Chevy TBI troubleshooting?

cj777

cj777

Well-Known Member
Joined
Mar 22, 2005
Location
Durham, NC
My grandmother passed away about 3 years ago and I am in the process of trying to get her car running again after sitting. The car is a 1989 Chevy Caprice with a TBI injected 305 with 68,000 original miles. After replacing the battery the car started right up ran great for a few minutes, drove up and down the driveway fine, and then died. It would crank up afterwards but die in a few seconds of idling or bog down and die when given gas. Figuring it had bad gas, I drained the gas tank completely and replaced it with fresh 93 octane. Now the car still does the same thing....cranks right up but dies within 3 seconds. If I give it gas it will have a small backfire out of the throttle body and die. Any ideas to help troubleshoot? I know nothing about these cars. The car was running perfectly 3 years ago. Thanks in advance.
 
cj777 said:
My grandmother passed away about 3 years ago and I am in the process of trying to get her car running again after sitting. The car is a 1989 Chevy Caprice with a TBI injected 305 with 68,000 original miles. After replacing the battery the car started right up ran great for a few minutes, drove up and down the driveway fine, and then died. It would crank up afterwards but die in a few seconds of idling or bog down and die when given gas. Figuring it had bad gas, I drained the gas tank completely and replaced it with fresh 93 octane. Now the car still does the same thing....cranks right up but dies within 3 seconds. If I give it gas it will have a small backfire out of the throttle body and die. Any ideas to help troubleshoot? I know nothing about these cars. The car was running perfectly 3 years ago. Thanks in advance.
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Check the fuel pressure. Those are classic low pressure symptoms for tbi. I bet the pump is shot from sitting and varnishing up. Tbi motors of that era call for 9-13 but I like to see 11-13. I've seen a few in spec at 9 psi acting just like that too. If the pressure is good do a flow test. I can't remember the spec on that right now but you should be able to Google it.

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Also the injectors could be varnished up. If the fuel pressure is good you may need to pull the injectors and soak them in carb cleaner, you want to see a nice solid cone pattern spraying out of them and hitting the edges of the throttle blades. Look at the spray pattern while holding a flashlight at 90* to the injectors from your vantage point.

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Knowing how old that car's tank is, and that it hasn't been run in 3 years, I'd change the fuel filter before getting too deep into troubleshooting. Cheap and easy, and very important to know the status of when troubleshooting possible fuel system problems.
 
Mac5005 said:
Could also be the ethanol fuels have ruined the hoses. Had this happen before on the small rubber line between pump and sending unit. Just another thing to check.

Start with fresh fuel and filter and then check pressure
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Thanks for the replies guys. I actually got more help from here than from the chevy forum. :) The pump is pumping fuel as that's how I drained the old gas out but the disconnected line was before the fuel filter so it's possible the filter is just clogged and killing the pressure. I'll try changing the filter and get a fuel pressure reading and write back.
 
Mac5005 said:
Could also be the ethanol fuels have ruined the hoses. Had this happen before on the small rubber line between pump and sending unit. Just another thing to check.

Start with fresh fuel and filter and then check pressure
Click to expand...

This happened with my '87 k5 with the 350 TBI, take the fuel cap off and have someone turn the key forward, if you hear any dripping/pouring I can promise you that hose has cracked. And for what it's worth it would build up enough pressure to flow out of the fuel filter but would only trickle at he throttle body.


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If all of that fails, try cleaning the throttle body, specifically the Idle Air Control valve. Those produce similar symptoms when they're gummed up from years of sitting.
 
CTS Sensor possibly? 10$ fix I unplug cts and see if it idles that'll tell the tale on it
 
C.Berry said:
CTS Sensor possibly? 10$ fix I unplug cts and see if it idles that'll tell the tale on it
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If you unplug the cts, the computer will think that coolant is super cold, and the engine will run very rich.

Most sensors either vary the resistance or voltage. Both as easy to check with a multimeter. A good repair manual will list the correct ranges for all practical sensors.

Just Ex: tPS can have 5v closed, approaches 0v WOT.

Cts and iat, can have 0v cold and approach 5v hot.

The individual specific of each sensor and model vary, but find the correct specs and acceptable ranges for your specific application.

First thing first, narrow down whether this is a fuel or ignition problem.

Back to fresh gas, filter, and check psi.
 
^ I'd go with what he said... ThTs how I determined my CTS was bad tho truck would idle sokn as YA touched gas it bogged I unplugged cts to drive it home!? Just my experience but I'll be honest I suck at electrical trouble shooting
 
fuel line problem
 
Mac5005 said:
Could also be the ethanol fuels have ruined the hoses. Had this happen before on the small rubber line between pump and sending unit. Just another thing to check.

Start with fresh fuel and filter and then check pressure
Click to expand...

iwaxmyjimmy said:
This happened with my '87 k5 with the 350 TBI, take the fuel cap off and have someone turn the key forward, if you hear any dripping/pouring I can promise you that hose has cracked. And for what it's worth it would build up enough pressure to flow out of the fuel filter but would only trickle at he throttle body.


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Click to expand...

:beer::beer:You guys win! I owe you one. Sure enough there was a hole in the line inside the gas tank going from the pump to the sending unit. Replaced it and it's running fine. Thanks
 
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