Too much pressure
Discussion
Hi all,
As I described in another thread, my 4.3 is slow to start. Especially when warm, takes like 10 seconds sometimes. Plugs are rather black, idle is unsteady.
(yes the fuel pump relay also sometimes does not work , immobiliser I know , have already kindly been given the instructions to bypass that, but first the mechanical issues!)
In the other thread (Rovergauge related) the problem solving is going towards new lambda sensors, and a new 14CUX (even if that one is not necessary).
But as I need to wait for those parts to arrive from the UK, I thought it was good to rule out other problems.
So I took out the fuel pressure gauge, made a connection with some difficulty (no schrader valve to be seen on my 4.3...) and switched the ignition on.
I heard the fuel pump relay, but no pressure on the system.
Started the car, and the pressure built up to:
52 psi!
And it is keeping that even after 10 minutes. No 6 psi drop after switching off the ignition etc.
Fuel pressure regulator at fault? I keep reading about fuel pressure too low, but not about being too high...
See pic:
As I described in another thread, my 4.3 is slow to start. Especially when warm, takes like 10 seconds sometimes. Plugs are rather black, idle is unsteady.
(yes the fuel pump relay also sometimes does not work , immobiliser I know , have already kindly been given the instructions to bypass that, but first the mechanical issues!)
In the other thread (Rovergauge related) the problem solving is going towards new lambda sensors, and a new 14CUX (even if that one is not necessary).
But as I need to wait for those parts to arrive from the UK, I thought it was good to rule out other problems.
So I took out the fuel pressure gauge, made a connection with some difficulty (no schrader valve to be seen on my 4.3...) and switched the ignition on.
I heard the fuel pump relay, but no pressure on the system.
Started the car, and the pressure built up to:
52 psi!
And it is keeping that even after 10 minutes. No 6 psi drop after switching off the ignition etc.
Fuel pressure regulator at fault? I keep reading about fuel pressure too low, but not about being too high...
See pic:
I don't know about the pressure reading but do know that if you heard the fuel pump relay click when turning the key to the ignition position there should have been a priming cycle take place and the pressure should have come right up
If the fuel pump isn't priming you could have delayed starting
If the fuel pump isn't priming you could have delayed starting
As said above ^
but also that pressure is too high .. std regulator is 2.5bar and that's with no vacuum on it so on tickover should be less than that even (2bar?) .. you've got a fault with pressure regulation for sure .. might be regulator itself or another blockage downstream to the tank.
but also that pressure is too high .. std regulator is 2.5bar and that's with no vacuum on it so on tickover should be less than that even (2bar?) .. you've got a fault with pressure regulation for sure .. might be regulator itself or another blockage downstream to the tank.
I did not really hear a click of the relay, but a running sound of the pump for 1-2 seconds. With rovergauge I can test the relay (did that a few days ago) and it makes the same noise of the pump priming.
But despite the priming, no pressure at the beginning of starting the engine). Takes about 2 seconds after turning the ignition to start, before the pressure builds up.
For me it does not seem logical: no pressure at start up after 1 day not running, but now it is keeping its pressure rather good.
After one hour it still is 48 psi...or maybe that is a valve in my pressure tester, I do not know...
If I wanted to check if the return line is blocked, can I use direct air pressure to test if I blow bubbles in the tank? Should it be an open connection to the tank, or is there a valve involved underneath the car and connecting my air gun is useless??
But despite the priming, no pressure at the beginning of starting the engine). Takes about 2 seconds after turning the ignition to start, before the pressure builds up.
For me it does not seem logical: no pressure at start up after 1 day not running, but now it is keeping its pressure rather good.
After one hour it still is 48 psi...or maybe that is a valve in my pressure tester, I do not know...
If I wanted to check if the return line is blocked, can I use direct air pressure to test if I blow bubbles in the tank? Should it be an open connection to the tank, or is there a valve involved underneath the car and connecting my air gun is useless??
