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Loosing INJ pulse while cranking

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Hi , I’ve been trying to diagnose what seems to be an electrical problem but with a little confusion with my testing , let me explain

Haltech elite 2500 hooked to a KA24DE inside a S14 chassis … loosing injector pulse while cranking .. tested power at injector while key on at 12v and between 9-10v while cranking .. inside the NSP software I’ve confirmed injectors pulsing and ignition pulsing while cranking .. also installed a noid light to injector pigtail and confirmed noid light flashes while cranking .. confirmed spark plugs sparking while cranking Although spark seems to be a little weak… the car will crank and crank with no signs of firing until the key is released , once released the car will try to fire .. on a very few attempts the engine did fire over once the key was released and seemed to run ok minus some needed tuning … you can audibly hear and feel the injectors start to pulse just as soon as you stop cranking and the engine will stumble and sometimes fire off …. I have traced down every ground I can find in the system and assured they are in decent shape ..

I’ve done some research on the eccs/egi relays in regards to powering these systems but it wouldn’t make sense that the injectors are pulsing with voltage if this were the issue (correct me if I’m wrong ) .. I’ve also tried shutting down the ECR output in the software with no change in symptoms .. thinking if there was a ECCS in play that it would have shut them down completely but no dice …

im hoping someone here and give me ideas or help lead me in the direction of a solution to something I may have overlooked … any and all ideas are welcomed and appreciated

The symptoms fit too much total voltage drop in the circuits when the battery voltage also drops on cranking.

I would suggest reviewing the wiring gauges used, how they're routed, and the ECU power wiring - not forgetting the relevant earth/ground paths.

If a manual you probably find it bump-starts readily, and with a fully charged battery and/or high capacity fully charged jumper battery, there is no - or at least a much reduced - problem, because the battery voltage will be higher.

There's a reason I generally recommend up-spec'ing 'power' wiring and grounds, it's to reduce, or avoid, this very thing.


I'm confused because you said you confirmed there's spark and injectors are pulsing during cranking, but then you say when you stop cranking the injectors start to pulse. Are they pulsing during cranking or not?

If they're pulsing during cranking but the engine isn't trying to start until you stop cranking, it can mean the fuel mass delivered during cranking is extremely excessive. When you stop cranking you may get a spark without complete fuel delivery and end up with something closer to the necessary air/fuel ratio for the engine to start.

Mike .. the injectors are active inside the software when cranking .. so is the ignition output .. when I test the injectors with a noid light the noid light confirms they are getting power and signal (pulsing at the connector )but the actual injector doesn’t pulse … very strange witch is why I ended up here.. I went from 0% cranking fuel all the way to top fuel amounts of cranking fuel and it makes no difference at all because the injectors won’t pulse while cranking .. this makes cold start tuning very difficult if you could imagine …Gord , I have fixed up some power cables and grounds today and made them as good as any would need to be… the engine cranks strong on battery alone .. still seeing around 9.5-10v while cranking at the injector … when I added a fully charged jumper I was sitting at 14v cranking and the engine cranks like a superstar .. tons of power at the injector .. getting signal from ecu and still won’t pulse the injector while cranking but as soon as I let off the key the engine fired right up..you can hear the injectors start to click as soon as you let off the key …. I’m leaning away from chassis electrical being the issue here …what could possibly cause a injector to not pulse when it gets power and ground ? Bad ECU doesn’t make sense either because it’s doing what it’s suppose to do .. 🤯 … P.S. this engine ran on the factory computer with the same engine harness and injectors

One quick test you could do is to bypass the switch for the cranking position, if you're comfortable doing so. You leave your ignition on, make sure the car is in Neutral, and crank the starter motor via a remote switch like this one :


This could be a bad connection in the ignition switch that cut the ignition power while in the cranking position. It's unlikely as your ECU would shut down at the same time but that's something I would try anyway.

Thanks for the idea Francis , I have a feeling that may work .. what has me scratching my head is I’ve tested pin A13 ignition input during cranking and have battV at the pin .. I’ve also tested pin A26 INJ power to also be active during cranking .. power is active at the injector during cranking and the ecu is grounding the injector also .. i really can’t wrap my head around how this is happening but I do know that when the key isn’t in the cranking position the injectors work and that they work with a factory ECU using the same ignition switch . It’s a brain buster

Another quick check would be to make sure the ground cable between the engine block and chassis is in good condition as it can create some wierd issues sometimes.

