Needs to crank twice to start, even just a little "blip" and it goes

[kingtal0n]

So in the morning my 5.3L Tahoe 411 swap, it needs to crank "twice". Duration doesn't matter.

If I crank first time for 5 to 10 seconds and it won't start.
Second time, perfect immediately fires.


If I crank first time for 0.250 seconds.
Second time, perfect immediately fires.


For the longest time I thought it was just a fuel prime issue because I have a returnless rail. I thought air was in the fuel rail.
Until I found out it will fire after only cranking for .25 seconds on the second try.
Must be a computer setting. I am seeing this one table that seems to have a delay in it, but I don't remember seeing anything about "second try" for it.

I am sure somebody knows exactly what the reason is. I wonder that maybe the delay is for oil pressure.

[HackAbuse]

Do some basic troubleshooting. Squirt some starter fluid in there and see if it goes on the first try. If so, likely a fueling quirk, if condition persists, spark quirk. That'll narrow things considerably

[kingtal0n]

Hmm I've been assuming its an injector delay. good point though I will try some startan fluises

[smokeshow]

What happens if you key on, crank, key OFF, and then key on and crank again? Will it start or does the key off interrupt the 'two cycle' pattern and require a third crank to fire in that case? If it starts on the second attempt even interrupting with the key off, what happens if you attempt to crank, key off and let it sit for 12 hours and then attempt to fire again? Sounds like you may have a cam/crank sync issue.

[kingtal0n]

It will usually require the 2nd crank again. I can drive for 20 minutes and shut it off, wait a couple minutes, and again crank the first time for several seconds with nothing happening. Then whenever I stop and restart it will fire right up. I never get a crank sensor or cam sensor code.... but I am not ruling it out either! It might be my imagination but I think it goes away when the engine is really warmed up. I have to pay more attn to it. Actually come to think of it I think the delay is like 700 seconds in the ECU for something and I am thinking that might be the length of time I am looking at in this "reset" sometimes.

Good idea on the third quick try in a row, that is pretty interesting test I will also perform and report thanks !

[evilstuie]

Hey Kingal0n,

I'm new to the forums and my HP Tuners suite only arrived today, but I've been messing with a Small Block Chev 24x conversion running the 0411 LS1 PCM and have the same issue. Mine is most likely an off tune, mixed with rich fueling, sooted spark plugs and a whole heap of other issues, but one thing I'd rule out is the fuel pump / priming.
Maybe the fuel rails aren't getting enough pressure on first key?
I did have that issue and found the fuel hose in the tank had come off because I didn't tighten the clamp enough. Fixed it for a while before the next problem came along.

[SultanHassanMasTuning]

i would check your cam sensor

[kingtal0n]

Something I remember from megasquirt setups is that the crank trigger can put out a low voltage at low rpm causing misfires. And my engine misfires when warmed up only in idle/drive.


They aren't hard to get to, either sensor. I'll be changing them around pretty soon I guess. I dont remember the wiring being shielded come to think of it either. But it was factory like that... maybe I am wrong though.

[cobaltssoverbooster]

MS shields those inputs but not the factory

[kingtal0n]

I've been rlly busy with school but today finally had a shot to change my front trans pump. It took 6-8 hours but I got it done and while I was in there the crank sensor replaced it with a brand new unit from ebay.

No fix yet. Still idle misfires and double starting. So hopefully I can swap that cam sensor asap next. its prolly the old 100k unit. Then move on to the wiring I guess. On the bright side, trans pump noise is fixed, no more death rattle in neutral.

[kingtal0n]

Today I swapped cam sensor, and no difference, no fix. So both sensors are good. Lets say for a minute the wiring is also good. the car runs fine anything over 700rpm. Its just at 550rpm idle or 600rpm idle it has a misfire. I might be getting the coils too hot under the hood, that is my best guess atm because they do get scorching, and it runs normal when cold.

It still does the same delay when cranking but at this point I can live with that. Im more concerned about the misfiring at idle. And warm. I am thinking of raising dwell or reducing dwell. might try turning it down some first. I should make a new thread cause my focus just changed.

[thebeewantsboost]

did you do a case learn after replacing those sensors? sometimes it just needs the learn done. i'm not familiar with your problem. but a little with cam/crank correlation.

[kingtal0n]

did you do a case learn after replacing those sensors? sometimes it just needs the learn done. i'm not familiar with your problem. but a little with cam/crank correlation.

well, no, but nothing changed behavior wise from the engine. identical behavior from the engine means its just as good as it was with the old sensor.

thanks for ideas keep em coming. Right now I am just thinking they are getting too hot. Ill try less dwell. then more. then implement some kind of cowl-induction to see if that helps alot. I really dont like to make my car look like its fast though. Right now I am packing everything pretty stealth and it would be a shame to blow it with a 1" raise or something.

Ill make a new thread with proper topic. thanks and I hope nobody minds but we can continue over there in a day or two. Ill eventually figure it out and make sure nobody has to go through what I went through.

