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

[Kccv23highliftcam]

On, or rather in, your mfrp do you have an internal or external line to pin 30 of the fpr.
(May as well start at the bottom)

"Interestingly this means that an EU2 MFRU will work with either an EU2 or EU3 loom, but an EU3 MFRU will only work with an EU3 loom as it requires that additional power supply on pin 8/1. So they are only incompatible one way round."

Edited by Kccv23highliftcam on Wednesday 31st October 23:03

[Penelope Stopit]

Kccv23highliftcam said:

On, or rather in, your mfrp do you have an internal or external line to pin 30 of the fpr.
(May as well start at the bottom)

"Interestingly this means that an EU2 MFRU will work with either an EU2 or EU3 loom, but an EU3 MFRU will only work with an EU3 loom as it requires that additional power supply on pin 8/1. So they are only incompatible one way round."

Edited by Kccv23highliftcam on Wednesday 31st October 23:03

I posted the OP a link https://www.lotus7.club/forum/techtalk/which-fault... to better diagrams and information that mentions the same as you have above

The thing is the OP's car was a runner and developed a fault that caused the fuel pump to keep running rather than for a 2 second or however long prime

Me bearing in mind that the OP didn't alter any wiring but did start (excuse the pun) switching the ignition on and off to check the priming function explained in another post what could cause the fuel pump to keep running, I also posted my thoughts on what may have been happening due to switching the ignition on and off up to 17 times (flooding came to mind)

The OP hasn't been back here to discuss all posters findings, at the bottom of this post are the good diagrams from the above link and my thoughts about the problem and causes

"Poster Mignon" mentioned that the "17 times and out" could have nothing to do with the problem and is correct, Mignon having mentioned about "17 times and out" and myself having thought about it am now 100 % certain the "17 times and out" is nothing to do with the pump continuously running or the engine running rough - The "17 times and out" mystery has very likely been there for much time and the OP has only noticed it recently due to another problem encouraging him/her to test it further by cycling the ignition on/off..............

What do you think?


**********************************************************************************************************************

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

**********************************************************************************************************************

[xtruss]

Can you make a temp power feed to the pump that you can control?
i.e disconnect the main feed, rig up some wire with a switch that you can control to turn the pump on and off manually, then turn on the pump and start the engine to see if it runs correctly.
I'm not sure what it will achieve, but at least it should show the pump and pressure regulator are working to make the correct fuel pressure.

[Toilet Duck]

Many thanks for the continued help etc.

I've asked the place my car is currently at some questions based on what's been suggested here, please see below. For some reason the formatting isn't working (I tried to put the responses in bold)


I was looking on various forums online and one thing was suggested that
I thought maybe worth passing on to you:

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.

[b]We can't access the ecu at binary level, however swapping the ecu should
have eliminated the possibility of the ecu being at fault.[/b]

Is the ECU constantly powered up during the "17 cycle"? If it
was losing power for some reason would that cause it to cycle the fuel pump
etc. each time?

[b]I did not check this, I only checked the fuel pump output from the ecu
which was cycling with the relay clicking. I would have thought that if
it was the main power supply that was switching on and off that the dash
would also switch on and off too and I didn't notice that happening.[/b]

One other thing just so I fully understand, if my ECU is plugged into
your diagnostic equipment is it able to run some sort of all
encompassing "system check" that would show any and all
faults/corruption etc (if present) within the ECU? Or is it just that my
ECU has been swapped out with a known working one and as the symptoms
remained it is believed my original ECU is "good"??

[b]The nearest I could get to checking sensors etc would be to lock the
Flashpro unit to your ecu and carry out some datalogs. As explained on
the telephone, if I do this the ecu calibration will be lost and the car
will have to be tuned on the dyno at a cost of £400.00 I can do this if
you wish.[/b]

I know you explained that the red thing by the fuel pump is a
pressure regulator that diverts fuel back into the tank if excess
pressure is delivered. If this regulator was faulty (either allowing too
much or too little pressure), could that cause these symptoms

[b]No, as the fuel pressure regulator (the red thing) is purely mechanical
and not linked to the electronics.[/b]

Kccv23highliftcam said:

On, or rather in, your mfrp do you have an internal or external line to pin 30 of the fpr.
(May as well start at the bottom)

I don't have my car at the moment (picking it up next week). Apologies but is the "MFRP" the same as the "MFRU" Freelander module? What is the "FPR"?

