fuel pump primes 17 times then stops, engine won't run

[Toilet Duck]

Evening knowledgeable people,

My Ariel Atom (supercharged Honda K20 engine) has developed a weird issue. I was at a track day yesterday and all was well. Parked up in a pit garage and put some fuel in and then switched ignition on just to get a reading off the dash fuel guage. The fuel pump normally primes and then cuts out after 3 seconds or so, but for some reason it kept priming. Having investigated a bit further today, it primes 17 times and then stops. It does it 17 times every time you put the ignition on and repeat. If you try and start the car whilst it is doing this fuel pump priming/cycling it will start but idle very rough. After the 17 cycles of priming the engine dies. The engine will not start at all after this (the fuel pump is not running)

Here is a video I took today whilst investigating:

https://www.youtube.com/watch?v=5vwAjCGWtNc

There is a relay at the front of the car that clicks/energises when the fuel pump activates; I swapped that out today and it makes no difference. At the back of the car near the ECU there is this thing which also clicks every time the fuel pump runs/cycles:





Googling the part number at trackside yesterday reveals its a "fuel pump module relay" and is from (amongst other vehicles) a Freelander. I found a localish Freelander breakers/specialist and they took one off a vehicle they had there. I got them to connect up the module from my Atom. Although I didn't see them start the Freelander, they said it ran but didn't sound "right". I was hoping it would make the Freelander cycle the fuel pump like my Atom and confirm this was the faulty part but no joy. However, they kindly let me borrow the unit they took off their Freelander so I took it back to the track and fitted it, it didn't make any difference. Today I also resoldered all the pads on the printed circuit board inside my original fuel pump module relay and again no difference. I'm fairly confident it has eliminated this part from being the cause.

The Atom has a factory fit immobiliser which blocks (among other things) the fuel pump when activated. If I turn the ignition on without deactivating the immobiliser, both the relay at the front of the car and the fuel pump module relay click 17 times but the fuel pump does not run. I don't think the immobiliser is causing the issue.

There is a quick release connection on the fuel line feeding the fuel rail. I disconnected this and aimed it into a bucket. When the ignition is on and the fuel pump starts cycling/priming fuel pisses out.

I've googled to see if the Honda K20 engine has a fuel pressure sensor incase that is the problem but it doesn't appear to have one.

I don't know if there is a fuel pressure regulator (maybe that red thing visible in the video?) or if a faulty one could even cause this issue?

I am at a complete loss now. I hate electrickery faults on cars. Can anyone help or point me in the right direction?

I would really appreciate any help as this has me stumped!

Many thanks

[Toilet Duck]

GreenV8S said:

That is wierd and I haven't encountered anything like that myself. I don't have an Atom or a Freelander and don't know how the fuel system works on those, but the vehicles I'm familiar with behave the way you describe - the pump runs for a few seconds when you switch the ignition on, then runs continuously when you start cranking the engine and as long as the engine remains running. If the engine stops, the pump will stop after a few seconds. Fuel pressure is regulated via a mechanical restrictor and this has no influence on the pump.

I agree the symptoms do not suggest a faulty immobiliser.

Based on this I suspect the ECU may be being reset at the end of the priming pulse. The fuel pump relay is normally controlled directly by the ECU and should include a fly-back diode to prevent a back EMF spike to the ECU when the relay is switched off. It's a WAG, but the relay or its diode might have failed in a way which is spiking the ECU and causing it to reset.

You might be able to confirm that by removing the fuel pump relay and connecting a small test lamp across the relay control terminals. You should see it power on for the length of the normal priming pulse and then switch off. If it still does the cycling thing, it disproves the relay theory and suggests you need to look elsewhere.

Do you normally see any other symptoms when the ECU switches on, such as sweeping dials or cycling warning lights? If so, that could also confirm/deny that the ECU is resetting.

