Timing figure during cranking phase?

[Richspec]

Having a tough time getting my newly built engine to fire up from cold.
As I'm using Omex I can set a timing figure purely for the cranking phase, whatever its at right now is obviously out because I suffer from drowning the plugs and /or backfires etc. Once its warmed through its just about ok. Fueling isnt perfect either which makes it worse to diagnose but its 'getting better' as i spend more time tweaking.

Engine is 1380, 10.5 ish CR, VP8C cam, 1.5 ratio rockers. Carb is 48 IDA.

Any suggestions as to what a cranking timing figure normally is?


ta

Rich

[smithyrc30]

Any suggestions as to what a cranking timing figure normally is?
ta
Rich

As you have programmable I would suggest TDC or 2~4deg AFTER TDC as a starting place.

With the centrifugal/points cranking would be around the static ignition setting for idle as cranking speeds are less than 1/3 idle speed.

If you fire it too early (BTDC) with the slow engine speed the fuel has enough time to ignite and stop the engine because the speed and inertia are too low.

Once you get above 5~600rpm the engine is running so moving back to a few degrees before TDC would be fine.

These days idle speed control is mostly done with spark timing anyway.

[Richspec]

Excellent, many thanks.

Thinking about that description of the 'fuel stopping the engine' - thats what it feels like, I'll get the laptop out tonight and have a quick try to see how it responds.

[Richspec]

umm
inconclusive, swinging the cranking timing made little or no difference, what 'might' have made a difference is powering the coil from the top part of the fusebox (constant live fuse), it did fire better but we'd already had it running briefly by then and the battery on charge so its a case of leaving it till tomorrow and trying again then when its properly cold.

I need to drive it this weekend if its going to make Blyton!

[minimans]

I would think it's more to do with low velocity through that honking great 48IDA! the fuel doesn't atomize very well and the large droplets wont Ignite very well at cranking speed's. do you have a geared starter motor you could try?

[Polarsilver]

Fuel ?.. if the fuel has been in your tank a few months replace the Dead Petrol.

[carbon]

Rich,

I would go for about 12 degrees static advance with at least 15 deg at idle. Could be as much as 18 or even 20 deg btdc idle if it's a long duration cam. All in crank degrees.

[Richspec]

continued advice appreciated
The fuel is relatively new as i ran out recently (the sender was telling lies..)
It should start better, even on the ida, as the ida has run virtually the same engine on a different cam before.
I'll be able to tell straight away tomorrow if the wiring change has improved the sparking, if it has then fine tuning the timing should be easier!

its just the typical new build with unknown fuel and timing required thats making it hard to get a baseline to work from.

[Richspec]

Getting to the root of the problem now, its running out of sparks, specifically on cranking the voltage is dying on its arse, which is why swinging the timing around seems to have little effect. Everything is new including the battery (EA640) and its running one of the gear reduction fancy starters. Dropping the plug gap to 32thou, and drying out the wet plugs was a wee bit better.
I'll put a load tester on the battery in the morning incase its had an internal failure. other than that bad earth somewhere? the one in the boot doesnt get warm, and theres zero resistance across it I'll have to look at the engine bay 1 (or 2, can't remember if i put an additional one on this or the other mk1)

[gr4h4m]

ECU things to check:

gap between the sensor and the trigger wheel
earths
wiring for the positive live
check the timing is correct with a gun to make that there are no issues with the sensor arrangement?

[Richspec]

gap is tiny, i did have to refabricate the cps bracket as it wasnt lined up properly, I cant recall if Omex counts the teeth it misses, there must be an error count in there somewhere.

earths, yes need to go through earths with a fine toothcombe,

which positive live do you mean?

yes this has been checked and offset set on timing so that map and actual timing are agreeing, its easier to set on dta though!