I haven't used one, but I'm 99% sure HALTECH have a test procedure that allows you to cycle test injectors and coils, to test they're working and correctly wired - if so, you could use that to check their operation, and rule that out.

OH, just had a thought - is it possible you have hooked the ECU up to the accessories terminal? It's not uncommon for ignition switches to turn off accessories in the crank position, and that would mean you have a "run" input with the ignition on, lose it when cranking, and regain it as the switch is released and the acc's terminal is re-connected. I have vague memories of I, or another mech', being caught like this, way back in the dark ages, when fitting an aftermarked ignition to something.

Gord, I have tested the outputs inside the ecu to confirm they are working correctly .. the ignition pin A13 wouldn’t have a constant power while cranking under the ACC wire .. I did test the ignition with a multi meter just to be sure and confirmed ignition switched constant is going to pin A13 and stays powered during cranking … the tough pill to swallow is after tracing everything back to the source I’m left with injectors that have power during cranking and ecu pulsing (grounding during cranking ) with no injectors working during cranking .. at this point I’d like to call the ECU bad but it’s hard to say it’s bad when it’s working how it should … dead end with testing ..


It still sounds like you have confirmed the coils and injectors are functioning, so it still sounds like the tune needs adjustment for the engine to start.

Mike , I have confirmed the injectors are getting power and ground from the computer but I have also confirmed they are not functioning during cranking .. you don’t even need a stethoscope to be sure ..they are loud enough to hear with the naked ear and feel to the touch of them pulsing and they are not pulsing during cranking but they are getting the stuff they need to do so … yup it doesn’t make sense right .. I know it sounds retarded but this is what I got


I really want to help, but you have stated a number of contradictory pieces of information so it's unclear what's occurring and that's making it more difficult to help you narrow down the problem and solution. We will continue doing our best to help.

You have reported you confirmed spark during cranking.

You have reported you've confirmed during cranking the injectors have sufficient voltage on one pin, and are also receiving ground control pulses from the ECU, as confirmed with a noid light. Those two things are what cause an injector to operate, so with both present, they are operating. That doesn't necessarily mean they are injecting any fuel, or the right amount of fuel, but they're operating unless they are physically broken.

You have confirmed voltage is not low during cranking at the ECU, injectors, and coils I believe. If only some of them, I'd check the others.

That combination of info does not mean the engine will start, but it means coils, injectors, ECU have power and are operating, which shifts the focus to other things things like are the injectors full of debris, does the engine have compression, is it mechanically timed correctly, is triggering and timing of spark events correct, is fuel pressure correct, and the amount of fuel and air delivered.

Since it tries to start right as you stop cranking, have you confirmed the fuel pump isn't losing power during cranking? If you have no fuel pressure during cranking, then you get fuel pressure right as you release the key, that is another thing that can cause the lack of starting. In terms of the fuel pump what you really want isn't just the fuel pump operating during cranking, you want to have an appropriate amount of fuel pressure. Have you confirmed what fuel pressure is during cranking yet?

If your timing is 180 crank degrees off, that MAY also cause what you're experiencing.

And as I've mentioned, if the amount of fuel delivered is too far from correct to allow engine start during cranking, sometimes you'll get pops as you stop cranking.

I'm confident you'll get the engine running, so stick with it and we will continue trying to help as well.

