1UZ won't fire, weak spark?

[jeremy]

Hi all,

I'm doing lots of head scratching trying to get the thing to start again, but not having much luck - thought someone might be able to point me in the right direction...

This all started on a sunday morning of a 4wd comp, it stated missing. We had a few stages still left to do, so we weren't going to pull the covers until after the event. On the way home we stopped at a gas station, we went to leave and it started, coughed, spluttered, and died. It hasn't started since.

The leads were still oem and in pretty poor condition. So I replaced leads, distributor caps and rotors. Spark plugs I replaced with some copper NGK BKR6ES11's as recommended by a friend.

The new rotors had paint (or something) on the end, should I have sanded that off?

The coils check-out as per the specs in the FSM, and igniters are grounded. Crank angle, and cam sensors are all within the FSM resistances. Timing belt is ok and lined up.

Injectors are obviously working at least to some degree as the plugs get wet when trying to start, and you can smell the fuel.

I have spark at all 8, but it seems weak. I get a better spark with the old (very worn out) platinum plugs?

Attempting to start with AFM and all sensors plugged in gives no diagnostic codes. With AFM, TPS, water temp, and o2's unplugged - still doesn't fire, but gives obvious diag codes.

So, anyone have any clues? What should I be looking at next?

 

[jeremy]

Update...

I've swapped out an igniter and coil, and still have the same weak spark. And the spark is the same directly from the coil, so that rules out rotor/cap/leads.

What should I look at next, any hints?

 

[samsdad]

Went thru this when wiring up a '99 hilux and it was a really odd one. Got it running and out it went and came back this week with some issues which turned out to be nothing that we'd done but a faulty amp in the stereo system pulling all the power out of the damn thing.. I kidd you not.. Amp disconnected and no problem (and no heat in the footwell either, wonder it aint caught fire)..

OK now the problems had with this thing are pretty much what you've described that has happened to yours (yes this particular lux is a 4wd as are all I do). And that is a weak spark. I'd be checking all of the power feeds to ECU and ignitors, injectors, coils etc and go from there as it really sounds like during the course of the event something has gotten wet (causing the miss) and now due to corrosion/dud connection really doesn't like it. So unless you go back to the wiring and check everything no matter what you do it aint gunna go. This is all going to be down to one power feed which is going to take you bl00dy ages to find and seconds to fix (then leave you feeling like an idiot) so while you're at it I'd suggest that you relocate the ECU and ignitors into a sealed box with marine grade cable glands for the wiring to pass thru (I seem to remember Corys selling such things reasonably cheap) as not to have this problem again.

Back to the case of my clients one doing the same (with the faulty amp) when cranking the engine over all the power feeds dropped to 7 volts so due to the resulting weak spark it wouldn't fire up. Added some extra relays and a new battery and away it went. Just did another of the same model without the same dramas and wondered what was different.. No big stereo...

So again check all the power feeds and go from there

 

[jeremy]

Thanks for the help,

I've had a bit more time over the holidays to work on this... On closer inspection the spark may be ok now? It still seems pretty small (my uneducated opinion), but it is a purple'ish colour. I checked the voltage at the coil while cranking and it's at around 10.3v, the same as at the battery - which seems right for a cranking voltage?

I can get it to start and idle using some starter spray, but it dies as soon as I stop spraying. Still no codes with everything plugged in.

Could I assume that because it runs on starter spray that the spark is ok, or could it still be too weak?

I went to pick-a-part yesterday to get a fuel line fitting so I could rig up a pressure gauge on the fuel rail, and fuel pressure seems to be normal, around 43 psi on cranking. Pressure holds at a lower pressure (can't remember what it was exactly but up in the high 30s) when you stop cranking.

 

[sideshow]

u might have blocked injectors
u need to manually trigger each one and hear them click
if it runs on aerostart then its definetly injector issue
u might have bad earth on back of mtoor
seen this done afew times
there is normaly 2 earths
one on each ehad on the back

 

[sideshow]

sorry i forgot u said it had been running
put noid light on all injector plugs see if it lights up and pulses
maybe u have bad coil so 4 cyls are weak and 4 are strong
first test to see if all injecotrs are working and flowing

 

[samsdad]

Before you get carried away testing injectors there's one simple thing to check at the injectors.. On one side of the injector plug there should be a black wire with red or orange trace. This should have 12v ignition to it. no power here means no go

 

[jeremy]

We have two earth cables, one from front passenger side head to negative terminal on the battery, and the other from the driver side engine mount to the chassis. I had cleaned the passenger side one previously, but pulled both off today, cleaned and refitted. I also checked the resistance of both while they were off - is there any other way to check the earth's?

I know 6 of the 8 injectors are clicking while cranking (the other two have too much stuff in the way at the moment). If they are clicking could they still be blocked or not?

I didn't mention it before, but I also checked the voltage at the black-orange wire to the injectors when checking voltage at the coils, and got the same 10.3 cranking volts.

