Car cranks but doesn't start
Discussion
GreenV8S said:
Disconnecting the MAF would exactly explain the error code.
The noid lamp would light while the injector is driven electrically. At low low these pulses can be too short to see with a meter. The noid lamp will produce a flash which is easy to see as long as you are not somewhere bright. Alternatively you can use an oscilloscope.
If the injector is being driven electrically you have proved the electrics are OK and the ECU is trying to run the engine. That means you're looking for a mechanical problem with the injector, or it isn't getting fuel pressure.
Brilliant thanks mate!The noid lamp would light while the injector is driven electrically. At low low these pulses can be too short to see with a meter. The noid lamp will produce a flash which is easy to see as long as you are not somewhere bright. Alternatively you can use an oscilloscope.
If the injector is being driven electrically you have proved the electrics are OK and the ECU is trying to run the engine. That means you're looking for a mechanical problem with the injector, or it isn't getting fuel pressure.
We didn't disconnect the MAF just pulled the intake pipe off the manifold but I imagine even that would be enough to throw a code (it has so it must've been enough)
Might have a look at this tonight if I've got time if not I'll update whenever I get round to it
I just really hope the wiring's all intact/ working not warm to the idea of fixing wiring issues
Edited by jrallye on Wednesday 8th May 14:55
Back again with another update!
Not really got any further although I have made a noid light from a brake light bulb, 2 pieces of wires and 2 hair clips
The injectors are getting a pulse so my guess is not enough fuel pressure or clogged injectors although we took one out and it looked like a clean injector
But before we delve too far into the injectors I bought a second subaru that runs (not a twin turbo) for parts and chucked the pump from that in the twin turbo, the pumps are a vastly different size but I'm hoping the pump from a 2.5L will at least get the 2L TT idling so we'll end up with a couple outcomes
And hopefully after that we'll be good and I can start doing some more exciting stuff to the car
Not really got any further although I have made a noid light from a brake light bulb, 2 pieces of wires and 2 hair clips
The injectors are getting a pulse so my guess is not enough fuel pressure or clogged injectors although we took one out and it looked like a clean injector
But before we delve too far into the injectors I bought a second subaru that runs (not a twin turbo) for parts and chucked the pump from that in the twin turbo, the pumps are a vastly different size but I'm hoping the pump from a 2.5L will at least get the 2L TT idling so we'll end up with a couple outcomes
And hopefully after that we'll be good and I can start doing some more exciting stuff to the car
GreenV8S said:
I wouldn't recommend that - the brake light bulb will be drawing too much current and will also be very slow to respond. Do something similar with a 12V LED and you'll be fine.
It works fine once the bulb warms up after a full cycle or two and you could clearly see the pulseIs there any worry with it drawing too much power or just that it won't work as well as an LED?
jrallye said:
GreenV8S said:
I wouldn't recommend that - the brake light bulb will be drawing too much current and will also be very slow to respond. Do something similar with a 12V LED and you'll be fine.
It works fine once the bulb warms up after a full cycle or two and you could clearly see the pulseIs there any worry with it drawing too much power or just that it won't work as well as an LED?
The brake light bulb (21 Watt) will draw close to 1.8 Amps
You need to know the injector resistance before using big bulbs to test
See this
Taken from here (a good read) http://fuelinjectorclinic.com/faqs/
jrallye,
Your determined and logical diagnostic process is admirable! I take back any implied previous criticism!
As you already know, if you want to see injector pulses, a multimeter won't do it. You don't say how much you paid for this clunker, but you might consider buying a "Picoscope". This clever bit of kit will turn your laptop into an oscilloscope, well able to display signals into the microsecond range. The simplest in the 2000 range costs £120 and would do this job, a full Picoscope Automotive 2-channel £700, or a Hantek 6022 equivalent (Chinese knockoff) is half that price.
JOhn
PS Oh! You've made a signal test lamp! Well done, but see comments above. These scopes don't have that problem. J.
Your determined and logical diagnostic process is admirable! I take back any implied previous criticism!
As you already know, if you want to see injector pulses, a multimeter won't do it. You don't say how much you paid for this clunker, but you might consider buying a "Picoscope". This clever bit of kit will turn your laptop into an oscilloscope, well able to display signals into the microsecond range. The simplest in the 2000 range costs £120 and would do this job, a full Picoscope Automotive 2-channel £700, or a Hantek 6022 equivalent (Chinese knockoff) is half that price.
