Hello everyone. I am out of ideas for my poor truck and need some help.
I have a '96 Dakota, 5.2L. Recently it has been hard to startup. When you do get it started, it runs so rich you can smell the gas, and if you give it just a little bit of gas it dies.

The strange thing is that it is not misfiring and there are no codes at all. I have replaced the plugs, wires, distributor cap and rotor, battery, and throttle body gasket.

I have also had a mechanic friend of mine check the fuel pressure with a gauge and it is fine.

Without a code, I do not know what to try next. Hoping you can help me. Thanks in advance.

 

I see you missed the O2 sensors.

Also, I'd NOID all the injectors, then make sure none are stuck open.

Since it's a 1996, you can also use a competent scanner (my preference is a ELM327 class ODBII/Bluetooth adapter and Torque on my Android cell phone) and monitor the ECU to see why it thinks it should be running so rich. I'd look for signs of sanity - is the ECT at about the right temp, or saying -20 or some such? How about the O2s, do they start switching? What's the MAP reading? Etc. etc. It could be that it's within the ECU's sanity limits but way off from the real world. (Also, how do you know it's not setting a code? Some codes don't light the CEL ... )

Plus, be sure to check the plenum (easiest is to peer down the throttle body with it wide open with the motor OFF) and make sure it's not oily; it may be causing a vacuum leak, which would cause it to enrich the air/fuel to compensate.

The factory service manual is linked to in the FAQ posting; I'd download that PDF to give you a good handle on it also.

When you say "check the fuel pressure and it is fine", what pressure did your friend get, under what circumstances?

RwP

 

Ok, so I just heard back from the person that helped me check it out. He said the fuel pressure was in spec for idling.

He used a snap on verdict d7 and it said that there were no pending, permanent, or stored codes. He did check the ECT and it is working.

For the injectors, we did unplug them one at a time, and it did throw a code for each, so the ecm did recognize that there was no resistance.

I will take a look at the plenum and the map sensor. I do remember that the upstream O2 said it was rich, but nothing else about O2.

Thanks for the feedback.

 

So I have replaced the ignition coil and MAP sensor. Plenum looks ok. Still no luck. I can get it started with some effort. It smooths out some as it warms up and once warm will start right back up if I shut it off. Runs rough at idle and shakes a little. Smooths out if I give it some gas. Still no codes. At this point I am just looking for more ideas on things to check. I even rented a compression tester. All but one cylinder is betwee 160 and 175 ft. Lbs. One cylinder is lower at around 130-140

 

Again, are you asking the computer why it's running rich?

RwP

 

I read this and it hit me that the OP doesn't say how the problem started. Did you add a new part just before it started to happen?
If you can get your friend to bring his d7 over again to look at the running processes as Ralph suggests. That will give you the data you need to chase this down otherwise its throw parts at it til it works or you give up.

 

So I did not replace anything prior to it acting up. It was really low on gas when this started. I have since put around 6 gallons and a little heet in it. Not sure if that gives any clues. I will ask my mechanic friend if there is anything else that can be done with the d7.

 

It's a 1996, full OBDII.

Worst case, a ELM327 ( OBDII/Bluetooth ) adapter and a copy of Torque (free; or shucks, Pro is like $6 or something!) can datalog what the computer is seeing.

RwP