Please Help

[mattwalder 0]

Hi everybody

 

Is there anybody that can help me out?

 

Ive got a 1.9 8v which I have recently put twin weber 40s on, but have an issue with the timing.

 

With a strobe light I can get the ignition timing spot on 10 degrees BTDC, I should mention, to do this I had to file the slots in the dizzy to enable me to retard it enough, with bolt roughly in the middle of the slots its about 40 degrees BTDC, straight away this didn't add up.

 

With the timing set at 10 degrees it idles like a little sewing machine and revs very well, but when under load it coughs and splutters and has no power.

 

If I advance the timing to about 40 degrees it doesn't idle as well but pulls very well up through the rev range when under load, this would be ok but when the revs are up near 6000rpm there is a massive back fire out of one of the trumpets, its that bad the last time it did it, it split the sock open and sounded as if the engine had blown to bits!

 

Everything is standard and I have checked the cam timing and all is ok, the timing marks are right in relation the cylinder 1 and with the rotor arm pointing to the correct lead, I have tried another dizzy to rule that out.

 

I have now run out of things to check, the most puzzling thing is the ignition timing has to be 30 degrees out for it pull under load but idles the best when the timing is spot on.

 

If anybody has any idea I would love to hear them.

 

Thanks

 

Matt

Edited June 27, 2010 by mattwalder

[DrSarty 90 1 Cars]

it split the sock open

 

Socks get an extremely bad rep on here. Many will swear never to use them again, and it's also common for them to affect power. Get a proper filter like a Pipercross or ITG.

 

(Sorry that's not a potential solution to your timing issue, but it is sound advice.)

[rallyman205 0]

hi is the vacuum advance working on the dizzy and where are you pulling the vacuum from is it from just one inlet or have you linked it together from more than one inlet also are you pulling vacuum for a servo and likewise is that from one bank or even the same place as the dizzy vaccum

sounds silly but where the vac points are can create a huge imbalance and cause a cylinder to run weak (hence backfire at high rpm) and also the imbalance will effect ign timing which could possibly be where your problems lie

try blanking the servo take off and retiming it if it is running a servo but remember no servo no brakes so dont drive it like that

[rallyman205 0]

and another little thought are your carbs mounted using thakray washers .if they are not set up correctly or the thakray mounts are perrished you could have an air leak which is sending it weak at top end .this will also give the same results

[mattwalder 0]

hi is the vacuum advance working on the dizzy and where are you pulling the vacuum from is it from just one inlet or have you linked it together from more than one inlet also are you pulling vacuum for a servo and likewise is that from one bank or even the same place as the dizzy vaccum

sounds silly but where the vac points are can create a huge imbalance and cause a cylinder to run weak (hence backfire at high rpm) and also the imbalance will effect ign timing which could possibly be where your problems lie

try blanking the servo take off and retiming it if it is running a servo but remember no servo no brakes so dont drive it like that

 

Thanks for the advice, the vacuum advance isn't connected as I was told is wasn't needed? The brake servo is connected to one side of the inlet manifold which is the side that is backfiring on, so this could explain the backfire.

 

The washers look ok but I will take a closer look to see if they are perrished.

 

Thanks again for the advice I will try that and see how i get on.

[quat-fro 1]

Thanks for the advice, the vacuum advance isn't connected as I was told is wasn't needed? The brake servo is connected to one side of the inlet manifold which is the side that is backfiring on, so this could explain the backfire.

 

The washers look ok but I will take a closer look to see if they are perrished.

 

Thanks again for the advice I will try that and see how i get on.

 

Lots of people throw away or disconnect the vacuum advance when carrying out performance upgrades but it's a very stupid thing to do.

 

The vacuum advance advances the timing when the engine is pulling the highest vacuums, such as when idling or cruising. So your dizzy is designed to time your ignition properly when everything is connected correctly and shouldn't be expected to time correctly when it's not getting all the right information! Advance is required at idle as the slow running and low lean charge volumes take longer to burn, when cruising the mixture is usually lean for economy and this also burns slowly.

 

Perished rubbers can cause all sorts of problems too. Blank off the brake servo line to eliminate it from the equation, or, substitute it for the vac advance.

 

Failing any other obvious problems like that, you may have some kind of blocked passageway in your carb preventing the choke that is blowing back from delivering fuel correctly. Once again, an unusually lean mixture in one cylinder when it should be rich on acceleration will take a very long time to burn so when the exhaust closes and inlet valve opens again it's got no choice but to come back out the wrong way!

 

Hope I've helped.

Edited June 27, 2010 by quat-fro

[mattwalder 0]

Lots of people throw away or disconnect the vacuum advance when carrying out performance upgrades but it's a very stupid thing to do.

