Really flippin' strange ignition and RPM anomalies!

ChrisJC · Post by **ChrisJC** » Tue Jul 10, 2007 7:05 am

I keep a complete spare set - but I'm flat oot busy until next week. But if you don't get any joy elsewhere I can send it down.

It's a 2 wire amplifier module distributor, with matching distributor cap, leads,
and coil.

Chris.

sowen · Post by **sowen** » Tue Jul 10, 2007 7:15 am

I've got a points dizzy on my 3.9 right now, with the wobbly drive gear at the bottom of the shaft. It worked when I started my engine on the floor, could do with cleaning up inside a little though. PM me if you're interested.

Simon

x.l.r.8 · Post by **x.l.r.8** » Tue Jul 17, 2007 12:03 am

A new vacum will probably do nothing, you need to disconnect it to set the timing anyhow, so leave it plugged at the inlet end for the moment, make sure you have no air leaks (spraying wd40 around the intake will usually show a leak with an increase in revs). I would also time the engine to 34 btdc at 3000rpm, then see if the timing is 'walking' around as you pass the 3000 rpm mark, you should have all the advance dialed in by this time. It should only take a second or two to set the timing. Once done the see what the dizzy is doing, while you take it from tickover to 3000rpm, it should be fairly smooth advance seen with the timing light, if it's jumping around like crazy suspect the bob weights to be at foul play and check float in the spindle of the dizzy. Also I haven't seen your build speck but are you sure you have the right indicator to the right pulley for timing marks, there are a couple of different ones for different front pulleys. Just make sure TDC is also TDC on your timing mark. Then if setting at 3000 rpm doesn't work think about buying a different dizzy or a kit to replace the insides (pextronic or the likes there all pretty much the same). Hope this helps some.
Adie

jrv8 · Post by **jrv8** » Tue Jul 17, 2007 9:25 am

Hi Adie,
Long time since we've heard from you, how are things ?
Jim

The Original Tom · Post by **The Original Tom** » Tue Jul 17, 2007 12:18 pm

Aide.
Thanks for the fresh look at things! I've had a play with the dizzy and this is what I've found: There is no lateral play in the bearings at all that I can feel, the bob-weights move freely when I turn the rotor arm forwards, and return well too.
However, there is a little bit of end-float in the shaft. I'd estimate this to be about 1mm or so, maybe less, but I guess for something as precise as a dizzy, that could be too much! Can I shim this out, or is it new dizzy time...

Because I'm unable to obtain an idle of less than about 1400rpm (for unknown reasons) the vac unit should be in play at this time yes? Would the shaft-float cause enough timing wander to make the engine hunt and not get a good idle?

I'm past the point of caring if I need a new dizzy now, I just want the fecking thing fixed properly!!!! (but obviously I'd rather not buy one if I don't have to. I'm a tight student you see!!)

Paul B · Post by **Paul B** » Tue Jul 17, 2007 12:58 pm

The Original Tom wrote:Aide.
Thanks for the fresh look at things! I've had a play with the dizzy and this is what I've found: There is no lateral play in the bearings at all that I can feel, the bob-weights move freely when I turn the rotor arm forwards, and return well too.
However, there is a little bit of end-float in the shaft. I'd estimate this to be about 1mm or so, maybe less, but I guess for something as precise as a dizzy, that could be too much! Can I shim this out, or is it new dizzy time...
Because I'm unable to obtain an idle of less than about 1400rpm (for unknown reasons) the vac unit should be in play at this time yes? Would the shaft-float cause enough timing wander to make the engine hunt and not get a good idle?

I'm past the point of caring if I need a new dizzy now, I just want the fecking thing fixed properly!!!! (but obviously I'd rather not buy one if I don't have to. I'm a tight student you see!!)

1mm shaft float up and down is fairly normal.

As Adie mentioned, vacuum should be disconnected, plugged and ignored completely until everything else is sorted, as it is purely an economy measure tool.

If you rotate the dizzy a little when it is running can you get the idle to rise or lower at all, or does it just die if you go too low. I'd say it is not a timing fault if it just refuses to idle below 1400rpm.

Do you have enough clearance to move the dizzy where you want to, or does the vacuum can hit something?

The Original Tom · Post by **The Original Tom** » Tue Jul 17, 2007 1:23 pm

Regardless of how I set the timing / mixture / air flow at idle, it will not idle below 1400 on petrol, 1500 on gas.
I can set the static timing fine, and do so without the vac connected.
There's plenty of clearance for the dizzy and it's been moved a tooth either way to make sure it's in the best possible orientation to allow for advancing and retarding. At 18degs atatic advence, the vac unit sits right in the middle of the swing, allowing adequate space for rotation to achieve more advance or retard.

