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

[Toilet Duck]

eliot said:

were are you in the uk ? (profile is /dev/null)

I'm in Essex

[stevieturbo]

eliot said:

Allow me to uncross those wires for you two:
Fuel Pressure Relay
Fuel Pressure Regulator




And yes, taking the live for the o2 heater from the ignition seems an odd choice instead of the main fused 12v supply. Again easy to eliminate; pull the o2 relay out.

Correct, FPR would commonly be fuel pressure reg.

[Penelope Stopit]

Penelope Stopit said:

FAO Toilet Duck "Toilet Duck" I chuckle every time I type Toilet Duck, it's a great user name, anyway moving on

I've now installed Hondata K Manager to my Desktop (You owe me a few Mb of SSD Chips)

K Manager shows me the below ECU Pin-outs that match up with the diagram I previously posted and have posted again below the pin-outs image

At present we are interested in ECU E Connector

You will notice that the Ignition supply to ECU pin 9 splices off to the Oxygen sensor relay Terminal 30 and when that relay is energised it continues onwards from relay terminal 87 to the Oxygen sensor element, a momentary short, open circuit or voltage drop due to something else on this ignition supply could cause the problem and this is why I mention take a close look at the Oxygen sensor and its wiring plus other wiring around the engine

What do you think? It's bed time for me now, I'll be back





Edit

I forgot to mention that what Atom have done is to do away with the 3 relays that are shown in the above diagram and used 4 relays in a plastic box from JLR which you know is named a Multi Function Relay Unit or the likes of, the 4th relay being the starter relay that isn't shown

I would never ever wire the Oxygen sensor in the way that Honda have, perhaps Atom have altered it but that's doubtfull

FAO Toilet Duck

Looking here - https://www.k20a.org/forum/showthread.php?t=230 Everything points to ECU A Connector Pins 4 and 5 (PG2 and PG1) being the Main ECU Return Paths (Earth's) ****They will need checking****

Below is what I have harvested from the Honda wiring diagrams and the JLR Freelander Multi Function Relay Unit



Image clicks bigger and bigger

Edited by Penelope Stopit on Friday 2nd November 18:59

[Toilet Duck]

Holy st, issue has been found!

Another Atom owner got in touch with me to say they had experienced a similar issue, ironically at a track day. They told me to check the wiring to the lambda sensor in the exhaust as it passes extremely close to the exhaust manifold, theirs had melted and the wires shorted. As discovered by posts within this thread one of the relays in the MFRU is for the lambda/O2 sensor so therefore linked to the fuel pump etc via the MFRU circuitry. Contacted the garage my car is at with this suggestion and after checking they confirmed that the wires are melted together. Cut back and removed and car now apparently starts and runs so just needs new section of loom making up and this time rerouting away from the exhaust unlike the OE wiring route.

Absolutely over the moon that the issue has been found. Many thanks to everyone who posted and for all the help offered, much appreciated

[Kccv23highliftcam]

Simple simple simple

Kudos to whoever mentioned the odd power supply arrangement in the first place

[Mignon]

Toilet Duck said:

Holy st, issue has been found!

I would say that the solution was already given here and full points to the following post.

Penelope Stopit said:

FAO Toilet Duck

Here are a couple of things that could be causing the problem but bear in mind I am still searching for a diagram

There is a possibility that a fault with the Oxygen sensor heater could drag the ECU's ignition supply voltage down which in turn would switch off the main relay, fuel pump relay and Oxygen sensor relay

Once the Oxygen sensor relay switches off, the ignition supply voltage to the ECU will rise and the whole cycle begin again

The thing is that the same fault could occur if there is a short circuit on or in the wiring harness somewhere

The techies that have posted here attempting to solve the "17 times and out" mystery are far more knowledgeable than myself when it comes to ECU internal electronics and they could very well be correct as they have done the maths and the figures add up.......But??????

There is a possibility that a wiring fault will be causing strange things to happen

Get someone to take a look at the Oxygen sensor and its wiring plus have a good look around the wiring harness especially in the engine bay or close to the exhaust

[eliot]

And if the live for o2 sensor was taken via a main fused supply rather than the daft arrangement via ignition live this may not of happened (as suggested by the other poster)

Also the live to the ecu would be sagging on each cycle which I would of thought the garage would of noticed? Unless the live was backfeeding the o2 input rather than a straight live-e short.

Anyway, interesting thread and shows that things can be fixed over the internet sometimes.

