wtnhunt Posted July 18, 2012 Report Share Posted July 18, 2012 Got an intermittent problem with my 98 3/4 ton chevy that started after it was ousted out of the garage with the new car taking its place, cannot remember it ever doing this before. Has only happened twice that I know of, both times in the past couple months after the humidity level was extremely high and after we had heavy rains, and unfortunately I did not check the spark either time. Basically the engine would roll fine and the fuel pump would whine like it has always done and shut off and it just would not fire up. Reason I think it is moisture related is Sunday afternoon I went to move the truck while I was mowing and it would not start so I just opened the hood and mowed around it and figured I would come back to it when I finished up. After I finished mowing the yard I came back to the truck and it started up. It had sat with the hood open for a couple hours with the sun shining, ran a little rough at first then smoothed out. Neither the coil or the ignition module have been changed on the truck(160,000+ miles), no service engine light on or flashing, if I take the truck to an autozone or another auto parts store would a code reader pick up the problem for either of these? How likely is a module or a coil on chevy trucks to be succeptible to moisture and give intermittent problems before going completely out? Distributor cap and rotor are not that old and I don't think they are the problem, but I suppose I need to check them too. Quote Link to comment Share on other sites More sharing options...
Shaun_300 Posted July 18, 2012 Report Share Posted July 18, 2012 Sounds like a coil or coil wire to me William. Could be the ignition module but usually they either work or don't work. One easy way to find it is to go out after dark with the hood open and start it to look for small arcing, or also in the dark take your spray bottle from your grill and with it running spray around the coil and distributor area, you'll see an arc and it'll quit immediately. Ignition systems are very sensitive to humidity and moisture, so that's the best diagnostic tool. Hope this helps, let us know how it goes. Quote Link to comment Share on other sites More sharing options...
wtnhunt Posted July 20, 2012 Author Report Share Posted July 20, 2012 Thanks Shaun, gonna try to work on it this weekend. Quote Link to comment Share on other sites More sharing options...
Shaun_300 Posted July 21, 2012 Report Share Posted July 21, 2012 Let me know how you fair out William, that test should point to the culprit if it's ignition, which by the sounds of it I believe it is, sounds like a split coil without even looking at it... Quote Link to comment Share on other sites More sharing options...
LETMGROW Posted July 21, 2012 Report Share Posted July 21, 2012 (edited) My first move would be to check the distributor cap and rotor. You will probably find the terminals covered with corrosion or green gunk which will hold moisture. If this is the case replace both with OE ( AC Delco ) parts. I have high regard for Echlin ignition except for GM applications. A little dab of Di-electric grease on the terminals won't hurt either. If there is a little screen about 3/8" in the bottom of the dist. housing knock it out and get rid of it. These screens get corroded closed and won't let air circulate within the dist. and will promote corrosion. There is a GM bulletin floating around related to this. Some of the plastic housing distributors don't have any opening though. I would also replace all the plug wires and the coil wire. With age these can have small perforations in them you can't see but will trap and hold moistuer and cause the problem you have. Lynn Edited July 21, 2012 by LETMGROW Quote Link to comment Share on other sites More sharing options...
redkneck Posted July 21, 2012 Report Share Posted July 21, 2012 Or you can always jack it up and run a new one under it. Quote Link to comment Share on other sites More sharing options...
wtnhunt Posted July 22, 2012 Author Report Share Posted July 22, 2012 Or you can always jack it up and run a new one under it. Wish that were an option. Don't think this impala we got will go under the truck. lol. My first move would be to check the distributor cap and rotor. You will probably find the terminals covered with corrosion or green gunk which will hold moisture. If this is the case replace both with OE ( AC Delco ) parts. I have high regard for Echlin ignition except for GM applications. A little dab of Di-electric grease on the terminals won't hurt either. If there is a little screen about 3/8" in the bottom of the dist. housing knock it out and get rid of it. These screens get corroded closed and won't let air circulate within the dist. and will promote corrosion. There is a GM bulletin floating around related to this. Some of the plastic housing distributors don't have any opening though. I would also replace all the plug wires and the coil wire. With age these can have small perforations in them you can't see but will trap and hold moistuer and cause the problem you have. Lynn Pulled the rotor and cap and checked them and no green gunk, did not think there would be as I replaced them with delco replacements not too long back. Rotor tip was barely dirty though, just enough to hit it with a wire brush a few times and it was like new. I did put a little dialectric on the contacts. Wires were all changed less than 20,000 miles ago, they look fine. Let me know how you fair out William, that test should point to the culprit if it's ignition, which by the sounds of it I believe it is, sounds like a split coil without even looking at it... Sprayed water on the coil with it running and it never missed a lick. Kinda stumped unless the rotor was just dirty enough and got moisture trapped inside the cap and kept it from getting good contact. Quote Link to comment Share on other sites More sharing options...
redkneck Posted July 23, 2012 Report Share Posted July 23, 2012 Know what you mean bud. My 2000 4x4 needs some work too, but it's going to just keep getting repaired for the foreseeable future. Quote Link to comment Share on other sites More sharing options...
