3000M bad misfire when hot

3000M bad misfire when hot

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plasticpig72

Original Poster:

1,647 posts

148 months

Wednesday 20th July 2016
quotequote all
I have added a return to tank "T" just after pump outlet. To act as a restrictor i have used a weber air corrector 175 inside the return petrol hose. I put a hose clip on outside to stop it moving inside hose.
Road test to follow
Alan

plasticpig72

Original Poster:

1,647 posts

148 months

Wednesday 20th July 2016
quotequote all
Just got back from road test of 30 miles and a big success . Fuel lines cool and NO VAPOUR LOCKbiggrin. Conclusion fit return line to tank just after exit from electric pump with a restrictor in return to tank. No cavitation in electric pump and cool petrol.Left return to tank and right supply to engine

Alan


Edited by plasticpig72 on Thursday 4th August 06:56

plasticpig72

Original Poster:

1,647 posts

148 months

Monday 25th July 2016
quotequote all
Well the saga continues, at least when you have a TVR there is never a due moment. When you have 2 you are looking for trouble.
Let's get to the subject. I went for a drive again today and after 6 or 7 kms my 3000M started to misfire again but with a BONUS the Windscreen Washers started to function and water everywhere. A small detail i hadn't switched them oneek which is quite a mind bender for me a TVR Virginconfused
I managed to get home with a very clean Windscreen. Switched off engine but would not start except when the Ignition Key was turned the Windscreen Washers worked by themselveseek
I went indoors to take a nice coooool beer and think. After the car had cooled down it restarted no problem, i'm confused. Any ideas chaps
Alan

anonymous-user

53 months

Monday 25th July 2016
quotequote all
Brains in the distributor or head gasket on the way?

plasticpig72

Original Poster:

1,647 posts

148 months

Monday 25th July 2016
quotequote all
I will try a new cable from the Ignition switched first position (white wire) to the Coil, thereby bypassing the wiring harness . To start from basics.
Results to follow
Alan

Slow M

2,726 posts

205 months

Monday 25th July 2016
quotequote all
You probably have a short in the harness! I would dig out the wires beginning at the wiper motor, and look for melted insulation/sheathing.

Disconnect the battery, when you're not working on it.

Best regards,
Bernard.

GAjon

3,721 posts

212 months

Tuesday 26th July 2016
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Check all the electrical joints and earths behind the dashboard and switch panels, especially those on knurled nuts that hold the gauges in place.

plasticpig72

Original Poster:

1,647 posts

148 months

Tuesday 26th July 2016
quotequote all
GAjon said:
Check all the electrical joints and earths behind the dashboard and switch panels, especially those on knurled nuts that hold the gauges in place.
Just looked behind dashboard and found some knurled nuts loose on backs of gauges that hole them in place and serve as earths. I had a look behind rocker switches and found the reason for washers running with switch off. It was an illumination bulb and metal clip loose, short circuiting washer switch terminals. Spades at back of switch without insulating sleeveseek
Does anyone know a source for rocker switches like original because i need one for the Wipers.
Alan

Slow M

2,726 posts

205 months

Tuesday 26th July 2016
quotequote all
plasticpig72 said:
Just looked behind dashboard and found some knurled nuts loose on backs of gauges that hole them in place and serve as earths. I had a look behind rocker switches and found the reason for washers running with switch off. It was an illumination bulb and metal clip loose, short circuiting washer switch terminals. Spades at back of switch without insulating sleeveseek
Does anyone know a source for rocker switches like original because i need one for the Wipers.
Alan
Glad that you found it, and that I was wrong.

Best regards,
Bernard.

plasticpig72

Original Poster:

1,647 posts

148 months

Tuesday 9th August 2016
quotequote all
Just got back from 20 mile run and suddenly starts to misfire again.
When i touched the carb it's very warm and i wonder if it's heat transfer to carb.
Has anyone fitted a heat shield to reduce heat transfer to carb.
Maybe i need to go for another run until it misfires then vaporise the carb with water to cool it down. Then see if it runs without misfire.
Alan

GAjon

3,721 posts

212 months

Tuesday 9th August 2016
quotequote all
Where do you buy your petrol from? Just a thought!

plasticpig72

Original Poster:

1,647 posts

148 months

Tuesday 9th August 2016
quotequote all
I buy the same place, same petrol and same grade for my 3000S also Lotus Elan Sprint NO PROBLEM.
I'm thinking 1. condenser
2. vent in filler cap.
3.carb float level wrong too high/too rich when hot.
4. dissy cap.
5. spark plugs wrong grade fitted.
6.rotor arm.
7. power valve carb.
8. H.T. leads breaking down when hot.
The spark plugs have heat insulating tape around the porcelaine, could it make them too hot.
Well that's my brain storming list for the moment.
Alan

anonymous-user

53 months

Tuesday 9th August 2016
quotequote all
It's nothing to do with fuel and heat IMO.

