Hey guys I’m new here but I have a problem I’m trying to figure out on my 1996 Chevy k1500 4wd automatic and 144k miles. I currently have a crank no start issue so here’s where I’m at. I purchased the truck not running, first thing I did was plug into the obd2 port, and I had no power up on my scanner. I replaced the fuse that powers it and now I can get my scanner to power up but it won’t read the ecm codes.
I have no spark and the fuel pump is not priming. So I started throwing obvious parts at it, such as cap and rotor, camshaft position sensor, ignition control module. I did have the ignition coil tested and it tested good.
So then I tested fuses to see if I was getting power to the important ones. Turns out ign-e, ecm-1 and eng-1 fuse were not getting power. I have no dash lights, after market radio turns on and goes into protect mode. So I looked up a schematic of all the wires hooked up to the ecm 1 fuse and started tracing, narrowed it down to a bad ignition switch or crank sensor.
I decided to check the crank sensor first first thing I noticed is that the 3 wire pigtail was covered in oil, and the base of the plug where the wires went in were totally exposed, so I unplugged it and pulled it up to the top to test it with a test lug by. I had power to one pin, but then I also tested my ecm 1 fuse again and I had power. (When I had the harness unplugged and pulled halfway to the top of the bay.)
Keep in mind I had not disconnected the bolt that holds the two ground wires to the block near the crank sensor (one ground wire is the battery ground, and the other ground wire goes into the same 4 or 5 wire harness as the crank sensor. So once I tested the fuse and got power again I thought oh it’s the Corroded pigtail connector on the crank sensor causing a short or something.
I ordered a new sensor and pigtail and it took about 2 days to get here, I put it in last night wired in the new pig tail and now I’m back to square one if not having power to the ign-e, ecm-1 and eng-1 fuse.
I’ve wiggled all the engine bay harness’s while test lighting and I haven’t even got a dim test light. It’s really confusing as to how I didn’t have power and then I did and now I don’t again. Any help or pointing me in a direction would be greatly appreciated thank you!!!
I can get my scanner to power up but it won’t read the ecm codes.
If the ECM doesn't have power, then nothing else will work. It won't start or do anything.
I have no spark and the fuel pump is not priming. So I started throwing obvious parts at it, such as cap and rotor, camshaft position sensor, ignition control module.
You won't get spark, and possibly not even pump pressure without a functioning ECM. You may have wasted money throwing all these other parts at it.
narrowed it down to a bad ignition switch or crank sensor.
Again, no ECM means no power to sensors.
I wouldn't be surprised if that ignition switch is causing most your problems.
You have to have Power on the Pink Wire(s) at the Ignition Switch connector in RUN or Start for fuses IGN E, ECM 1, and ENG 1 to have Power
If you don't and the 40 amp IGN A fuse is good then it's probably the switch
I’m getting power to everything I should be
That's great news.
my battery I think is just toast
Yeah, you want to proceed with a fully charged, healthy battery.
it seems like (eyeballing it) it has good pressure
don't eyeball. Measure.
one that keeps popping up is p1351 which I looked up and is a ignition control module
Codes never just translate into the name of a module. They tell you when very specific specific conditions have been encountered.
This code can be triggered when you have extended cranking, and can be set for a variety of reasons. I would ignore this code for now until you get the truck starting reliably.
is that hooked Into the fuel injector pulse some how?
Fuel injection timing and ignition timing are both controlled by the engine computer, but they are completely separate circuits. No, a bad ICM will not affect your fuel injectors.
These are the things that you need to focus on, that your truck won't work without :
1 - get yourself a fully charged battery that passes a load test . It's free at Autozone (and at some point you should get your alternator tested too)
2 - Measure the fuel pressure.
I’m suspecting maybe clogged fuel injectors,
I would say that's a strong likelihood. You bought a truck that didn't run. Who knows how long it has been sitting. (you can see now what a pain it can be to buy somebody else's problem).
The only sure way to find out would be to perform an injector flow test.
Ok thank you for the input joe ! Do you know if there is any way to maybe test the ignition switch, or is it possible for them to be intermittent? Explaining how I had power for a minute and then I didn’t?
yes it can definitely be intermittent. Try jiggling it around.
Do you have schematics for the ignition? they should tell you where you need to probe for power.
I don’t have any schematics but I’m sure I could find one, I’ve changed a lot of parts but never a ignition switch, so I’m not even sure how to test it?
I don't have a schematic either, so you might want to pick up a haynes manual, and a multimeter.
The key ignition is just a glorified light switch. There should power going into it at all times via a big fat red wire which is fused at your main underhood panel with a jumbo fuse. When you turn the key, it should switch power to the run circuit (1st position) and start circuit (2nd position. probably a yellow wire). It's these circuits that energize all the various fuses and the main computer.
Use the multimeter in voltage mode with the black negative lead on ground (any bare body metal) and the red positive on the circuit you are measuring. It's a 12V system. That's the basics.
Ok so I changed the ignition switch cuz it tested bad, and I’m getting power to everything I should be, just not getting any spark. And my battery I think is just toast it’s deader than a door knob, it’s cranking really slow even with a Jump I’m wondering if a slow crank can cause no spark.
