Perhaps unrelated but after replacing my crankshaft position sensor on my green 8.1 truck it did the same thing.
The actual mounting hole in the sensor is about 10mm and the bolt was about 8mm and I did not have the sensor seated down all the way.
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.
L18 8.1L swap resource thread
- Thread starter Larry
- Start date
The actual mounting hole in the sensor is about 10mm and the bolt was about 8mm and I did not have the sensor seated down all the way.
I read about many horror stories similar to that.
Several have said that a bad crank sensor will set off the cam sensor.
Not sure I believe that. My ECM has been programmed to my engine. No drive by wire throttle. Manual throttle, with IAT, TPS, MAF. Plus got rid of 4 of the 6, O2 sensors.
It’s just weird to have a new cam sensor, right out of the box, sat for 2 years, then have it be bad.
I was super diligent about wiring my wiring harness. I spent a few weeks doing it, exactly the way the diagrams showed.
Time to go out and disturb the peace…
Several have said that a bad crank sensor will set off the cam sensor.
Not sure I believe that. My ECM has been programmed to my engine. No drive by wire throttle. Manual throttle, with IAT, TPS, MAF. Plus got rid of 4 of the 6, O2 sensors.
It’s just weird to have a new cam sensor, right out of the box, sat for 2 years, then have it be bad.
I was super diligent about wiring my wiring harness. I spent a few weeks doing it, exactly the way the diagrams showed.
Time to go out and disturb the peace…
My MSD distributor new in box for three years died while trying to crank my motor for the first time. Stuff just ain’t built right anymore.
Yeap easest test would trying a new sensor. Autozone will take it back if it results are same.
That was it!
Cam sensor, bad, right out of the box!
Cam sensor, bad, right out of the box!
hearing a lot about cam sensors and try your best to stick to ac delco or gm original .
hard for us 01-02-03 guys tho .
hard for us 01-02-03 guys tho .
I have a standard in mine, still have the old one, probably why no troubles with the standard
Keep this in mind, the 8.1 used three different cam sensors over the production run that match up to changes with the timing cover. They did change the pin out in the harness too. I have think back but I think we had to swap pins to make mine work.
I had to file off the alignment tooth from inside the sensor where the pins are located. The harness plug’s alignment slot for the tooth was on the opposite side than the sensor.
Exacto-knife and needle file got it handled. So, no, it was not “correct”, but, it allowed the plug to fit, which got it fired up.
Exacto-knife and needle file got it handled. So, no, it was not “correct”, but, it allowed the plug to fit, which got it fired up.
And timing gear on cam .
It's the same at the ECM because it's the same ECM, but at the sensor A and C are swapped.
I believe this is one of the heavy duty truck versions. Crank pulley is way longer than my original, plus it has a 13 quart oil pan.
Parts coming off in the morning…
Parts coming off in the morning…
Yes c4500-up size truck .
My water cross over doesn't have and studs on it, must be HD belt system.
I read the other day when I was ordering my Silverado oil pan to replace the 13 quart big truck oil pan I have, that I needed an oil pick up tube to match the new oil pan.
And, that pickup tube lengths came in 8”, 9” and 10” versions.
Then on further reading discovered that all were superseded down to an 8” version.
Any of you guys know anything about the actual truth of the matter? I have ordered an 8” pickup tube, not knowing what I had already bolted to the oil pump in the 13 quart, big truck pan currently under residing on my engine. Upon taking the 13 quart pan off, I discovered an 8 inch pick up tube in the 13 quart pan. Now I’m really confused.
And, that pickup tube lengths came in 8”, 9” and 10” versions.
Then on further reading discovered that all were superseded down to an 8” version.
Any of you guys know anything about the actual truth of the matter? I have ordered an 8” pickup tube, not knowing what I had already bolted to the oil pump in the 13 quart, big truck pan currently under residing on my engine. Upon taking the 13 quart pan off, I discovered an 8 inch pick up tube in the 13 quart pan. Now I’m really confused.
Yeah you got me dude!
Big truck pans and power plant pans just get longer a lot of the time not deeper .
Fueling issue:
When starting, my 8.1 cranks and cranks and cranks, then backfires once or twice, then fires up and runs, fine.
I have not measured the fuel pressure, yet, but, I’m using a brand new AC DELCO pump.
I was thinking of adding a physical switch on the dash, to turn on the pump, by activating the Fuel pump relay. That way I can power up the pump prior to the ECM doing it while cranking.
My question is, will this harm the ECM by supplying power to the ECM side of the relay? It shouldn’t, because it’s all the same 12 volts. But,…
When starting, my 8.1 cranks and cranks and cranks, then backfires once or twice, then fires up and runs, fine.
I have not measured the fuel pressure, yet, but, I’m using a brand new AC DELCO pump.
I was thinking of adding a physical switch on the dash, to turn on the pump, by activating the Fuel pump relay. That way I can power up the pump prior to the ECM doing it while cranking.
My question is, will this harm the ECM by supplying power to the ECM side of the relay? It shouldn’t, because it’s all the same 12 volts. But,…
My pump turns on with ignition on until it builds pressure. Then I start. I think the priming is/should be a stock setting, correct...?
The stock ecm should be turning on the fuel pump relay for three seconds to prime the system. It typically won’t run the pump while cranking since it has already technically primed the system. Once the ecm sees the engine running it will energize the relay.
So before you put a switch inline, put your finger on the relay why someone turns the key to the run position. You should feel it click on then off. If it’s not doing that you need to sort out why.
If it is cycling and it still having a long crank or multiple cranks before starting I’d say you have a leak letting pressure bleed off. Could be a leaky injector(s) or the check valve in the pump isn’t holding.
Put a fuel pressure gauge on it and cycle the key two to three times to build pressure. It should hold steady for a few minutes and will start loosing pressure over time. Slow and gradual is pretty normal. If it’s dropping completely in 10-15 minutes there’s a leak.
The problem you have is if it’s priming for three seconds it’s working under the premise that there is fuel already in the line and that three seconds puts it under pressure. If the line has drained back to the tank or dribbled out of an injector or two now you have to refill the fuel line with fuel AND pressurize it. 3 seconds won’t do it.
Easiest test is to pinch off the return line somewhere under the truck and cycle the key to get pressure back up and watch it again. If it still goes down, you got an injector leak. If it stays steady it’s the check valve in the pump.
I know the pump is GM and new, but that’s the roll of the dice anymore. Some work, some don’t.
So before you put a switch inline, put your finger on the relay why someone turns the key to the run position. You should feel it click on then off. If it’s not doing that you need to sort out why.
If it is cycling and it still having a long crank or multiple cranks before starting I’d say you have a leak letting pressure bleed off. Could be a leaky injector(s) or the check valve in the pump isn’t holding.
Put a fuel pressure gauge on it and cycle the key two to three times to build pressure. It should hold steady for a few minutes and will start loosing pressure over time. Slow and gradual is pretty normal. If it’s dropping completely in 10-15 minutes there’s a leak.
The problem you have is if it’s priming for three seconds it’s working under the premise that there is fuel already in the line and that three seconds puts it under pressure. If the line has drained back to the tank or dribbled out of an injector or two now you have to refill the fuel line with fuel AND pressurize it. 3 seconds won’t do it.
Easiest test is to pinch off the return line somewhere under the truck and cycle the key to get pressure back up and watch it again. If it still goes down, you got an injector leak. If it stays steady it’s the check valve in the pump.
I know the pump is GM and new, but that’s the roll of the dice anymore. Some work, some don’t.
