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91 Silverado hard starting!

Discussion in 'GM Powertrain' started by rock141b, Jul 7, 2011.

  1. rock141b

    rock141b New Member

    Hi to all, well solved the no spark issue turned out to be a bad distributor. Driving around today ran like butter, got home turned it off then tried to start it a min later and just cranked and cranked no start %$%$^&!!!. Checked and had spark YEA!! so I poured some fuel in the TBI and it started right up, turned it off and it took 10 or so seconds to start. Then tried again and no start again until I primed the TBI and then it started right up again. I put a new fuel pump, fuel filter, fuel pump relay, fuel pressure regulator, runs like butter but then wont start, what could it be, thanks for any help.
  2. stephan

    stephan Rockstar 4 Years 5000 Posts

    It's starting fine every time you prime it so, the next time it fails, pull the air cleaner off & watch the injectors while a helper cranks it for you. Are they shooting fuel as soon as it's cranked?
  3. rock141b

    rock141b New Member

    Hi thanks, I did just that had my wife crank while I looked at the injectors and they were not shooting fuel like they should, so do you think the fuel pressure is too low from the %%$$k new fuel pump I just put in, thanks.
  4. stephan

    stephan Rockstar 4 Years 5000 Posts

    No I don't think fuel pressure is low or it wouldn't run so good when it does start & run, but the next time you have a fuel problem it would probably be good to check that first before you spend $$$ on fuel pump & all other parts you replaced.
    What's happening is your ECU is not grounding the injectors & making them open. Your injectors have 12V power when the key is on, & the ECU grounds them & opens them & makes them inject fuel. This is what's not happening (no grounding from the ECU) This could be because the distributor pulse signal isn't getting to the ECU to tell it to ground them. Since you recently replaced the distributor, I would check the 4 wire plug going to it. It's the big plug with black/red, tan/black, white, & purple/white wires. Unplug it & look for loose or oily/greasy wire connectors. Pay special attention to the purple wire. This is the one that pulses the ECU when you're cranking the engine. Spray the connectors with some elect cleaner, or carb cleaner, or alcohol (whatever you have that will clean them). Plug it in & unplug it a couple times. Make sure you have a good connection here, then have your helper crank it over again while you watch to see if the injectors fire fuel. I'm hoping this is it since you just had it unplugged recently. If not, post back & I'll give you a another check to make.
  5. rock141b

    rock141b New Member

    Thanks Stephan I'll give that a try, and your right I refuse to throw any more parts at this until I find the real problem, you read how many parts and $$$ I have put into this truck, thanks again, Roger.
  6. rock141b

    rock141b New Member

    Hi Stephan, well I tore off all the covering on the wire bundle going into the distributor all they way into the fire wall and all the wires look like new including the connector. So any other suggestions or things to try? thanks for all your insight, Roger.
  7. stephan

    stephan Rockstar 4 Years 5000 Posts

    OK I have another test that might narrow it down then. Disconnect the 4 wire plug at the distributor. You'll need a test light. **Hook up your test light clip to your positive battery cable/post. Turn on the key & touch the purple wire connector for a split second. Don't leave it on there, just hit it for a brief moment. This should fire the injectors. If it does, then your ECU & all the wireing to it is good & your dist is not sending a pulse to the ECU. Since this is a different distributor than what you had before I think that this might be the problem. During cranking speed it is not sending a strong pulse to the ECU, but once you prime it & it fires over at greater speed, the pulse generated is stronger & it fires them. Don't use a voltmeter or a jumper wire for this test!!
    If this test doesn't fire them, then you have an intermittant continuity problem in the wiring from the dist to the ECU or the ECU is bad. If this is the case, then it's important that you thoroughly check the wireing & the connector, as ECUs are expensive.

    **edit, When you have the 4 wire plug disconnected, you need to run your test on the plug half that goes into the firewall, not on the half that goes into the distributor. I should have clairified this above cuz doing the dist half won't do anything lol

    Well duh!! 3 times I've edited this now. I hope I finally got it right

    ** Just curious, what brand is this replacement dist & where did you buy it?
    Last edited: Jul 10, 2011
  8. 1991 Suburban

    1991 Suburban Rockstar 100 Posts

    I have a '91 V1500 Sub. Same issue. It is intermittent at best. One thing I have noticed it when it doesn't want to start, I can't hear the fuel pump prime. For a long time I was just spraying it with starting fluid and it would fire up after a moment. Now, I have noticed that if I give it 1/8 throttle, it will start on it's own...After a bit of cranking that is. If you get it figured out, please let us know!
  9. rock141b

    rock141b New Member

    Thanks Stephan, this is why Im a car guy (I have a 51 chevy fleetline street rod) car guys will always help others and are just great people. I'll give this test a try and see what happens. I purchased this dist from a local parts house here in Tacoma, (baxters) I dont know off hand what the brand is but I will find out tomorrow as the manager is a local street rodder and a good guy, so if there is a problem with it I can get a replacement, take care.
  10. stephan

    stephan Rockstar 4 Years 5000 Posts

    Hey Roger, If it came in a box check the packaging. You could also look for a vendor logo on the dist. I'm not saying it's a Taiwan or Chinese one, but I suspect the control module might be since they have been known to give out a weak signal at cranking speeds. Either way, whether you get a whole new dist or just a module, check the new one he gives you so you don't have the same problem

    *the '51 sweet, post a pic
    Last edited: Jul 10, 2011

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