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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Tjerica1201 on January 16, 2015, 01:01:38 pm
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Lookin for the diagnosis guys!! My diagnosis knowledge is pretty primitive, my abilities are not. Are there any guys out there are a little more intelligent on the matter.
Here's what it's doin. Turns over strong, I can see fuel sprayin out the injectors, I've grounded the #1 plug and it's hitting when I crank, I've shined a timing light on it and it's spot on.
I rebuilt the injectors and tbi a couple years ago. Newer plugs, wires, cap, rotor.
I know my way around a multimeter but have no idea what use it on to see what's goin on.
Thanks
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Could be a vaccum leak? Just a thought.
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Your diagnosis steps so far eliminate most every normal failure I can think of for an engine that was running previously. Was this running previously with no issues, and then wouldn't start, or is this a recent rebuild of some kind?
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It ran perfect prior to parking. I built it 5 yrs or so back. It's a 383.
As I went out today to work on it, it now will not roll over. It acts like it wants too but won't. Acts like its a really low battery. I hook jumpers to it and am getting 13 volts to it, same thing. Ideas? I have replaced the starter wire and am getting zero ohms on the negative.
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Ok, It's cranking now but the original problem persists. It's back firing thru the tbi with a misting gieser of fuel. Help!
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Sounds like timing to me. If the dizzy is 180 deg. out, it will do that very thing. Out of curiosity, how do you know it's timed if it won't run?
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Its been sitting 5 years and with the old fuel still in it.
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Good point. If that is several year old gas your injectors are spraying, it could be more water than anything else. Is this old gas?
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It's not been sitting for 5 years. Motor was rebuilt 5 yrs ago. I drive it all the time. It sat for a month when these problems started. Water in the gas is a distinct possibility. I will drain and refuel and see if that works.
As far as knowing the timing is correct, I'm putting the timing light on it while im cranking it. Is this not a correct method of checking it for the current situation? At #1 TDC, rotor points forwardish. Leans a little tward drivers side, so #1 plug. So 180 out isn't not the culprit, right?
Thanks for the help guys, keep the advice coming.
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If the rotor points toward the#1 plug connection on the cap while #1 is at tdc on the compression stroke then you're not 180 out. "On the compression stroke" is the key. If you haven't verified that, you can have an assistant crank the motor while you hold your thumb over the #1 spark plug hole (plug removed). Once you feel it blow your thumb away you can double check that the rotor is where it should be.
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It's not been sitting for 5 years. Motor was rebuilt 5 yrs ago. I drive it all the time. It sat for a month when these problems started. Water in the gas is a distinct possibility. I will drain and refuel and see if that works.
As far as knowing the timing is correct, I'm putting the timing light on it while im cranking it. Is this not a correct method of checking it for the current situation? At #1 TDC, rotor points forwardish. Leans a little tward drivers side, so #1 plug. So 180 out isn't not the culprit, right?
Thanks for the help guys, keep the advice coming.
It's not the way to set timing. You have to set it when the engine is warm and running. Until then, you want the rotor pointing at the #1 spark plug when the crank and camshaft are at TDC. From what you describe, being 180 deg. out is a definite possibility.
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If the engine ran a month ago and all off sudden timing jumped,180 degrees exactly would be extremely unusual.Pull the filter and check for water,then if you find it there go to the tank.Lots of other stuff to check like rotor burn through or tracking\moisture in the cap
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Jared, your method for determining TDC is the same one I used.
Dr_Snooze, I realize that that is not how to set the timing. That is just a method I used to determine that I didn't jump a tooth on the timing. Not that I am entirely sure how far off the tdc mark on the HB would be if it DID jump a tooth. Any idea?
Big ten, let me know if I follow your line of thinking. Since it isn't starting but the injectors are flowing, the motor is flooding itself with water/fuel. Water/fuel is sitting on top of the cylinders, eventually draining past the rings and into the pan. Water being heaver that oil will collect in the bottom of the pan or in the filter. So if that is the case, then wouldn't my oil level rise and show as over serviced on the dip stick? And what is rotor burn through? and Tracking/moisture?
Isopropyl alcohol, I am told, will cause the water to become able to burn (in some magical physics based way). Is this something any of you guys are familiar with?
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how was it running when you parked it?
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It was running perfectly last time I parked it.
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so that would eliminate timing. i would unplug the injectors and see if you can run it briefly of starting fluid.
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I have tried that as well. cranking occasionally stalls when I do that.
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does it keep running as long as you keep spraying the starting fluid?