Penelope Stopit said:

I posted the OP a link https://www.lotus7.club/forum/techtalk/which-fault... to better diagrams and information that mentions the same as you have above

The thing is the OP's car was a runner and developed a fault that caused the fuel pump to keep running rather than for a 2 second or however long prime

Me bearing in mind that the OP didn't alter any wiring but did start (excuse the pun) switching the ignition on and off to check the priming function explained in another post what could cause the fuel pump to keep running, I also posted my thoughts on what may have been happening due to switching the ignition on and off up to 17 times (flooding came to mind)

The OP hasn't been back here to discuss all posters findings, at the bottom of this post are the good diagrams from the above link and my thoughts about the problem and causes

Sorry if I've misunderstood, but my fuel pump is NOT continually running. The place my car is currently at have pulled the spark plugs after repeat primings etc and apparently there isn't any signs of excess fuel

Penelope Stopit said:

"Poster Mignon" mentioned that the "17 times and out" could have nothing to do with the problem and is correct, Mignon having mentioned about "17 times and out" and myself having thought about it am now 100 % certain the "17 times and out" is nothing to do with the pump continuously running or the engine running rough

The fuel pump is NOT continually running

Penelope Stopit said:

The "17 times and out" mystery has very likely been there for much time and the OP has only noticed it recently due to another problem encouraging him/her to test it further by cycling the ignition on/off..............

This is incorrect. The 17 times cycling of the pump etc was not present before it started mid way through a trackday. I always let the fuel pump prime before starting the car so would have noticed if it kept priming. You hear all sorts of noises on the Atom due to it being "open" so could not have missed the fuel pump repeatedly priming. Also, it cuts out after 17 times and then won't run

Penelope Stopit said:

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 MFRU was replaced with a known working one whilst stuck at the trackday as per my opening post - it didn't make any difference

If I can't get this resolved locally, which is looking highly likely, then I'll take it back to the factory

Cheers

[Penelope Stopit]

Ok I think I've got it now
Yes I have been wasting my time on this due to misunderstanding your opening post

Where you comment - "The fuel pump normally primes and then cuts out after 3 seconds or so, but for some reason it kept priming" I misunderstood this as meaning the pump kept running

Am I right in thinking you switched the ignition on and left it on and the fuel pump was auto switched on and off 17 times before stopping?

Do you understand how your opening post that mentions "kept priming" could be read as kept running?

You surely do mean that when switching the ignition on the priming stage is repeated automatically 17 times

Have I got it now, I think I've got it?

[Toilet Duck]

Penelope Stopit said:

Ok I think I've got it now
Yes I have been wasting my time on this due to misunderstanding your opening post

Where you comment - "The fuel pump normally primes and then cuts out after 3 seconds or so, but for some reason it kept priming" I misunderstood this as meaning the pump kept running

Am I right in thinking you switched the ignition on and left it on and the fuel pump was auto switched on and off 17 times before stopping?

Do you understand how your opening post that mentions "kept priming" could be read as kept running?

You surely do mean that when switching the ignition on the priming stage is repeated automatically 17 times

No, I think I was quite specific. "Priming" is not the same as "running". Priming is normally a one time affair to pressurise the fuel lines etc. Once a car is started the fuel pump runs continuously. You've obviously misread my post but no harm done.

Did you watch/listen to the video clip I linked to? It shows exactly what is happening - fuel pump priming 17 times and then cutting out

Toilet Duck said:

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

[GreenV8S]

Those replies from your mechanic all seem sensible.

One thing I'm uncertain about and don't remember whether you already told us this: will the engine actually start and run while the fuel pump is going through its cyclic priming? If there is any life from the engine I'd consider jerry-rigging a permanent supply to the pump so it runs continuously and see whether the engine then behaves as normal. If so, it suggests the ECU problem is specific to the fuel pump supply logic and not a more general failure.

[jeremyc]

Toilet Duck said:

I know you explained that the red thing by the fuel pump is a
pressure regulator that diverts fuel back into the tank if excess
pressure is delivered. If this regulator was faulty (either allowing too
much or too little pressure), could that cause these symptoms

[b]No, as the fuel pressure regulator (the red thing) is purely mechanical
and not linked to the electronics.[/b]

It is possible that there is some fuel pressure sensor somewhere (in the fuel pump itself, in the fuel system) that feeds back a go/nogo to the ECU (either only when priming or also when running). If there is a loss of fuel pressure, which could be caused by a faulty FPR or a faulty pressure sensor, then the sequence could be explained:

1. Ignition on.
2. ECU instructs pump to start priming process (applies power to relays).
3. ECU doesn't see adequate fuel pressure (faulty FPR, sensor, pump, whatever) so turns off power to relays, restarts sequence for step 2.
4. When ECU has retried steps 2 to 3 seventeen times it gives up.

