Mk2 GTI 8V (EV engine so K/Jet) timing Q please?

Just looking for some input on my timing. Car runs ok but misfire on cold start however think that’s fuel related.
Timing wise, at idle I’ve set the diamond on flywheel with strobe gun so she’s running at 6degs BTDC with the vac line off the dizzy and line plugged. When I re-plug the vac line the timing advances to 14degs to the diamond so 20degs total timing to the static timing dot. Raising the revs to approx 4000rpm this is giving a total timing of 38degs advance to the static dot. That total timing is 95% in at about 3000rpm which I’m thinking may be a bit early through a fault with the spring loading on the centrifugal advance in the dizzy itself. Any thoughts much appreciated? Ta!

 

20 degrees advanced at idle??

 

Yeah, so that’s throttle closed giving full vacuum pressure to dizzy vac capsule so the timing’s going to 20degs advance to the timing dot on the flywheel which in turn is 14degs to the diamond on the flywheel. If I open throttle in vacuum pressure drops then the vacuum timing will retard but centrifugal vacuum will kick in and counter that retard with an advance. Complicated init!

 

What's your distributors Bosch number, it'll start 0 237...

 

It’s Bosch number is 0237 020 133 and VW 026 905 205AA.
Just to check, I am correct in thinking that with the throttle closed the vacuum capsule will give its maximum advance to the distributor??

 

You've the correct dizzy for a 08/1985 to 07/1986 MK2 GTI, presumably yours?

These are figures RJ posted elsewhere, your's appears in them and might help.



Just in case your vac. canister isn't correct and you're able to take it off, the arm should have 3021 stamped on it.

I've found the diaphram in the canisters don't always fail completely, but sometimes can slowly leak off vacuum.

Put your mouth to the pipe and suck, then seal the the tip of it with your tongue, should hold indefinitely if it's OK.

 

Thanks dude. Looking at the chart I think my centrifugal advance is going all in too early up the Rev range. I’ve sent my distributor for overhaul at Ignition Car Parts in Basildon. We’ll see what that yields.

 

This might be interesting... as you've taken various measurements pre-submitting it to them, I'd be curious to see what they are after their refurb.

Might not want to tell you, but would also be interesting to learn what work they claim to have done / repaired / renewed etc.

 

Shall post all here to be revealed. Should have it back by end of next week.

 

Get it back yet?

 

Not yet. Was hoping to get it back this week but they’ve not called yet to say it’s ready so will prob be next week now. I’ll call em tomorrow.

 

How'd you get on?

 

Yeah, not great if I’m honest. Got it back and it looks great, been vapour blasted and looks the part but put it on the car and can’t get the car to run right. Fiddled about advancing and retarding a couple of degrees over and under 6degs BTDC and runs fine when warm but until it’s properly warmed up if I load the accelerator it momentarily loses power then picks up again. Phoned them and asked how they’d set the specs up on the vac and counterweight advance (I.e thinking of trying a different set of springs on the counterweights) and they said they’d just re-built it to specs that it arrived to them with, which is fine if it’s a new or even working example but if not then they’re rebuilding it to an off setting which I found slightly frustrating. I asked if they had the specs in like a Bosch catalogue and the guy said “no” as they’d then need books and specs for every dizzy from every manufacturer which, ok, it’s a few big books but for a specialist distributor reconditioning service that’s surely the only way of doing it properly and rebuilding it back to original specs which is why I sent it in the first place. They also replaced the Bosch original grey dust cap (goes between the cap and body) with some cheap knock off version (that was cracked) and lost the earth spade terminal that goes on the outer body that the metal can type shield goes earths to. They said they’d phone me back about that and still waiting. Bit of a disappointment really.
I measured both on the car as follows;

Original (old one that’s always been on the car.)
120mbs of Vacuum advanced timing 23degs (full advance). And at 2800rpm advance peaked at 22degs advance.

Reconditioned one back from bugger-lugs.
160mbs of Vacuum advanced timing 21degs (full advance). This one peaked at 4500rpm to 20-21degs advance.

So quite different specs and car runs better on the old one. However, the new one maybe correct and I’ve got something else in the setup of the car off.

 

I'm lost when it comes to timing so alot of what you've said goes straight over my head, would love to understand it better - bit of reading needed!

I'm guessing the gist's that it doesn't match RJ's chart?

Is that both for the vacuum and centrifugal figures?

Does look the doggies, but that's not much consolation if it's not working as it should.

Can't tell for certain from an image, but it's possible they've changed the Hall sensor.

The vac. cannister's possibly still the original, but painted?

Have they had the drive cog off, is that a roll pin instead of the original soild item?

Did they mention any of that?

Apologies for all the ?'s

 

I wish I could jump in and help but unfortunately I am still waiting for my fuel distributor to come back. When I did get it running I hadn't fully set it up as I spent forever measuring fuel rates. Have you checked your fuel pressures?
Doing this will allow you to see if the WUR is functioning correctly especially on cold running. Have you measured the WUR resistance and checked it gets a voltage too?
Just a start but no help with the distributor I'm afraid. Annoying that paying good money to a company and they don't seem competent

 

Yeah, when you go into the timing of these old dizzies it’s quite clever. The vac advance is for load sensing/throttle position on the engine and centrifugal for engine speed. Theory being the faster the engine speed the faster the pistons are moving so the further in advance the timing has to be to generate a high tension in the coil, then distribute it to a spark plug, which produces a spark to ignite the fuel (while all this is happening the piston is of course moving) and allow the flame front to travel to the crown of the piston to give maximum pressure just a hair after TDC for most power and fuel efficiency that’s the centrifugal side of it. The vac side is for low engine load like cruising at 50-60 mph at light throttle loads and low revs in 5th gear, low revs means little centrifugal advance and low throttle pedal is less fuel that burns slower hence the need again for something to advance to time the burn/pressure flame front onto the piston again a hair after TDC. If that isn’t the coolest I don’t know what is.

And you’re right. The new one doesn’t match RJ’s chart nor my old distributor. But RJ’s chart is for a DX engine code mine is an EV so not sure how that translates. Think DX is an American market engine and I know they have tighter emission laws in some states even back in the 80’s which the diz will be a part of.
It is a new hall sender and yes a roll pin to replace the original pin. I did ask them to return all the old bits but alas it wasn’t sent. They said that they had opened the vac capsule to replace the rubber diaphragm but can’t see how they could do that without there being a trace of the capsule having been opened?.

 

Thanks for the suggestion. I have checked my WUR and system/control pressures are spot on. New injectors and metering head is delivering equal and correct fuel quantities. It’s nearly running right, maybe 95% right, it’s just chasing down that 5%. Maybe I’m being too demanding on a 40 year old system.

 

Interesting that they're opening the vacuum canister.

Had read that another outfit was able to do it, can't recall their name now.

I'd a leaking one and opened it (it's on another thread), even got it to work again too, but you'd definitely be able to tell.

They sell (or possibly even make?) those Ultra Spark latter day dizzies and canisters, I wonder are they maybe rebodying the original Bosch arms, perhaps they have 'blank' front / back canister pieces that can then be crimped together with the right bit of kit?

I'm convinced it's the spec. of the cut out on the arms that dictates the start/end mBar points, basically just the extent of travel.

The canister body / diaphragm seems to be universal.

 

Yeah, I should give them another shout really to see if they can sort it. I remember watching a YouTube on a guy in America and he had this awesome machine like the wizard of oz to set up dizzies, wish he was here in the uk.