Ignition cutting out over bumps

Talk about the E-Type Series 3

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Lambo911
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#1 Ignition cutting out over bumps

Post by Lambo911 » Fri Oct 16, 2015 8:20 am

On several occasions a jolt though the car from a bump in the road has caused the ignition to cut for a second or two which is a bit disconcerting. It also happened the other day when I was having some fun with a 911. At quite high revs in fourth it suddenly started to lose power and the rev counter needle was bouncing all over the place, I slowed up and it started to behave again but it did spoil my game!

I have a new coil, leads, dizzy cap and rotor arm as well as new Opus ignition. Where I can see them the wires and connectors seem ok.
Are there any other areas of the ignition system that would give this kind of issue?

Or is it the car telling me to drive sedately !! :oops:

Cheers
Richard
Richard
____________
1972 S3 2+2 - Black with Red leather, 4 Speed and Wires
1966 S Type 3.8 MOD - ex South Africa
1994 XJS V12 coupe - 59,000 miles

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mgcjag
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#2

Post by mgcjag » Fri Oct 16, 2015 8:43 am

Hi Richard...is it loss if ignition, or loosing power.....The latter could be fuel pump intermittent loss of electric supply causes engine to loose power then pump coming back on and engine picking up.....A friend had a similar fuel problem on his S3 with just one of the pumps cutting out now and then....car ran fine on one at lower revs but on higher the two together were needed.... Steve
Steve
1969 S2 2+2 & Building a C type replica

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Lambo911
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#3

Post by Lambo911 » Fri Oct 16, 2015 9:08 am

Hi Steve,

I did think about fuelling but ruled it out because the car should run on its float chambers for a while and with the 'jolt' related issue the power loss was immediate.

If fuel pump wasn't keeping up with the fuel requirement at high revs I'd expect the car just to feel like it was holding back (lean mixture) but in this case I think the erratic rev counter points to ignition.

cheers
Richard
Richard
____________
1972 S3 2+2 - Black with Red leather, 4 Speed and Wires
1966 S Type 3.8 MOD - ex South Africa
1994 XJS V12 coupe - 59,000 miles

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mgcjag
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#4

Post by mgcjag » Fri Oct 16, 2015 9:43 am

Hi Richard...I don't know why...but that's exactly the same as my friends...He would lose power and the Rev needle would start to get erratic. ....The only way we found the fault was as soon as it happens pulled over and touch the pumps and found one was not running....If we tapped it it would start again....replaced and all ok Steve
Steve
1969 S2 2+2 & Building a C type replica

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Lambo911
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#5

Post by Lambo911 » Fri Oct 16, 2015 10:16 am

Ok, fair point, I'll check the pump.

It has given problems in the past. I should be able to give it a whack to simulate a bump to see what happens.

Thanks
Richard
Richard
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1972 S3 2+2 - Black with Red leather, 4 Speed and Wires
1966 S Type 3.8 MOD - ex South Africa
1994 XJS V12 coupe - 59,000 miles

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jonhall88
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#6

Post by jonhall88 » Fri Oct 16, 2015 12:16 pm

Have you checked out the ignition switch and the fit of the key, if its badly worn can the barrel turn slightly
1974 ser 3

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Lambo911
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#7

Post by Lambo911 » Fri Oct 16, 2015 12:40 pm

From memory the key was a good fit but I will take a closer look.

Thanks
Richard
Richard
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1972 S3 2+2 - Black with Red leather, 4 Speed and Wires
1966 S Type 3.8 MOD - ex South Africa
1994 XJS V12 coupe - 59,000 miles

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abowie
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#8

Post by abowie » Fri Oct 16, 2015 10:24 pm

There's a loose wire somewhere +/- something that moves more over bumps than normal is breaking the ignition circuit somewhere.

Sorry that's not very specific.

Start from the battery one one side and check every single wire and connector for resistance while jiggling them about. Don't leave out the main earth strap between the body and the engine.
Andrew.
881824, 1E21538. 889457..oops. Jezza the V12 XJS race car.
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia

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JagWaugh
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#9

Post by JagWaugh » Sat Oct 17, 2015 5:30 am

In terms of cutting out, electrical problems move at the speed of light, fuel/air problems move at the speed of the vehicle... ergo, the cutting out is electrical.

Suspect the ignition switch first. One way to localise the fault is to run a temporary (fused and with a switch at the battery end) feed straight from the battery and connect it progressively along the chain that ends up at the coil/ignition, driving over bumps known to cause the cutout as you hotwire past each leg of the chain. Don't forget the switch in your temporary hotwire, as otherwise you won't be able to switch off the engine once started.

Andrew

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PeterCrespin
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#10

Post by PeterCrespin » Sat Oct 17, 2015 1:52 pm

Agree the first (and only mechanical) suspect in the LT ignition circuit is the switch. The detents get worn and contact riveting loosens off so even delicate movements of the key affect continuity. I had the issue on my S2 with the same type of column switch.

Pete
1E75339 UberLynx D-Type; 1R27190 70 FHC; 1E78478; 2001 Vanden Plas

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#11

Post by Lambo911 » Sun Mar 13, 2016 5:28 pm

I think the issue is with the wire from the coil to the dizzy and the 3 pin connection between the two sections of wire. I've cleaned it up and hopefully that's sorted it out.
Richard
____________
1972 S3 2+2 - Black with Red leather, 4 Speed and Wires
1966 S Type 3.8 MOD - ex South Africa
1994 XJS V12 coupe - 59,000 miles

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