1999 Ford KN Laser No Start Condition with a twist - HELP

[GrahamKNlaser]

As per title I have a 99 Ford Laser with an intermittent no start condition and I'm stumped.

Car will crank all day but not fire. The car has spark, and plenty of fuel getting to the rail, but won't go on it's own. There is also constant 12V power to the injectors when key set to 'ON'; however, no grounding signal from ECU while cranking (screwdriver and test light methods).

The Cam and Crank Sensors have both been replaced in the past 12 months.

The twist: The car will fire if starter fluid sprayed into the throttle body. It will also continue to idle on its own (i.e. not continually spraying starter fluid) after it has been started this way. I've had it idle for 10 mins without it cutting out (turned it off after this out of boredom). Also, once started, injector pulse is present (again, screwdriver and test light methods).

I have gone through the fuses and relays. All seem OK and, given car will fire up and continue running after priming with starter spray, I'd assume issues with these might be ruled out?

I guess what the question here is: what could cause a loss of injector pulse which then disappears after the car is forced to start??

ECU failing is absolutely a thought; however, trying to rule out all other possibilities before going down that route. Maybe a sensor/component (except cam + crank that have been replaced), or possible grounding issue, that could also cause this kind of condition.

Thanks in advance!

[aussiblue]

How much spark? I am no Laser expert and don't have access to a Laser workshop manual but...a thought.

On most post 1988 Falcons and many other computer controlled fuel injection cars and perhaps your Laser, the ECU will turn off the injection system (hence no injector ground) if no ignition or insufficient ignition spark is detected . This to prevent a) a build up of unburnt fuel in the inlet manifold and cylinders that might otherwise subsequently damage parts in a catastrophic backfire once it fires (usually blowing the air cleaner box apart or even blowing the valve cover off) and b) also to prevent the destruction of the catalytic convertor with unburnt fuel soak (raw fuel kiils expensive convertors). The minimum specified spark length for most Falcons measured at number one plug at the end of HT lead is 6mm a and most will produce a spark at least 3 times that length. I don't know what the minimum spark for the Laser is but it is likely similar. Worth a check as the symptoms fit; best measured with one of these: https://www.supercheapauto.com.au/p/.../SPO81648.html or https://www.supercheapauto.com.au/p/.../SPO81644.html or https://www.repco.com.au/tools-equip...spark%20Tester etc The things that just flash a light to indicate a spark won't cut the mustard. Note starter and ether spray being more volatile will fire with less spark. The ECU will likely have detected the firing on starter spray and having detected ignition switched the injection system back on.

If you have access to a factory workshop manual it should specify the minimum spark length in the section relating to trouble shooting the ignition system/.

[aussiblue]

Also note the information about this spark tester at Repco https://www.repco.com.au/tools-equip...spark%20Tester states

Electronic ignition minimum gap (10mm) indicated by 'E'. .

So that's a good benchmark to be aiming for as a minimum. If there is insufficient spark it's probably time for a new coil pack.

[aussiblue]

Also please note modern computer controlled fuel injection cars also typically produce a very accurately timed but short duration and very high voltage spark. Often it is in the kilovolt ranges so using a screwdriver or such against block risks both a) giving yourself a nasty shock (enough to induce a heart attack and b) damaging the ECU and other fragile electronic components.

Similarly, it's probably also worth investing in a noid light to test the injectors e.g. https://www.repco.com.au/tools-equip...g_q=noid+light and https://www.amazon.com.au/Lrocaoai-1...s%2C258&sr=8-2 If you know the injectors electrical connector pin type (Falcons for example usually use Bosch 2 type) you can buy individual ones e.g,. https://www.ebay.com.au/itm/15596239...Bk9SR_jc-6OjZQ and https://www.ebay.com.au/itm/26259154...Bk9SR_jc-6OjZQ etc. These noid lights can often also be used to test the ignition switch supply to the coil pack where the injectors and coil pack has the same electrical connector type.

[aussiblue]

Also check for stored fault codes per https://codes.rennacs.com/Petrol-Engine.php or better Forscan For Windows with a Laptop https://forscan.org/download.html and the recommended USB Dongle OBLinkX https://www.obdlink.com/products/obd...x/?ref=forscan . The car may well be able to tell you what is wrong with it.

[russellw]

We have the KQ WSM in the tech portal and I have the KA-KM manuals here as well so that covers all but the 2 years of the KN but should still be largely relevant.I can't find any mention of spark length in any of them but the KQ one might help with troubleshooting and given it is EOBD it should be throwing some sort of error codes.

[aussiblue]

Yes the KH is also too old for the online manual to be available for download.

But reliable Russell seems to have also found a KF to KH one for you at https://fordforums.com.au/wsmpub/laskf37/G.html

This implies there should be a strong spark at 5 to 10mm at Page G-19 so I think the suggetsed 10mm test is still valid. Note the instruction to use insulated pliers but using one of the spark testers I suggested is amuch better way.

But the more relevant Laser KC-KE / Meteor GA (1985-1990) **NEW 01/2025** engine electrical system pages here seem empty https://fordforums.com.au/wsmpub/laskc44/05.html. I have advised Russell and doubtless he will fix it in due course.

[aussiblue]

This implies there should be a strong spark at 5 to 10mm at Page G-19 so I think the suggested 10mm test is still valid. Note the instruction to use insulated pliers but using one of the spark testers I suggested is a much better way.

Ditto with page 5-41 of the now working (Thanks Russell) Laser KC-KE / Meteor GA (1985-1990) **NEW 01/2025** engine electrical system pages here: https://fordforums.com.au/wsmpub/laskc44/5.html

[aussiblue]

Just noticed Transquip have these spark length testers on special https://transquip.com.au/products/ki...rk-tester.html

[GrahamKNlaser]

Hey Aussiblue!

Thanks heaps for the direction and sorry for the delay, it's been a long week.

I've had access to a spark tester and can confirm spark is strong (gapped 10mm).

I don't have access to a scan tool but no CEL's have been present. Any idea if there is a way to jump the engine bay scan port to check codes? Alternate is getting it to a shop some time next week.

Another thread linked a no start to TPS sensor signalling WOT (approx 5v) with no throttle input. I've just checked mine as I'm completely lost and its at 2.5v with no throttle input. I can't find specs of TPS values for laser... any idea if this could be the issue? Unplugging doesn't change no start; however, in the post I read of this was also the case.

Any other ideas as to where this problem could be coming from. Would an electrical ground issue at the ECU or somewhere else in the system cause a condition like this?

Thanks for anything else you can provide here!!

[aussiblue]

Have you done a fuel pressure test?

[GrahamKNlaser]

Not with the correct tools (again). Removed fuel hose just before rail, put it in a bottle, and it pumped about 300mL with 4 cranks. Assuming the go here will be to hook up an actual tester to confirm PSI rather than flow?!

Just baffling that with starter fluid it jumps and runs without intervention. Wouldn't we expect that, if a pump issue, there would be some kind of idle issues when idling?

Thanks AussiBlue