4.3 will not stay running

[jfred41]

I have a 1998 Chevy S10 Blazer with a 4.3. It sat up for a long time and am trying to get it running again. It will crank up and run for just about 3 seconds and then dies and is hard to crank again unless you let it sit for about 5 seconds. I have replaced the Fuel Pump, (thought maybe weak) replaced fuel filter, Replaced plugs and wires. I read somewhere that maybe the crank sensor was the problem? Does anyone know what could cause such a problem. It runs great for just a few seconds then dies and hard to crank again unless you turn the key off and wait a few seconds. HELP.

 

Thanks

[prideclaw]

Alothough it's obviously not the same engine,search for Hauli' 8.1 and cranck sensor in this forum

[prideclaw]

Sorry, I meant Haulin' 8.1

[Haulin' 8.1]

Thanks for thinking about me Panther Pride but the problem is that that it sounds like something else.

 

Sat up for a very long time.

Runs perfect for a few seconds, dies and will crank but won't restart unless left alone for a short while.

 

I would think your basic stuff in in good shape if it runs like this. It's going to be something that the engine is dependant on to run when all the basics are in order.

 

Hmmm, sounds like a clogged up exhaust system, mainly because it's sat up after running fine. Have you checked to see that an animal didn't take up residence in the tailpipe? Something like a dirt dobber nest?

 

Another thing, when you first turn the key to "ON" the fuel pump is activated for a moment to charge up the fuel rail with pressure so that when cranked the engine can fire right up. The engine can/will run a few seconds on that initial charge. Once it's used that up the engine won't restart until you cycle the key "off" and "on" again like your doing. The problem is that your fuel pump isn't being reactivated once your engine fires up to keep it running until shut off. Since you have that initial charge you know several things, the pump works and has power (fuse, relay, wiring, etc.).

Where the problem might be is in the Oil Pressure Sending Unit, which is located on the drivers side, top, rear, of the engine block just under the distributor. The fuel control circut uses oil pressure as a prerequisite for turning on the fuel pump when cranking. The turn on signal for the pump relay must go through the Oil Pressure Sender to get to the relay. If the oil pressure is below 15 PSI during cranking or the sender is disfunctional you only get the initial prime charge of fuel from turning the key from "off" to "on" but no pump reactivation during "crank" or "run".

The fuel pump oil pressure check switch and oil pressure light/guage are on two different circuts (sharing a common power) inside the same sender. Crank your engine for at least 10 seconds then let the key go and observe the oil pressure guage, if it's low check for oil pressure manualy at the same port as the sender with a real guage. If oil pressure reading is high enough, it will fall quickly, to start the fuel pump then replace the sending unit as it's fuel pump check circut is faulty. If you have an idiot light you have to make sure it's off for a moment after releasing the key from crank to run. If the light is off for a moment the pressure is adequate.

These senders aren't very expensive so it might be more convienent in your situation to just replace it if it's suspected. This mainly depending on how many diagnostic skills and or tools you have at your disposal. If it turns out to be the problem you're done, but if not you're out a few bucks and some time but closer to the real problem.

 

Hopefully one of these hunches will get you going. Good luck.

Vernon