'89 chevy won't start.

Discussion in 'Mechanic and Repair' started by TClawn, Nov 1, 2005.

  1. TClawn

    TClawn LawnSite Silver Member
    Posts: 2,036

    it is a GMC '89 chevy 1500. manual tranny, efi.

    now this truck worked fine just a half hour ago, and everything was normal. but now, it will not start. my dad said that when you tried to accelerate, it would jerk, like it was not firing a second, than go back to normal, and happen again, it died just as he got home.

    I have already started trouble shooting, and am assuming that is has good compression.

    the first thing I did, was guess that someone had syphoned gas from the truck overnight (it is parked in a local construction companys baseyard) and that the gas gauge was broken or stuck. I put in two gallons of gas and tried starting it. before you ask, I have been trying for the last 10 minutes to make sure that gas was pumping through the fuel line.

    now to me, I think that is sounds like it is not getting any spark, it will just crank, but will not start up. is it possible that the efi ground wiggling loose could cause this? do you know where the efi ground is located so I can check it?

    my other question, is what is a safe way of checking the spark plugs for spark? I am assuming that the charge is much larger than I lawn mower engine, and don't want to get electrocuted.

    thanks. chris.
  2. xcopterdoc

    xcopterdoc LawnSite Senior Member
    Posts: 752

    You can get a cheap but good spark tester at any autoparts store.
    Check the basics, spark, fuel ect. go from there.
  3. ASEGuy

    ASEGuy LawnSite Member
    Posts: 6

    Some down and dirty testing-

    Easiest thing to do first is make sure the check engine light comes on when you first turn the ignition on. This proves that the ecm is powering up. If ok, then pull off the air cleaner and watch to see if the injectors are spraying into the throttle body while someone cranks the engine. If this is ok, you know that the distributor is turning, the pickup coil and ignition module are working, along with the ecm, fuel pump and injectors. This leaves the igntion rotor, cap, or coil as the most likely suspects.

    If there is no injector spray, check for spark. If there is no spark and no injector spray, the most likely cause is the ignition module.

    Once you have done these tests, let us know the results as there are more defined ways of testing things.

    The advice on the spark tester is good, every shop should have one. Getting hit with 30,000+ volts from a GM ignition system is not likely to hurt anyone, but it will sure wake you up in a hurry. ;)
  4. sheshovel

    sheshovel LawnSite Fanatic
    Posts: 5,112

    Check the fuel filter also,if the gas tank is old and the truck has been run low or run out of gas,it can pick up crap from the bottom of the gas tank and clog up the filter.Do not try to start it again right now.Take off the air filter and move the throttle on the carb manualy and look for gas squirting into the carb.If it does then gas getting there is not the problem,check fuel filter,make sure all fuel lines are secure and not leaking.Then check all your vacume hoses coming off the carb too.If every thing is ok then go to your electrical problem check all wires and grounds.But I think the problem is he ran it out of gas,clogged the lines or filter,then you flooded it trying to start it up.Let it sit and try again
  5. steve45

    steve45 LawnSite Bronze Member
    Posts: 1,325

    Take the air filter off and put a teaspoon of gas down each side of the throttle body, then try cranking it. If if doesn't fire, you're probably not getting spark.

    If it DOES start for a couple of seconds, you have a fuel problem. Bad pump, plugged filter, contaminated gas, etc.

    If it doesn't fire, pull a wire off a spark plug and stick a screwdriver in the end of the wire. Hold the screwdriver shank within 1/4" of the engine block, cylinder head, etc. and have your dad try cranking it (hold the plastic handle of the screwdriver). You should see a spark jump from the metal to the screwdriver. Don't worry, the ignition system will NOT electrocute you. It puts out very high voltage, but very little current. If you don't get a spark, remove the distributor cap and wipe the inside of the cap and the rotor with a cloth moistened with alcohol. You may have carbon buildup that is causing the spark to arc to ground, rather than across the plug. Put the cap back on and check the spark again, or try starting it. If that doesn't help, you likely have a bad coil. Probably a good idea to replace the cap & rotor if you replace the coil. The coil is in the top part of the distributor cap.