JOhn
PS Oh! You've made a signal test lamp! Well done, but see comments above. These scopes don't have that problem. J.
Penelope Stopit said:
GreenV8S make a good point here
The brake light bulb (21 Watt) will draw close to 1.8 Amps
You need to know the injector resistance before using big bulbs to test
See this
Taken from here (a good read) http://fuelinjectorclinic.com/faqs/
I'll have a read through this and see if i can get my head round it allThe brake light bulb (21 Watt) will draw close to 1.8 Amps
You need to know the injector resistance before using big bulbs to test
See this
Taken from here (a good read) http://fuelinjectorclinic.com/faqs/
So are we saying that the brake light bulb even though it pulses on and off might not mean that the injector wiring isn't faulty?
tapkaJohnD said:
jrallye,
Your determined and logical diagnostic process is admirable! I take back any implied previous criticism!
As you already know, if you want to see injector pulses, a multimeter won't do it. You don't say how much you paid for this clunker, but you might consider buying a "Picoscope". This clever bit of kit will turn your laptop into an oscilloscope, well able to display signals into the microsecond range. The simplest in the 2000 range costs £120 and would do this job, a full Picoscope Automotive 2-channel £700, or a Hantek 6022 equivalent (Chinese knockoff) is half that price.
JOhn
PS Oh! You've made a signal test lamp! Well done, but see comments above. These scopes don't have that problem. J.
At the start I think the comment was warranted I had missed some pretty big steps out, I'm starting to map out my problems and try and figure stuff out in a way that makes sense on paper first before just going for it!Your determined and logical diagnostic process is admirable! I take back any implied previous criticism!
As you already know, if you want to see injector pulses, a multimeter won't do it. You don't say how much you paid for this clunker, but you might consider buying a "Picoscope". This clever bit of kit will turn your laptop into an oscilloscope, well able to display signals into the microsecond range. The simplest in the 2000 range costs £120 and would do this job, a full Picoscope Automotive 2-channel £700, or a Hantek 6022 equivalent (Chinese knockoff) is half that price.
JOhn
PS Oh! You've made a signal test lamp! Well done, but see comments above. These scopes don't have that problem. J.
I'm trying to get this started on a low budget and the amount of times I plan on starting a non runner are fairly low so I'll see if I can borrow a better tool from my dad or brother
jrallye said:
Penelope Stopit said:
GreenV8S make a good point here
The brake light bulb (21 Watt) will draw close to 1.8 Amps
You need to know the injector resistance before using big bulbs to test
See this
Taken from here (a good read) http://fuelinjectorclinic.com/faqs/
I'll have a read through this and see if i can get my head round it allThe brake light bulb (21 Watt) will draw close to 1.8 Amps
You need to know the injector resistance before using big bulbs to test
See this
Taken from here (a good read) http://fuelinjectorclinic.com/faqs/
So are we saying that the brake light bulb even though it pulses on and off might not mean that the injector wiring isn't faulty?
The bulb pulsing suggests that the injector circuit it is connected to is working correctly
If they're being driven electrically, they should be opening. That makes quite a loud tap which you can easily hear if the engine is stopped, but is quite hard to pick out from a running engine unless you are familiar with the sound.
If you are still feeling brave enough to experiment, you could try unplugging an injector from the loom and briefly touching a fused 12V supply across the injector. If the injector is mechanically working you will hear a loud tap as it opens when you apply power and closes when you remove it.
The last test needs a fuel pressure gauge to measure the fuel rail pressure. It should build up when the pump runs and more or less hold steady when the pump stops. If you briefly operate an injector now, the pressure should drop quite sharply. If so, it proves the injector is both opening and flowing fuel.
If you are still feeling brave enough to experiment, you could try unplugging an injector from the loom and briefly touching a fused 12V supply across the injector. If the injector is mechanically working you will hear a loud tap as it opens when you apply power and closes when you remove it.
The last test needs a fuel pressure gauge to measure the fuel rail pressure. It should build up when the pump runs and more or less hold steady when the pump stops. If you briefly operate an injector now, the pressure should drop quite sharply. If so, it proves the injector is both opening and flowing fuel.
GreenV8S said:
If they're being driven electrically, they should be opening. That makes quite a loud tap which you can easily hear if the engine is stopped, but is quite hard to pick out from a running engine unless you are familiar with the sound.