Mike , I greatly appreciate your continued support here I truly do .. let me explain a little further for you so you have a better idea of what’s going on …. This is going to be long winded , the engine has 160psi of compression and I tested that before anything, even before having the customer purchase the Haltech elite 2500 so I knew I was dealing with a healthy engine to tune … I have done many many Nissan engines and have developed a very strong reputation over the last 20 years in my area in SW Florida of building hi performance engines… particularly Nissan and Toyota platforms … I have only been tuning for 5/6 years now but with my background as a long time mechanic learning to tune was fairly easy for me … that being said I just want you to know that your talking with a experienced tech … all the things you listed are very valid points so I will list the following things that have been tested and confirmed working. .. compression 160psi on all 4 … locked timing at 0 degrees (TDC) and firing 109 degrees ignition angle and used a timing light and it’s right on the money ( yes compression stroke ) ignition output confirmed to be pulsing in software while cranking (single IGN dizzy with built in ignitor ) Haltech only has one option for KA24de trigger setup that I have used on dozens of other KA24de and never a single issue (using Haltech ) (Haltech is awesome stuff !!) I’ve confirmed the dwell settings in comparison to other saved tune files I’ve made on these engines .. the settings are correct .. injection outputs (all 4 ) confirmed to be pulsing in software … injectors have power 12v when key on and between 9-10v while cranking .. dizzy has power while key on 12v , 9-10 while cranking … confirmed spark is happening during cranking on all 4 plugs but seems a little weak but not terrible ..injectors are usually pretty loud with clicking when in operation and there doesn’t seem to be clicking during cranking .. so i test the pigtails (all 4) with noid light and confirmed all injectors are seeing power and ground because the noid light flashes .. testing the outputs all injectors fire on the correct cylinder .. fuel pressure sensor installed into Radium fuel rail and calibrated and wired to Haltech .. 43psi in rail while cranking … .. here is the curve ball , when cranking there is no signs of firing at all .. no putt or stumble or anything at all .. symptoms are, no spark or no fuel during cranking .. when you release the key it will fire … 2 or 3 times now I’ve been able to get it to start .. if you time it just right when you get off the key you can get just enough engine revolution to pop the engine off .. so the engine is running now and sounds beautiful .. got it to run long enough to dial in the Base VE table and adjust the post start correction etc … the engine runs and sounds dam good .. let it warm up until the fans turned on , everything is great , very happy engine seems ready to tune ..I re confirm timing with light after warm ($$$$).. give it some revs and it’s happy there also … from here I can do my normal tuning routine without a problem but I don’t because I want to be able to fire this thing on Key … shut the car off and I’m right back where I started … no fire during cranking … I use a stethoscope to listen to the injectors while cranking …(tested today) SUPPRISE!! They are clicking during cranking but very very slightly .. when you let off the key you can hear the injectors start clicking loud (normal) for a split second before the engine stops to rotate .. just about the same time she likes to pop off … I bet if I tested them while engine running they would be super loud with a stethoscope … not even noticeable clicking during cranking … what to do next …. I lean the cranking fuel out all the way down to 0 … like literally 0% inj duty while cranking .. I shut down everything .. no prime pulse no nothing and then I slowly start to increase the cranking fuel up and up and up until the car starts to pop off when you let off the key and that happens around 3% duty while cranking … to get it to actually fire and stay running I’ve had to give it a lot of cranking fuel ( more than should be needed ) .. so I’m going in circles now … I remove the plug wires and crank away at 3ish% inj duty .. I pull the plug and it’s WET !!! It has fuel !!! WTF ..not enough spark ? !! I’m loosing my mind … 160psi of compression .. perfect timing .. runs and sounds beautiful .. has spark while cranking and has fuel while cranking … you can give it all the fuel you want or as little as nothing and it just won’t make a peep during cranking .. some of these findings were uncovered today .. I just keep plucking away at it but this is getting retarded .. I have remade or re cleaned every ground and power cable in the chassis making sure they are clean , tight and of sufficient size .. the engine cranks strong .. I did put a fully charged jumper box I use for starting dead diesel engines on it and have had 14v cranking this thing with absolutely no change in symptoms .. thing sounds like it’s making 50whp under the starter lol … I really don’t know what to say anymore … something is def wrong here… I’ve started dozens of these engines with the same ECU’s without any issues whatsoever .. im going to get what Francis recommended and try and manually operate the starter with a spare battery and see if this thing will fire under cranking and report back to you guys .. if you can think of anything in the meantime feel free to post a reply … and I Thankyou for your support

About the only thing I can think of, and I expect you've already checked them, is a mis-match between the impedances of the injectors and/or coils to the driver settings for them? Some injectors are rather problematic at starting voltages, IIRC, Flannigan (sp?) had some issues with his hemi' hot-rod?

Other things to try, to isolate things and maybe narrow it down -

Rather than use the ignition key to crank, use a "bump button" - I expect you've got one around the shop, as they're very useful for setting valve clearances, but if not I mean a momentary contact switch between a 12V source and the starter solinoid, that can be used to bypass the ignition crank position.

The second thing is to try completely disconnecting the starter from the vehicle's electrics, and power it from the jump battery alone.

