Let me begin by advising all that this post is for a transplanted 2001 5.9 which is installed into an early Dart using the 95 OBD1 computer.

The engine is installed and all of the necessary computer controls/sensors are in place. These include MAP, IAC, O2 (1), Cam Position, Crank position etc.

The engine starts and runs for about 7-8 minutes. At about the 7-8 minute mark, the engine goes lean and dies. During the time up to that point, you can see the O2 sensor driving the computer for more fuel until the computer reaches it's max and the engine dies.

If you sprinkle some fuel into the throttle body, it will stay running.

After the engine dies, it takes about 5 hours for something to change which allows you to restart it. If you try it before then, it will start and die. Every test we have done indicates that all of the sensors are working. Fuel pressure is 45 lbs.; There are no codes.


EGR/Purge valve solenoids are connected to wiring but not installed.


Any suggestions on possible causes???

 

what exactly is the signal voltage of the oxygen sensor? It should bounce around between 0 to 1 volt. Also how many oxygen sensors do you have? If you have an OBD I PCM, it only recognizes 1 sensor, not 2. 2 or more were used in 1996-newer PCMs with OBD II. If the signal voltage of the oxygen sensor stays above .5v (mostly .75-1.0v) the engine is running rich and the PCM is leaning out the fuel curve. 45 psi is kinda high, in my opinion, most Magnum motors run on 39 psi.

 

Hi.
Don't have the O2 sensor voltage handy but can answer a few.
1 O2 sensor installed. Connected to "right" side input at computer. There are 2 inputs. Does it matter which one you use?

What the scanner said was that the O2 sensor was driving the fuel up as far as the PCM could take it. It was using up the cushion that the computer has.

 

Anyone able to help??

Discuss by phone??

 

What computer was used? If you are using a '95 5.2L PCM, you could very well be starving the engine. I only ask because you brought this question up in this section of the forum (1st gen dakota), and the 5.9 was not available. So if you got the computer out of a dakota, its for a 5.2L.

As for the time issue, it sounds temperature related. Do you have BOTH engine coolant temperature sensors installed correctly?

Make sure there are no vacuum leaks or open vacuum ports since you don't have the EGR and purge valves connected.

 

The computer that was used was set up for the 5.9. We've been advised that one for a 5.2 and 5.9 are the same.
When you say BOTH temp sensors are you referring to inlet air and engine water temp? There is only one of each installed.

Will check again for vacuum leaks but none have been found so far unless it is on the underside of the intake.

Suggestions?

 

In 1995 there were 2 engine coolant temperature sensors. One of them was for the computer and the other one drove the temperature gauge on the dash. As long as there is one connected to the computer, you should be fine.

Also, I was just thinking... o2 sensors don't start working until they reach a certain temperature, so it almost sounds like the engine quits running after the o2 sensor starts sending a signal to the computer. Are you sure the o2 sensor is good?

Here is what I know about how the computer runs...

When you first start the engine and its cold, the computer is running in an open loop mode. In this mode, it takes input from these sensors to run the engine:
Crankshaft Position Sensor
ECT Sensor
IAT Sensor
MAP Sensor
TPS
Camshaft Position Sensor

When the engine reaches a certain temperature (somewhere between 160 and 180 degrees), it switches to a closed loop mode. In this mode it takes input from all the sensors to run the engine.

In open loop mode, the computer runs the engine based on throttle position, manifold vacuum, engine speed, and plugs all that info into a predetermined fuel map. In closed loop mode the computer does real time tuning on the engine using the o2 sensor. If either the o2 sensor or computer are bad, the computer cannot do its job. Try forcing the computer to stay in its open loop and see if the problem persists. You can do this by putting a 160 degree thermostat on the engine.

As for the computers being the same, its possible, but they have different part numbers, so it seems odd.

 

I'll do some more checking on the computer.

Still looking for suggestions.
We gained access to a Scanner for Saturday so we'll look at the data again and i'll post any positive or negative results.

 

Hi all. Here's some more info.

The engine runs for 8 minutes. During that time it does not go into closed loop. At the 8 minute mark it goes into closed loop and the stalling starts.

3 items
1) Should the engine be going into closed loop sooner and what drives it there (O2 temp?)?
2) The O2 sensor can be connected to either the right or the left input at the computer. Is there any difference in the 2 input points? At the moment the O2 is feeding the "right" input.
3) After the engine dies it takes a 5 hour cool down to restart. What could take that long to reset or cool off to enable a restart.

Any additional info would be appreciated.

 

If I remember right the once the engine warms up to temp it switches to open mode. The Engine Coolant temp sensor tells the computer when it is warm enough. I think it is at 165-180 Deg. The Thermostat can delay when the engine warms up. When the engine and coolant cools below its range, that is when you can start it. I would look at the Coolant sensor as stated above. Make sure you have the correct one a 2 wire sensor.