If you are still feeling brave enough to experiment, you could try unplugging an injector from the loom and briefly touching a fused 12V supply across the injector. If the injector is mechanically working you will hear a loud tap as it opens when you apply power and closes when you remove it.
The last test needs a fuel pressure gauge to measure the fuel rail pressure. It should build up when the pump runs and more or less hold steady when the pump stops. If you briefly operate an injector now, the pressure should drop quite sharply. If so, it proves the injector is both opening and flowing fuel.
Brilliant mate, thanks again!If you are still feeling brave enough to experiment, you could try unplugging an injector from the loom and briefly touching a fused 12V supply across the injector. If the injector is mechanically working you will hear a loud tap as it opens when you apply power and closes when you remove it.
The last test needs a fuel pressure gauge to measure the fuel rail pressure. It should build up when the pump runs and more or less hold steady when the pump stops. If you briefly operate an injector now, the pressure should drop quite sharply. If so, it proves the injector is both opening and flowing fuel.
I'll try and get the injector to open myself and listen for a tap
I should probably buy a pressure tester regardless as they're not crazy expensive and it'll come in handy if any of my other cars start running poorly I can rule out the pump right away
Have been messing with this a little more and we've got somewhere but I don't know how or why
I'm not sure if I said before but I put the pump and filter from a working 2.5 na car onto the twin turbo just after we burnt out the starter motor
I replaced the started motor and noticed there was a hose clamp missing from the smaller turbo when I went to re install the top mount inter cooler, so found one I had lying around and chucked it on and put it all back together and tried to start the car to make sure the starter was working and now the car coughs and splutters like it wants to start
I've opened 3 of the 4 injectors with a 9V battery and they all open nice audible click (can't get to one of them without moving ac pipes so thought i'd leave it for now)
I've retested the injectors with a lower watt bulb I had lying around still not an LED but it lights up much quicker and again 3 of the 4 pulse correctly (I haven't tested the forth again but I read these injectors shares a ground so if 3 of the 4 are getting a signal they all should be unless the wiring is physically broken)
The tank is pretty grim inside lots of rust and gunk so will be replacing it with the tank from the other Subaru I have I drained the tank completely and put it some fresh fuel 95ron not sure if they run very well on 95 or at all as they were designed to run on 97-99 over in japan could be wrong there again just what I've read/ been told
I've tried the old original pump and the second hand 2.5 na pump and it coughs in the same way
If I unplug the pump it goes back to cranking with no coughs or splutters so fuel is there but maybe not enough to start the car
I started it with cold start again and stop spraying once the car gets going and nothing so I'm leaning towards the fuel pump at this point
Here's a video of the old girl trying her best Legacy Twin Turbo No Start
I personally think I just need to grab a new pump at this point and stop messing around with second hand units
I know the injectors are working to some extent they get the correct signal and the open and close as they should
The car runs on cold start so it has spark and all that but it sound to me like it's not getting enough fuel?
Any more ideas or anyone who can hear why it's not starting will be greatly appreciated, we're close now!
I'm not sure if I said before but I put the pump and filter from a working 2.5 na car onto the twin turbo just after we burnt out the starter motor
I replaced the started motor and noticed there was a hose clamp missing from the smaller turbo when I went to re install the top mount inter cooler, so found one I had lying around and chucked it on and put it all back together and tried to start the car to make sure the starter was working and now the car coughs and splutters like it wants to start
I've opened 3 of the 4 injectors with a 9V battery and they all open nice audible click (can't get to one of them without moving ac pipes so thought i'd leave it for now)
I've retested the injectors with a lower watt bulb I had lying around still not an LED but it lights up much quicker and again 3 of the 4 pulse correctly (I haven't tested the forth again but I read these injectors shares a ground so if 3 of the 4 are getting a signal they all should be unless the wiring is physically broken)
The tank is pretty grim inside lots of rust and gunk so will be replacing it with the tank from the other Subaru I have I drained the tank completely and put it some fresh fuel 95ron not sure if they run very well on 95 or at all as they were designed to run on 97-99 over in japan could be wrong there again just what I've read/ been told
I've tried the old original pump and the second hand 2.5 na pump and it coughs in the same way
If I unplug the pump it goes back to cranking with no coughs or splutters so fuel is there but maybe not enough to start the car
I started it with cold start again and stop spraying once the car gets going and nothing so I'm leaning towards the fuel pump at this point
Here's a video of the old girl trying her best Legacy Twin Turbo No Start
I personally think I just need to grab a new pump at this point and stop messing around with second hand units
I know the injectors are working to some extent they get the correct signal and the open and close as they should
The car runs on cold start so it has spark and all that but it sound to me like it's not getting enough fuel?
