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jazzmaster
jazzmaster, ASE Certified Technician
Category: Chevy
Satisfied Customers: 2258
Experience:  ASE .AUTO TECH FOR THIRTY-FIVE YRS,ELCTRICAL,FUEL INJECTION ETC.
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Chev 1500: I have 1991 chevy truck, 305 throttle body injection.

Customer Question

I have 1991 chevy truck, 305 throttle body injection. It will not run and stay running. I have replaced the fuel pump,mas,fuel filter, pressure regulator,distributer, iac,spark mod, put a kit in the throttle body ass. tryed a different computer
Submitted: 1 year ago.
Category: Chevy
Expert:  jazzmaster replied 1 year ago.

hi, my name is XXXXX XXXXX X will try to help you ....

does this start right back up and does it start ok after sitting over night ?

so, in other words it starts but stalls right away ..please describe more on the starting and kind of running it will do ....

Customer: replied 1 year ago.

no if i have someone hit the gas and i put gas in the intake it might start.


 

Expert:  jazzmaster replied 1 year ago.

if it starts and then stalls or feels like it wants to start then we can basically rule out a spark /ignition problem.

try spraying carb cleaner into the intake and see if it does anything different /please let me know ...

it getting late so can we continue this tomorrow ?...let me know what happens when you spray carb cleaner ...

Customer: replied 1 year ago.


I'll try the carb cleaner. untill now i was just spraying gas. The motor will run untill the gas is gone but sometimes the injectors will spray and the truck will run. Then it will Quit. I would say the ignition / spark is good also.


 

Expert:  jazzmaster replied 1 year ago.
did you replace the ignition module that sits in the distributor ?
Customer: replied 1 year ago.


I did have a shop do that they told me they replaced the distributer. I guess my question is would the ignition module be part of it?

Expert:  jazzmaster replied 1 year ago.

well it should be .but sometimes they dont ,I guess it all depends on where they got it .and if it was new or not . a shop may have said they replaced it but they should also have told you if it was new ..

like I said most come with a new igniton module but some dont .

if in doubt ,you can take off the module and get it checked at autozone for free ,so it really cant hurt to get it tested anyways ,this contols the injector pulse .

you might want to check for injector pule with a noid light ,if you dont have one of them you can use a bulb with wires attached and plug them into the connector of one of the injectors .

or with a test light ,unplug one of the injectors and turn the key on ,there will or should be bat positive voltage on one of the wires and then the ground side /the other wire on the connector will pulse a ground signal when the motor is cranked over ...

Customer: replied 1 year ago.


going to cheak now.


 

Expert:  jazzmaster replied 1 year ago.
ok
Customer: replied 1 year ago.


The ignition mod tested good but the truck still will not run.

Expert:  jazzmaster replied 1 year ago.

ok, but it will still run for a few seconds when fuel/carb cleaner is sprayed into the throttle body ?

and if you have a noid light(good tool to have)please check for injector pulse ..

if not use the test light or bulb to check the injector pulse

the one wire on each injector will have bat voltage with the key on

the other wire at each injector is a ground and will pulse/blink as the motor is turned over

also while cranking it over the injector will pulse fuel through them

Customer: replied 1 year ago.


The noid light did not light up. Both sides were dark.

Expert:  jazzmaster replied 1 year ago.

ok ,good

now check for bat voltage to one of the wires at each of the injectors with the key on .you should have voltage to at least one of the wires at each injector connector ,disconnect them to test .

Customer: replied 1 year ago.


no voltage on the one wire and12.2 or so on the other

Expert:  jazzmaster replied 1 year ago.

ok, please check all the fuses in the fuse box I say this because as long as you are checking ,check them all for there might be a bad/blown fuse you didnt know about and in the meantime I am lokng for an ecm voltage pinout diagram for you to check the wiring from the injectors to the ecm .

also that ecm that you tried may not have been the right one ,were the numbers the same on the ecms ?

Customer: replied 1 year ago.


So I have 2 fuses that were in bad shape. The wiper and the heater (no AC). The first ecm #16136581 ARPC. The second was 16136291 ARJT

Expert:  jazzmaster replied 1 year ago.

ok, replace them(fuses) and here is a diagram this should help you ,trace the wires from the injector connectors to the ecm and see if they are good as far as continuality

the ecms may not be interchangable ,also look for the powers(voltage) and grounds going into the ecm. I have to go to town and will be back in about an hour ..while you are checking the injector wires and things ..is that ok ?

graphic

I think this is the right diagram

Customer: replied 1 year ago.


of corse


 

Expert:  jazzmaster replied 1 year ago.
thank you ,I will talk to you in abuot an hour os shortly after ,,thank you
Customer: replied 1 year ago.


The blue wire was good I didn't get any thing from the green ,white ,or red.

Customer: replied 1 year ago.


The blue and the green r good . The red and the white not easy flow. .882 or so?

Expert:  jazzmaster replied 1 year ago.
ok, the blue and green are the grounds which should pulsate a ground signal when the motor is cranked over the red and the white -both have bat voltage when the key is on?
Customer: replied 1 year ago.


That is correct so does that mean the wires are good and the brain box is junk?

Expert:  jazzmaster replied 1 year ago.
just make sure that the injector/ecm fuse has voltage on both sides of the fuse with the key on , also the pink/black wire that comes from that fuse also has bat voltage with the key on
Customer: replied 1 year ago.


never mind I see what u r saying

 

Customer: replied 1 year ago.


life is good but i need a ecm.Thanks for all the help I thought u r the best.

Expert:  jazzmaster replied 1 year ago.

ok, yeah the ecm does pulse the ground signal with has imput from different sensors and mainly the ignition module and if the wiring is good to the ecm from the injectors and you have bat voltage to one side of the injectors and power and grounds at the ecm ,it looks as if the ecm is the issue ,thank you .I am posting this now as an answer post so now if you want to you can rate my service and hopefully give me a good rating ,thank you again .

as an added note ,just keep this post or ask for jazzmaster in the future if you need my help ....jazzmaster...

Expert:  jazzmaster replied 1 year ago.
the ecm fuse is in the fuse block in the inside of the vehicle
Expert:  jazzmaster replied 1 year ago.

hi, do you still need help or did I help you ?

if so let me know please ...jazzmaster ...

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