 

The vacuum advance advances the timing when the engine is pulling the highest vacuums, such as when idling or cruising. So your dizzy is designed to time your ignition properly when everything is connected correctly and shouldn't be expected to time correctly when it's not getting all the right information! Advance is required at idle as the slow running and low lean charge volumes take longer to burn, when cruising the mixture is usually lean for economy and this also burns slowly.

 

Perished rubbers can cause all sorts of problems too. Blank off the brake servo line to eliminate it from the equation, or, substitute it for the vac advance.

 

Failing any other obvious problems like that, you may have some kind of blocked passageway in your carb preventing the choke that is blowing back from delivering fuel correctly. Once again, an unusually lean mixture in one cylinder when it should be rich on acceleration will take a very long time to burn so when the exhaust closes and inlet valve opens again it's got no choice but to come back out the wrong way!

 

Hope I've helped.

 

Thanks for the info,

 

Would the vacuum advance be the reason the timing is way out when using the strobe light?

[quat-fro 1]

Thanks for the info,

 

Would the vacuum advance be the reason the timing is way out when using the strobe light?

 

Yes.

 

With the vacuum advance functioning, the same timing would be achieved with the dizzy in a vastly different position. The fact that you needed to file the slots should've rung some alarm bells!

 

I do think however, judging by the info supplied, that it may be another problem exacerbated by the lack of vacuum advance and not solely due to its absence.

Edited June 27, 2010 by quat-fro

[mattwalder 0]

Yes.

 

With the vacuum advance functioning, the same timing would be achieved with the dizzy in a vastly different position. The fact that you needed to file the slots should've rung some alarm bells!

 

I do think however, judging by the info supplied, that it may be another problem exacerbated by the lack of vacuum advance and not solely due to its absence.

 

Ok, I will connect the vacuum advance and see what happens.

 

Many thanks

[quat-fro 1]

Ok, I will connect the vacuum advance and see what happens.

 

Many thanks

Yes, do let me know how you get along.

[mattwalder 0]

I've run out of ideas now, I have tried just about everything now!

 

I have tried blanking off the vacuum pipe to the servo, no change!

Another coil, module, leads, and dizzy, no change.

There are no air leaks as far as I can tell.

 

Another weird thing is that when I tried a friends module which is from a 1.9 8v and also a brand new one, neither worked, engine did not fire unless the ignition was fully retarded and just ran poorly.

 

I don’t understand what’s wrong, with the timing fully retarded it idles like a dream but is crap under load, if I set the timing up by ear it pulls ok but still backfires badly out of the carbs and idles badly, lots of hunting!

 

Could it be a fault with the carbs and not the ignition timing?

 

Please if anyone has any ideas I would be very grateful as I'm on the verge of giving up.

 

What was supposed to be a fun project is turning out to be a real night mare!!

Edited July 11, 2010 by mattwalder

[quat-fro 1]

If the carbs are too lean they'll need lots more ignition advance than if it was properly stochio or rich, perhaps they were the problem all along?!

[large 33]

TBH if I was you i would look to get rid of the 8v stuff and get a 3 row ecu loom and afm for the mi.

[mattwalder 0]

If the carbs are too lean they'll need lots more ignition advance than if it was properly stochio or rich, perhaps they were the problem all along?!

 

Cheers

 

I'm begining to think so but not really sure which to change, the jets in at the moment pretty well match my mates car which is also a 1.9 8v, could there be a blockage of some sort? or would the set up not be the same on every 1.9 8v engine?

[mattwalder 0]

TBH if I was you i would look to get rid of the 8v stuff and get a 3 row ecu loom and afm for the mi.

 

Thanks for the info but I'm afraid you have lost me, what is it and how could help?

[mattwalder 0]

TBH if I was you i would look to get rid of the 8v stuff and get a 3 row ecu loom and afm for the mi.

 

Thanks for the info but I'm afraid you have lost me, what is it and how could help?

[quat-fro 1]

Bollocks to that, you need your current set up sorted so that you can have some fun.

 

For your own sake don't d*ck around on this forum any longer, get yourself in touch with a local tuning firm / rolling road who can see the problems first hand so they may use their knowledge and experience to sort it out there and then.

Forums can work for a lot of things but problem solving an engine over the internet isn't the best way forwards.

 

You might have to spend a little, but having a working car quickly is far better than growing grey hairs doing it on the cheap.

 

Let me know how you get along, via pm if you like.

Edited July 13, 2010 by quat-fro

[mattwalder 0]

Good news everyone!!

 

I've solved the problem, turns out the 2 wires from the dizzy to the module were the wrong way round, not sure if it was me when I was repairing the buchered loom or it was round the wrong way in the first place, I bought the car as a none runner so so don't know, the main thing is its sorted

 

An hour on the rolling road to set the timing and the carbs up and I can finally have some fun on the track

 

Thanks to everyone who replyed with advice.

[quat-fro 1]

Good news.