Just to be sure, I have a pressure tester that normally need a schrader valve to test.
As I have a pre-serp engine, I do not have that valve to connect to.
So I disconnected the supply hose from the fuel rail, connected the one hose of the tester to the supply hose, and the other hose of the tester to the fuel rail.
In line so to speak.
But is that the way to test it? Normally with a schrader valve, there is no fuel passing through the testing system, and now there is.
Can that screw the test up?
Edit: yes it can.
I have a 70 part testing kit (incredible what you buy for 50 euro these days on Chinese tools), and between those parts there was a special t-piece as well.
I connected it, and now it shows 35 psi at priming.
So it seems ok .
lesson learned: be sure to test the right way...
As I have a pre-serp engine, I do not have that valve to connect to.
So I disconnected the supply hose from the fuel rail, connected the one hose of the tester to the supply hose, and the other hose of the tester to the fuel rail.
In line so to speak.
But is that the way to test it? Normally with a schrader valve, there is no fuel passing through the testing system, and now there is.
Can that screw the test up?
Edit: yes it can.
I have a 70 part testing kit (incredible what you buy for 50 euro these days on Chinese tools), and between those parts there was a special t-piece as well.
I connected it, and now it shows 35 psi at priming.
So it seems ok .
lesson learned: be sure to test the right way...
Edited by RobbeS on Wednesday 6th June 15:21
RobbeS said:
Just to be sure, I have a pressure tester that normally need a schrader valve to test.
As I have a pre-serp engine, I do not have that valve to connect to.
So I disconnected the supply hose from the fuel rail, connected the one hose of the tester to the supply hose, and the other hose of the tester to the fuel rail.
In line so to speak.
But is that the way to test it? Normally with a schrader valve, there is no fuel passing through the testing system, and now there is.
Can that screw the test up?
No, that's not the way to use it, as you are not allowing fuel to flow back to the tank until you press the release button! That 'secondary' pipe is only there to release residual pressure into a pot in a safe way at the end of a test, it is not intended as a flow through!As I have a pre-serp engine, I do not have that valve to connect to.
So I disconnected the supply hose from the fuel rail, connected the one hose of the tester to the supply hose, and the other hose of the tester to the fuel rail.
In line so to speak.
But is that the way to test it? Normally with a schrader valve, there is no fuel passing through the testing system, and now there is.
Can that screw the test up?
What you are measuring is absolute fuel pressure developed by the pump, not the rail pressure taking into account the excess fuel escaping past the regulator to the tank. So all its telling you is that the pump is working...
If you need to measure rail pressure you need a 'T' adapter where the straight ends are barbed pipes that you fit in series in the fuel line to the rail, and the off-shoot contains a Schraeder valve that the gauge connects to. That should come with any half decent kit.
Rule of thumb is that the engine should run regardless of whether the gauge is attached to any adapter or not.
Edited by TwinKam on Wednesday 6th June 15:17
By using the t-piece (which was amongst the 70 parts in the suitcase that came with the tester), I managed to get the right pressures, thanks all for helping me.
I guess I do not need to check the flow rate now I know that it has the right pressure at normal operating circumstances, has a max pressure of 52 psi and keeps good pressure in the system.
Combined with black plugs I am sure that I am not running lean.
I guess I do not need to check the flow rate now I know that it has the right pressure at normal operating circumstances, has a max pressure of 52 psi and keeps good pressure in the system.
Combined with black plugs I am sure that I am not running lean.
Belle427 said:
You need to confirm the fuel pump circuit is functioning properly first as you mention the relay is suspect.
You could be getting a large volt drop at the pump itself.
Check your fuel filter too, dont overlook the basics.
Right you are, the fuel pump relay is suspect, or rather the immobiliser that relays to it.You could be getting a large volt drop at the pump itself.
Check your fuel filter too, dont overlook the basics.
But that is on my To Do list once I have cured the rich running and hard starting.
