Another Misfire

[Shandylegs]

.

Edited October 21, 2011 by Shandylegs

[Big Jim]

Are you running socks on the carbs? if so, try it without them, I had this on the Vauxhall engine, it took ages before we twigged it. It was sucking the socks onto the trumpet and choking the engine. I now have elastic bands around the trumpets half way up, so as to stop them going right up against the trumpet ends.

[Bob Tucker]

Reminds me of a time long past when I ran a Lambretta (I also ran several 650 BSAs) so dont call me a mod...

The Lambretta was stripped of all bodywork & I took the girlfriend to see her brother, a trip of about 30 miles. After about 2 miles we spluttered to a halt, got off, looked around, found nothing, but it started again after a bit of persuasion.

Another few miles, same again, then repeated every few miles till we arrived an hour late.

 

When we went indoors, the girlfriend shrieked....one leg of her flared trousers had a dozen dirty, oily, petrol smelling circles....the leg next to the open carb intake, which had repeatedly sucked her trousers in & choked the engine.

She got her own back by marrying me....

[Big Jim]

It would have been much cheaper to have bought her a new pair of trousers!!

[Shandylegs]

.

Edited October 21, 2011 by Shandylegs

[Guest Guy]

I cant remember if the Tacho is driven from the ECU or the coil, if the tacko is giving trouble as well then the fault is befor it i.e. the pickup from the dizy, ECU or ignition amplifier.

 

I would suspect a bad connection in the loom. Different bits resenate at different frequincys, it sounds like somthing is resenating when you are around 4.5K RPM and is showing up a bad connection.

 

Start it up, wiggle the wires. Check the connections. If you cant make it misfire, cable tie bits of the loom and see if you can stop it doing it (by changing the resenant frequency of the fault). if you can then you'll still have to fix the bad joint but at least you'll know where it is!

 

It could be a dry joint on the ECU circuit board, did you rubber mount it?

[Guest Stuart Ainslie]

I believe that the tacho is fed direct from the LT side of the coil.....

 

Stuart

[Big Jim]

Try a new coil. I've come across similar problems and it was the coil. A new coil is only around £15, or just borrow one to try.

[Guest Simon cooper]

The fact that you can drive through the problem means that you are looking for an ignition fault. If it was starvation, the harder you push it, the worse it would be.

As you are on 40's/45's I assume you are on standard sierra electronic ignition with amplifier (module) rather than a mapped ecu.

A few basics first:- at idle it takes about 8 thousand volts(KV's) to fire your plugs. As load increases on the engine it takes a higher voltage to fire it off, normal acceleration- about 15-20 KV, accelerating hard up hill- about 20-30 KV. When the engine is at its peak power around 4-5,000 rpm, the loading on the ignition system is at its greatest. When the revs get above this point, the ignition gets an easier time so the spark needed can drop to 10 KV.

There lies the clue I think. Some of the sierra systems had constant and some had variable dwell amplifiers. If you have a dwell meter, this would be usefull.

as said previously, the rev counter is affected and in most cases this is switched from the negative side of the coil (some are posative, but they are rare).

The most likely cause is the dwell time of the amplifier. This can have 3 causes:- poor 12 v feed (on the black wire) at the amp, crap amp earth or an internal fault in the amp. Get down the scrappy's and grab 2 of them. One for the engine and one for a spare to keep in the boot. If that does not sort it, drop me a line and i will take you through some tests that are too long winded to explain on here.

Simon

[Guest joni]

Hi Everyone

 

I took my car on its first trip for SVA at Leighton Buzzard last month and found the same problem. Everything seems fine at idling speed and up to about 2000 rpm ish (i don't have a rev counter so I don't know exactly) but then completely chokes, the engine starts to stutter and it won't pull any more. As you said in another post it only does this under load. Sitting on my drive it will rev quite happily all the way up, but moving along it willonly accelerate at very low revs especially doing about about 40mph. I have a 1.6 pinto with standard pierburg 2v carb. I have ditched the ECU and am running a points dizzy. Although the car failed on a few points it is getting pretty close but I'm really stuck with this one. Do you think its my different dizzy thats causing the problem or something else?

 

Please help I'm pretty well out of my depth with this problem!

 

Jon

[Peter Bell]

Joni it sounds like it could be a fuel problem to me if it revs ok with no load. Have you any filters in the system? check them for crap, a common problem is if you have used sealant on your tank it falls in and blocks the feed pipe. It could also be a failing fuel pump.

Peter

Where are you by the way?

[Guest daveg]

Another tip....

 

Run your engine in the dark of night...

 

...if there is any tracking you will see blue halo's and/or sparks very easily

 

Dave

[Guest chris brown]

running a points dizzy

make sure the points are set correctly or go and find your self a electronic disy and amplifier (just thought I would beat Jim to that)

[Guest salty_monk]

Or get the Aldon conversion kit... works well for me...

[Guest joni]

Wow thanks guys I wasn't expecting so many replies so fast. Definitely got a lot to look at.

 

I'm using the sierra fuel pick up into a RHE tank so i guess there is a filter in there which i havent checked. Otherwise the vapour seperator might be causing the problem?

 

I was also wondering if using a points dizzy with the non points coil could cause problems. i heard there are two types of coil one for points and one for non points, and they supply different amounts of current. Could mean a weak spark. What do you all think??

 

Peter im in witney in oxfordshire by the way. Dave q what is tracking?? not heard of that before except with wheels!

 

I figured i should use a points system cos i hate electronics. having said that i dont seem to be having much luck with them either! i think the main problem is that ive never seen a problem like this before and i dont know if its fueling or electrics. and its really difficult to test it cos it only shows up when im driving and the damn thing isn't road legal!

 

I'll have a check to see where filters are and if they are ok. otherwise i can take another look at the points etc but i think theyre set up ok.

 

thanks for all the quick replies

 

joni