Not as simple as it may sound! Had a serious head gasket failure. Replaced the gasket and checked and rechecked the timing! Changed oil and filter Engine started first turn of the key. Found considerable hesitancy when throttle floored. Did 50 miles like this and then started to think what trouble could be.
Seemed like bad plugs or leads and replaced these, slight improvement. Left the car for a few days and tried again, now MUCH better! In fact almost right! Thought that I just might have a slight inlet manifold leak and retorqued the nuts. The awkward lower ones were a little loose.
Tried starting and no joy. Checked fuel and there was no pressure at the Schraeder valve. Tried again. Pump worked for a second. Enough for the engine to catch but only splutter and then it cut. From then on no fuel pump at all.
Checked the fuel pump relay off car. That worked. Checked fuel pump with a supply from a power supply unit. Pump worked fine in tank! Plenty of fuel too. The engine has been replaced at some time, it is a slightly later model than expected. It is the 8 valve SOHC with an ignition block on the end of the cam. The supply to the fuel pump relay coil is from the ignition switched 12 volt line and is sunk by terminal B6 of the ECU. The 12 v on the switched terminals of the relay is from the permanent 12 V supply. (and yes I do have a good earth on the pump connection!)
Is the fault likely to be on the ECU (terminal B6 not sinking the coil current?) or should I be looking at some other area that I may have missed with my usual tunnel vision? Any suggestions much appreciated as I am running out of ideas!
Thanks in advance
Tonsberg.
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Just to add to the possible problems! The cr is fitted with a Turret Securities immobiliser. Seems to be in the place normally reserved tfor the door central locking unit! There are 3 fuses associated with this unit and I would hazard a guess that it switches the Fuel pump and the the starter motor relays (in line with the normal ECU O/Ps. Suspect the 3rd channel interrupts the ignition. The unit appears to be functioning correctly, but have never heard of this aftermarket immobiliser! It also has a piezo sounder, but this has never worked!
HELP! Don't know where to start looking now. Any suggestions most welcome!
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Just checked for spark with a Gunson strobe. HT is present, so that is another possibility out of the window!
I presume that it is the ECU that turns the Fuel pump on and off? If the fuel pump switches itself on and off by means of some sort of preset pressure switch, then concievably I could unhook the earth end of the fuel pump relay coil, from ECU B6 terminal and simply earth that wire. At least the fuel pump would work and give me fuel at the fuel injectors! Don't know what regulates the fuel pump, so I am a bit bothered about leaving B6 terminal unhooked on the ECU! Thoughts?
Tonsberg.
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I don't know anything about your imobiliser.
However, if you are getting HT sparks, then, the ECU must be reading the signal from the crank sensor, and working on a fundamental level.
What is the voltage at B6 with the ignition on?
What is the voltage at B6 when cranking?
Is the cable from the fuel pump relay to B6 continuous, or, does the imobiliser interrupt this wire?
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Hello,
Just picked up your response.
Voltage at B6 with the ignition on is 12v. ie B6 is not going low as it should do to switch the fuel pump relay coil on.
I have not measured the voltage when cranking. The fuel pump does not turn on during cranking, so I assume that the voltage at B6 must still be 12 volts (or whatever the line voltage drops to during cranking).
I have sussed out the immobiliser and it doesn't switch the fuel relay coil. It in fact interrupts the switched feed to the pump. I have checked out that it does make this line when the immobiliser is switched out. Thus the immobiliser is working just as it should!
I don't have much experience with fuel injection systems as I am a carb man at heart! I am certain that if I simply disconnect the line to B6 on the ECU and earth it, then the fuel pump will operate.
I don't know if letting B6 terminal float will damage the ECU (can't believe it would, but it may confuse the ECU!)
The second thing I am ignorant about is how the fuel pump maintains pressure in the fuel line. Is the regulating pressure switch integral with the pump, or is there a sensor in the fuel line which communicates with the ECU and the ECU does the pressure regulation by switching the pump on and off? Looking at the circuit diagram (Haynes Manual), I can't see a separate fuel pressure sensor connected to the ECU, so I am assuming that the fuel pump does the regulation by itself. Its easy enough to check, but its getting dark right now and I have had a glass or two of wine, not the best state to do more checks tonight! Will do in the morning!
Thanks for your help, I have got to the state of thinking of scrapping the beast, but it is in excellent condition after a recent thorough overhaul, lots of cash invested and its my son's car!
Tonsberg.
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Just realised that I am missing the point by trying to bypass the ECU switching of the fuel pump. I should be asking why B6 is not going low to switch on the pump.
Is there some input that the ECU is missing that will cause it not to switch on the pump? Find it difficult to believe that this may be the case, because if there is some fault or missing input, I would expect the ECU would shut down the ignition circuit as well as the fuel pump and it certainly isn't shuting down the ignition.
If it is a faulty ECU then are there some relatively cheap sources of replacement ECUs? Should think that a Vauxhall item would be an arm and a leg! Taking a look at mine with an electronics eye, says that to build one should cost around 30 to 40 pounds in volume. Bet the Vauxhall price is 10 or 15 times that amount, if they can supply one! They know when they have a captive market!
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>>so I assume
Let me stop you right there!
To solve the problem, you must not assume. You'll end up being misled.
Find out what happens at B6 before going further.
>>I am certain that if I simply disconnect the line to B6 on the ECU and earth it, then the fuel pump will operate.
Again, it's best to check, to rule out simple problems elsewhere in the circuit.
