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Old 04-26-2009, 09:43 PM   #1 (permalink)
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Need help TBI no injector pulse

My 91 small block in a early model body truck died. Ran great, parked overnight, wouldn't start in morning. Could have had a power surge, I use a disconnect at battery so truck can't be stolen. I also hit the poles on the battery together to test that the battery did have current. I checked and replaced fuel pump, ign module, ecu, prom. I can ground the injector wire at the ecu and make the injectors fire, when there is gas in the intake it does start and run, I have verified spark. The ecu does have a limited program chip, it only needs o2 sensor and coolant sensor to make it run in closed loop. The origonal chip will also work just runs a little rich. Is there a common wire break in these harnesses? Is there an internal harness fuse? I am getting continuity from the injectors to the ecu, and have tested all the grounds. All of the power wires are at 12v . Please pm me if you have a suggestion, it would be a great help.
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Old 04-26-2009, 10:04 PM   #2 (permalink)
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Any codes?
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Old 04-27-2009, 05:14 AM   #3 (permalink)
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had a chip burned that doesn't need a engine light, so no there are no codes shown.
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Old 04-27-2009, 06:05 AM   #4 (permalink)
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Old 04-27-2009, 06:34 AM   #5 (permalink)
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Ignition module?
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Old 04-27-2009, 05:06 PM   #6 (permalink)
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Go here and read the FAQ. You have lots of reading to do.......My only question is you say you can ground the injector wire at the ECU and get the injectors to pulse? They pulse just one time I hope?....You can get the codes with a trouble light. Read the above FAQ to find out how.
Sounds to me like you probably have a fuel delivery to the throttle body problem.
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Old 04-27-2009, 09:34 PM   #7 (permalink)
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i agree with binder, sounds like a fuel delivery issue. check your fuel pump relay, power and ground @ the fuel pump connector, i had a similar problem with my 4.3, lost ground @ the connector to the fuel pump, drove me crazy for a couple hours before i found it.
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Old 04-28-2009, 05:55 AM   #8 (permalink)
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Yeah that's why I said module, IIRC they are tied in to the fuel system through the ECM. They also go bad like instantly which sounds like what happened to you. Binder has the right idea with the FAQ, sometimes you just have to go back to basics before you get in to deep
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Old 04-28-2009, 11:08 AM   #9 (permalink)
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I did go through the basics, ign mod is new, and is getting spark, ecm is now new, no change, fuel pump good and working, continuity going to ecu from both sides of injectors, and I can make the injector fire if I ground it for just a second at the ecu side. What tells the ecu to fire the injector, I think I have a broke wire in the harness from what ever tells the injector to fire to the ecu. I believe that is the dist module. Will the est unit on the valve cover create a no fuel or just used for spark advance.
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Old 04-28-2009, 08:30 PM   #10 (permalink)
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Try once to start it with the TPS unplugged. There is a clear flood mode if you were to hold the pedal to the floor. If the TPS went tits it could think it's in clear flood mode...
Does this thing have a anti theft device for the key?
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Old 04-28-2009, 09:00 PM   #11 (permalink)
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Also keep your battery charged if you've been cranking on it alot. If the voltage drops too low it won't start even if it cranks.
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Old 04-29-2009, 08:34 PM   #12 (permalink)
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Have tried the tps plugged and unplugged. I have now pulled the engine computer harness and am testing all the wires and connectors. Will let you know if I find a prob. Keep the suggestions coming, I do appreciate it, could make a long diagnosis shorter.
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Old 05-06-2009, 07:50 PM   #13 (permalink)
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I found the problem. I had to scrap the old engine loom, it didn't have a check engine light, it had been patched by someone else. I got a good harness with a check engine light and a real fuel pump circut and was able to pull codes. I had burned up two different prom chips, probably something with in the old harness. After I put the new harness in and it still didn't start, I pulled code 51. I couldn't believe I had two bad proms, an origonal and a performance. I went to the junk yard and found a same ecu and pulled the prom out of it and this thing runs fine now. P.s. I have also discovered for any one who is testing for injector pulse, the purple and white wire on the ignition module will send .8 to 1.8 volts while cranking, and is the signal wire for the injectors, this will save time when diagnosing modules on no fuel problems
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Old 03-07-2011, 05:35 AM   #14 (permalink)
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Quote:
Originally Posted by bowtied1 View Post
I found the problem. I had to scrap the old engine loom, it didn't have a check engine light, it had been patched by someone else. I got a good harness with a check engine light and a real fuel pump circut and was able to pull codes. I had burned up two different prom chips, probably something with in the old harness. After I put the new harness in and it still didn't start, I pulled code 51. I couldn't believe I had two bad proms, an origonal and a performance. I went to the junk yard and found a same ecu and pulled the prom out of it and this thing runs fine now. P.s. I have also discovered for any one who is testing for injector pulse, the purple and white wire on the ignition module will send .8 to 1.8 volts while cranking, and is the signal wire for the injectors, this will save time when diagnosing modules on no fuel problems
I have the same problem... the truck ran fine before I used it for a donor vehicle... I put everything in a Camaro. I have pulse at the purple and white wire(ref pulse hi) but the injectors are not firing... I guess I need to track the wiring since it ran fine before I did the swap... I'm guessing it may be a bad ground or something that got unconnected. WHat would you suggest I check next?
Also, is the ref pusle lo (red/blk wire) supposed to have a pulse when turning over the engine?
I do have spark...
Thanks in advance!
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Old 03-07-2011, 05:59 AM   #15 (permalink)
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My bbc and my son in laws sbc did the same thing it is where the plug was plugged into the dist. They were a little dirty we used a paperclip to clean out the plug end and they both work great after that.
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Old 03-07-2011, 06:37 AM   #16 (permalink)
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Originally Posted by ray299 View Post
I have the same problem... the truck ran fine before I used it for a donor vehicle... I put everything in a Camaro. I have pulse at the purple and white wire(ref pulse hi) but the injectors are not firing... I guess I need to track the wiring since it ran fine before I did the swap... I'm guessing it may be a bad ground or something that got unconnected. WHat would you suggest I check next?
Also, is the ref pusle lo (red/blk wire) supposed to have a pulse when turning over the engine?
I do have spark...
Thanks in advance!
Ok... so I just found out that the red/blk wire is a ground... so if I have ref pulse, why is the computer not telling the injectors to fire? What else does the computer need to see in order for it to tell the injectors to fire?
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Old 03-07-2011, 07:58 AM   #17 (permalink)
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You've resurrected an old thread. It would be best for you to start your own (new) thread, giving all the details associated with what you've done, symptoms, etc.
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Old 03-07-2011, 09:30 AM   #18 (permalink)
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will do- thanks
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