Fuelpump/fuel filter, or something else

[kasin]

Hi 

My Caterham (K series - 1.8 - running Emerald and ITBs +++) has suddenly stopped a couple times the last two days. Yesterday the car suddenly stopped, just like it ran out of fuel. I got it running a couple of meters again before it stopped. I got my wife to help me get more fuel, as I thought I had run out - even though the needle was between red and 1/4. After getting the extra fuel I drove straight to the petrol station and brimmed it. I had some small issues with stuttering at after this - in the first couple of km after brimming it - but everything cleared up. 

Today the car was perfect for a long trip, we did over 400 km, but in the last couple of km on the way home the car stopped again. After a stop, where a car came to tow, I got it going again. After 3 more km we were almost home, and it stopped. This time we didnt try anything, just hooked it up, and towed it back home. At the time of the stop today the tank was almost full, we had stopped for fuel 40 km before this. 

When the car stopped it would sputter when I tried to start it, but only did so for 1 - 2 seconds. I have a pressure gauge at the fuel line, and it shows a pressure of around 2 - 3 bars, just after turning the key over - so the pump tries to prime the system. The lines also get noticably harder. However the pressure really quickly drops off during cranking. 

This evening I tried starting the car, and it fired right up. The symptoms makes me think that it might be a weak fuel pump, or a dirty fuel filter. Will these thing lead to this behavior? 

Is it difficult to pull the pump and filter? Will I have to drain the tank? 

Kristoffer

 

[7 wonders of the world]

Does the pump still run when it stops - ie can you hear it prime as you turn the ignition on..?

 

[kasin]

Im not totally sure, I couldnt hear it clearly, but I was out just beside a road with traffic. In the garage this evening it was clearly priming. 

[7 wonders of the world]

Does the LED on the emerald turn green during cranking...? or stay red...?

These intermittent faults are a bugger, much better it stops and wont restart........

[kasin]

The emerald was green the whole time as far as I could see. 

[EEK]

Almost identical problem, happened some time ago but coincidentally yesterday again and the solution for me is to make/break this connector, but yesterday needed a bit more cleaning for the problem connection - see 2nd photo, this is the fuel pump feed. Really need to get round to moving it out of this connector and into something that can take the current better. 

A quick check could save a lot of faffing.

CONNECTOR

 

PROBLEM

[revilla]

Certainly on the standard MEMS3 ECU, the ECU turns the pump on as soon as it gets any kind of signal (basically any transitions from positive to negative voltage) from the crank position sensor. It doesn't need to synchronise to any kind of pattern, so as soon as the engine moves when cranking the pump turns on. If your fuel pressure is dropping during cranking it suggests that the ECU might not be getting a crank sensor signal, which would stop the engine dead. I would check the crank sensor and wiring carefully.

[7 wonders of the world]

Emerald also needs a functioning TPS too, if yours has failed or you have a poor lom of a pin pushed out in the multiplug this will show these symptoms.

[revilla]

Does the Emerald need a good TPS voltage to run the fuel pump though? I know it would kill the engine, but would it lead to fuel pressure dropping off when cranking? That was the clue I was going after. Not much Emerald experience though.

[7 wonders of the world]

Not to prime, but I'm not convinced it is the pump..... OP is unsure as to wether pump was indeed running when the car stopped. He only confirms it was working in the garage and the car started then.... 

 

[kasin]

Hi

Update: Starting and driving the car yesterday was problemfree. However this was just a very short trip close to home, so that I could push the car back into the garage if it happened again. Intermitten faults are the worst. 

I don't think there is any problem with the TPS or the crank sensor. However I can check them - and have them in the back of my head for the next time this happens. I guess I need to drive with my laptop in the car, so that I can connect to the Emerald to look at the signals that it is getting. 

Kristoffer

[kasin]

Hi

 

New update: The problem was back again yesterday after around 15 minutes of driving - like just after getting hot. 

As I was a bit more prepared now I have some more info:

The Emerald ECU has a green light when i try to crank the engine after it stopped. Cannot see any faults on the sensors on the engine. 

The fuel pump was priming the fuel system when the car wasnt starting - but the sound was perhaps less audible. When I was trying to start the engine it trys to start a couple of times, but doenst really get up to full speed. 

After waiting around 15 minutes the car started back up, and I could drive home at very low throttle opening. If I tried to open up the taps, it would hesitate and then backfire - so I had to back off. 