Cheers for the reply GreenV8S

The dials sweep when you first switch the ignition on. This is functioning correctly i.e. they sweep once whilst the fuel pump does it's cycling/priming dance

Sorry but what does "WAG" mean?

I'll give the fuel pump relay lamp trick a go and report back, probably be after work tomorrow.

I might also see if I can borrow an ECU off another Atom owner and see if I can do a quick swap, but that will take some time to organise

Someone on the Atom forum kindly posted up some wiring diagrams which I think may help:









I have a multimeter etc but on the face of it this issue is far more complex than anything I've worked on (electrics wise)

Many thanks again

Edited by Toilet Duck on Wednesday 19th September 19:33

[Toilet Duck]

This gets weirder....

The relay at the front of the car that clicks 17 times in sync with the fuel pump priming isn't the relay for the fuel pump. It's the throttle pedal relay (it's drive by wire). Could the throttle position/pedal be somehow causing this?

[Toilet Duck]

GreenV8S said:

What does a "throttle pedal relay" do?

I have no idea, google has not helped. I assume it's because it has a drive by wire throttle so "electric" rather than cable and the relay feeds that, but even if that's correct surely a DBW throttle wouldn't pull enough current to require a relay?

[Toilet Duck]

I just did a test. With the ignition on (and the fuel pump dancing on/off), when I operate the throttle pedal you can hear the butterfly valve in the throttle body opening closing. I'm fairly confident that's normal i.e. if the fuel pump was behaving and just priming once, it's "normal" for the throttle pedal to actuate the throttle butterfly with the ignition on but not the engine running.

What I did notice is that once the fuel pump has cycled 17 times, the throttle pedal no longer activates the butterfly, it goes dead. So Is that pointing more towards an ECU fault i.e. its making the fuel pump dance and then killing the DBW?

With the ignition on and the fuel pump dancing, if I remove the "throttle pedal relay" the throttle pedal no longer actuates the butterfly

[Toilet Duck]

Steve_D said:

Have you tried pulling that relay or disconnecting the throttle pedal.

Steve

Yep tried both, neither effects the fuel pump dancing 17 times. It is bizarre!

[Toilet Duck]

Toilet Duck said:

Steve_D said:

Have you tried pulling that relay or disconnecting the throttle pedal.

Steve

Yep tried both, neither effects the fuel pump dancing 17 times. It is bizarre!

Just tried again for piece of mind and the above is correct.

Just to confirm though, whilst I can actuate the butterfly valve with the throttle pedal, each time the fuel pump completes one of its 17 cycles and both the fuel pump module relay and the throttle pedal relay click, the butterfly valve shuts as the relay closes then opens up as it energises. So effectively, both the fuel pump and drive by wire throttle cycle 17 times in perfect sync before both going dead

[Toilet Duck]

Krikkit said:

On each occasion when the pump primes, then stops, does that take longer or about the same as it usually would to prime and get up to rail pressure?

I'm wondering if it's the pump failing to pressurise sufficiently, then the ECU resetting for another try.

I think it takes about the same time as a "normal" single prime when the car would ordinarily start and run fine

Kccv23highliftcam said:

Is there such a thing as a fuel rail pressure or pump pressure sensor ? Is the Honda K20 engine supercharged "by Honda" [sorry I don't know just throwing thoughts in]

Is the inertia switch environmentally sealed?
What should the output pressure of the fuel pump actually be?

I can't find any reference to a fuel or pump pressure sensor when googling K20 Honda engine etc.
The supercharger (Jackson Racing) is aftermarket and fitted by the Ariel factory.
I don't know if there is an inertia switch or what the actual pump pressure should be unfortunately.

Kccv23highliftcam said:

But why the 17 times???

I only wish I knew, it is bizarre! I think I have exhausted my DIY skills. I suspect it's ECU related so I'm going to contact a place familiar with Hondata ECU's and get this looked at by professionals.

