92 chevy 305 keeps flooding

[flips87c30]

Not sure who else to ask and you guys have always helped me fix my truck problems. So here is the story.
I am trying to get my 92 Chevy 1500 road worthy. It sat for a few years before I bought it, due to a fuel pump issue. I brought it home replaced the fuel pump and lines and fuel filter. Replaced a lot of other things too, headers, exhaust, spark plugs, cap and rotor, ICM, ignition coil, oil change, rear differential fluid, and a coolant temp sensor. Now I figure it kind of has to run good now.

 But it wont start unless you hold the throttle wide open. It started the first time just fine but after 5 minutes or so it flooded, and now you have to hold it WOT to start it at all and if you let it idle it tends to die. The plugs are soaked and Im sure I have to change the oil again. What is causing this? Tomorrow Im planning on rebuilding the throttle body. But I don't believe that's the problem.

[bd]

Are all of the sensors plugged in and vacuum hoses connected?  Any wiring or grounds left disconnected?  Which coolant temp sensor did you replace - gauge or emissions?  When did you first notice the problem - before or after replacing the temp sensor?  Have you verified a strong stable spark?

Check fuel pressure and write down any stored codes.  Remove the ECM B fuse to clear any stored codes from memory. 

Remove the air cleaner.  Place a piece of clean white paper under each injector, so that they sit on top of the throttle plates w/o touching the injector tips.  Cycle the ignition key ON for two seconds then OFF for ~5 - do not open the throttle, crank or try to start the engine - just switch the ignition ON-OFF to build fuel pressure.  Repeat the cycle half a dozen times.  Is the paper wet with fuel or is fuel dripping off the injector tips?

Remove the oil dipstick and let one drop of oil fall onto your clean finger tip.  Does the oil quickly track out along the friction ridges of your finger or hold together and maintain its shape?

[flips87c30]

all sensors are plugged in and vacuum hoses are connected all wiring and grounds look good. There is a small connector pigtail that comes from one of the coil connections and appears to go nowhere I assume it is a test location?

unfortunately I am not equipped to check fuel pressure I removed the ECM-B fuse when I checked all the fuses

I performed the paper test. The paper was dry nothing even dripping off the injectors. Does this mean theres no pressure building?

I did the oil test as well it did seem to run off quickly and seems a little thin to me but it did hold its shape briefly   

[78BIG-TEN]

Several things to look at,like mentiond earlier the coolant sensor and grounds.I'm assuming this is a TBI system.Grounds at t\stat housing I have seen this bolt really corroded down in the intake threads.Also look at the map seen many tbi plugged with carbon on the bottom side at map and pcv passages or the map itself.Could have stuck pressure regulator or plugged return line,this where a pump pressure test would be valuable.Canister full of fuel.I would assume that tps is ok since you say it starts at wide open,this is clear flood mode

[Irish_Alley]

coolant sensor would be 1st on my check list. but just heard a story where this boys tbi would pop/miss and smoke on idle. come to find out his brake booster was bad and caused his problems. idk how a vacuum leak would cause running rich symptoms

[flips87c30]

I did change the coolant sensor and thoroughly cleaned all the grounds. It wants to start but just kind of sputters Im thinking I need to dry/clean my spark plugs

[bd]

Here are a few more things to do:

TBI engines are exceedingly fuel pressure sensitive.  You should add a fuel pressure gauge to your tool kit and check the pressure.  I also suggest that you visually check the fuel for quality and contaminates.

Your description of engine oil consistency suggests moderate fuel contamination of the oil.  By all means remove and inspect the spark plugs to see if the electrodes are soaked with fuel.

Check for any stored codes.

Heed 78BIG-TEN's comment about the MAP & PCV vacuum ports and lines - verify that full manifold vacuum is reaching the MAP sensor and that the line isn't restricted or leaking.

Disconnect the EGR valve vacuum hose and remove the EGR valve from the engine.  Flip the valve over and spray some light penetrant into the circular steel orifice at the pintle valve - observe whether any of the fluid seeps past the pintle valve into the adjoining chamber.  If it does, replace the EGR valve.  Check for vacuum on the line from the EGR solenoid - if the engine will start, vacuum should be zero at idle.

Unplug the EST bypass connector to see if the engine starts and idles.  If it does, replace the distributor pickup coil and module.

Unplug the two harness connectors from the ECM, spray the connector terminals with contact cleaner (Radio Shack, CRC, etc) and plug the connectors back in.  Recheck engine starting.

[flips87c30]

thanks everyone. I will check back after looking into these things. bd Where is the est bypass connector?

[bd]

The EST bypass (timing) connector is a single wire connector with a tan/black stripe wire that breaks out of the harness either in the vicinity of the firewall bulkhead connector OR under the dash in the area of the glove box.  The procedure for setting timing or forcing the distributor into bypass mode is similar between 1992 vehicles and your 1987 TBI engine.

[flips87c30]

Truck is running great  New spark plugs and an oil change did the trick. I believe the coolant temp sensor was the culprit. And the plugs were so gas drenched that it wouldn't start. Thanks for all the help. Now that this trucks on the road I can put my squarebody in the shop this winter. I will start a build thread once I get it going.

[78BIG-TEN]

glad you got it worked out