Ok so I was able to get the battery enough juice to crank my truck, and I’m getting spark now thankfully! From what I can tell the fuel pump is new and fuel filter. I poked the shredder calve on top of the manifold to see if I have fuel going through the rails and I do, it seems like (eyeballing it) it has good pressure. But it’s still not starting, I’m suspecting maybe clogged fuel injectors, because when I sprayed starting fluid it definitely started up for a minute and than back fired through the throttle body with a massive blue ish flame. Any ideas from here?
I’m also able to finally read the obd 2 port and after clearing all codes the one that keeps popping up is p1351 which I looked up and is a ignition control module, is that hooked Into the fuel injector pulse some how? If it’s bad it won’t be letting the injectors pulse?
Got it! I’m going to go rent a fuel pressure tester and see what kind of pressure I’m getting tomorrow morning as well as getting my battery tested I’ll tune back in with some results tomorrow! 😁
Ok so I did a pressure test at the fuel rail shrader valve before the injectors, and I’m reading above 60 psi almost 70 while cranking. It bleeds off with key off but it bleeds very very slow and stops around 58 psi what should I check next?
It's time to grab a test light and check for Power on the Pink wires (with key ON) and the Ground pulse on the Control wires (while cranking the engine) on the fuel injector harness. You can probably backpin the wiring connectors
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Ok so I’m response to checking injector pulse I just got done checking them and I am getting injector pulse so that leads me to believe it’s the spider injectors themselves, explaining why when it sits over night they drip fuel into the engine and causes it to try and start up upon crank. Fuel pressure is good I’m getting power to everything no it’s just dependent on the injectors.
leads me to believe it’s the spider injectors themselves,
yeah if you have a 4.3L engine, those spider injectors were failure prone. GM produced an upgraded part.
Alright guys so just a little update on the pickup, I replaced the injectors thinking that would solve the problem literally all my testing checks out, injector pulse fuel pressure, spark air. When spraying ether it sounds like it wants to start up a little better than before. But it just won’t start up and stay running. Any ideas at this point? A friend of mine suspects I could be building good “pressure” in the fuel lines but not good “fuel pressure” he thinks it’s clogged lines filter or fuel pump. A new sound has arose after replacing the injectors when ever I turn the key to prime the pump I’m hearing a weird creaking noise coming from the fuel lines and almost like a gurgling sound going into the injectors! Running low on faith I’m going to get this thing running.
You have a good battery
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You have spark (hopefully you tested with an HEI spark tester)
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You have good fuel pressure
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You have Power going to the Pink wires at the fuel injector harness connector
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You have Ground Pulse to the control wires at the fuel injector harness connector
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It should start, right?
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But you say it doesn't even fire up when you spray starting fluid into the intake
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It should
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Could this be an ignition timing issue? You said you replaced the rotor and cap. When you did that did you grab the rotor and make sure you couldn't spin it back and forth? It's not supposed to move. If it does then the drive gear on the bottom of the distributor is worn down and that's going to throw off the spark timing and also the camshaft position sensor (it's in the distributor)
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Also, you said the truck didn't run when you bought it. So after you check the rotor for movement consider that maybe someone else was working on it so check the ignition timing
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With cylinder #1 at Top Dead Center on the compression stroke the rotor should point to the number stamped on the distributor housing
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If you have a 6 cylinder you'll see a 6. If you have an 8 cylinder you'll see an 8
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If all that checks OK then consider other stuff that could prevent it from starting. Poor compression (do a compression test). Stuck open EGR Valve (test the EGR valve). Stuck open PCV Valve (check it). Maybe even rig up a smoke tester (youtube paint can smoke tester) and check for a massive vacuum leak.
not to mention wires need to be plugged into the right place.
https://www.youtube.com/watch?v=Pw_gwEDvaLs
Ok jack! I will look into it, I did try to wiggle the rotar back and forth when I was working the cap and rotar and I did not feel any play, I did also change the cam shaft sensor. I’m kind of wondering if maybe it’s still a fuel related issue, ever since I put the new injectors in it I can tell it has an easier time trying to start up. But with that has come a terribly loud creaking noise coming from the pump and the lines when I first turn the key. So I’m wondering if maybe it’s just got really old fuel in the tank who knows how long it sat before the guy sold it to me? I am going to double check my gear on my distributor isn’t bad tomorrow night, and I will post another update, and if my engine is in time the rotar should be pointing to the #8 on my distributor, when it’s at tdc? Is that another way to do it with out a timing light? Thank you for the continued help and support I’ll come back with updates tomorrow!!!
And I guess I should add when I tried to move the roter under the cap it did move a little about a half inch in either direction with no resistance and then it stopped hard. So I guess I should ask if that’s normal and want to make sure that’s not the kind of movement your referring too!
Hey guys, just figured I would give a little update. I did a little bit of inspecting at the fuel pump and whoever put the fuel pump in before me, put the gasket on the wrong side, on the lock ring side lol. That being said with no gasket and a hole being cut in the bed from the previous owner, I suspected the water got into my tank and diluted the gas. I pulled all the old gas out and took it down to the shop to have the fuel tested, and just as I had suspected water was in the tank, filled it back up with new gas and she runs good! Now I have a new problem where coolant is leaking between my motor and transmission. Hoping it’s nothing more than a cracked freeze plug. Thank you for all the help you guys , this is my solution as promised lol