So I now have two main thoughts: 

• Dirt in the fuel filter that dislodges after standing still a while? 
• Problem with spark? Might the coil be overheating? 

Thoughts? 

 

[revilla]

When you say it "backfires", are we talking about firing back into the inlet manifold or popping and banging from the exhaust?

Popping and banging from the exhaust usually suggests a lean mixture and if it means out as soon as you open the throttle that suggests fuel supply problems to me rather than coil pack or ignition.

You say you have an inline fuel pressure gauge ... what exactly is that doing when the issue occurs? It should rise to pretty much exactly 3 bar / 44 psi while the pump is priming. When running it should drop off by approximately the manifold vacuum level, so typically around 2.35 bar or 34 psi when idling (but I'd it's running rough or failing to idle properly this will affect it). The fuel pressure should then kick back up to close to the 44 psi value again if you blip the throttle sharply as the MAP rises.

If a problem with the fuel pump or filter is causing this, the fuel pressure will be low when it happens. If the fuel pressure is normal when it happens then it suggests a problem with the injectors (I've seen a poor ECU earth connection lead to sluggish injectors and weak spark more than once).

Have you tried removing the fuel tank filler cap when it happens? More of an issue with carburettor cars but a blocked tank vent can cause a vacuum in the tank which then fights against the pump.

[kasin]

Hi

I meant popping and banging in the exhaust, not back into the inlet.I thought this might be an indication of a rich mixture and point at spark, but if lean mix also does this, then everything points towards fuel. 

There isn't any manifold as I have ITBs. I haven't been able to look at the fuel pressure while driving, but during cranking - while the car isn't starting the fuel pressure drops down, quite a bit. As the reference is constant, this pressure should also be constant - but it isn't. 

The tip with the fuel tank cap was good, I will have to look at that this evening. Is there any drawings avaliable of the tank area for a 2000 ish S3? And of the fuel pump/filters? 

 

 

 

[revilla]

Ah yes, sorry I really shouldn't check and reply to these threads when I've only just woken up! I forgot you had ITBs. Is the vacuum reference on the fuel pressure regulator just left disconnected? If so they yes I would expect about 44 psi at all times.

[7 wonders of the world]

or the TPS is failing and the Emerald is only getting sporadic information as to the throttle position and hence the erratic running with interesting fueling

[kasin]

The reference is just disconnected - yes. The differential fuel pressure will rise with the vacume in the inlets, but as I understand this should be less of an effect when there is ITBs mounted compared to using a manifoil. 

Will an intermitten signal from the TPS make the ECU stop the fuel pump? Shouldnt the idle values kick in?

[revilla]

Certainly on the standard MEMS ECUs, the fuel pump will run whatever happens to the TPS. Not 100% an Emerald is the same but seems odd to be otherwise. That is why I really wanted to pin down what the fuel pressure was doing, to help distinguish between the possibilities. If the fuel pressure is falling off significantly below 44psi with the reference open to the atmosphere then there's a fuel delivery issue.

[7 wonders of the world]

you didn't confirm the pump was or wasn't running when it died aside from when it was in the garage so I assumed this was a guess rather than fact.

If there's a fault with the TPS or harness the Emerald has no reference this could be part of the time with a worn track if you run that type of TPS or start / not start with a harness fault.

Emerald will still dictate the idle fueling with reference to the TPS, 

 

[kasin]

So today I had progress after spending a lot of time on the car during the weekend. During the weekend I did a lot of swapping sensors, changed the plugs, dismantled the fuel filter/hoses to the filler, changed a plug wire, but nothing worked. The car was not driving great, but at least it ran. Everything in the fuel system looked good. The pump primed every time I turned the key, and the fuel pressure was at 42 - 44 PSI. As I was alone I couldn't see the fuel pressure during cranking or driving, but during priming it was good.

After some thought I got the computer out and hooked it up to the Emerald K6 ECU. Everything looked correct, and I even recalibrated the TPS. The only thing that made some strange behavior was the coolant sensor, that would spike to 100 degrees randomly, even when the car was cold and not running. I think that might be unrelated. 

Today I did two things, I turned the adjustment screw on the adjustable fuel pressure regulator to turn the fuel pressure up a bit, and I went over the distributor cap with emery cloth - on the points as I could see some discoloration. After this the car ran great. I think the fuel pressure regulator was to blame. 

I hope this was all the problems for a while, if not I will change to the original fuel pressure regulator when I will be mounting a airbox over the ITBs in some weeks time. 

Thanks for all the assistance. 

Kristoffer