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-   -   Help with throttle body on 1992 1500 silverado?? (http://www.hotrodders.com/forum/help-throttle-body-1992-1500-silverado-159114.html)

Robbie 05-26-2009 03:07 PM

Help with throttle body on 1992 1500 silverado??
 
my son has a 1992 silverado 1500, with a 4.3 engine, The truck has been sitting for about 3 months but has been cranked just about everyday ,the other day we added gas and about two days later it started running rough,and now it want run. I changed the fuel filter thinking maybe the old one might be cloged up.But that didnt fix it. Then i took the fuel line back off of the back of the fuel filter and turned the key on ,and it has good gas presure coming out there,and then i did the same thing at the throttle body and it has good presure there.But there is no gas coming out the fuel injectors,I checked all the fueses,and the wires on the injectors and they have power going to them.I can spray starting fluid,or a mist of gas in the throttle body and it cranks right up and runs as long as i keep spraying it..
I was going to take the fuel presure regulator out of the T/B and see if i could see anything,but sence i havent never worked on one before i thought i better ask first, any help would be great..
thanks Robbie

T-bucket23 05-26-2009 05:30 PM

There is a ground wire on the firewall for the injectors. It is known to corrode or break.

Robbie 05-26-2009 06:49 PM

I got it to run ,but i have to keep pumping the gas to keep it running,but as soon as i take my foot off the pedel,it stops.Im thinking maybe its my fuel pump,even tho its pumping gas,it might not have enough presure to keep it running. Does anyone know what the fuel presure should be?? and am i guessing right??

va4cqd 05-26-2009 06:51 PM

fuel pressure when running should be 9 to 13 psi

T-bucket23 05-26-2009 07:06 PM

Quote:

Originally Posted by Robbie
I got it to run ,but i have to keep pumping the gas to keep it running,but as soon as i take my foot off the pedel,it stops.Im thinking maybe its my fuel pump,even tho its pumping gas,it might not have enough presure to keep it running. Does anyone know what the fuel presure should be?? and am i guessing right??

Pumping a fuel injected vehice should have no effect. Check teh voltage the the injectors. Use the injector ground to the injector + it should show a good strong pulse. If the 12 volts is solid and the pulse doesnt look good, the ground is bad. This is common on these trucks. It is the ground for the computer theat the injector groung pulls up to. If you can get a schematic, it should be easy to find. Check the Autozone site, that have a lot of schematics for that vintage vehicle.

Robbie 05-26-2009 07:34 PM

i have checked all the grounds straps,and retighten them,and even ran another ground just to make sure,if the ground was bad,it wouldnt run right??
and yes,me pumping the gas kept it running..The ground i checked was on the passenger side firewall going from the frame to the firewall to the engine,and the other was near the battery,and another one was on the intake.


Quote:

Originally Posted by T-bucket23
Pumping a fuel injected vehice should have no effect. Check teh voltage the the injectors. Use the injector ground to the injector + it should show a good strong pulse. If the 12 volts is solid and the pulse doesnt look good, the ground is bad. This is common on these trucks. It is the ground for the computer theat the injector groung pulls up to. If you can get a schematic, it should be easy to find. Check the Autozone site, that have a lot of schematics for that vintage vehicle.


cobalt327 05-26-2009 08:39 PM

You might give the TB a good cleaning w/spray carb cleaner. I've had them run pretty ratty until cleaned up. Maybe not as bad as you're describing.

Quote:

Originally Posted by Robbie
pumping the gas kept it running.


sbchevfreak 05-27-2009 08:46 AM

Quote:

Pumping a fuel injected vehice should have no effect
I've had pooched TPS sensors display this type of symptom.

Robbie 05-27-2009 03:59 PM

what you mean by pooched??? Im still thinking its my presure,I havent ckecked it yet. And how can i ckeck my presure,I dont see no fittings on the fuel lines. Can i take the line off the TB and hook a gauge up to it and spin it over and ckeck it there???

(I've had pooched TPS sensors display this type of symptom.)

va4cqd 05-27-2009 04:53 PM

pooched means bad

Robbie 05-27-2009 07:35 PM

I knew that :D jk

Quote:

Originally Posted by va4cqd
pooched means bad


fast68 05-28-2009 02:09 PM

howdy there,

check or replace cap and rotor if they are old at all. 4.3L are bad about eating caps and rotors and it causes all kinds of issues.

check the pink and white wires from the coil to the distrib they like to break inside the insulation where you cant tell and it will cause no fuel injection and no spark both i have found out in the past. mess around with them while cranking or running and see if it changes anything.

took me a year to figure this one out the first time on a 92 4.3L we had that randomly wouldnt start or would randomly die, we replaced everything only to find out it was the pink wire of this short harness the whole time!

make sure the distributor is set to zero also


bad ground is not a common issue on these, but its worth checking them sure.


fuel pump death syndrome is extremly common on these along with the bad cap and rotor syndrome


these two and the coil primary wires is where i would be looking

good luck!

Ripper 410 07-09-2012 08:21 PM

Stop!!!!!!!!!!!!!!!!!!!!!!!!!! You say it has sat up for awhile and now it runs if you pedal it the iac is stuck (idle air contol) the little 4 prong plug nut looking thing on the back of the throttle body passenger side rear cost about 50bucks local parts house clean the throttle body with carb cleaner before you change it


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