Any more ideas or anyone who can hear why it's not starting will be greatly appreciated, we're close now!
Everything points to a lack of fuel pressure. It would be sensible to get a fuel pressure gauge so you can confirm that.
It could be caused by either the fuel supply (pump, filter etc) or the pressure regulator.
Newer engines tend to use a dead ended fuel rail where the pressure is managed by the pump, but older ones typically used a pressure regulator at the end of the fuel rail which blew off at the required pressure and returned excess fuel to the tank.
If yours has a regulator on the return side of the fuel rail, you can lose all fuel pressure if it fails to close/seal. As a quick test you can restrict the return fuel hose while the engine is firing and see whether it leaps into life. Note that if the pump is working properly and you block off the return completely you will get massively excessive fuel pressure which will cause over-fuelling and may even burst hosts. You're looking for a restriction, not blocking it off completely. If restricting the return makes no difference, this points to a problem with the pump.
It could be caused by either the fuel supply (pump, filter etc) or the pressure regulator.
Newer engines tend to use a dead ended fuel rail where the pressure is managed by the pump, but older ones typically used a pressure regulator at the end of the fuel rail which blew off at the required pressure and returned excess fuel to the tank.
If yours has a regulator on the return side of the fuel rail, you can lose all fuel pressure if it fails to close/seal. As a quick test you can restrict the return fuel hose while the engine is firing and see whether it leaps into life. Note that if the pump is working properly and you block off the return completely you will get massively excessive fuel pressure which will cause over-fuelling and may even burst hosts. You're looking for a restriction, not blocking it off completely. If restricting the return makes no difference, this points to a problem with the pump.
I've gone ahead and ordered a pressure tester!
It arrives Wednesday so I'll update then
I didn't really want to buy one but I'm sure it'll come in handy given the average age of my cars
I'll test the fuel pressure first and see what's going on there, and if it's low I'll look at the pressure regulator before going straight for a new pump
Thanks for all the help again I don't think I'd have got this far doing research alone!
It arrives Wednesday so I'll update then
I didn't really want to buy one but I'm sure it'll come in handy given the average age of my cars
I'll test the fuel pressure first and see what's going on there, and if it's low I'll look at the pressure regulator before going straight for a new pump
Thanks for all the help again I don't think I'd have got this far doing research alone!
Almost a month late but the pressure tester came and the fittings leak so I bodged it together with some silicone and got a reading of 43-45psi when primed so there's pressure there
I still need to test the pressure when cranking but as a start this isn't horrendous there's pressure it'll very slowly loose pressure when the pump switches itself off after priming but that could always be the gauge leaking and not the fuel system
Would it be worth trying to force the fuel pump always on and see if it'll start that way? Obviously not what I plan on doing in the long run but would definitely rule out the fuel issue for testing?
I still need to test the pressure when cranking but as a start this isn't horrendous there's pressure it'll very slowly loose pressure when the pump switches itself off after priming but that could always be the gauge leaking and not the fuel system
Would it be worth trying to force the fuel pump always on and see if it'll start that way? Obviously not what I plan on doing in the long run but would definitely rule out the fuel issue for testing?
That's encouraging and shows that the fuel pressure is within a sensible range. I don't know what the fuel pressure is supposed to be on that car but what you're seeing looks reasonable to me.
If you're up for a little more testing, I suggest you run the pump briefly to build up the fuel pressure, then stick 12V across one of the injectors. You should hear it click open. When the injector is open the fuel pressure should drop much quicker. If you see that, it proves that the injector is flowing fuel.
Seems unlikely that all injectors have failed at the same time but for the sake of a few minutes it would be good to prove that at least one is working.
If you're up for a little more testing, I suggest you run the pump briefly to build up the fuel pressure, then stick 12V across one of the injectors. You should hear it click open. When the injector is open the fuel pressure should drop much quicker. If you see that, it proves that the injector is flowing fuel.
Seems unlikely that all injectors have failed at the same time but for the sake of a few minutes it would be good to prove that at least one is working.
Gassing Station | Home Mechanics | Top of Page | What's New | My Stuff