[Kccv23highliftcam]

Still, the harness routing should never have been left like that from the factory-robust electrical installation has never been the strong point of small volume producers though, never mind how clever the mechanical design/packaging...






Never actually failed mind!! The joys of buying the development car lolol...

Edited by Kccv23highliftcam on Saturday 3rd November 08:38

[Toilet Duck]

Mignon said:

I would say that the solution was already given here and full points to the following post.

Penelope Stopit said:

FAO Toilet Duck

Yep, special thanks to Penelope Stopit, he was like a man possessed in his efforts to get to the bottom of this issue. Very much appreciated

[Penelope Stopit]

Toilet Duck said:

Mignon said:

I would say that the solution was already given here and full points to the following post.

Penelope Stopit said:

FAO Toilet Duck

Yep, special thanks to Penelope Stopit, he was like a man possessed in his efforts to get to the bottom of this issue. Very much appreciated

I am happy to have been able to help, the fault was a goodun
If you wan't to modify the wiring to how the factory should have wired the Oxygen sensor and ECU post back here and I will gladly knock you a diagram up

[eliot]

Penelope Stopit said:

Below is what I have harvested from the Honda wiring diagrams and the JLR Freelander Multi Function Relay Unit

So it looks like the starter solenoid also shares the switched ignition live - which would seem odd as well, as even the solenoid is quite a load to drive via the relatively low amperage rating of an ignition switch (unless there's an upstream relay - which we assume there isn't).
You would expect at the very least for the o2 sensor and starter solenoid to share a fused supply from the battery.

[Kccv23highliftcam]

Just as a matter of interest are their any soldered joints in the relay panel?

[Sardonicus]

And like I was taught in the the 80's you should never substitute presumed faulty parts with confirmed known good units as you can create further damage to now substituted part had the integrity of the loom been checked previously by specialist this would of been found far sooner glad you have got your car sorted though and great you updated these guys

[Penelope Stopit]

eliot said:

Penelope Stopit said:

Below is what I have harvested from the Honda wiring diagrams and the JLR Freelander Multi Function Relay Unit

So it looks like the starter solenoid also shares the switched ignition live - which would seem odd as well, as even the solenoid is quite a load to drive via the relatively low amperage rating of an ignition switch (unless there's an upstream relay - which we assume there isn't).
You would expect at the very least for the o2 sensor and starter solenoid to share a fused supply from the battery.

You've got it. I was going to post more about my findings and also ask Toilet Duck if he/she was willing to open up the original Multi Function Relay Unit to see if a part of the PCB had been modified
I didn't bother to continue posting here due to the fault being found, there was more to come if needed

In noticing that you had asked for Toilet Duck's whereabouts in this world, I gathered that you were going to have a run out and check the circuits through, I was going to contact you about my above findings and how I came about them so as to possibly save you some time, I will post more later so that you can view it and give your opinion (if you wish to). I'm too busy right now. I would have enjoyed checking the circuits myself but live too far away from the Toilet

[Penelope Stopit]

Kccv23highliftcam said:

Just as a matter of interest are their any soldered joints in the relay panel?

See opening post

[Penelope Stopit]

Sardonicus said:

And like I was taught in the the 80's you should never substitute presumed faulty parts with confirmed known good units as you can create further damage to now substituted part had the integrity of the loom been checked previously by specialist this would of been found far sooner glad you have got your car sorted though and great you updated these guys

Dead on, the circuits needed checking through by someone that knows the job and there is no way that units should have been swapped as they were
Unfortunately the automotive repair business gets a very bad reputation due to those without the knowledge taking on jobs that they shouldn't be.
I did mention that they shouldn't be working on this particular fault and there are many knowledgeable posters here that will be of the same opinion....To me it stood out like a TVR in a supermarket car park that they were going about the job the wrong way
There are too many automotive repair shops with all the gear and........

Edited by Penelope Stopit on Sunday 4th November 13:48

[stevieturbo]

Sardonicus said:

And like I was taught in the the 80's you should never substitute presumed faulty parts with confirmed known good units as you can create further damage to now substituted part had the integrity of the loom been checked previously by specialist this would of been found far sooner glad you have got your car sorted though and great you updated these guys

Some proper and very basic checks from the outset would definitely have helped discover what or where the problem might be, but unfortunately basic diagnostics seems above and beyond most so called mechanics/garages etc.

It was a strange problem, but without proper testing/inspection it was going to take a huge bit of luck to find out what was wrong.

