running rich

[Elmo]

topic seems old but hope some one still watches it

I have a 1990 5.8 auto that will not start unless I shoot it with ether ,check eneine light is on,is running very rich, if i move throttle it chokes sometimes will stall othertimes will just spit and cough,has no power ,fuel pump will cuntinue running after truck stalls, then when restarted and running at oper temp for a minute it will stumble then recover and run like there is no problem, plenty of power,plenty of throttle response, if i turn the truck off the fuel pump doesnt continue running, truck will restart fine, untill it cools down then it starts all over again. Fuel press is 35-40. Tring to check codes with a POS code reader from autozone is not comeing up with any conclusive results gonna try the jumper wire method will post results. I know my way around a vehicle can build an engine with no problem but never got too deep into the drivability diagnosis part. This thing is ******* me off though it ran through 5 gal of gas just idleing in my shop while i looked for vac leaks bad wires did notice the plugs are gapped way more than .042. this beast is completely stock no mods at all. I have replaced the air bypass valve jst because i had one on hand.

 

[Shadow_D]

How old is the FPR? It sounds almost like the problem I had with mine that ended up being the Fuel Pressure Regulator...

 

[BroncoJoe19]

If I recall correctly Haynes has about three pages on checking the fuel pump, lines. and fuel pressure regulator. I vaguely recall that they said it was difficult to diagnose a FPR problem. At any rate, at $4 a gallon it could be replaced for about 6 gallons. /emoticons/[email protected] 2x" width="20" height="20" />

Other things to cause it to run rich would include an exhaust leak BEFORE the O2 sensor, bad O2 sensor, Bad Connection to O2 sensor.

Here's a litty ditty on how to check for a vacuum leak, I know that you already checked them, but this might remind you of something.

Checking for vacuum leaks.

Some of the sensors and some of the actuators either read the amount of vacuum, or use vacuum to move controls, therefore it is important to the proper functioning of the engine that your vacuum system is fully intact. Otherwise one may get codes falsely indicating that there is a problem with a controller/actuator, or a sensor when in reality it is caused by a lack of vacuum.

Look at your rubber vacuum hoses (they are about 1/4 - 3/8 inches in diameter, if they are dry rotted or cracked, replace them. IF they slip on/off of their connectors too easily, they may have stretched out a little bit, cut the ends off, and put them back on.

You may listen for a leak. Sometimes using a cut off piece of garden hose is a good aid to listen with. Sometimes a cardboard tube (like from gift wrapping paper) is helpful. Just remember that whenever you stick your head inside a running engine compartment, that you are not wearing any loose clothing or jewelry that can get caught.

Another suggestion is to use a spray can of carb cleaner and spray around the bottom of the intake manifold, and the base of the throttle body assembly. IF there is a leak, you should hear a change in your engine.

Keep a fire extinguisher handy, or use water instead of carb cleaner (it works, but not as well.) Be aware that if you use water and the wires get wet and it runs worse... your wires may be bad, and the water is allowing them to arc instead of jump the gap of the spark plug.

Another suggestion is: to take a propane torch, turn it on (but don't light it) and move it over the vacuum hoses and connections. The engine RPM's will increase if there is a leak and the propane gets sucked in.

Also remember to check the PCV valve, hose and grommet.

 

[BroncoJoe19]

In this thread I have a pic of the Data Link Connector. I marked it to depict teh pinout for testing the fuel pump. All one needs to do is to ground that pin, and the pump will continue to run. This is for testing purposes, not a suggestion for running that way.

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