Sparking problem

[Penelope Stopit]

[Bigfish_74]

Hi Guys, sorry not been around for a while as didn't realise the debate had continued. Update, I found a hot wire to ign fuse that I replaced also rebuilt a couple of relay connections that were iffy, still only 11v with coil earthed. Spent time swapping around amplifiers, coils (yes it is a12v coil) plugs etc. The new amp had packed in so back to the original but I now have a good spark at all plugs earthed to plenum and with the inline spark tester. Still the anomaly with the timing gun but put this down to a poor quality gun. Unfortunately for the debate can't attribute it to any one thing. Managed to set the timing as gun works with plug earthed to engine.
Car still doesn't start...... Now also seems to be a fueling problem (previously had been fueling so not sure if I'd fried sonething) been testing other components and I'm only getting 0.75v at the throttle pot and AFM, articles say it should be 4.5v, ECU presumably drops the voltage so I sent both ECU and AFM for rebuild (everything else on the car has been rebuilt so what the heck) to ATP but still no fuel. Currently speaking to ATP to find out the results they got, will let you know and will start a new thread as this is long.

[Penelope Stopit]

Bigfish_74 said:

Hi Guys, sorry not been around for a while as didn't realise the debate had continued. Update, I found a hot wire to ign fuse that I replaced also rebuilt a couple of relay connections that were iffy, still only 11v with coil earthed. Spent time swapping around amplifiers, coils (yes it is a12v coil) plugs etc. The new amp had packed in so back to the original but I now have a good spark at all plugs earthed to plenum and with the inline spark tester. Still the anomaly with the timing gun but put this down to a poor quality gun. Unfortunately for the debate can't attribute it to any one thing. Managed to set the timing as gun works with plug earthed to engine.
Car still doesn't start...... Now also seems to be a fueling problem (previously had been fueling so not sure if I'd fried sonething) been testing other components and I'm only getting 0.75v at the throttle pot and AFM, articles say it should be 4.5v, ECU presumably drops the voltage so I sent both ECU and AFM for rebuild (everything else on the car has been rebuilt so what the heck) to ATP but still no fuel. Currently speaking to ATP to find out the results they got, will let you know and will start a new thread as this is long.

Thank you for the update

You've gained half a volt

Are you not concerned about gaining some more ?

If you were paying me to fix your cars ignition system, I would first get that voltage closer to battery voltage

The coil supply is very important

I'm not one for misleading people

Due to you not seeming to be over concerned about cost, it would be worth your while to pay an auto electrician to sort out the supply

A heavy duty (70 Amp) relay wired with 15 Amp or above rated cable will get that voltage up, should someone wire a relay in for you, make sure they don't forget the rev counter loop if yours has one

[Bigfish_74]

Your are very wrong, incredibly concerned about how much I'm spending on this bloody thing, but I'm commited now. Yes I will continue to search for the missing voltage (could it be the ignition barrel)?

[Penelope Stopit]

Bigfish_74 said:

Your are very wrong, incredibly concerned about how much I'm spending on this bloody thing, but I'm commited now. Yes I will continue to search for the missing voltage (could it be the ignition barrel)?

Ooops, didn't mean to offend

Bigfish_74 said:

I sent both ECU and AFM for rebuild (everything else on the car has been rebuilt so what the heck)

The above influenced my thought process

I wish your car was here by me now, would gladly fix it for free

There are always question marks about what's fitted to a vehicle that's not within reach

First prove that there is definitely a relay supplying the coil

If there is a relay supplying the coil, the answer to your question is - No, any ignition switch volt-drop will not be causing the volt-drop to the coil, the ignition switch will trigger the ignition relay and that same relay will supply the coil

There could be a problem with the supply from battery positive to the relay, at the fuse holder, from relay to rev counter if wired in or from rev counter to the coil positive

I have a hunch that the positive from the battery to the relay could be connected to the positive battery terminal or close by

The problem is that a low voltage supply to a v8 engines coil is a proper pain, the coil is so busy (2 x 4cylinder work load) that it needs to have a good voltage supply to build up the magnetic field as quickly as possible

You can easily verify what I am now posting and have posted to this topic by contacting one of the following

They are very helpful

In no particular order

spitfire4v8 https://www.pistonheads.com/gassing/profile.asp?h=...

