The tests that I ran measuring fuel pressure did not show any fuel pressure reduction (stable at 46 psi) with the fuel pump off but will run the tests again to make sure there is no leakage.Originally Posted by Alvin
The tests that I ran measuring fuel pressure did not show any fuel pressure reduction (stable at 46 psi) with the fuel pump off but will run the tests again to make sure there is no leakage.
Not finding any problems with fuel pressure, fuel leakage or fuel flow. Injector duty cycle at 6200 RPM is only 80%.
Last edited by DetRedWingsFan; 03-31-2023 at 09:47 AM.
The fix for your cranking/starting problem is getting correct injector data - all of it, not just flow rate. And that data does not exist for Accel injectors.
Used to have a lot of Corvette's come in with those horrible Accel injectors. You are right they used to leak like crazy. Long crank, fuel smell on startup etc. Always got replaced with the GM green stripe injectors.
Following your advice and ordered a $530 set of Trick Flow TFS-89030 injectors.
Could not find a data/flow sheet for the Trick Flow injector but I did find a data/flow sheet for the Accel 150830 injector.
Both are rated at 30lb/hr or 309.0cc/min at 43.5 psi.
Will update once I replace the injectors.
Don't buy injectors without first having the data.
Why are you not looking at GM injectors?
Yikes. $530 for 30lb injectors with no data. I'll stick to the GM 50lb E85 compatible injectors with perfect data for all current and past ECM/PCM's that you can get brand new for under $100 shipped.
Is this data in GM format?
The guy still hasn't verified the fuel pump is priming and holding pressure when it is failing to start the first time, but not second time. This might not be a pump prime issue but sure does sound like it..
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I managed to cancel the Trick Flow injectors order. I guess you guys don't like Trick Flow either.
I'd be happy to look at GM injectors. Would appreciate it if you could give me a link to 30lb/hr GM injectors with data. I did a search and found plenty of GM injectors but no specs.
I thought I had made it clear that the fuel pressure held at 46 psi with the pump off. Tends to make me think that the injectors are not leaking as I would expect the pressure to start to drop after awhile. And that when it doesn't start right away, I usually can smell fuel. Sounds like too much fuel.
But going back to my original inquiry - really would like a definition and usage for the Cranking Parameters. By my count, there are 22 parameters associated with Cranking.
Last edited by DetRedWingsFan; 03-28-2023 at 01:28 PM.
You don't need 30lb/hr. They can be bigger, the ECM can adjust down (within reason) if it has good data. But it has to have that data for the low flow, not just the max flow rate.
These have been confirmed as being the real deal by many on here, otherwise I would stay away from EBAY/Amazon.
https://www.ebay.com/itm/274424906026
:lolsob:
It's not about not liking particular brands, it's about not liking brands that sell injectors without providing all the data needed for use with a GM ECM/PCM. Lots of those no-data injectors will work just fine with aftermarket ECUs where they don't bother with all the fiddly stuff.
Injectors you can find all the data for, in stock GM calibrations:
19421333 - 29lb - LY5/LH6/LH8, lots of '05-up Gen 4 truck stuff (old# 12580681)
12587269 - 33lb - '09-'10 LY6/L76
12580426 - 35lb@58, 33lb@51 Gen 3 L59 (old#s 88894361, 89017586)
12594512 - 36lb - '07-'09 LMG
12613411 - 38lb - '10-up LMG
12576341 - 42lb - LS3/L99
12609749 - 50lb - L92
12613412 - 51lb - L96 - these are extraordinarily cheap, like $55/set cheap
innjector dimensions.jpg
For about the fourth time now, the cranking parameters you're obsessing over typically only need to be changed if you have some other problem you're trying to mask like bad injector data. None of the cranking stuff is 'injector data' and should not need any changes after an injector swap as long as the actual injector data isn't all jacked up.
'Injector data' means:
Injector Flow Rate
Min. Injector Pulse
Offset vs [whatever] vs [whatever]
Short Pulse Adder
If those aren't readily available from a known-reputable source (note, this does not include 'well my buddy used this data and got it to run pretty OK') for an injector, and you are using a GM ECM/PCM, Do Not Buy.
Let me reiterate, the engine runs perfect for all other conditions. It runs that good because I understand all the other parameters (after lots of research) and their effect on how the engine runs. But my research into the cranking parameters failed. However, I do agree that changing injectors, camshaft, pcm, ignition system, throttle body, exhaust, etc would have no effect on cranking. I do appreciate all the ideas and hypothesis and gives me some other avenues to pursue for diagnostics.
Yes, that's exactly the kind of weird, illogical problems that pop up and drive you nuts when injector data is wrong. Been trying to tell you that. These weird annoying problems are the symptom of something else, not a thing to fix by adjusting other parts of the tune.
And a warning: If you've been diddling stuff all over other parts of the tune for a while trying to improve things while it had bad injectors/bad injector data in it, you're going to have to un-fuck a lot of stuff. Don't you dare put new injectors in, find that it then has other problems, and come back here whining that it isn't any better than it was before.
Thank you I'll check that out. Much appreciated
1997 30th SS. Torqhead 24x, TFS heads, 223/235 cam, 4l80e, S60 D1SC 14psi
You guys were right on. Problem was a fuel issue and specifically a Prime issue. I spent most of yesterday looking at logged data and comparing the Cranking parameters on last tune with other similar tunes. It appeared that some of the Cranking parameters had odd values. So I did more comparing, some parameter adjusting and to make a long story short, turns out the problem was the First Prime Pulse with Soaktime and FA Mult. To test my theory, I zeroed out the First Prime Pulse, set Soaktime to 0 and eliminated the FA Mult. Now there is no overfueling, no smell of fuel and it starts every time within 2-4 revs. Have other work to do right now but I think I can get it to start within 1-2 revs if not instantly by further adjusting those parameters. It looks like that under the right conditions, the engine would get overfueled and be difficult to start. So Thanks for all your suggestions and ideas.
I'm assuming its "fuel pressure delay" it says "delay after key on, before pulse is delivered to allow pump to build pressure."
1997 30th SS. Torqhead 24x, TFS heads, 223/235 cam, 4l80e, S60 D1SC 14psi
This is purely the time in seconds that the fuel pump will stay energized after an ignition on event. I use this sometimes to drain fuel tanks, but also if there is no check valve (stock have them otherwise one should be added). Let's the system fully build pressure instead of a quick top off like stock
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