With the pressure kit correctly fitted, wait until the pressure drops right down or carefully release it into a container. Once the gauge is reading less than 10 psi now watch the gauge when you switch the ignition on. The pump should prime and run for 2 seconds. The gauge should immediately rise to at least 30 psi.
If it does then the fuel delivery system and pressure would appear okay.
Now turn the key to start and the pressure should be maintained throughout.
If it does not rise then either the relay is suspect (or immobilser as you already know), the fuel filter is blocked, the pump itself is not running or a bad connection behind the B pillar.
If it does then the fuel delivery system and pressure would appear okay.
Now turn the key to start and the pressure should be maintained throughout.
If it does not rise then either the relay is suspect (or immobilser as you already know), the fuel filter is blocked, the pump itself is not running or a bad connection behind the B pillar.
Just re read the two threads- you are jumping all over the place trying to fault find. Your print out shows 0% long term trim to start with- either you have unplugged the ECU and the trim has not reset, or your car is perfect! Whats the short trim doing? This is the important one to start with, as it sets the long term trim but this takes several minutes on a hot engine at idle only. Do you not have the RoverGauge instructions?
Edited by blitzracing on Thursday 7th June 16:25
The short trim is 100% (green to the right) And does not vary to the left, only sometimes a little less than 100% to the right, like 75%, before it is 100% again. But never less than 50%. So that can't be good.
I have read the whole RoverGauge description, which also points towards misbehaving lambda's.
As the problem also can be a lot of other things, and parts (Lambda's) take time to arrive due to shipping and the ebay global shipping detour program, in the meantime I am checking all other things that can cause hard starting and black plugs.
Just sit and wait for 10 days and do nothing is not my style.
At least my throttle pot is adjusted at .33v now, instead of the Original 12% which was like 0.5v or so. So that progress has been made, and due to that the base idle has been set as it should be.
I hoped to find a problem with the fuel pressure stabiliser, but that part of the equasion is ok. And my fault measuring it wrongly led to this thread, which I had not started if I had measured the right way from the start. My apologies for that.
I appreciate all the answers to my sometimes amateur questions!
My car has obviously been neglected by previous owners, and I am trying to improve it bit by bit.
As they are pretty rare in The Netherlands, there is not much to choose from, so I ended up with a less than perfect car. I am sure with all the knowledge over here I will improve it to some sort of reliability.
As long as it does not develop new problems, like an immobiliser that does not react anymore to the fob, like today. Only after disconnecting the battery twice it started to react again.
I already have the schedule for how to bypass that, so I hope to do that very soon, otherwise the engine part will have to wait some more.
I have read the whole RoverGauge description, which also points towards misbehaving lambda's.
As the problem also can be a lot of other things, and parts (Lambda's) take time to arrive due to shipping and the ebay global shipping detour program, in the meantime I am checking all other things that can cause hard starting and black plugs.
Just sit and wait for 10 days and do nothing is not my style.
At least my throttle pot is adjusted at .33v now, instead of the Original 12% which was like 0.5v or so. So that progress has been made, and due to that the base idle has been set as it should be.
I hoped to find a problem with the fuel pressure stabiliser, but that part of the equasion is ok. And my fault measuring it wrongly led to this thread, which I had not started if I had measured the right way from the start. My apologies for that.
I appreciate all the answers to my sometimes amateur questions!
My car has obviously been neglected by previous owners, and I am trying to improve it bit by bit.
As they are pretty rare in The Netherlands, there is not much to choose from, so I ended up with a less than perfect car. I am sure with all the knowledge over here I will improve it to some sort of reliability.
As long as it does not develop new problems, like an immobiliser that does not react anymore to the fob, like today. Only after disconnecting the battery twice it started to react again.
I already have the schedule for how to bypass that, so I hope to do that very soon, otherwise the engine part will have to wait some more.