Zener https://www.pistonheads.com/gassing/profile.asp?h=...

blitzracing https://www.pistonheads.com/gassing/profile.asp?h=...

If you need any advice in carrying out a wiring job to improve that supply voltage, please do feel free to ask

[pk500]

Bigfish_74 said:

Your are very wrong, incredibly concerned about how much I'm spending on this bloody thing, but I'm commited now. Yes I will continue to search for the missing voltage (could it be the ignition barrel)?

I lost power on my 400 turned out the Rev counter had shorted took me a while to find it I unplugged Rev counter and joined wires and away it went

[blitzracing]

Bigfish_74 said:

Hi Guys, sorry not been around for a while as didn't realise the debate had continued. Update, I found a hot wire to ign fuse that I replaced also rebuilt a couple of relay connections that were iffy, still only 11v with coil earthed. Spent time swapping around amplifiers, coils (yes it is a12v coil) plugs etc. The new amp had packed in so back to the original but I now have a good spark at all plugs earthed to plenum and with the inline spark tester. Still the anomaly with the timing gun but put this down to a poor quality gun. Unfortunately for the debate can't attribute it to any one thing. Managed to set the timing as gun works with plug earthed to engine.
Car still doesn't start...... Now also seems to be a fueling problem (previously had been fueling so not sure if I'd fried sonething) been testing other components and I'm only getting 0.75v at the throttle pot and AFM, articles say it should be 4.5v, ECU presumably drops the voltage so I sent both ECU and AFM for rebuild (everything else on the car has been rebuilt so what the heck) to ATP but still no fuel. Currently speaking to ATP to find out the results they got, will let you know and will start a new thread as this is long.

Id of given it a squirt of Easy Start to see if it would fire. What is the ecu in this car?

[adam quantrill]

Ad you are back on BigFish please fill us in with the details of the car, year of manufacture, and whether the rev counter is the old style one or the new style upside-down one? (Yes, it's relevant!) Later one looks like this:



Good idea to start a new thread on fuelling and keep this one to ignition.

Edited by adam quantrill on Wednesday 17th June 10:36

[KKson]

blitzracing said:

Id of given it a squirt of Easy Start to see if it would fire. What is the ecu in this car?

ECU is Rover EFi 4CU. If there was no fuel then I'd have checked fuel pump. If it wouldn't run via the AFM/ECU then I'd have fitted a very temporary supply to it to ensure it's running, plus checked fuel pressure and fuel regulator. If pressure and fuel on the fuel rail and still no fuel down the injectors then either the injectors are all blocked up with crap (doubtful) or could be the ECU/EFi not driving them, in which case I'd do a point to point wiring check to see if there is a damaged wire in the loom and if the wiring is good then an inspection and rebuild of the ECU would probably be next on the list.

Edited by KKson on Wednesday 17th June 10:33

[O mage]

Bigfish_74 said:

Hi Guys, sorry not been around for a while as didn't realise the debate had continued. Update, I found a hot wire to ign fuse that I replaced also rebuilt a couple of relay connections that were iffy, still only 11v with coil earthed. Spent time swapping around amplifiers, coils (yes it is a12v coil) plugs etc. The new amp had packed in so back to the original but I now have a good spark at all plugs earthed to plenum and with the inline spark tester. Still the anomaly with the timing gun but put this down to a poor quality gun. Unfortunately for the debate can't attribute it to any one thing. Managed to set the timing as gun works with plug earthed to engine.
Car still doesn't start...... Now also seems to be a fueling problem (previously had been fueling so not sure if I'd fried sonething) been testing other components and I'm only getting 0.75v at the throttle pot and AFM, articles say it should be 4.5v, ECU presumably drops the voltage so I sent both ECU and AFM for rebuild (everything else on the car has been rebuilt so what the heck) to ATP but still no fuel. Currently speaking to ATP to find out the results they got, will let you know and will start a new thread as this is long.