I really would check for healthy head gaskets as the next step.

plasticpig72

Original Poster:

1,647 posts

148 months

Tuesday 9th August 2016
quotequote all
If it was head gaskets surely it would misfire from cold or am i missing something. Plus coolant would be pressurised and blow back into expansion bottle.
I will remove all the spark plugs to look at the colours first.
How can it be head gaskets if it only misfires when hot. Sorry but i find it difficult to follow the reasoning here. Could you explain please, i'm always ready to learn.
many thanks
Alan

anonymous-user

53 months

Tuesday 9th August 2016
quotequote all
plasticpig72 said:
If it was head gaskets surely it would misfire from cold or am i missing something. Plus coolant would be pressurised and blow back into expansion bottle.
I will remove all the spark plugs to look at the colours first.
How can it be head gaskets if it only misfires when hot. Sorry but i find it difficult to follow the reasoning here. Could you explain please, i'm always ready to learn.
many thanks
Alan
Depends where it blows and how long it takes for the pressure to build up in the cooling system. I would get it checked at the local garage, just a quick check for gases in the cooling system.

My race car would start to misfire after 3 or 4 laps till I fitted gas filled rings instead of a gasket that incorporated a fire wall.

Easy to eliminate, got to be worth a try?

plasticpig72

Original Poster:

1,647 posts

148 months

Tuesday 9th August 2016
quotequote all
Yes i see what you mean, i'll have a chat with a local garage to check for gas in coolant.
thanks
Alan

Dollyman1850

6,316 posts

249 months

Wednesday 10th August 2016
quotequote all
Do you have the correct bakelight spacer between carb body and inlet manifold?

Are you sure your ignition timing is OK, you may be running hot after a period due to poor timing.

You could have the beginnings of gasket failure which is only manifesting itself once the car is hot and things have expanded hence symptoms after 20 - 30 miles…If so however this will get worse over time.

Have you changed plugs and leads…You may have one or both breaking down due to heat.

How is the misfiring showing itself? is it 1 pot or more than 1 pot off..Is it the same sounding miss fire each time.

In my view It will be electrical.. Mechanical miss fires are seldom intermittent.

N.


Edited by Dollyman1850 on Wednesday 10th August 06:41

anonymous-user

53 months

Wednesday 10th August 2016
quotequote all
Dollyman1850 said:
Do you have the correct bakelight spacer between carb body and inlet manifold?

Are you sure your ignition timing is OK, you may be running hot after a period due to poor timing.

You could have the beginnings of gasket failure which is only manifesting itself once the car is hot and things have expanded hence symptoms after 20 - 30 miles…If so however this will get worse over time.

Have you changed plugs and leads…You may have one or both breaking down due to heat.

How is the misfiring showing itself? is it 1 pot or more than 1 pot off..Is it the same sounding miss fire each time.

In my view It will be electrical.. Mechanical miss fires are seldom intermittent.

N.


Edited by Dollyman1850 on Wednesday 10th August 06:41
Neil,
I'm not so sure a 3000M after 20 miles will be hot enough under-bonnet to cause failure of any electrical component?

Dollyman1850

6,316 posts

249 months

Wednesday 10th August 2016
quotequote all
TVRMs said:
Neil,
I'm not so sure a 3000M after 20 miles will be hot enough under-bonnet to cause failure of any electrical component?
It shouldn't be…But may exacerbate an all ready knackered one.
As you say a gas in water sniffer test is minutes then at least head gasket failure can be eliminated….I would be looking for more than the average amount of steam and white vapour from the exhaust….
Headgasket failure though bad enough to cause a miss fire would be consuming enough water to quench the fuel burn…..And if I remember correctly the initial fear was choke due to water level in header…..
OP should check his water level again.

N.

plasticpig72

Original Poster:

1,647 posts

148 months

Wednesday 10th August 2016
quotequote all
o.k. i'll do a test for gas in coolant to check head gasket but i hope it's not the head gaskets. I've never taken the heads off a V6 beforeeek. I'll cross my fingers when i do the test and hope it proves head gaskets to be goodsmile
I've just ordered the kit RESTOM DETECT 8840 it's a pink liquid that changes colour if gas present
Alan

Edited by plasticpig72 on Wednesday 10th August 08:23