Is your crank and cam sensor loosing signal at this time? Sounds possible it’s a short in the wire or as the relocktor wheel spins it doesn’t catch it.
CK5
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If it was loosing track of the reluctor, wouldn't it show a loss in the RPM?
Yes, what about the cam sensor?
I would think that would show up as a code and one of those is the rpm signal right? No issues with that from what I’ve seen. Secondly, I can make the engine bog and dip timing just about anywhere in the rpm range with throttle input.
and the only two codes this engine has provided are P0172 & P0175 for rich conditions bank one and two. Those were present coming off the trail when I found fouled plugs on bank 2.
There a hot rod shop in town you could talk to about this?
Does it seem like the cam signal is dropping out at all? I’m grasping at straws here. But since we are confirming stuff are you sure you got the cam sensor for the year of the engine? There are two different versions. And I could see if you had the wrong combo of sensor/timing cover/cam gear the relationship between the sensor and reluctor could be off where might not read correctly. Though I’d think it wouldn’t read at all.
Compare against this:
It will run with out the cam signal, but you’ll notice an extended crank as the engine has to spin over enough to reference off the crank sensor value to find #1.
To me I don’t think that’s it because I think you would have other issues if the cmp value was missing completely.
Compare against this:
Vortec 8100 8.1L Chevy GM Camshaft Position Sensor Guide - 496cid Cam Gear Sensors - Raylar Engineering
Find the right camshaft position sensor and cam gear for your Vortec 8100 8.1L 496cid.
www.raylarengineering.com
It will run with out the cam signal, but you’ll notice an extended crank as the engine has to spin over enough to reference off the crank sensor value to find #1.
To me I don’t think that’s it because I think you would have other issues if the cmp value was missing completely.
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So, Mark asked for a copy of my K10s tune, which I can get early next week sometime. Unfortunately, my buddy’s tuning laptop crashed during his last tuning session and the computer is in getting fixed.
I don’t really see having my tune changing your life at all. I’ve read through the last few pages and the biggest glaring issue that doesn’t look to have been resolved is the low fuel pressure. 51/52 is way too low. It really needs to be 60 psi minimum at idle then jump up anywhere 3 to 6 more psi when the throttle is snapped. I actually like to run my rigs a few psi on the high side as they respond very well to a little more pressure. That was an old trick one of our Field Service Engineers used to do to get a little more power out of early 8.1s with adjustable regulators. Turn the screw up a few more psi. Low fuel pressure/volume will cause vicious circle of tail chasing as the Lean Bank 1/Lean Bank 2 codes drop then the ECM starts tossing more fuel to compensate for the lack of fuel therefore you end up with an engine running pig rich….but yet, it all stems for lack of fuel.
It looks like you already replaced the fuel pump with no change so I’m thinking a couple things need to be checked. Make sure the fuel pump is well grounded and getting full system voltage. If there is a major voltage drop, it is not going to produce what it should but the most likely issue is with the fuel regulators themselves. They must not have enough adjustability to them to get up where you need to be.
Unfortunately, all the AC Delco/GM/ Standard Motor products, etc. fuel regulators are no longer adjustable (as you already found out) but I found some Chinesium fuel regulators on fleebay that are adjustable and very inexpensive. I bought a couple to have around. In fact, one of them is on Rob’s 8.1 right now and the other is in my Suburban.
Whatever you do, DO NOT BUY A Deatschwerks regulator. They are adjustable but there is something majorly wrong with their regulators where they instantly drop fuel pressure to 0 psi once the engine is turned off. It should not be that way, as that will cause a prolonged crank on the next key cycle, which my Suburban did after installing theirs regulator. They sent another and it did the same thing. I went round and round with them about this dropping fuel pressure and they said that it was normal. That’s absolutely not normal to dump fuel pressure instantly. Overnight, or over several hours, yes…but not instantly. That’s when I bought and installed the fleebay Huy Fong China’s Finest Counterfeit Auto Parts regulator and they work just as well as the original adjustable ones. They just probably won’t last as long so buy them in pairs
Some way, some how, your low fuel pressure needs to be addressed before you move on to chasing other dogs. Low fuel pressure will cause a pig rich running condition.
It falls flat on its face with throttle. The more load, the quicker it falls. Once the engine catches up with the throttle input I can blip the throttle like a normal proper running engine should react. Remember I’m running 5.13 gears so it gets around pretty good 1-55mph even with the old peanut port BBC w/FiTech.
It’s an 03 setup and I did the research on the raylar site and looked at what I had in the engine.
Here’s the part numbers for the timing set and sensor.
