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andynz3800
Learner
8 Posts
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 Posted - 20 Aug 2011 : 5:30:40 PM
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hi guys,
my 1990 vn v6 manual suddennly started to die at traffic lights.
checked fuel pump for flow - works fine
checked ecu check codes - got 12 (all is fine apparently)
sometimes when switching igniion fuel pump will prime for maybe 5 secs(not enough to get fuel into my empty fuel line at motor.
i've got the fuel intake hose removed off manifold and into a coke bottle so i can check.
today i stripped back the green/white wire at fuel pump relay(this is wire that runs to ecu), wrapped a thin piece of wire around that and with ignition on touched on positive batt terminal and voila the coke bottle starts to fill.
(also proves relay is not faulty)
so the ecu isnt sending signal to fuel pump.
any ideas why this could be, or any conditions that could be causing ecu to not activate pump? keeping in mind engince check codes come up all clear.
will try starting tomorrow with this hotwired method once ive reconnected fuel hose.
i'm at a dilemma as to replace ecu $50 nzd, or just permamemtly hot wire fuel pump and chuck a switch in their, and snip the wire from ecu, would obviously prefer to fix my current equipment rather than blow money( only to maybe have it fail again because unknown condition hasnt been met)on new ecu or madmax hotwire it.
TIA for any help/response
- stuck kiwi
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MrNutter
P Plater
55 Posts
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Posted - 20 Aug 2011 : 9:41:26 PM
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Sounds more like the fuel pump dying to me rather than an ECU problem, though I don't mess with the electronics much so I could be wrong. If you can hear the pump priming though & there's still no fuel at the manifold it sounds like the pump isn't operating at full pressure (bout 30psi in the line I think) & that the engine is starving of fuel. I had this exact same problem about a year ago & replacing the pump was all it took. Remember there should be plenty of pressure in the line, just flowing isn't enough for an injected car.
If there is lots of pressure I'm afraid you will have to wait for one of the others that has more experience with fault codes & electronics to help you. |
VN Sedan Series I.
Stock aside from steering wheel, airhorn & stereo system but is exceptionally tidy. |
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VNSVLE
Forum Moderator
1316 Posts
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Posted - 21 Aug 2011 : 12:27:26 AM
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I would under no circumstance put 12 volts onto the ecu signal wire due to possibility of back feed to the ecu and frying it.
First thing I would be checking is fuel filter.
Now when your car is running this relay is completely bypassed by the oil pressure switch and serves no real purpose other than to supply fuel on start up.
The fuel that should be in that line is enough for the engine to start and build oil pressure allowing the fuel pump to kick back in.
If there is no fuel in that line I believe there is a one way valve built into the pump to hold the fuel upto the rail. This could possibly be stuck also allowing the fuel to return back to tank in which a new pump will need to be purchased.
Check those couple of things buddy and let us know how you go.
Cheers
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What's the difference between understeer and oversteer?
Understeer is when the driver is scared.
Oversteer is when the passenger is scared. |
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VNGRPA
Fully Licenced
426 Posts
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Posted - 21 Aug 2011 : 12:45:15 AM
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yer my guess would be a blocked fuel filter if its not blocked then the pump is no good
as vnsvle said I would under no circumstance put 12 volts onto the ecu signal wire due to possibility of back feed to the ecu and frying it.
at the moment i have been playing around with fuel and the pressure and i have been told that the ecu controls the injectors not the fuel pump if it controlled the fuel pump i would of just reprogramed the ecu to make the fuel pump work faster rather then having to buy a upgraded fuel pump |
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andynz3800
Learner
8 Posts
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Posted - 21 Aug 2011 : 12:17:48 PM
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i would say the reason the line were empty is because when i first had the problem i kept starting and trying to gently nurse it back to life. that would of used up any excess pressure, also had fuel line off at both ends would probably allow it to drain out. that why i think that maybe the few seconds of priming is just not quite enough.(and it seemed that it only primed interfmittently anyway, not everytime i turned key)
Yes fully aware about the wire possibly frying ecu(thats why i used thinnest wire i could find to limit amperage) also wasn't to concerned at the time because i thought the ecu itself was faulty.
and if i replaced ecu it would probably remove my vn top speed 140km governer (it really sucks cause i got opportunity for fun day at ruapuna motorsprt park this coming weekend)
yes i too am aware that the ecu controls injectors (i think sends signals to open for so many milliseconds at a time. i was under the impression that a fuel pump was simply on or off, no variable speed.
havent quite got my head around the oil pressure switch(maybe that my problem)
havent got opportunity to check today as its in storage.
im gonna go ahead and try start the engine with the madmax wire in place(ill just snip it to ecu to prevent damage, can re-connect later) and see how that goes.
when i had the pump out and tested it in a bucket of petrol it did semm too flow quite well, so i'm skeptical that its a fuel pump problem, if the engine starts when i get chance it'll surely put that too rest. |
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VNSVLE
Forum Moderator
1316 Posts
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Posted - 22 Aug 2011 : 05:30:08 AM
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With the oil pressure switch once you have sufficient pressure the contacts close essentially joining the orange and the violet wires to the relay which I am assuming will be power into relay (orange wire which gets power from fuse 21 fuel pump relay and should be 15 amp) and power out of relay (violet wire which goes directly to the fuel pump. Looking at the schematics it changes to a red wire before getting to the pump)
The other wires to your relay which you already know are the green/white (ecu switch wire) and black (which is the earth side of the relay coil)
Your oil pressure switch should have corresponding orange and violet wires.
If you have a multimeter there are a few tests you can do if you do not i would suggest buying yourself one as they are worth their weight in gold when it comes to this sort of thing. It does not have to be expensive, they are all accurate so a $10 special with be more than adequate.
If you can find your diagnostic connector you can do this mostly by yourself if not get a mate to give you a hand. At the diagnostic connector test the violet wire while cranking to determine if it have power once your oil pressure light goes out.
The violet wire is connected directly to the power out of the relay/oil pressure switch.\
If you get power here your pump should be running while you are cranking.
If you do not get power here you will need a mate to give you a hand to test the oil pressure switch is functioning correctly.
To do this remove wires from the switch and set your meter to ohms. Now this switch is a normally open switch meaning that the switch in its normal position when sitting on the bench (or in your case while the engine is not running or being cranked) will have an open contact. So with your meter test between the 2 contacts (making sure that the wires are off) and you should get an open circuit message on your meter which is usually depicted by OL or overload.
As the oil pressure builds up this contact will close meaning when you crank the engine with your meter on the oil pressure switch it should change state or become closed and you should get a reading of approx 0.000 ohms.
Also when testing make sure that your "madmax" wire is removed :D
Do these couple of tests see what you find and let us know
Happy hunting
Cheers |
What's the difference between understeer and oversteer?
Understeer is when the driver is scared.
Oversteer is when the passenger is scared. |
Edited by - VNSVLE on 22 Aug 2011 05:32:15 AM |
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andynz3800
Learner
8 Posts
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Posted - 24 Aug 2011 : 3:58:15 PM
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so, i didnt get chance to check oil switch.
but i think my one must be faulty, i chucked some small nails inside the terminals of oil pressure switch plug and wrapped some wire round them. started straight away (once i recharged battery) so i think i can almost say for certain this is where my problem lay, will be replacing switch next week sometime, so hopefully my car cn opearate the way it was intended without any madmax nonsense. thankyou "vnvsle" you saved me a electrician fee, and brought my car back to life once again. now that its going again i could race it this sunday, but probably not as im quite crook. cheers |
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So my ECU is failing to trigger fuelpump