Try swapping out that red FPR and/or find out if there is some kind of fuel pressure sensing going on?

[Toilet Duck]

GreenV8S said:

Those replies from your mechanic all seem sensible.

One thing I'm uncertain about and don't remember whether you already told us this: will the engine actually start and run while the fuel pump is going through its cyclic priming? If there is any life from the engine I'd consider jerry-rigging a permanent supply to the pump so it runs continuously and see whether the engine then behaves as normal. If so, it suggests the ECU problem is specific to the fuel pump supply logic and not a more general failure.

Hiya

Yes, when at the trackday and this fault first materialised, I tried starting the car during the fuel pump cycling and it did start. However, it idled very rough and wouldn't accelerate cleanly (gearbox was in neutral, I just reached in and blipped throttle with my hand). After 17 cycles the fuel pump stops.

During this time the throttle relay also cycles 17 times in sync. If pressing the throttle pedal during this cycling (and without engine running) I can hear the DBW butterfly valve opening, but it shuts every time the relay cycles.

[Toilet Duck]

jeremyc said:

It is possible that there is some fuel pressure sensor somewhere (in the fuel pump itself, in the fuel system) that feeds back a go/nogo to the ECU (either only when priming or also when running). If there is a loss of fuel pressure, which could be caused by a faulty FPR or a faulty pressure sensor, then the sequence could be explained:

1. Ignition on.
2. ECU instructs pump to start priming process (applies power to relays).
3. ECU doesn't see adequate fuel pressure (faulty FPR, sensor, pump, whatever) so turns off power to relays, restarts sequence for step 2.
4. When ECU has retried steps 2 to 3 seventeen times it gives up.

Try swapping out that red FPR and/or find out if there is some kind of fuel pressure sensing going on?

I rang the Ariel factory yesterday to ask whether there is a fuel pressure sensor in the pump, I was told that there definitely isn't. There are 4 wires on the connector going to the fuel pump, apparently they are just for the running of the pump (power?) and the others go to a fuel level sender that gives a reading on the dash.

From what the current place has told me, as the fuel pressure regulator is purely mechanical it has no link to the electronics/ECU side of things. It doesn't appear that there is any way for the car to "measure" fuel pressure via a sensor. This seems very odd to me but I'm far from being qualified to say different. I can try swapping the red FPR when I get the car back, but so far have been advised it won't be causing this issue.

Cheers

[Penelope Stopit]

Yes I know how the system works and I'm trying to help and not get into a debate over any misunderstanding
Where you commented it kept priming can easily be read as the initial priming didn't stop and I'm no bothered about it in any way, this is all part of internet fun getting something totally wrong due to how something could be and was read

What makes this funnier is that my PC is partially dismantled and has no speakers connected so I didn't visit your video link
I am now going to find and connect my speakers up and then visit your video link

I doubt I will come up with anything different to what's already been posted by many others but I do like solving electrical mysteries, the thing is so do many others enjoy solving issues like this and it's not been solved

Keep smiling.....I'll be back.....maybe

[Toilet Duck]

No problem, any and all help appreciated

[jeremyc]

Toilet Duck said:

I rang the Ariel factory yesterday to ask whether there is a fuel pressure sensor in the pump, I was told that there definitely isn't. There are 4 wires on the connector going to the fuel pump, apparently they are just for the running of the pump (power?) and the others go to a fuel level sender that gives a reading on the dash.

It's not low on fuel is it, or a faulty fuel level sender?

Maybe the ECU won't allow it to start if there's no petrol in the tank.

[Toilet Duck]

jeremyc said:

It's not low on fuel is it, or a faulty fuel level sender?

Maybe the ECU won't allow it to start if there's no petrol in the tank.

If only!