I'm interested to see some data on this, as at the base level you'd expect low pressure to be setting positive trims. In this case, the trims are +/- normal, except under certain operating conditions, where they are bat crazy.
How does it run with MAP unplugged? How does it run with MAF disabled?
The question is whether timing is killed by TPS, MAP, MAF or RPM.
Also, does Howell have any explanation for your torque being limited to 350?
The voltage and ground are good at the pump, I'm seeing 13.73v. I've tried three different FPR's without any luck. Can the stock FPR be gutted so I can run an aftermarket on the 6an return?
MAP unplugged, hard to start and still falls on it's face.
MAF unplugged it still falls on it's face and I saw knock retard for the first time.
MAP unplugged, hard to start and still falls on it's face.
MAF unplugged it still falls on it's face and I saw knock retard for the first time.
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Regarding the fuel pressure; when I remove the vacuum source the pressure increases to 60 therefore should I see an improvement if the fuel pressure was the issue?
yes
I tried and didn’t see a difference however I saw a small KR.
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I would say no, unplugging the vacuum source is not going to make an instant improvement with O2 readings or fuel trims as it takes a bit of run time for the fuel trims to adjust to changes unless you did a fuel trim reset at the same time. With the GM Tech II the fuel trim reset is a super easy one button poke to reset them then the engine will smoothen right out if everything is kosher. If not, it will go back to running less than sterling and fuel trims will go back wonky. I am not familiar with tuning software to know if you can easily do fuel trim resets or not.
I’ve seen it referenced a few times that you removed the vacuum hose to the regulator. There are only 2 tests in any GM strategy based diagnostics that require the vacuum source to the regulator to be removed. The first test is to see if fuel pours out of the vacuum port when the engine is running, which leads to a broken diaphragm in the regulator like Rob’s 8.1 did. The other is to add 12 inches of vacuum to the regulator to get the pressure to DROP 3 to 10 psi. All that test does is make sure the regulator is working with a specified amount of vacuum. Just snapping the throttle and watching the fuel pressure go UP is just as effective to make sure the regulator is working and get an idea of the fuel pump performance as well as validate the engine vacuum source is clean and free and not plugged with carbon.
As I said earlier, the fuel pressure situation needs to be addressed first. 51/52 PSI is not enough for an 8.1 to live happily ever after. I’m really surprised if Troy was given that fuel pressure reading that he would send another ECM until the fuel pressure was increased. In the end, you probably have more than one issue but low fuel pressure is definitely one of your issues that should be step 1.
Believe me, with FPR, you can try 10 and find one decent one especially if they are not adjustable. I have a whole box of old regulators here that none can be cranked above 60s. Rob has seen this collection of dud FPRs himself. Try one of those Chinesium adjustable regulators I linked earlier. So far, 2 out of 2 of those could be cranked up as high as I wanted them (~65 psi at idle/70 psi with throttle snap)
In the short term, until you get a good adjustable regulator, you can pinch a restriction into the return line somewhere convenient with a pair of vice grips to boost the fuel pressure up a few PSI then resume with testing. I suspect getting the pressure up then resetting the fuel trims will take care of a lot of the issues, if not all of the issues if I am understanding all of your issues correctly that were discussed in the past few pages.
Is that antiseize on the threads? If so, what did you use?
Also, misfire tables are under engine diag
If they've been set up like seen here - 32767 it basically nullifies them - my 98 LS is known for bad readings so someone along the line nullified them.
Looks like your FPR is the same as mine so you could put a plug in place of it to run one in the return. https://www.amazon.com/gp/aw/d/B084KN6CHH?psc=1&ref=ppx_pop_mob_b_asin_title
This is interesting because it's the only plot without retarded timing, yet you imply power didn't improve. A good portion of the STFT could be that it's fueling for -38F instead of 115F or whatever, but I can't find where that table is - only ECT adjustment. If does say the timing would advance about 8 degrees from that temperature error. What is changing about 1/4 of the way in, where it shifts from LTFTs around -12 to up near zero?
While I would not want to change to a return less system like the later 8.1’s had, you could run an aftermarket pressure regulator in front of the rail that way.
But like Larry said to facilitate the test pinch the return side off to get the pressure up. They make pliers with smooth jaws to pinch off hoses so it won’t damage the hose. You don’t want it completely pinched as it will dead head the pump and you’ll likely see over 100psi in the process. You are just restricting it enough to raise the pressure.
But like Larry said to facilitate the test pinch the return side off to get the pressure up. They make pliers with smooth jaws to pinch off hoses so it won’t damage the hose. You don’t want it completely pinched as it will dead head the pump and you’ll likely see over 100psi in the process. You are just restricting it enough to raise the pressure.