You'll never damage the ECU by allowing a terminal like this to float.
There isn't a pressure switch at all. The fuel pump runs all the time, and supplies all the fuel it can. On the fuel rail (or in the throttle body if single point) there's a pressure regulating valve which simply sends any surplus back to the tank. The pressure regulator usually has a vacuum connection because it strives to maintain a constant pressure difference between the fuel rail and the intake manifoild - in this way, the fuel delivered is simply proportional to the time that the injector is switched on for.
Keep going - if you persevere, you will find the fault.
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Does the engine management light work? Does it flash while you're cranking?
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Thanks!
You are quite correct! I should not assume any result. I am a physicist by profession, so I should not fall into that trap!
Will check B6 voltage on cranking and will observe the management light while doing same. If it flashes, then I can probably interrogate the ECU using the paperclip method.
Will sober up and check tomorrow morning, will post as soon as I get the results.
Thanks again,
Tonsberg
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Well you are not going to believe this, but here goes. Checked the voltage at B6 with the ignition on and the reading was 12.4 volts. Got my wife to switch off immobiliser and then crank the engine. Reading was around 3.8 volts on the DVM. Obviously there was no engine start. Tried again with same results. Just about to tear my hair out, but decided on one last try. Suddenly the DVM reading went to around minus 0.5 volt plus or minus 0.2 volt
varying and then I realised that the engine had started!
Idling was not perfect, but not really bad. As the engine warmed up, the idling became worse and then the engine management light came on. As the thermostat opened, the management light went out and the idling got better, as the engine continued to warm up, the idling became worse again. Tried restarting several times and it fired up every time. The only thing that I did yesterday morning was to charge the battery in situ and removed the live terminal on the battery. Just maybe this was the equivalent of switching off a glitched computer and restarting it, who knows?
I am now back to square one as the idling problem was there before the problem with the fuel pump started. Obviously I don't know about any hesitation when the throttle is floored while driving. The car isn't fit to drive with wiring looms all over the place and even the steering wheel off to get at the immobiliser touch pad when checking out the immobiliser circuit.
I suppose I had better box everthing up and get a test drive. Obviously a bit worried that as I have not done anything to cure the problem it may reoccur, unless removing power from the ECU did something ?
If the problem doesn't reoccur then I still need to sort out the slight hesitation and the erratic tickover, sounds as if something is wrong as the engine mangement did come on, albeit it went off again! Looks as if I need to look up the bumpf on reading the ECU with the paperclip method.
I just hate faults that disappear like this! At first I thought that it may have been the impedance of the DVM between deck and the terminal B6 but subsequent starts were without the DVM in place.
It looks as though I may have a problem with the head temperature sensor, this would explain the tickover getting better when the thermostat opened and the engine management light went out. But I am NOT going to assume anything from now on!
Any thoughts would be welcome!
Thanks,
Tonsberg.
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Here goes again, I tried the paperclip method of reading out the faults and it didn't work, zilch! Left the engine running and the temp gauge was on zero. If I very gently pressed the accelerator pedal, there came a point where the engine would blip repeatatively. This was wth constant pressure on the pedal. As the engine warmed up the engine management light came on. The blipping phenomena disappeared too. The temp gauge reached the half way mark and the cooling fan came on, at virtually this time the tacometer started to work, it had previously been dead, must be a coincidence! The engine temp dropped a little and the fan cut out. Engine management light still on. At this stage, I turned the engine off and then restarted it. The engine management light went out and stayed out. Did another abortive attempt to read the error code and no luck whatsoever!
With the bonnet down, the tickover seemed better, probably because I couldn't hear it so well with the bonnet down!
Obviously some intermittent fault is still there. I think that some sensor was probably damaged during the head gasket failure or during the strip down or rebuild phase. Or maybe there is a leak somewhere on the induction side. There certainly seems to be a slight exhaust blow somewhere, although I can't trace where, its probably on the exhaust manifold to downpipe, but just can't locate it.
Have read somewhere that one of the sensors on the inlet side can be damaged(?) by excess oil coming from the engine breather pipe into the inlet manifold. I certainly had a huge amount of oil coming from the breather into the inlet tract. The air filter and filter box had oil in them! I will take a closer look and see what might have been affected and clean out any potential trouble spots.
Wonder why the paperclip method of interrogation didn't work? I certainly located and shorted out teminal A and B on the diagnostic plug. Yet another mystery!
Tonsberg.
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One thing to check is that every connector has been plugged back in to the correct socket - as the connectors are all the same type, it's sometimes possible to plug them back together incorrectly.
The other obvious thing to check is that all the earth wires were correctly refitted to the head upon reassembly - on many Vauxhalls, there are a cluster of wires which all go to an earth point on the head.
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Tried another run, the engine started and warmed up nicely. No sign of an engine management light. No sign of the blipping phenomena at fixed low accelerator. I had cleaned the gunge from what is called the idle speed control motor. The tickover was 800rpm, blipping to 1000rpm about every 12 seconds, well I can live with that. I tried disconnecting the plug from the idle speed control motor, expecting to see the engine management light come on. IT DIDN'T! So much for ECU sensor diagnostics. Disconnecting the plug did not seem to make any difference to the idle. Maybe this is faulty?
Tonsberg.
P.S. I will put everything back together and give it a road test.
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Yes checked all the earth wires, there are a lot of them! Will recheck the plugs in case I have got any swopped over.
Thanks,
Tonsberg.
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