The level sender purely talks to the dash and not the ECU. It's notorious amongst Atom owners as being crap, it fluctuates so much its unbelievable, especially on track. What I can say is that if the fuel level does drop too low on track, on extended left handed bends you can get fuel starvation as the fuel sloshes to the right. However, there is plenty of fuel in my tank

[GreenV8S]

Toilet Duck said:

From what the current place has told me, as the fuel pressure regulator is purely mechanical it has no link to the electronics/ECU side of things. It doesn't appear that there is any way for the car to "measure" fuel pressure via a sensor. This seems very odd to me

That's an arrangement that used to be very common in recirculating fuel systems. Essentially the pump runs continuously producing more fuel flow that the engine needs, and the regulator bleeds off the excess to keep the fuel rail at the desired pressure. Typically the pressure is based off the manifold pressure so will vary as the engine load changes, but it's all done by the dumb mechanical regulator.

Another question you may already have answered - what is the throttle relay for? Is it something that would normally be powered up from the engine run signal, presumably together with the fuel pump and lambda sensor heaters?

[Toilet Duck]

GreenV8S said:

Another question you may already have answered - what is the throttle relay for? Is it something that would normally be powered up from the engine run signal, presumably together with the fuel pump and lambda sensor heaters?

I'm afraid I do not know the answer to this, google let me down

[eliot]

What if you disconnect the wire (or fuse if it's after the relay) to the actual pump?
Does the relay(s) act the same or do nothing?
Theory: Fuel pumps draw quite a bit of current, maybe you are getting a volt drop that is causing the ECU to reset.
Removing just the wire to the pump would prove if it's a volt drop / surge issue or a pure logic (ecu) issue (which has sort of been eliminated).

I would have a scope or decent meter across the live and earth AT THE CONNECTOR to the main ECU and observe for large fluctuations (as it could be a bad earth too)

No experience of this ECU, but with megasquirt the ECU will fire the injectors during the pump priming phase as well. You could have a faulty low impedance injector that could also be tripping the ECU. Prove by removing all the injector connectors. (may also explain bad running when it does run)

Also be wary of repeatedly cycling the ignition - you could be slowly filling the cylinders and the block with fuel, watering down your oil - when you finally fix it you can expect trashed big ends. Check oil level and smell it too.

[Penelope Stopit]

Ok my speakers are back on and I've viewed your video

Some of what I'm posting here may have already been advised but I don't think so, the topic is getting too big for me to read all the way through right now



I'm posting the following assuming that the pin numbers in the above image are for your cars MFRU and ECU's pin-outs

The first thing to do is connect a multimeter between the battery positive (not any positive....it must be the battery positive) and the cable going to or the terminal in the MFRU 6 way plug (6/3) White/Pink or Pink/White, the MFRU must be fully connected

Is that ECU Switched Negative switching on and off 17 times?

[Penelope Stopit]

You asked the person that is attempting to fix the fault -

Is the ECU constantly powered up during the "17 cycle"? If it
was losing power for some reason would that cause it to cycle the fuel pump
etc. each time?

The reply you got was -

I did not check this, I only checked the fuel pump output from the ecu
which was cycling with the relay clicking. I would have thought that if
it was the main power supply that was switching on and off that the dash
would also switch on and off too and I didn't notice that happening
_______________________________________________________

I don't wish to sound bhy but......Whoever is attempting to fix your car is not a good automotive electrician, it is obvious that the instrument cluster isn't powered by the ECU supply fuse

I have witnessed many a fault multiply into several man made faults due to a testers lack of knowledge
Be carefull

Just a thought

Edited by Penelope Stopit on Thursday 1st November 14:58

[Toilet Duck]

eliot said:

What if you disconnect the wire (or fuse if it's after the relay) to the actual pump?
Does the relay(s) act the same or do nothing?

I don't know. However, with the connector block going to the fuel pump disconnected (which I believe has the same effect as what you have suggested?), the relay(s) within the MFRU and throttle sensor relay both continue to click/cycle 17 times

eliot said:

No experience of this ECU, but with megasquirt the ECU will fire the injectors during the pump priming phase as well. You could have a faulty low impedance injector that could also be tripping the ECU. Prove by removing all the injector connectors. (may also explain bad running when it does run)

Before taking my car to the garage it's currently at, I tried unplugging all the fuel injectors from the loom and it didn't make any difference to the fuel pump cycling etc

eliot said:

Also be wary of repeatedly cycling the ignition - you could be slowly filling the cylinders and the block with fuel, watering down your oil - when you finally fix it you can expect trashed big ends. Check oil level and smell it too.

Unless an injector is leaking/faulty, would it actually squirt any fuel when the fuel pump is just priming and the engine not actually running? I will be changing all fluids anyway once it's fixed. As mentioned before, the spark plugs (when removed by the garage after fuel pump priming etc) apparently did not show signs of being "wet" with fuel.

Cheers