Im sure you haven't caught up with the madness in this tread. You have checked the feed 12v and can pull 5 amps (bulb test) you then connect the good feed to the coil and are now measuring across the coil. You are now measuring the coil with it engaged /switched on. This reading is a coil reading so you are measuring the coil circuit now not the feed. The reading you are getting is standard KKson has 2 and they are reading similar across the coil and the both run fine.

If the feed can pull 5amps to light the bulb it can pull 5 amps to run the coil. Across the coil you are checking the circuit inside the coil and it is pulling down voltage in readiness to fire.

You are testing the coil now and blaming the feed.!
Please tell me you understand this and then you can stop wasting time.

[Bigfish_74]

Penelope Stopit said:

The above influenced my thought process

I wish your car was here by me now, would gladly fix it for free

There are always question marks about what's fitted to a vehicle that's not within reach

First prove that there is definitely a relay supplying the coil

If there is a relay supplying the coil, the answer to your question is - No, any ignition switch volt-drop will not be causing the volt-drop to the coil, the ignition switch will trigger the ignition relay and that same relay will supply the coil

There could be a problem with the supply from battery positive to the relay, at the fuse holder, from relay to rev counter if wired in or from rev counter to the coil positive

I have a hunch that the positive from the battery to the relay could be connected to the positive battery terminal or close by

The problem is that a low voltage supply to a v8 engines coil is a proper pain, the coil is so busy (2 x 4cylinder work load) that it needs to have a good voltage supply to build up the magnetic field as quickly as possible

You can easily verify what I am now posting and have posted to this topic by contacting one of the following

They are very helpful

In no particular order

spitfire4v8 https://www.pistonheads.com/gassing/profile.asp?h=...

Zener https://www.pistonheads.com/gassing/profile.asp?h=...

blitzracing https://www.pistonheads.com/gassing/profile.asp?h=...

If you need any advice in carrying out a wiring job to improve that supply voltage, please do feel free to ask

No offence taken stopit just don't suggest to a Yorkshireman that money is no concern🤣😂
Although spark is now ok I too think there is a fundamental fault with the wiring that is also causing the ECU to drop voltage to t pot and afm

[Penelope Stopit]

Bigfish_74 said:

No offence taken stopit just don't suggest to a Yorkshireman that money is no concern????
Although spark is now ok I too think there is a fundamental fault with the wiring that is also causing the ECU to drop voltage to t pot and afm

Noted with a smile

Mentioning that you're a Yorkshireman has brought back fond memories of Hebden Bridge and other places close by, them were the days

Will take a look at a diagram later, no time at present, others will very likely be taking a look

[adam quantrill]

Penelope Stopit said:

This is getting boring now

No, it's reaching its climax! Out friend is just about to explain something under our bonnets that could be truly groundbreaking.

I;m just waiting for an answer to my last question:

adam quantrill said:

So what is this phenomenon, energy lost to heat? Or "inductive" energy? Please clarify!

[Penelope Stopit]

adam quantrill said:

Penelope Stopit said:

This is getting boring now

No, it's reaching its climax! Out friend is just about to explain something under our bonnets that could be truly groundbreaking.

I;m just waiting for an answer to my last question:

adam quantrill said:

So what is this phenomenon, energy lost to heat? Or "inductive" energy? Please clarify!

It was read and appreciated

What wasn't viewed by many was something that was posted at approx 00:30 hours PH time and later deleted, I am not going to repeat any part of it as doing so could lead to me being accused of being a liar and making it all up, it was absolutely crazy

Anyway, let's move on

Having given things much thought I now understand what it's all about and wish I had never posted here

It always was so obvious and I do suffer from missing the obvious

See below

[adam quantrill]

That would be better redrawn - as a circuit.. If you have time Get rid of the earth symbols, and add in the ignition switch, fuse and anything else in the way.