Oh, again something that you've probable considered, and I doubt is relevant but throwing it in, is some older vehicles used a ballast type ignition. Most ran the bypass from the starter solinoid in parallel, but a few switched between them.


Thank you for the info and for running through it all.

At this point it sounds like spark plugs may be fouled, so I'd use a fresh set.

It sounds like you're dealing with a bad battery since voltage is in the 9-10s cranking. When voltage gets down below 11 volts, certainly below 10 volts, some electrical components no longer work in typical fashion. They can become not just weak in output, but unpredictable in behavior. Just to rule it out, have you tried cranking while this vehicle's battery is jumper cabled to a running engine, or attached a shop charger to keep voltage up around 12 volts during cranking and see what the behavior is? That will get both injectors and ignition working much better.

With fresh plugs, proper battery/voltage, I think you're down to the amounts of fuel and air.

Gord , I’m going to explore some of these things you mention to check them off the list .. I ordered a thing on Amazon for manually running a starter and going to completely disconnect the starter from the system and power it using a spare battery or jumper box to see if that makes a difference , unfortunately I won’t have it until late in the week …. Mike , I did install a brand spanking new battery in the car with 800cca .. on top of that I added a jumper box to it and had 14v at rest and very close to 12v while cranking (with fully charged jumper pack ) .. brand new plugs and already on the 3rd set as I have been testing and cranking they have been getting a little fouled .. I keep frequently changing them and had a fresh set in when I did the cranking fuel testing .. … I will report back as soon as I can get this engine to turn over using a separate power source from the car too see what happens .. based on what what I’m experiencing in person I have a feeling it’s going to start right up ….it seems crazy but could the ignition itself cause this ? I’ve tested it and it seems to be doing what it suppose to do … merry Christmas guys !

If you've tested with a better battery that maintained 12V during cranking then you've sufficiently done that test already.

Sorry if I missed it. How did you determine you're not 360 crank degrees off on ignition timing? Or did you try starting at 360 out?

Mike , I’ve had the car running and running good … the ignition angle firing at 109 degrees also confirms the timing for me because of the way Nissan trigger wheels work with 4 windows and 360 teeth .. in the software I have full sync and no trigger errors except for the common error that happens during shutdown on these particular trigger wheels but this doesn’t affect them whatsoever … when I get the car to fire it runs great and also re confirmed with a timing light while running .. the ignition fires right when I want it to .. if the timing were the problem it would not run as good as it does if not at all …. Just to be sure I went ahead and put the engine on TDC compression and looked at the rotor cap and it’s right where it needs to be (double , triple confirming timing is correct ) …the car running isn’t the problem .. the problem is it won’t fire during cranking .. it’s very hard to say it’s a power problem at this point .. I’ve had the car hooked to jumpers sitting 14.5v and and 12.3v during cranking now … still no sign of fire under the key .. soon as you release the key boom it fires but this is a difficult way to get it to fire .. but the ECU gets contant IGN power during craning .. the injectors get constant power during cranking and the spark plugs get spark during cranking … yeah I know it sounds impossible or that it would have to be in the calibration … I’ve manipulated the calibration fuel amounts from literally zero fuel gradually up to when it fires when the key is released … absolutely no signs of fire while cranking .. I plan to operate the starter from a separate power source while disconnected from the cars circuit to see if it fires right up but I haven’t got the fancy cheap tool in the mail yet

Dangit, this is a puzzler - about the only thing I'm sure of it's going to be a "duh" problem that you just never thought of, ot thought you'd checked off.

I do apologise for all the "granny-egg" suggestions, but if it triggers some thoughts that solve it, it's all good.

Meant to ask before, but when you checked the injectors, did you confirm that voltage was with the injector(s) receiving an 'open' signal, as that can make a big difference - and if it seems a little low then, it's going to be a LOT lower when it's trying to open.

I did mention some injectors can be problematic during cranking, because of the current and resulting voltage drops - if you can supply the brand and model, it can be looked up and checked.

Depending on the size of the shop, and your work flows and budgets, might be worth picking up a basic 2/3/4 channel digital CRO - maybe s/hand - as any on-board one can only work with the signal voltages at it's location, and actual voltages, etc, at the senders, coils, injectors, etc. may be quite different.

