beags86
Eastbound and Down
Where is this starter from? Junkyard or ??
You probably should just have nice new shiney unit on there anyway.
You probably should just have nice new shiney unit on there anyway.
CK5
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'86 Jimmy 4in Lift, 40’s, tons, 8.1 Swap- 700r4 said PNNNNN
- Thread starter GWeakland620
- Start date
This is not a dedicated trail rig, but does trailer to the destination usually. I am currently in the planning phase of doing a 52/56" spring swap, and getting back to being more road worthy.
It was the starter that came with my engine accessories. I just picked up a new unit. Headed back home.
Ok, on to the next issue. No spark now.
Bad ground.
I checked. All grounds are good.
beags86
Eastbound and Down
Check your coils?
But it's spinning over fast now, which is nice..
Sorry, just trying to get a chuckle from you. I know you could be tearing your hair out being this close.
So go back to your fuse panel. Stock gm wiring would have a fuse marked "INJ 1" and "INJ 2". While providing power for each bank of injectors, they power the coils too. Check to make sure both fuses are ok. While there make sure the pcm fuse is good and has power with the key on.
If all three of those fuses are good and have power key on it's time to look at a couple other items. Check for a crank sensor signal. If you got a tach or access to some kind of scan tool you should see Rpm when cranking. No rpm signal = no spark or injector pulse. I'm hoping you put a new crank sensor in prior to install because it's impossible to change in the truck. I can't remember if you did or not. If anything check the connection at the sensor. Make sure it's not loose or fell off. You might have a circuit issue at the sensor. If the connection is good, let me know and I can shoot you the diagnostic charts for the crank circuit.
Sorry, just trying to get a chuckle from you. I know you could be tearing your hair out being this close.
So go back to your fuse panel. Stock gm wiring would have a fuse marked "INJ 1" and "INJ 2". While providing power for each bank of injectors, they power the coils too. Check to make sure both fuses are ok. While there make sure the pcm fuse is good and has power with the key on.
If all three of those fuses are good and have power key on it's time to look at a couple other items. Check for a crank sensor signal. If you got a tach or access to some kind of scan tool you should see Rpm when cranking. No rpm signal = no spark or injector pulse. I'm hoping you put a new crank sensor in prior to install because it's impossible to change in the truck. I can't remember if you did or not. If anything check the connection at the sensor. Make sure it's not loose or fell off. You might have a circuit issue at the sensor. If the connection is good, let me know and I can shoot you the diagnostic charts for the crank circuit.
Here’s my sensor. Looks fine to me.
How did you determine that you have a spark issue?
I recall this truck fired off a few days ago. So if it's a spark issue, something has changed since then. But you didn't post anything about whether the newly fixed fuel pump has been suitably tested.
Looks good to me too, but that ain't telling us if it's generating a signal for the ECM. So we are back to trying to see if we have a signal. We could loose the cam sensor signal off the front of the engine and it will still run. It takes a few more revolutions to go around for the ECM to reference where #1 is off of the crank signal alone, but it will still start. But since it's not starting or popping at all it's not got any spark. If you don't have any type of scan tool to plug in and get a reading on the crank signal take a tach and hook it up. Your harness should have a circuit marked for the tach signal coming off of the ECM that you haven't hooked up yet. You typically need to switch the tach to 4cyl mode to be accurate, but in this case it don't matter. You just want to see the tach needle move while cranking. IF it does we can rule out the crank sensor and or wiring to the crank sensor. If the tach don't move then we have a few checks to make on the circuit itself which aren't too hard other than accessing the plug at the crank sensor.
Campy's got a point that it started the other night but you shut it down right away to keep from waking the kiddos. Other than the starter issue could anything else had been touched or changed on purpose/accidental when you shut it off? Go over the connectors on the engine. The coil harness on each side to the main engine harness would be one place to focus on. Work backwards from when you shut it off to retrace your steps.
Checked spark with a test light. No go.
Fuel pressure steady at 60psi.
Currently wiring in the OBD2 port for diagnostic work tomorrow.
Fuel pressure steady at 60psi.
Currently wiring in the OBD2 port for diagnostic work tomorrow.
Sorry, I have to point out that this is false. Cause when I was having issues with my first 8.1 when I was doing my swap, I was able to change the crank sensor while the motor was in the truck. Only part that was a little hard was getting the little bolt that holds the sensor in place loose/tight, other than that, not that big of deal to replace the sensor.
Just thought this was worth pointing out
Thanks for the correction. I'm used to the gmt800 fun of removal.
Mine looks easily accessible from under the truck as you can see in that picture. But I’ll know more today when my buddy gets here with his laptop.
I had to do it while laying on top of the motor, because I don't know if you've seen the sensor while it's out, but it's about as long as a ruler. So you have to pull it out from the top and as you're sliding it out, it barely clears the firewall all the way up and out.
And as @ZooMad75 was saying, 9 times out of 10 when you have fuel pressure, but no spark on these, it's crank sensor. Double check that you didn't have a fuse blow that ZooMad already mentioned (which can happen when you doing all these cranks, and who knows if you accidentally surged something while doing all the other wiring, it can happen), but if you've ruled out that fuses are good, and you still have good fuel pressure, I'd put my money on crank sensor.
So this weekend didn’t go very well. Was never able to get the ecu to communicate with the laptop. Wired in the obd2 port, and the computer wouldn’t connect to it. We also started having issues with a 30amp fuse blowing. Any time we turned the key on, the fuse would get super hot then eventually blow. What’s weird is that started after the obd2 was wired in. Double, triple, and sextuple checked my wiring to make sure I didn’t wire something wrong. The only thing we are thinking is that the ecu maybe has a bad ground in it causing the issue.
I did however decide to order an new crank sensor just to have that on hand in case that ends up being an issue.
I did however decide to order an new crank sensor just to have that on hand in case that ends up being an issue.
I did find an old tach I had sitting around, so I’ll hook that up after I remove the obd port and see if I’m even getting tach signal.
FYI, make sure to set the switch on the back to 4 cylinder. Also, I used the same style tach, and I had to add a resister to the signal wire of the tach to a key’d 12v source to get it to work. Without the resister, the tach wouldn’t work. I’m thinking its because that older analog style tach needs a bit of a boost of signal to work with the electronic tach signal the ECM is putting out (who knows if thats true or not, but its the only thing that makes sense to me).
New computer doing the same thing. Blowing the fuse for the 12v constant as soon as the key is turned on.
12v Constant reads 12.5v with the key off. Once the key is cycled on, the 12v constant drops to 10.5v and never comes back up. Is that normal?
I keep thinking there is a ground issue, but 3 of us have checked and all grounds are good.
12v Constant reads 12.5v with the key off. Once the key is cycled on, the 12v constant drops to 10.5v and never comes back up. Is that normal?
I keep thinking there is a ground issue, but 3 of us have checked and all grounds are good.
I can’t say the 10.5v supply is an issue with a GM ECU but I know for a fact some other EFI’s will not send an ignition signal with voltage that low. I’d jumper it to the battery and see if it fires.