    Based on the apparent mis-firing you mentioned, I would suspect the cap is the culprit.
  6. TClawn

    TClawn LawnSite Silver Member
    Posts: 2,036

    I checked the fuel prob. with the fuel, and it started up, so definatly a fuel problem. I also put a hose a bit down the gas line, and turned the key to "run" and only heard a click, instead of a low humming that you hear from a fuel pump being on, so I suspect it is a bad fuel pump. maybe the filter? is there a way to check the filter? this gas tank has about 12 gallons of gas in it, and I don't want to have to drain it all out. not to mention I can't find a pressure release so I don't have fuel spraying all around when I take it off.
  7. steve45

    steve45 LawnSite Bronze Member
    Posts: 1,325

    If the pump isn't working, you probably won't have any pressure in the lines to worry about. Just put a rag over it when you disconnect it and have a fire extinguisher close by. Make sure you disconnect the battery first.

    I've never done it on a pickup, just Suburbans & Tahoes. I'm told that you can remove the mounting bolts from the front of the bed and loosen the bolts on the back, then use an overhead crane to raise the bed up to access the pump. That way, you don't have to remove the tank. Be very careful to secure it so it doesn't come down on you!

    While you have the fuel level sender unit out, make sure you clean the wire windings on it with some lacquer thinner or similar solvent. Sometimes, when you take them out and let them dry, they won't read correctly when you put them back in.
  8. lawnboy dan

    lawnboy dan LawnSite Gold Member
    Posts: 3,712

    i own this same vintage chevy truck -dont worry about fuel line pressure . it automaticly bleeds off when the engine is shut off on this model. i bet its the fuel pump which as stated above is in the gas tank. check filter first . its real easy to change . its on the frame under the drivers door.
  9. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    If you hear any noise at all from the tank it may not be the pump, Go for the fuel filter first as stated. There is a pressure switch built into the pump to shut it down should you get into a accident and break a fuel line so if you try to test the pump with the filter off it will not pump. When you get the filter off wipe the end and blow through it briskly with your mouth, There should be little to no restriction.
  10. ASEGuy

    ASEGuy LawnSite Member
    Posts: 6

    The ecm activates the fuel pump relay for only approx 3 seconds when you first turn the key on. It will then shut it off if the engine is not turning over. Meaning- if you turn the key on and then go back to listen for the pump, it will have probably already shut off.

    Based on what you have determined and the mileage of the vehicle, the pump is very likely bad. If you want to be sure, you will need to test for power and ground at the connector near the tank. Remember- there will only be power for approx 3 seconds unless the engine is cranking.

    The filter is a possibility, but if it is so restricted that the truck won't run, the pump will have been damaged by this regardless. These trucks run on a 12 psi pump, and there is little if any residual pressure when the pump is not running. It is wise to replace the fuel filter at least every 30K miles. When you change the pump, definately do the filter at the same time. Also, when you buy a new pump, be sure to buy the "sock" filter and change it also. It is inside the tank, connected to the intake port of the pump.

    I have found on a pickup with an empty bed and the tank inside the drivers side frame rail, the easiest thing to do is remove the bolts holding the drivers side of the bed to the frame and loosen the bolts holding the passenger side of the bed to the frame. 2 guys (or a pole jack) can then lift up the drivers side of the bed, allowing it to pivot on the passenger side bolts. Lift it up off the frame high enough (about 18") to allow another person to get some wood blocks between the frame and bed, allowing enough space to remove the sending unit from the tank. Make sure you have the bed blocked up well, or it could fall and cause massive injury. When lifting, pay close attention to any interference around the rear bumper ends that might cause body damage. Also closely observe the wiring harness for the rear lights, as you might need to manuver it for added room to lift.

    Hopefully your truck has not been overly exposed to salt spray- sometimes the fittings on the tank sending unit can be tough to get loose and a new sending unit is $$$.

Share This Page