I do need the vac unit as I have a couple of dead-spots, which are timing related - the correct vac will cure this.

The RPM has been measured with 2 separate gauges, 1 gunson testune and one tachometer from a mates car.

My problem is that either it does rev too high at idle, but I can't get it lower because the dizzy's wandering all over the place, or I have a problem which causes any gauge to mis-read.
I suspect the latter as it also shows 7000rpm as being easy to reach at the top end. As my engine has no porting, standard carbs and the only thing that's non-standard (although I did balance all opposing pairs of pistons to within 1g) is a torque-biased cam I seriously doubt that 7k is possible without blowing it up.
Also if I crunch the numbers for RPM to speed using gearbox/transfer box/ axle ratios the gauges read differently to the numbers, and I'm more trusting of cogs than I am of electrickery.

I've been advised to get a manual tachometer that you attach to the crank, but I can't afford £50 to be told something I already know.

So - any thoughts on what could be making my gauges mis-read. As said I've already replaced all ignition components except the dizzy and the amplifier (which appears to be in A1 condition, and I've tested it).
Hence my suspicion of the dizzy.

Cheers
Tom.

r2d2hp · Post by **r2d2hp** » Tue Jul 17, 2007 1:38 pm

Have a look at these, some look very reasonably priced.

http://search.ebay.co.uk/search/search. ... age=search

x.l.r.8 · Post by **x.l.r.8** » Tue Jul 17, 2007 3:15 pm

If i remember reading you run the opus, these are great systems when working properly in standard tune, however when they go there gone, like a unilite, there prone to breaking down, the circuitry insude sends half the signal to the coil and half is used to prevent crossfire, once you have a break down you no longer have that protection. Thats why you seen the problem in lower rpm, at any PRM the vacum should not make any difference, you can drive well without it and many of us who ran nitrous on the road did becasue as soon as you pressurise the manifold the positive pressure on the diaphram ruptured it making it useless. So we did without. My only sudgestion is to replace the insides with something keeping the body as this would be the cheapest way out. 1mm play is less than desirable but the bodys are not collared so again, once they wear, they wear. The opus has a thicker shaft than a unilite so it's not likely your seeing any distortion in the dizzy shaft but I'll bet my breakfast your problems will majic away once you rectify the dizzy. I spent many hours trying to get broken things to run right, thats why I came up with the upgrade I STILL use on my road car and I still have not changed a single thing on it. Forget the rev counter, there a waste if time, use the money to buy a rpm activated light, and set it to 3000, then you set it to what ever you want to shift at, no one really cares if they change at 4000- or 4200 rpm

you just want to have a rough idea and you don't need a 6 inch rev counter to tell you that. I really think your flogging a dead horse with carring one trying to get your dizzy to work, you should be able to turn your rpm down to 500 without any problems (mine is at 650 on my race car and although it struggles to keep the alternator spinning it is very stable) if your reading wandering timing your not firing at the right time on your no.1 lead, which means the dizzy is sending information at the wrong time. Believe me if I were back in hte UK (NEVER going to happen) I would come and do it. I never kept any spare opus stuff as I did the upgrade on everything that came my way as whatever way you look at it your dizzy was obsolete in the 80's they changed with good reason and 20 years is a long time for electronics to be working in the harsh environment of the car.
jrv8, I've been working flat out for ages and I just couldn't face admitting I have done nothing but drive my car, it's getting tired now as it needs some new shocks (the city roads here are pretty bad) and it has a sump gasket leak (I built it 10 years ago when I was still of the belief that sumps and exhausts needed gaskets) and the road tyres are pretty crap on the snow. So I decided pop back after remembering the revamp.
I now work on leyland TRACTORS and allis chalmers combines now I'm a country bumkin.