[rich@minispares.com]

for sale

1 x aldon red, points and a standard coil

'old reliable'



joking apart, I feel you pain, this is why I took all the electric magic of my sprint, it just drove me round the bend

[ian2988]

Trigger wheel fitting, CPS to line up with tooth no9 when no1 piston is at TDC, tooth zero being the missing tooth then tooth 1 being the first tooth after the gap in the direction of crankshaft rotation.
That's pretty much the standard on after market retro fits as per Ford EDIS I think it is. Recently fitted Emerald system to my MG. Start from scratch check all wires are correct, switched supply's permanent supply's etc..
Your rolling road tuner if you have a good one that knows the system can tell the ECU where the sensor is regardless of where you actually put it. Where are you located, I found a fantastic Rolling road tuner who only does race/performance mapping, Omex specialist!

[smithyrc30]

What is the sensor to wheel gap?

All the ones we use at work need to be about 1mm to 1.5mm away from the teeth, otherwise the increasing speed pushes the output voltage too high and the ecu 'loses count' and resets the count, which stops the engine.

From the picture it does not look to be a hall effect trigger, just a variable reluctance one.

You mentioned earlier that the voltage was falling low. Was that the voltage at the ECU, the battery voltage or the coil feed voltage?

Did you fix that?

If not can you power the coil and ECU from a different battery/power source?

[Richspec]

Been going through the system looking for voltage drops found one large resistance on the battery terminal to main lead, corrosion on the connector and post, cleaned that up and sorted that but still have a drop of circa 1.5 volts from the battery cable in the boot to the end if the cable at the starter under cranking, the only thing in this line is the battery master cutout, so dash out to check voltage drop across it next.

It will fire if the battery charger is connected but that's not exactly practical! Lol!

[Richspec]

What is the sensor to wheel gap?

All the ones we use at work need to be about 1mm to 1.5mm away from the teeth, otherwise the increasing speed pushes the output voltage too high and the ecu 'loses count' and resets the count, which stops the engine.

From the picture it does not look to be a hall effect trigger, just a variable reluctance one.

You mentioned earlier that the voltage was falling low. Was that the voltage at the ECU, the battery voltage or the coil feed voltage?

Did you fix that?

If not can you power the coil and ECU from a different battery/power source?

The voltage is dying at the end of the cable on the starter, therefore effecting everything attached, as I'm about to take the dash apart I could look at powering the ECU and or coil from the good side of the battery cutout, if that's what I find at fault. I don't think it's anything to do with trigger wheel gap, at this stage anyway, the software is seeing the engine fine. It's more I'm losing the spark and drowning the plugs. Yes I can easy power the coil from another source. Nearly 30 batteries here to use so not short of ways to cheat the system

[smithyrc30]

A 1.5v drop on the battery feed during cranking is not that bad.

Is that is what the ECU is seeing?

Normally they have a minimum operational voltage of about 8volts, depending on manufacturer. In other words they will drive the coil at 8volts and still function correctly.

It should be in the specification of the system you have under minimum system voltage or similar wording.

Once it is running does it run cleanly?

If you snap the throttle open does it try to stall?

I just looked at the Omex site and see it has programmable dwell dependant on battery voltage, how is that set?

[smithyrc30]

BTW which Omex do you have?

[Richspec]

When it's running it's fine, it's fine after the first start. It's omex 200 quite an old one, not sure if we've adjusted any dwell settings, I'd need to have a look to find it. Revs clean when warmed, with the proviso that fuelling and ign aren't optimised yet. Dash coming out now..

[Richspec]

no voltage drop across the cut out switch so still a circa 2 volt drop when cranked, however this is much beter than before which was more like 3+. (normal drop at battery + drop from front to back)
There is a setting for adjusting the dwell depending on battery voltage, its the same value all the way from 7-14 volts then it drops. We've never touched these settings. don't mess with settings I dont understand fully!

So dried plugs, fully charged battery and crank timing changed to 3.4 deg and it started and ran fine, maybe a tad weak until it warmed up a bit and the idle control dropped the idle back to 1050 rpm.

So as its run i need to let it cool off before i try again, and get some fuel as i've run out again..