[kingtal0n]

I was standing in line to see if they had any TR7's, staring at the wall of injector cleaner, remembering I had put a bottle in not so long ago. I figured for $5 more though, it couldn't hurt to try again, since these are the original injectors I received with the used LS1 intake manifold from who knows what year (1998 maybe?). I did have a look down the intake ports of the head yesterday and they all looked to be an even spray pattern on brand new head surface with approx 5k miles of my driving also fwiw.


Within 5 minutes the misfire was gone. /facepalm

I think the delay is programmed. I blip the key way 2 seconds and it fires perfectly on the first beat every time. Ill try priming pulse and stuff and report on that.

I am still not convinced it was the cleaner because I feel that the change was too sudden. And also I tried running the engine rich several times 12:1 13:1 and still it misfired. Why wouldnt the clogged injector flow more when i richend it up? Something isn't quite right here.

Right now I have rock solid silky smooth idle at 580rpm in gear with a hood surface temp of perhaps 180*F or more, I can smoke water from it at traffic lights or parking lots, making fog from zephryhills. I bought an ebay $2 shipped water pump I am going to try to get some water running down in the bay, slow enough not to hit the ground.

[MrPhotographer06]

I have a similar issue. When the car runs for a couple minutes and I turn it off, first time i turn it back over I get long no-start. Usually involves backfire, a few echoing fuel sparks in the exhaust.. key on for 5 seconds, off, on, first spark it goes.

I?m thinking cam sensor, but going to check wiring to be sure.

[mecanicman]

5.3 swap into what? What is your fuel system? Not having a check/residual pressure valve does this. Most aftermarket pumps don't have one, you have to add one.

[MrPhotographer06]

Mine is a 240z. I dont have a check valve, of which I understand. Its not that issue tho. I can key on-off 100 times to prime it. Doesnt restart without turning over.

[MrPhotographer06]

FWIW, just checked OHMS between CPS and ECU.. Nada.

Ran jumper wire, started 10-15 times no issue. Id start there. the 2 pins together on the connector had close to 12v, the other was the sensor wire. Fixed now.

[kingtal0n]

UPDATE:

Pretty sure I fixed this issue (startup problem, with having to re-crank re-crank to start)

This is what I was working on when I fixed it:
https://forum.hptuners.com/showthrea...l=1#post521685

All I did was run a new shielded wire pair from the Camshaft sensor to the ECU directly, skipping the wiring harness of the 5.3 completely. Now the engine starts every 3rd or 4th compression stroke every time.

[kingtal0n]

Today I am pretty sure it happened one or two times. It was out of around 10-12 total cranking tries, lets say 10 flawless and 2 needed re-cranking, driving in hot weather.

Just once or twice out of so many. Am I being picky of a 10-25% frequency of this issue? Is it possible the engine stops right on top of the CPS and 'misses it' has to go all the way back around... I don't know how many teeth on it maybe I should look that up...

...at first result somebody said 50% dc cam tooth so I am guessing its a single big 'tooth' on one side. If I am wrong pls lmk. I only let it go crank for around 4 events before I let go of the key and expect the motor to fire on its own, sometimes just barely coughing to life on that last 4th stroke, So the maximum number of cylinder events should be usually 4, 4 being worst case scenario of cam sensor being positioned directly on top of the cam tooth when cranking began. It would miss the 'low' for 4 cylinder events until it came back to the 'high' on the other 180* of the camshaft.

Thing is, mine always takes 4 when it 'works'. always 4. meaning, it must be my incredible impossible luck to always land directly on top of the cps. Which of course is completely impossible. This tells me that the computer must be waiting for both the 'high' and the 'low' to appear as expected before sending spark. I know the fuel is going in from prime pulse. So really, in a true worst case scenario, if it missed that initial 'low' it would need to go through 4 compression strokes to get to the 'high' and then another 4 strokes to get to the low and fire on the 8th event. So my next test will be to allow cranking to go at least 9 compression strokes, hopefully it still won't start from no spark, 10, 11, 12, 13, 14, 15 if I can get it going sometimes it just keeps cranking and there is no firing up. Then that would be something else!!!?? I am having fun and amazed the factory 20 year old LS1 starter is putting up with this. Its a real trooper boy I dragged that thing through a junkyard compression tested 10 different, some 220psi engines, I drenched it in oil from a rear main leak to the point it would stop working till I shot brake cleaner in there.

4-17-18
Nothing yet. Everytime I pay attention to the force in the ignition key and push it hard, deliberately, and I'm ready to hold the key down for a minute, it fires up on the second compression stroke. And everytime I forget to hold the key down it either died or started of course. lol maybe its the key itself, pressing harder into the ignition start position. Also I confirmed that the ecu can actually fire on the second stroke, or even first, if it can tell that the first CPS signal is either HIGH or LOW. The 4 compression strokes I refer to above seems the norm for absolute cold starts, not recent running engine. I think overnight or after a long time the ecu needs both high and low, and if it was just running then 1 will do fine. thats what it seems like anyways.

Ign switch supposedly 23 years old fwiw 95 240sx