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As far as water in the fuel I was speaking of fuel filter.If water is there then go to the tank.Cheap ignition rotors would burn through the center and spark would go to distributor shaft,least path of resistance.Tracking in the cap is possible,look for small squiggly black lines from the wire posts.Also any moisture in there will \can cause a no start with occasional backfire either through exhaust or intake.All basic stuff to check before you get to deep in it.always check the basics first,can save a lot of time
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It doesn't start on the starting fluid. The starting fluid causes the cranking to "choke" and stall the cranking.
As far as water in the fuel, I still havnt ruled that out. That's pretty much the only thing simple thing left. One of my fuel pumps is bad so I've got another coming from summit and will put that in and a fuel filter. Will completely drain the tank at the same time. If that fixes the issue, I'll drain the good pump tank as well.
I do not recal seeing any black wiggle lines, but I've replaced the cap and rotor so the old ones are easy access. I'll take a closer look at them when I get home.
Any other things I can check while I'm waiting on this pump to come in?
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You mean when you use the fluid the engine stops turning or tries to kick back?
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Pour some gas "SAFELY" down the intake move the the source well away and try to crank it. Sounds like bad gas...
You can pull a hose off the back of the throttle body and turn the power on/off a number of times and fill a jar and let it settle overnight then check the separation,
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Yes big ten, that's exactly what's it's doing. I guess that when referring to engines choke is the wrong word for this situation. Kick back is a much better description.
I am currently swapping the pump. Prior to dropping the tank, I have siphoned the gas into a clear jar and it doesn't show any water.
I have tried dropping good gas down the tbi. Nothing changes.
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Starting problem probably coming from being out of time or moisture inside distributor cap or possibly crossed plug wires.Pull cap and look for small beads of moisture,if there spray it out with wd40,reinstall and try to start
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Ok I will give that a go tomorrow after I finish with the pump
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Someone has to help me understand how bad gas would cause backfiring out the intake. As far as I know, that's a timing problem but maybe there's something I don't understand.
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i dont understand how when he parked it years ago it ran fine .and somehow the timing gets screwed up with no one messing with it. the weights could get siezed but that wouldnt cause it to not start. but maybe it has spark just a weak spark
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I'm still leaning on condensation in the cap.Only takes 5 minutes to check,what 2 screws and your there
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Again, the truck hasn't been sitting for years. I don't know why this keeps coming up. I never at any point said that it did.
As far as moisture in the cap, I've already replaced it with a new one and rotor as well.
I've now replaced the pump and drained the fuel and put fresh gas it. No change.
I've tested the ohms of a few of the plug wires. I'm getting 6-8 kilohms. I've testd a couple msd wires off my suburban and they read 0. The wires on the truck are nothing special. you think that could be the problem?
I'm gunna drop the dizzy out of my 88 k5 in it next weekend and see if that does te trick. Unless someone here can walk me through troubleshooting it befor I pull it out.
Any other ideas befor I dive into that headache??
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Its been sitting 5 years and with the old fuel still in it.
but then you said
It's not been sitting for 5 years. Motor was rebuilt 5 yrs ago. I drive it all the time. It sat for a month when these problems started. Water in the gas is a distinct possibility. I will drain and refuel and see if that works.
As far as knowing the timing is correct, I'm putting the timing light on it while im cranking it. Is this not a correct method of checking it for the current situation? At #1 TDC, rotor points forwardish. Leans a little tward drivers side, so #1 plug. So 180 out isn't not the culprit, right?
Thanks for the help guys, keep the advice coming.
but to clear things up you said it sat for a month since the problems started. are you saying, last month it wouldnt start and now its been a month or ar you saying it started screwing up for a month and its been sitting since?
when the problems started did it just stop running or did it act up to bad to drive and now it wont start?
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This problem sounds more like a bad ignition module to me. The module can be removed and taken to AutoZone for a test. Also- Do you know how to check for fault codes to see what codes the ecm is throwing?
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It was sitting for a month before I went out to start it and found that it wouldn't start. I've been trying to fix it for an additional month. So grand total, it has been sitting for 2 months. When I parked it, it was running perfect. I didn't park it intending to leave it sit for a month or anything. It just so happened through day to day life that I had no need to drive it. With high gas prices and such, I would always run all my errands in the car leaving the truck to sit. One day I needed a Christmas tree and had no choice to drive it and went out to start it and it would just crank and crank but no fire. This is the same thing my Dad's 93 did. A new dizzy fixed his issue.
The ignition module is in the distributer isn't it? Yes, I've jumped the A/B wires and its throwing 12. That is an "everything's good" code isn't it?
