Please visit the Club's website https://www.dloc.org.uk/ to join. Visit https://www.dloc.org.uk/adhoc to DONATE towards the cost of the forum.
Please don't post someone's email address to avoid it being harvested by spambots and it's against GDPR regulations.
Always look at "ACTIVE TOPICS" to see all posts in date & time order as they are sometimes moved; or look at "Your Posts".
Please add Reg. nrs. when posting a photo or anything about a car as this will help searches. Don't add punctuation next to nr. as this negates search.
CHANGED YOUR EMAIL ADDRESS since registering?, click your username and check your address in User Control Panel, Profile, Account Settings.
If you want help to register, use "contact us" at page bottom for help.

Ignition noise

Post Reply
Sonus
Posts: 208
Joined: Wed Apr 13, 2016 2:19 pm

Ignition noise

Post by Sonus »

My Daimler V8 powered TVR has an extraordinary amount of ignition noise. I have no radio, but it interferes with my turn signal relay and makes my mulitmeter go crazy when I start the engine. The turn signal relay works fine with the ignition on and engine off, but goes crazy with the engine started. Is there a quick fix?

tjt77
Wise Man
Wise Man
Posts: 525
Joined: Wed Mar 23, 2016 7:01 pm

Re: Ignition noise

Post by tjt77 »

this is an odd problem.. not sure I can help, and likely no 'quick' fix.. you dont state what the 'crazy' reaction of turn signal relay is exactly.. if its something simple such as speeding up of the intervals of cutting in/out that would be due to voltage variations with engine running V turned off.. more voltage shortens the intervals between on and off.. more 'resistance' lengthens them .

As regards 'radio interference' noise ( hailstorm like sound in radio) there are a number of possible solutions.. firstly check that all connections and wires in distributor are in good shape.(often the connecting wires are frayed where they enter the connectors which ads resistance..requires very close inspection..make sure to to check the earth wire twixt baseplate and distributor body.. if the connections are comprimised , the result is added resistance, (which increases electrical interference noises) also any pitting of the points will add noise.. in essence anything that MAY add resistance to the circuit is likely to produce problem.. a weak condenser (capacitor) will also add noise as it increases sparking accross the points and seriously shortens their life.. if the low tension circuits is in good health.. check the rotor arm and contacts in distributor cap for corrosion.. and rectify as necessary.. check gaps on spark plugs.. should be no more that .025" ..larger gap = more noise..you can always add 'modern' plug wires, and radio compliant plug caps, which are designed specifically to reduce radio interference.. often noise form dynamo is present..this can be mitigated with a capacitor.
another possible issue is, that given you have glass fibre body (as per Sp250) this does little to limit transmission of electrical noises .. but you can add some insulation that has a metal component to both underside of bonnet and on firewall..the more costly versions have a thin lead film in them.. 'dynamat' should be effective.. good luck..

Sydsmith
Extremely Wise Man
Extremely Wise Man
Posts: 1369
Joined: Sun Feb 14, 2016 11:15 pm
Location: Aberystwyth Wales

Re: Ignition noise

Post by Sydsmith »

Hi Sonus, all that has been said is good but I am interested to know how you have identified ignition interference as the culprit?

Have you got a dynamo or alternator fitted to the car? If you have an alternator is sounds like you may have raw AC from the alternator getting through the charging system, in which case you may also have battery voltage problems.

Digital multi-meters are a pain when it comes to checking 12 volt electrics and can be misleading, try setting the meter on AC instead of DC to prove that you have an alternator problem.

I have a good old Avo 8 meter which is great for car electrics, a bit bulky and batteries are getting difficult to find but they are cheap as chips on fleabay, they give you a much better indication of what is going on with your electrics.

User avatar
JohnM
Posts: 206
Joined: Thu Feb 11, 2016 1:31 pm
Location: N W London

Re: Ignition noise

Post by JohnM »

Hi Sonus,
yes, like you I have huge RF pickup from my SP - I can't use an inductive pickup timing light, as just dangling the pickup lead anywhere near the engine picks up all the plugs at once! Ditto the digital multimeter.
Wierdly, my Gilbern - also GRP body, steel chassis - doesn't show this problem at all ! And both are running high-energy electonic ignition systems with silicon leads, so no difference there.

Like Syd I use an AVO for measurements and an inline pickup for my timing light, but if you find an answer I'm all ears!

Cheers, John
John M in Middlesex, NW London
1962 SP250 "B" Spec
DLOC Herts Region Sec

bakergh
Posts: 109
Joined: Wed Feb 24, 2016 1:57 pm
Location: New Forest, Hampshire

Re: Ignition noise

Post by bakergh »

Could it be that the HT coil either has no earth or a poor earth connection to its body if mounted on fibre glass?

Graham

User avatar
JohnM
Posts: 206
Joined: Thu Feb 11, 2016 1:31 pm
Location: N W London

Re: Ignition noise

Post by JohnM »

Hi Graham,
don't know about Sonus's car, but mine has one of the main earth points on the coil mounting bolts so I don't think it's that I'm afraid.
thanks for the thought, though!

regards, John
John M in Middlesex, NW London
1962 SP250 "B" Spec
DLOC Herts Region Sec

Post Reply