Thanks for everyones help, if anyone has any ideas in the meantime that are DIYable I'm all ears. I changed the fuel filter earlier but it didn't make any difference.

Cheers

[Toilet Duck]

eliot said:

if the fuel system is "returnless" it will almost certainly have a fuel pressure sensor in order regulate the pressure. Older returned systems have a pipe running back to the tank after the mechanical fuel pressure regulator - I would be surprised if that was the case on a modern engine.

As suggested above, it might be cycling trying to get a valid fuel pressure and giving up - would also explain rough running. Is there a shrader valve on the fuel rail where you can check the pressure (you may need someone with the same engine to tell you what normal looks like, i.e. static pressure, pressure during prime pulse, pressure on crank and running)

No shrader valve that I can see. I can't see any pressure sensors etc in the fuel line/rail either





I'm wondering if this red thing plumbed into/near the fuel filter is a pressure regulator, and if so could this cause the issue if it's somehow gone tits up?:

stevieturbo said:

You're wasting your time fking about.

Interrogate the ecu, check for codes and ensure all sensor feedback appears normal and that the ecu is actually alive and happy ( or not )

I know, I hoped I could fix it but it's pretty obvious it's beyond my skill level. I've already emailed a Hondata ECU specialist who are due to do some work on my car in a few months anyway, I'm hoping that they can have a look soon.

[Toilet Duck]

stevieturbo said:

although who on earth is using crappy worm drive clips on those fuel lines. Totally the wrong type of clip.

Ariel Motors finest

[Toilet Duck]

Just to answer the above questions/points:

Yes, the brackets visible in the pics are what the fuel filter and red regulator clip into. I removed them and pulled a lot of the hoses about trying to get access. Everything is "neater" when put back correctly. Ideally you need to be an experienced farmyard vet in order to stuff your arm up the tight space to gain access to the filter etc

The worm clamps on the fuel filter are original.

The crimped on clips are original.

The other (stevieturbo correct clips ) on the braided lines etc were fitted by myself when I fitted an oil catch can. They are Mikalor clips.

The bolt used to block the vaccum hose was fitted by yours truly as that vaccum point is no longer needed with the oil catch can (it previously connected to the PCV valve). Whats the correct method of blocking off such a hose then? The factory block off a redundant hose on the expansion bottle using a bolt so I assumed it was "ok"?

[Toilet Duck]

Holy thread resurrection!

Right, my car is currently at a reputable specialist and authorised dealer in Hondata ECU's. They are unable to solve this issue. They have swapped the ECU for a known working one, fitted a new immobiliser (I purchased a new one from Ariel after calling them and explaining the symptoms, it's a "plug and play" unit), checked all relays etc, removed fuel pump from circuit, and it's still producing the same symptoms i.e. fuel pump primes 17 times and then stops (with the fuel pump disconnected it obviously doesn't run but the relay/control module still clicks 17 times. They suspect it may be a wiring issue somewhere i.e. a short. In my mind this would be strange due to the consistent 17 times that the pump primes, it's as if something is "telling" the pump to prime that specific number of times but I have been advised that there is nothing within the ECU that could do this.

Any of the resident experts on here have any further suggestions before I curl up in a foetal position in a dark corner?

Cheers

[Toilet Duck]

stevieturbo said:

And can Ariel provide you with a wiring schematic ?

I'm going to call them tomorrow, but I suspect they might not divulge the wiring diagrams as that wouldn't necessarily make good business sense. The place it's currently at, and who have experience of working on Atoms, don't have access to Ariel's wiring schematics

[Toilet Duck]

Penelope Stopit said:

Was it those that said there is nothing in the ECU to cause this that also said they suspect a wiring fault

Correct

[Toilet Duck]

Sardonicus said:

