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

[Mignon]

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.

[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.

[Mignon]

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.

[Penelope Stopit]

Mignon

17 times, it's all about what is causing 17 times then out

[Penelope Stopit]

Toilet - Are you a member and able to reach this topic?

ECU /relay box wiring diagram - Ariel.Club Forum

https://ariel.club/forum/viewtopic.php?t=15749

[Penelope Stopit]

Toilet Duck said:

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

Have you a factory diagram?

Did you build/buy the car new?

[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

[Mignon]

Penelope Stopit said:

Mignon

17 times, it's all about what is causing 17 times then out

Maybe, and maybe that's just a red mackerel. Maybe 17 times is the correct and built in response to something breaking and we need to find the broken thing and not worry about the 17 times. The job of the fuel pump is to provide let's say about 60 psi to the fuel rail. Is it doing this? If not then swap the fuel pump.

[Toilet Duck]

Penelope Stopit said:

Toilet - Are you a member and able to reach this topic?

ECU /relay box wiring diagram - Ariel.Club Forum

https://ariel.club/forum/viewtopic.php?t=15749

Yes I'm a member on there. I posted a duplicate thread on that forum the same time as on here but didn't get any luck solving. To be honest that community is pretty small, especially compared to the number of experts on PH

To answer your other questions, the Atom comes prebuilt (you can't buy it as a "kit") and I've had it circa 7 years

Edited by Toilet Duck on Tuesday 30th October 19:54

Edited by Toilet Duck on Tuesday 30th October 19:55

[Penelope Stopit]

Toilet Duck said:

Penelope Stopit said:

Toilet - Are you a member and able to reach this topic?

ECU /relay box wiring diagram - Ariel.Club Forum

https://ariel.club/forum/viewtopic.php?t=15749

Yes I'm a member on there. I posted a duplicate thread on that forum the same time as on here but didn't get any luck solving. To be honest that community is pretty small, especially compared to the number of experts on PH

To answer your other questions, the Atom comes prebuilt (you can't buy it as a "kit") and I've had it circa 7 years

Ok I thought there may be a diagram in there at that link

That Honda diagram I posted up is not even close to what you have, ECU Pinouts are nothing like

I'm looking for a complete Atom/Honda engine diagram but struggling

Have you a bigger diagram than the below one that you posted? This is what you have isn't it?

[Penelope Stopit]

It's ok I've found a better diagram for the MFRU https://www.lotus7.club/forum/techtalk/which-fault...

[Mignon]

Toilet Duck said:

I think (assume)

Don't assume - measure.

Toilet Duck said:

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 does the engine run rough exactly in sync with the pump cycling or is it rough all the time?

Toilet Duck said:

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

I'm not really fussed about the 17 times thing. Presumably the ecu has to have some number programmed in to it to try and operate something before it gives up. 17 times sounds as good a number as any except maybe 42 which is obviously the universe's best number. Stop trying to figure out how every bit of the ecu system is designed and measure the things that are important. Fuel pressure for starters.

Try sticking a 12v feed direct to the fuel pump. Does the engine start and run ok?

[Toilet Duck]

Mignon said:

Toilet Duck said:

I think (assume)

Don't assume - measure.

I don't have the tools to measure fuel pressure

Mignon said:

Toilet Duck said:

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 does the engine run rough exactly in sync with the pump cycling or is it rough all the time?

Can't remember 100% but I think it was in sync. Would need car back to check for sure

Mignon said:

Toilet Duck said:

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

I'm not really fussed about the 17 times thing. Presumably the ecu has to have some number programmed in to it to try and operate something before it gives up. 17 times sounds as good a number as any except maybe 42 which is obviously the universe's best number. Stop trying to figure out how every bit of the ecu system is designed and measure the things that are important. Fuel pressure for starters.

Try sticking a 12v feed direct to the fuel pump. Does the engine start and run ok?

Don't have car so unable to check that or anything else. Also, I'm not trying to figure out "every bit of the ecu system."

[Penelope Stopit]

Toilet Duck said:

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)

• **********************************************************************************************************************

The first problem you noticed was that the fuel pump kept running rather than going through its ECU timed priming cycle

This fault was caused by a sticking relay or the ECU not switching the priming signal off

• **********************************************************************************************************************

You happened to notice when checking the priming cycle that you could get it to operate 17 times before it shut off
You I and many others here all know about the unsolved 17 cycle mystery.......but......

There is a possibility that due to another problem such as a weeping injector, some fuel that shouldn't have been was injected into the engine and that would explain the engine running rough when carrying out several priming cycle tests before attempting to start it

• **********************************************************************************************************************

The Multi Function Relay Unit that is being used is 4 Relays in a box with some internal links and resistors to dump any back EMF
The MFRU keeps things tidy rather than having seperate relays, there is no timing device in it

• **********************************************************************************************************************

You could replace the MFRU in an attempt to eliminate the fuel pump running on rather than priming, there is more of a chance that the fuel pump relay stuck closed rather than the ECU having a fault

The only other way you can prove that the fault is the MFRU (Sticking Relay) or ECU signal keeping the pump running is to get a multimeter on the ECU to fuel pump relay signal wire when the fault is on the car, you would be looking for a constant negative that should be a timed one, if the signal checks ok the relay will be sticking and you can prove that by disconnecting it

• **********************************************************************************************************************

The "17 times and out" remains a mystery but isn't preventing your engine from starting as it should start first time on the button

17 Times and out To Be Continued

[stevieturbo]

Priming is simply a time based from key on. Nothing more than that. The ecu will not be monitoring pressure, or care where the fuel is going etc.

Cant be arsed reading every reply...but has the OP confirmed that the ecu is staying live throughout these 17 cycles, or more likely for whatever reason the ecu is losing power and going live again...hence priming every time it powers up ?

[Mignon]

Toilet Duck said:

Mignon said:

Toilet Duck said:

I don't have the tools to measure fuel pressure

https://www.ebay.co.uk/p/Fuel-Injection-Pump-Pressure-Gauge-Tester-Gasoline-Test-Tools-Tuner-Car/2194604668?iid=232472510813&chn=ps

[Toilet Duck]

stevieturbo said:

Cant be arsed reading every reply...but has the OP confirmed that the ecu is staying live throughout these 17 cycles, or more likely for whatever reason the ecu is losing power and going live again...hence priming every time it powers up ?

No, but I will call the place that currently has my car tomorrow and ask, good question!

[Penelope Stopit]

Mignon said:

Penelope Stopit said:

Mignon

17 times, it's all about what is causing 17 times then out

Maybe, and maybe that's just a red mackerel. Maybe 17 times is the correct and built in response to something breaking and we need to find the broken thing and not worry about the 17 times. The job of the fuel pump is to provide let's say about 60 psi to the fuel rail. Is it doing this? If not then swap the fuel pump.

Well thought out, although the "17 times and out" is a mystery it isn't on its own stopping the engine from running, it does sound like possible flooding when priming, priming and priming more

I get the impression that the engine did run after the OP noticed the pump not switching off and that was and still is the only fault, I doubt very much that pressure has anything to do with this problem as it's the ECU timer and fuel pump relay that operate the pump

[Kccv23highliftcam]

jeremyc said:

n uneducated guess, but the ECU could be using a 4 bit "retry" counter that starts at 0000 (binary) and increments by one after each cycle.

By the time it's got to 1111 (binary) it will have tried 17 times.

It doesn't help identify the problem though, which presumably is some kind of failure with the ECU deciding it can't (or shouldn't) start, so tries the cycle again.

....