Edited by RobbeS on Thursday 7th June 20:27
OK- so what should happen is the short therm trim is cycling on one side only, and the long term trim should then start to move slowly to increase / decrease the fuel until the short term starts to cycle around a mid point. The cycling to one side is not a problem if the long term trim has not yet stablised, and yours is showing at 0 in the screen shot, so it looks like you have un plugged the ECU or battery at some point and its lost the long term trim. You need to get the engine hot, and leave it to idle for at least 2.5 minutes and watch the long term trim move, and once its stopped moving, the short term trim should cycle around the mid point if alls well. It is possible if you have a misfire or AFM fault, that the long term trim will reach 100% and the short term still cycles on one side, as the fault condition exceeds the ECUS ability to fix it with mixture control. In term of Lambda failure, the fact that the short term trim is moving at all means they are working, but as they age the response can become slow, and the fueling accuracy suffers.
Thanks for your explanation of the short/long term trim. Clear that they do not behave as they should.
Today the new lambda's arrived, so excellent time to reset the ECU again and fire her up with the new parts.
But even after 10 minutes, the long term is still in the middle, where the short term is 100%.
Only when I rev the hot engine a bit, I get readings of 70-75% before it quickly turns back to 100.
Long term does not move at all, only a small green line at 50%.
The new lambda's (Original NTK) do not show an expected patern, but only show a rich mixture and no real long term trim, so what can cause this?
Looks to me like the ECU is not using the lambda signal to adjust the mixture, and the lambda's never get below 50%.
Can it be leaking injectors then? They are the green band Lucas ones.
Or a ECU that is not working well? Or the EPROM in it?
(I still have to check the plugs if the are 6 or 7 serie.)
(I will post this in my other thread as well, best to discuss it there further (more on topic)
Today the new lambda's arrived, so excellent time to reset the ECU again and fire her up with the new parts.
But even after 10 minutes, the long term is still in the middle, where the short term is 100%.
Only when I rev the hot engine a bit, I get readings of 70-75% before it quickly turns back to 100.
Long term does not move at all, only a small green line at 50%.
The new lambda's (Original NTK) do not show an expected patern, but only show a rich mixture and no real long term trim, so what can cause this?
Looks to me like the ECU is not using the lambda signal to adjust the mixture, and the lambda's never get below 50%.
Can it be leaking injectors then? They are the green band Lucas ones.
Or a ECU that is not working well? Or the EPROM in it?
(I still have to check the plugs if the are 6 or 7 serie.)
(I will post this in my other thread as well, best to discuss it there further (more on topic)
We need to be careful here- your code is already so old that its not reading the target idle, so its possible the long term trim is not in the same memory location RoverGauge was designed to read and thats why you are not seeing it. The idle period for the long term trim has to be hot (low 90'c at least) and you must not rev the engine at all. Adding new probes has just compounded your issues as at least the old ones cycled so where working, I have no idea what the new ones are doing. At its most basic a 0 volts output on the black wire means very lean mixture or no heater supply, or 1.2 or above means a very rich mixture. The ECU should be going into error status and throwing a code if the Lambdas are faulty after some minutes.
To make sure things are clear:
Lean mixture or no lambda voltage- ECU adds fuel (removes trim)
Rich mixture- lambda over 1.2 volts ECU removes fuel (adds trim)
Have a read here: http://www.g33.co.uk/img/fuel/14cux-fault-finding....
Can we keep to one post, so like fault finding is logical and we can see the history easily?
To make sure things are clear:
Lean mixture or no lambda voltage- ECU adds fuel (removes trim)
Rich mixture- lambda over 1.2 volts ECU removes fuel (adds trim)
Have a read here: http://www.g33.co.uk/img/fuel/14cux-fault-finding....
Can we keep to one post, so like fault finding is logical and we can see the history easily?
Edited by blitzracing on Friday 8th June 21:01
Message Board | Chimaera | Top of Page | What's New | My Stuff