This ^ come on 17 times always how can that be a wiring issue EVER bloody hell at least come back to you with a tangible possibility for the cause , there must be another control relay/module to do this 17 cycle thing if its been confirmed that the Immobilizer and ECM have been substituted with known good units the only ECM/ECU I know of that cycles the FP output repeatedly if there is a config/conflict error is the Megasquirt after market unit this is just an example , I am not familiar with the Hondata unit however

I know, I know

The thing is, I've gone to an authorised Hondata ECU dealer specialising in Honda engines so would assume they are ideal for this type of fault. This problem is beyond my technical ability. I've been told it's not the ECU, it's not the immobiliser, it's not the fuel pump. Granted, they haven't changed that Freelander "fuel pump relay module" but I already tried swapping that with another one as per earlier in this thread, so it's highly unlikely it's that. I also don't get why the "throttle pedal relay" clicks 17 times as well. It's doing my head in and now I'm back to square one.

[Toilet Duck]

jeremyc said:

Did you determine whether there is a fuel pressure regulator, and if so tried swapping it out?

The place it's at advise the red thing is a fuel pressure regulator and that it has a spring operated diaphragm type thing that if overcome by excess fuel pressure let's by and allows the fuel to return to the tank. They tell me it's not causing the issue.

[Toilet Duck]

jeremyc said:

ust so long as it's not faulty and acting to reduce the fuel pressure ...

I will call them tomorrow and clarify this

[Toilet Duck]

Penelope Stopit, I appreciate you taking the time to post those diagrams etc but unfortunately the Freelander fuel pump relay module is factory fit and everything ECU wise etc is how it left the factory. I know from scouring the Internet the "main relay" can play up on civics etc but it isn't present on the Atom. I have no idea why the Freelander part is fitted etc. The Atom uses (I believe) a standard Honda ECU but with the Hondata add on inside it that allows reprogramming etc. I think the loom is a mixture of standard Honda and Ariel specific

Mignon said:

I know next to nothing about electrickery so this is really not my area but I like logic puzzles and with sufficient information the topic of the puzzle should not matter. So I have questions. When the ignition is switched on the fuel pump primes for a bit and then switches off. All cars obviously do this. So how does the pump know when to stop priming? One way would be for a fuel pressure sensor to send a message to the ecu. Does your engine have this? Is there something inside the pump that detects back pressure so it knows it's primed the system?

It sounds to me as though the 17 times thing is built in such that if the ecu doesn't get the right message that fuel pressure is correct it tries priming for 17 attempts and then switches the pump off again in case it overheats.

Methinks either the pump is bksed so it's not actually priming the system or the pressure regulator is bksed and sending the fuel back down the return line to the tank or the ecu is not getting the signal that the system has primed.

I don't believe that there is a fuel pressure sensor present. The place it's at said (I think) that on some civics there is some sort of fuel pressure sensor built into the fuel pump. However, even if that's the case on my Atom and that sensor has crapped out, it wouldn't explain why with the fuel pump unplugged/disconnected both the Freelander fuel module relay and the throttle relay both cycle 17 times when the ignition is switched on, as this would be removing the fuel pump pressure sensor from the equation.

[Toilet Duck]

Just to add, early on in the thread I posted to say that I disconnected the fuel line at the fuel rail and when the pump primes fuel pisses out so it does appear to prime.

[Toilet Duck]

Mignon said:

I suggest you check the fuel pressure when the engine is started. You say it does start but runs rough. Maybe the pump is working well enough to spit fuel out when you disconnect the coupling in the fuel line but not well enough to generate the pressure the injectors need.

I think (assume) it runs rough because the fuel pump isn't constantly running, it primes for 2-3 seconds then stops, then repeats a total of 16 times. So I'm guessing the injectors are getting fuel but the delivery pressure is fluctuating with the cycling pump. Even if the pressure wasn't "right" I don't understand why that would make the fuel pump (and throttle relay!) cycle 17 times.

What makes it even stranger is that with the fuel pump disconnected the Freelander relay module thing and throttle relay STILL cycle 17 times