x.l.r.8 · Post by **x.l.r.8** » Tue Jul 17, 2007 3:37 pm

Ok scratch that, I jsut reread the post, you have a good dizzy it just sends a signal and nothing else, the gap need to be set up well for it to work and 1mm play is a bit much IMHO, it will close the gap and fail to spark. one way to have a very rough look is hook the timing light onto the coil lead and see what our getting, you should have a seemless pulsed light sorce. I have a feeling you will get a spluttering one. I would also like to know how you tested the dizzy and would you not think about looking at the rpi amplifer. These dizzys are not as easy and a lot of companys make out and thats whay a lot of people just decide to change the unit for a mallory. That does solve the problem but without any understanding of why, than all hail the mallory, you would get the same results with a brand new original dizzy. You need to spend about 3 minutes with your set up before giving up, if you can get the timing locked down at 3000 then your done, if it sdoes not play they your dizzy needs some overhaul and needs to be removed. If someone has had the dizzy apart then the plate can possibly be moved up and down. This happens when you take the collets off to remove the spindle, there hard rubber rings that locate in the shaft the rotor sits on, if this happens you will also get eratic timing and it will allow the springs to come off the weights. There is not a lot else going on inside the dizzy than that but play it the shaft does nothing to help, the opus was far more tollerant of play. After that it's going to be down to your amp. If your supplying enough fuel to run at 1400 don't worry to much as you will have enough for lower rpms so I wouldn't change that to much. I would ensure a constant spark and then hook back to no.1 lead and dial it in at 3000, if still no luck then get it out and make sure the springs are attached and recheck for play. If you wanted a project you could try and bush the shaft but I would want NO play in the shaft of my dizzy, especially if I set the air gap correctly. Try and open the pick up gapa little and see if that also helps and chack the pointy star for contact marks on the pick up.
Adie

x.l.r.8 · Post by **x.l.r.8** » Tue Jul 17, 2007 3:44 pm

http://cgi.ebay.co.uk/LANDROVER-3-5-V8- ... QssPageNam
May be worth picking this up as a spare. you jsut remove the box on the side and there will be 2 plugs that would be the same as your 2 wires from your dizzy.

Paul B · Post by **Paul B** » Wed Jul 18, 2007 7:31 pm

The Original Tom wrote:Regardless of how I set the timing / mixture / air flow at idle, it will not idle below 1400 on petrol, 1500 on gas.
I can set the static timing fine, and do so without the vac connected.
There's plenty of clearance for the dizzy and it's been moved a tooth either way to make sure it's in the best possible orientation to allow for advancing and retarding. At 18degs atatic advence, the vac unit sits right in the middle of the swing, allowing adequate space for rotation to achieve more advance or retard.

I do need the vac unit as I have a couple of dead-spots, which are timing related - the correct vac will cure this.

The RPM has been measured with 2 separate gauges, 1 gunson testune and one tachometer from a mates car.

My problem is that either it does rev too high at idle, but I can't get it lower because the dizzy's wandering all over the place, or I have a problem which causes any gauge to mis-read.
I suspect the latter as it also shows 7000rpm as being easy to reach at the top end. As my engine has no porting, standard carbs and the only thing that's non-standard (although I did balance all opposing pairs of pistons to within 1g) is a torque-biased cam I seriously doubt that 7k is possible without blowing it up.
Also if I crunch the numbers for RPM to speed using gearbox/transfer box/ axle ratios the gauges read differently to the numbers, and I'm more trusting of cogs than I am of electrickery.

I've been advised to get a manual tachometer that you attach to the crank, but I can't afford £50 to be told something I already know.

So - any thoughts on what could be making my gauges mis-read. As said I've already replaced all ignition components except the dizzy and the amplifier (which appears to be in A1 condition, and I've tested it).
Hence my suspicion of the dizzy.

Cheers
Tom.

You don't need the vacuum advance to set the engine up and get it running, and vacuum advance is not designed to cure 'dead spots'. Block it off, lock it solid in the dizzy, just so you know nothing to do with it is moving.

In fact I'd waste no more time with the current dizzy. Beg, borrow or steal another just for testing, as several have been offered already in the last week or two. I have one in my garage, replete with amplifier and coil, but I'm on a ship in the Gulf of Mexico, so not much use really.

There is only a minimum of components involved in the spark side of your motor, and you have changed all but the dizzy and amp, so the answer is laying before you.

The Original Tom · Post by **The Original Tom** » Thu Jul 19, 2007 9:27 pm

Ok, a new dizzy it is. I might take up the offer of one of you guys soon, but I'm looking to get a cheap replacement to fit and forget.
I'll get back to you when I sort it.
Tom.

Coastcard · Post by **Coastcard** » Fri Aug 10, 2007 8:06 am

Tom,

Just wondering if you have this issue cracked yet. I am having something similar with my efi flapper. Revs all over the place, clouds of smoke from the exhaust, stench of petrol, runs with less smoke when retarded by some stupid amount.

I have tested the efi components twice, apart from the ECU (which I am about to swap), but reading your thread it sounds very similar, so maybe my dizzy?

Look forward to hearing.