Then Kirchoff's law can be more readily applied, and Mr O(h)mage can explain himself.

[Nickl911]

Morning

Well I didn't want to reply again as i feel this post is getting too personal, however....

My 350i (1985 reg) is a very slow single handed body off rebuild so still not near being on the road but...

It is now on twin SU's because of starting and running problems similar to the OP.

I have measured the same very low voltage at the Flapper unit and the Throttle Potentiometer. I didn't want to waste money getting the ECU rebuilt because the other two units will be unreliable unless also rebuilt, not to mention the extra air valve, dodgy injectors, overrun valve etc. I've gone for simplicity so I can get the damn thing out of my garage, and on the road, before I go to the next restoration steps.

So looking for 4.5 volts from the ECU and seeing 0.34 ?? is a similar problem to the OP.

I'd really appreciate to know if this gets the fix done, and how much it costs. (welshman / yorkshireman = careful with money. I don't mind spending money but I do like getting value in return).

I'll post separately on other things I've found.

[Nickl911]

So what interesting things have I found recently while pondering BigFishes problem.

Well I disconnected the battery positive terminal and connected up my cheap multimeter to

The white wire going to the coil and to the brown wires going to the battery positive. This gave an initial reading of 45 ohms which must be wrong so I started to chase down the source of the high resistance. Long story short, the ohms reading will vary wildly from 50 ohms to 130 ohms to zero depending on how I wiggle the key and the contacts at the end of the key barrel. Fortunately I can see the reading change while I wiggle because I set up a solid connection to those wires and propped up the mutimeter where I could see it through the windscreen.

So I would respectfully suggest the OP looks at this first.

[Nickl911]

However, I think 10.5 volts is going to be somewhat the norm with 350i's of that era. Quite a few report similar readings and I think the OP's problem with starting lies elsewhere.

Even my car starts (well when I don't have another problem like fuel and water exhaust leaks) and will it start again after I have fiddled with the key wiring??

And in looking at my wiring,

A. It doesn't follow precisely any of the wiring diagrams in the Bible, nor is the relay layout the same.
B. Someone has butchered the wiring to fit a clifford alarm (and then butchered it again to remove it).
C. no sign (yet) of a ballast resistor cable.

The joys of owning a TVR I suppose

[adam quantrill]

Thanks Nick, some interesting stuff.

Yes the Bible only had limited room for the variants of wiring diagrams. I supplied Steve with my copies and I think he got more from elsewhere, so he chose the most representative ones.

The 1985 350i's are more like the SD1 layout, but then TVR got fiddling I am guessing in an attempt to improve reliability with ignition components subjected to much higher underbonnet temperatures, not to mention engines running higher up the rev range when driven hard compared to your average SD1 flat cap driver.

You resistance readings seem very high, coil primaries are in the order of a few ohms, so you need to look at this before attempting a startup I would think. But yes, the ignition barrel is a potential culprit, operate it back and forth 50 times to see if the contacts clean up internally.

[O mage]

Nickl911 said:

However, I think 10.5 volts is going to be somewhat the norm with 350i's of that era. Quite a few report similar readings and I think the OP's problem with starting lies elsewhere.

Even my car starts (well when I don't have another problem like fuel and water exhaust leaks) and will it start again after I have fiddled with the key wiring??

And in looking at my wiring,

A. It doesn't follow precisely any of the wiring diagrams in the Bible, nor is the relay layout the same.
B. Someone has butchered the wiring to fit a clifford alarm (and then butchered it again to remove it).
C. no sign (yet) of a ballast resistor cable.

The joys of owning a TVR I suppose

Wanted to save this for posterity in the thread so that anyone in future who see's the 10.5v reading across their coil can understand that this is quite normal and will not stop the engine from running..