for the suggestions. I am concentrating on the alternator first. I have battery power to the output terminal on the alternator and traced it to the pdc. The fuse there is also good. I had changed the fuel filter, not the oil filter. Is there anything I could have disturbed there?

 

I finally broke down and replaced the crank sensor. Alternator and tach problem solved. I guess it was just beginner's luck it went out while I was changing the fuel filter. The fuel filter seems to have solved the top end probmen. Thanks for all the replies and suggestions