Thanks,

 

[sideshow]

pull covers of ecu check for bad capacitors
if it fires on aerostart then it should run on injectors
maybe get check spark plugs for it the ones with big fat electrodes
not the gay iridiums or platinums as they fowl up very quick when yr trying to diagnose

when u spray fuel stuff down throttle body does it seem to run on all cylinders

its one of these problems where u go over everything 5 times before u figure it out
ive got a proffessional coil tester that puts heaps of load on coils pretty good unit but worth a bit
have u got another 1uz of a friend u can borrow parts

 

[sideshow]

if u have one half bad coil or one unplugged coil motor still feels half ok when u run it on aerostart
so therefore hard to tell bad coils
if u have a bad coil it wont send signal to ignitor which in turn sends signal to ecu to fire injectors
can u put a multimeter on an injector to test for millisecond pulse
should be under 15 ms i suppose when cranking and 3 ms when running

 

[jeremy]

It seems like its running on all 8 when it starts on starter spray at a normal cold idle.

I don't think our multi-meter will read pulse width, but I might be able to borrow one off a friend.

How could I test to see if the ecu is getting an igf back from the igniters?

 

[sideshow]

now easy way to test ecu except for plugging into another car
i dont trust these shops that say they can test em
costs more to test than buy 2nd hand one

u need to check igt and igf terminal on ecu for both ignitors
it will be an rpm pulse signal

it should come up with a code but sometiens strange things happen

does check engine light come on with just ignition on
or is there one hooked up
if so when u check for codes do u get just constant flashes

 

[jeremy]

I'm not getting any diag codes with everything plugged in (afm, tps etc...)

I tried disconnecting one coil at a time - makes a noticeable difference when attempting to start on starter spray. It still starts, but roughly. Same result with either coil disconnected, and ecu gives the corresponding code for each (15 & 14).

With both coils connected, I think its starting on all 8 - vacuum gauge reads 'normal'.

I found today that the hose from the tank to the charcoal canister had perished and had a split. It looks like it has taken in some mud+water. Who knows how long it's been like this! I can see some mud in the bottom of the charcoal canister as well. Do you think mud/water could have made it back to the tank, through the pump, filter and has gummed up the injectors? They are clicking, and some fuel is obviously making it's way through as all plugs are getting wet when attempting to start. They don't appear to be leaking either, as it takes a couple of days for fuel rail pressure to drop to 0.

I changed the fuel filter earlier, before I had rigged up the pressure gauge to the fuel rail. I still have the old one here and am wondering if I should try and open it up and see what's inside, although I'm not sure how I would do that considering it's still got a fair bit of fuel in it that doesn't seem to want to drain out?

 

[jeremy]

I forgot to mention - I had a look inside the ecu a while back... it all looks good, but I guess capacitors can still go bad without showing any visual signs?

We don't have a CEL, just a plug with a light and a jumper than we can plug in to read codes. Would the CEL be on without the ecu having any diag codes to give?

 

[sideshow]

strange y plugs r wet
is this due to fuel from injectors or
stuff u spray down butterfly
it's hard to say hat might be without
having car in front of me
there's many little things I check but hard to
explain on forums as its time consuming going
back n forth

but maybe check compression and timing
check afew leads for correct timing
might something silly like cam timing just as a guess

sometimes the aerostat is so flammable
it runs better than fuel and hides other issues
remove return line and if fuel comes out in ok flow
then that's fine
maybe u have issue with start sig to ecu
but on these even if u don't have start connected they r ok

 

[jeremy]

Will have to check compression - haven't done it yet, as I need to make an adapter to get down the spark plug tubes.

Timing was one of the first things I checked. I did notice that one of the pulleys had obviously had some water in it and was feeling pretty rough -that shouldn't be enough to stop it running, right?

Spark plugs get wet when trying to start without any starter spray, and the cold start injector isn't plugged in, so the fuel injectors are working to some degree. They all seem to be equally wet, none are dry.

I had checked fuel flow out of the return with fp and b+ jumped - it seemed normal. I tried starting it with the return emptying into a can, rather than back to the tank - no difference.

This one has me beat! I really appreciate your help though

 

[sideshow]

yes its weird how injectors are wetting spark plugs but wont start
but engine will start on spray
thats y i think maybe just as precaution do a comp test

would have been nice to tackled one like this hands on heheheeh

cel light should come on and stay on with just ignition on
then u start it and it goes out if no codes present
with just ignition on and u bridge te1 and e1 cel should blink
constant blinks every 1/2 to 3/4 second means all good

 

[jeremy]

Ignition timing is 5 degrees while cranking - is that right?

It should be able to start on the cold start injector right? I plugged it back in today, and still no go? I looked down the throttle body while cranking and it has a nice spray pattern.

So even though it starts and idles well on starter fluid, could the spark still be too weak?

 

[jeremy]

Ok, better update this thread...

I solved the problem after much head scratching.

I bought a spark tester, one like this...

...and it proved to be a brilliant little gadget. Using it I was able to quickly see that the voltage output was still not great. I tried sanding the new rotors (to remove the coating they came with, whatever it was) and that made a big difference. Then I found that one of the coil's output was low, so two new coils were sourced.

So now I had good voltage to the plugs but still no go. Long story cut short, I ended up draining the tank and putting in 20L of fresh fuel and she leapt into life.

I had a mix of BP 98 and Gull 98 in the tank. The Gull stuff is an ethanol blend, which I read on the interweb, doesn't have a very long shelf life, so I'm guessing the fuel went bad over the period of time I was trying to sort out the weak spark problem ... that's my theory anyway. I'm just glad to see the end of that saga!

Thanks to all who offered advice.