Thanks Gord , I appreciate all input and in a lot of cases the very simple things can get overlooked so any suggestions is a good suggestion even if it’s something I have already tested because you never know if I overlooked something … I do have a lab oscilloscope that I can test some things with but haven’t tried to test this with it yet … the injectors are deachworks 18U-02-0800 .. they are 800cc … I will say that I used the latency data on their website for these injectors and the data was pretty far off .. I had to adjust the data quite a bit to get the VE around 50% at idle running 14.5:1 AFR .and made sure no other corrections were being added ... I’ve considered throwing in some injector dynamic injectors 1000cc I have laying around the shop to see if that makes a difference .. I know and trust the data from ID as that’s the only injectors I typically use or recommend .. this car isn’t one of my builds tho it’s just something that was on a ROM tune and was having tuning related problems that I was hired to install a standalone management system and tuning… so I have to deal with what I have here for the most part unless I determine a failure in any of the components needed to get this thing tuned ….. here is some more info that has me leaning towards a spark related issue ( around in circles I go ) …. Fresh set of plugs installed and I sprayed ether inside a vacuum line direct to the intake to see if it would fire on ether … no signs of fire during cranking .. soon as you let off the key it fired up .. pulled the plug wires and popped some plugs in them and it has spark while cranking … not a super strong spark but def enough to light ether … … it hurts my brain to see spark during cranking and manually insert fuel like ether and not see this thing fire off or putt or stumble or anything at all while cranking but then immediately start when you stop cranking … has to be the most bazar thing I’ve ever tried to diagnose …. I’m sure I’ll figure it out eventually but when I see things like this particular test it makes me pull my hair out … it has to be something super stupid …I just can’t wrap my head around how it has all things to fire while cranking but just won’t fire when cranking 🤯🤯🤯.. the engine runs great tho haha !

I'm still leaning to 360 deg out, and when you stop cranking, this is causing a pulse on the cam/sync signal and the ECU switches phase. Can the ECU be configured to run wasted spark?

David , I’m willing to try anything at this point .. yes I can configure in wasted spark .. however I have tried using the quick start function witch uses wasted spark and batch fire injection during cranking and switches over to sequential once the engine sees the running RPM … but I have to ask … when confirming mechanical timing and the rotor firing (pointing ) on cyl1 compression stroke and then using a timing light to confirm cyl 1 is firing at my locked firing angle how could the timing possibly be anything other than correct ?.. 360 out would fire on exhaust stoke ? … trying to do the math in my head , I’m firing at 109 degrees witch is where every single KA24 I’ve configured fires at .. if for some reason this one is different and I’m firing 360 out then the correct firing angle would be 469 degrees ? This trigger wheel has 4 windows 1 is unique and 360 teeth … I’ve never had one fire outside of 108/109 degrees before providing the distributor is in the correct orientation … I usually set them at 109 and adjust the dizzy until the light fires on locked timing target … I’m going to thoroughly explore the firing angles and see what I come up with using the light

Thanks for the input and support guys … the problem was a bad timing module inside the distributor … the coil was good and allowing the plugs to spark but the spark was too weak to ignite the fuel mixture .. to my knowledge the module isn’t testable as it plays a internal role and I can’t explain it’s engineering .. however … replacing the distributor fixed the problem and the car fires right up while cranking now .. even tho the testing with a oscilloscope shows no changes or increases in voltage at the injector or changes in the signal from before and after the new distributor was installed you can still notice a distinctive louder clicking in the injector while cranking, and a much brighter flash in the timing light aswell .. testing with a modern timing light was sensitive enough to pickup flash on every ign pulse .. but when I used a old school snap on timing light from wayyy back it would only pickup 1 flash right as the key stopped cranking ... my hypothesis is that the older timing light wasn’t sensitive enough to pickup the weak signal from the module during every flash but only when the voltage drop from cranking returned to the module would have a strong enough signal to flash and spark good enough to light the fuel and that’s why I was able to get the engine to start and run when the key wasn’t in the cranking position ..a fault at the module that only occurred during (normal) voltage drop during cranking …I do feel in this particular situation the engine would have fired if operating the starter from a separate power source although this was never tested .. this one was a tuff one to solve due to having spark , fuel ,compression and verified ignition timing with a light with a no start symptom during cranking ..I’m sure this is a rather uncommon scenario for most .. but KA24DE owners beware

I'm so glad you figured it out!

It sounds like you've fallen into a trap many have with newer timing lights. I have a couple Craftsman ones that are around 40 years old because they work much better.

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