Is there any way for ME to test the ignition module? I'm somewhat versed on the use of a multimeter.
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the icm can be tested at a parts store. sometimes they have to test them multiple times to heat them up
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Generally speaking the icm either work or they don't,have you checked for spark at the plugs,and is it continuous while cranking,and yes code 12 is normal
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Ok I will pull mine out and get it tested. I did not check each plug, just #1 and yes it is continuous through cranking.
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So you have spark at the plugs and the injectors are pulsing,that tells me module is probably ok.Are you sure the cap is clean and the rotor is indexed and pushed down all the way
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Yes the cap is clean and the rotor is seated. I've even pulled all plugs to make sure they weren't all fouled up and they all looked almost brand new (they have like 20k miles on them). I don't know what else to check, that's the only reason I'm leaning toward the dizzy. its worth at least checking.
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Checking the module with an ohm meter will give weird readings . It can be checked in the truck (The location of the ignition module is on the distributor plate beneath the cap and rotor.)
http://www.ehow.com/how_8000853_test-ignition-control-module.html
Did you check your fuses?- particularly the ecm2 fuse? Also, when the injectors are spraying, are they ticking as well? That ticking is the ecm opening the injectors, or better said- it's providing a ground for the injectors to pulse..
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On Saturday I swapped dizzy out of my blazer and it started right up. I guess it was the module after all. Now I am having fuel delivery issues. After I got it started with the "new" dizzy, I shut it off and went in for the night. Sunday morning I went out and tied up all the loose ends and went to start it and drive it, and it wouldn't start. No fuel is coming out of the injectors. I can dump a little fuel down the throttle body and it will fire just fine. Should I hear the fuel pump kick on every time I turn the key to run? or is there a pressure switch that kicks the pump on only when its low on pressure?
I went out this morning (Monday) to start it and it fired right up. When I switch tanks to the new pump, it dies. I switch it back to the first tank it starts up. When its on the original pump and running, fuel is pouring out the fuel fill port. a lot of fuel. I don't know if the two issues are tied together or not. As for the truck dying when I switch tanks, I would automatically lean toward the switch that is mounted to the frame under the passenger seat but I changed that out a year ago when I was having other issues (that didn't fix the problem then so I still have the original that should still be good).
Any ideas?
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http://forum.73-87chevytrucks.com/smforum/index.php?topic=29825.msg249543#msg249543
read this it may help you out. i think my problem was the tank switch having bad connections
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Don't have a lot of time to look through it in depth right now, I just skimmed it but it looks like it that's gunna help. It ended up being the switch in the end?
I will give it a good read through this evening. Thanks.
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cant say for sure but i know the 1st one broke apart in my hands as soon as i unplugged the wires. the second used one was all gunked up with dirt and grime brake cleaner helped but it still screwed up from time to time even just dies going down the road. got a brand new one, had the truck running and unplugged it and the truck died like it had been put the new one in and never had the problem again.
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Final Update. I swapped out the tank selector valve and all the problems went away. So I am now getting accurate readings out of both tanks (gauge needle was pegged out past full) fuel is no longer dumping out of the drivers tank fill port when that tank was selected, and the switch actually switches between the tanks.
Only issue I have now is that I think that the drivers tank pump is weak. When I select that tank, it slowly starts to spit and sputter and eventually dies. When I select back to the passenger tank before it dies, it picks back up and runs normal. I'm going to make sure I'm getting the correct voltage at the plug going into the valve and if its good I guess its a bad pump, unless you guys have another idea. That pump is less than a year old.
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Do a fuel pressure test at the output from the drivers side tank, if it's below spec then your probably right about the pump being weak.
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could also be the rubber line that connects the fuel pump to the assembly
(http://contentinfo.autozone.com/znetcs/product-info/en/US/dlp/CFE0115/image/4/)
it comes with a new pump anyway but it can rot and crack and cause loss of pressure.
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Makes sense. A pressure test that LTZ will eliminate that as an issue i the test shows normal. I'll try that this weekend. Gotta figure out which hose goes to that tank. I could always unplug one and click the key on and if I get soaked, I got it right. Haha
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Usually it's the the biggest hose from the pump going to the switching valve.
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theres a difference in flow vs pressure. if the hose is cracked you might have the flow but not the pressure cause the hose wont split till it builds up pressure
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I just wanted to throw this out there. I wouldn't use the provided hose with the pump. If you are where E85 is used it will eat it up. I would buy some submersible E85 safe hose.