[eliot]

Penelope Stopit said:

In noticing that you had asked for Toilet Duck's whereabouts in this world, I gathered that you were going to have a run out and check the circuits through, I was going to contact you about my above findings and how I came about them so as to possibly save you some time, I will post more later so that you can view it and give your opinion (if you wish to). I'm too busy right now. I would have enjoyed checking the circuits myself but live too far away from the Toilet

Yeh - I’ve got good electronic test equipment including a digital scope - i wanted to look at the feed into the ecu for sagging/spikes. It was your drawings that led me in that direction - so props for looking into it and posting it up.

[Penelope Stopit]

eliot said:

So it looks like the starter solenoid also shares the switched ignition live - which would seem odd as well, as even the solenoid is quite a load to drive via the relatively low amperage rating of an ignition switch (unless there's an upstream relay - which we assume there isn't).
You would expect at the very least for the o2 sensor and starter solenoid to share a fused supply from the battery.

eliot said:

Yeh - I’ve got good electronic test equipment including a digital scope - i wanted to look at the feed into the ecu for sagging/spikes. It was your drawings that led me in that direction - so props for looking into it and posting it up.

Ok, I apologise for this reply being so late

In looking at the above original Honda wiring diagram I noticed that the ECU switched negative outputs were connecting to teminals 86 of the relays and I expected them to be connected to terminals 85, In looking at the Multi Function Relay Unit's internal circuit I didn't need to work out which terminals those ECU switched negative outputs were connecting to as I didn't have a choice, I had no choice because the Main Relay and Oxygen Sensor Relay have internal links and those links told me that the ECU switched negative outputs had to connect to terminals 85 of their circuits relays

Having drawn up the diagram of how I expected the MFRU Main, Fuel Pump and Oxygen Sensor Relay's to be wired I was left with a starter relay with no home to go to and noticed as you did that the ignition supply to the ECU and MFRU was connecting to the starter relay contact terminal 30, as we already knew that the starter circuit was very unlikely to be causing the problem I didn't delve any deeper with it but there is a possibility that the immobiliser is wired into this relay and there is another relay elsewhere for cranking
As you have mentioned, there would be a high load on the ignition wire if the starter relay terminal 87 was connected directly to the starter solenoid and that load being at a guess (because starter solenoids differ so much) 15 to 25 Amps Pull-in and 10 to 15 Amps hold-in would very likely overload the ignition supply and cause the same fault as the Oygen sensor was doing

All of what I post above is assuming that the MFRU hasn't been modified and we both know what assuming can cause don't we. It would have been good if Toilet Duck had noticed if the MFRU had been modified in any way but I doubt we will ever find out as he/she is very likely screaming the Atom around for the foreseeable future

I hope Toilet Duck presents you a Blue Peter Badge for your kind thoughts of making a journey to his part of the world to fix the fault
I don't own a scope. You, your knowledge and scope would have no doubt soon found the fault

It was the below post that once and for all took my mind away from the 17 times and out thingy,(it's very likely that all of the same type ECU's will do this under certain circumstances), although like many others here I thought the 17 times and out was being caused by the ECU I hold my hands up and admit that I went back to it for a while rather than move on and look for what a possible wiring fault could create

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.

Someone with a logical way of thinking does often help, my mind sometimes wanders back to what I've already discounted, I have noticed that you didn't fall into the trap that I did

[Toilet Duck]

Penelope Stopit said:

eliot said:

Yeh - I’ve got good electronic test equipment including a digital scope - i wanted to look at the feed into the ecu for sagging/spikes. It was your drawings that led me in that direction - so props for looking into it and posting it up.

I hope Toilet Duck presents you a Blue Peter Badge for your kind thoughts of making a journey to his part of the world to fix the fault
I don't own a scope. You, your knowledge and scope would have no doubt soon found the fault

It's in the post Some very generous people on here, really grateful for all the invaluable help

Penelope Stopit said:

All of what I post above is assuming that the MFRU hasn't been modified and we both know what assuming can cause don't we. It would have been good if Toilet Duck had noticed if the MFRU had been modified in any way but I doubt we will ever find out as he/she is very likely screaming the Atom around for the foreseeable future

I haven't got the Atom back yet, I'm letting them redo the burnt bit of loom as I just want a fully working car when I pick it up. When I get it back, I will double check the MRFU internals but I am 99.99% sure it was unmodified. I went over all the pads on the back of the PCB with a soldering iron and re-blobbed them in case of a dry joint (obviously a pointless exercise knowing what we do now). and it all looked "original" to me