MUDRUNNER Posted July 23, 2012 Report Share Posted July 23, 2012 Hmmm. So the fuel pump does not whine when it does this? I did have a buddy that had a Chevy truck with the 4.3, and his fuel pump would occasionally not work. I'm wondering if that could be your problem. Quote Link to comment Share on other sites More sharing options...
Shaun_300 Posted July 23, 2012 Report Share Posted July 23, 2012 Fuel pump whine can be a sign of failure in the near future but I've heard some loud pumps that just whine and there's nothing wrong with them, I think William put a new pump in this truck a couple years ago. May have got some moisture in the cap, that's my best guess. Quote Link to comment Share on other sites More sharing options...
wtnhunt Posted July 23, 2012 Author Report Share Posted July 23, 2012 Dunno why, but the pump on this truck has whined the same since day one that I have owned the truck, I bought it used so don't know if it did it when it was brand new. Changed the fuel filter earlier this year. Changed fuel pumps on my 92 Z71, it never whined but went out with no warning. Quote Link to comment Share on other sites More sharing options...
LETMGROW Posted July 25, 2012 Report Share Posted July 25, 2012 '97-'98 chev. or GMC PU if it ain't whining it ain't working. Doesn't seem to matter what brand you buy, it's normal. Lynn Quote Link to comment Share on other sites More sharing options...
MUDRUNNER Posted July 25, 2012 Report Share Posted July 25, 2012 '97-'98 chev. or GMC PU if it ain't whining it ain't working. Doesn't seem to matter what brand you buy, it's normal. Lynn LOL no doubt. Them year GM trucks are all noisy. That is what I was trying to get at unless I misunderstood Williams post. If the whining stops when it acts up maybe the fuel pump is the cause. Quote Link to comment Share on other sites More sharing options...
wtnhunt Posted July 25, 2012 Author Report Share Posted July 25, 2012 Thanks for the replies. If or when it does it again, I will pull the cap regardless of what else I got going on and see if there is any moisture inside it. Only take a few minutes and that is the only way I am ever gonna be able to rule that out or in as the problem. Biggest downside is that this is the vehicle Christina is driving and I hate the idea of her breaking down somewhere between here and the school. LOL no doubt. Them year GM trucks are all noisy. That is what I was trying to get at unless I misunderstood Williams post. If the whining stops when it acts up maybe the fuel pump is the cause. When I have had the problem the whine only stopped after the pump delievered enough fuel for it to cut off, seemed about what I am used to. Quote Link to comment Share on other sites More sharing options...
LETMGROW Posted July 26, 2012 Report Share Posted July 26, 2012 (edited) You might try this. You said the cap and rotor weren't all that old. How old? Most replacement parts are warrantied for 1 year. If less than 1 year I'd talk to the store and explain your situation. I would hope they could do a warranty claim and replace your parts with new replacements. That is their call as you can't prove yet they are in fact defective. It might be worth the effort. If they replace them at least you will know you have or have not cured the problem. The only other thing that comes to mind that hasn't been mentioned is the crankshaft positioning sensor behind the harmonic balancer. It could have a hairline crack letting moisture enter. Usually though this condition will trip the malfunction indicator light on. If the light is on or has been on recently it might pay to have the codes retrieved to help in diagnosis. I know you previously said the light wasn't on. If it fails to start again check the tach. Does it read or move during cranking? Pull a plug wire, slide the boot back and hold the wire close to the head or block. Have a helper crank the engine. Do you see a spark jump between the plug connector and the block? If you have a spark your problem isn't secondary ignition. If you don't see a spark pull the coil wire out of the cap and test it the same way. Got a spark now? If so the cap or rotor is at fault. If not you could have a bad coil or ign. module. Some parts stores can test these off the vehicle. This could save you buying a lot of parts you don't really need. Most if not all stores won't accept returns on electrical parts. ( For good reason ) It is up to the repairman to diagnose problems, not trial and error. My shop is connected to the largest parts store in the area. You wouldn't believe the condition of some parts folks try to return because they didn't fix the problem they have. Hope this helps, Shaun, if I missed anything feel free to jump in here. Lynn Edited July 26, 2012 by LETMGROW Quote Link to comment Share on other sites More sharing options...
MUDRUNNER Posted July 26, 2012 Report Share Posted July 26, 2012 When I have had the problem the whine only stopped after the pump delievered enough fuel for it to cut off, seemed about what I am used to. Gotch ya. Probably not the problem then. Quote Link to comment Share on other sites More sharing options...
Shaun_300 Posted July 26, 2012 Report Share Posted July 26, 2012 Nope, good way to test it Lynn! This is why I love the new LS style engines like mine, 8 coils with a crank and cam sensor to tell them when to fire. Never seen an ignition problem on one yet. Quote Link to comment Share on other sites More sharing options...
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