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jim73vw
27-03-2008, 10:45 PM
Hi all,

As you have probably all seen from my posts in the electrical section and fuel section Nena currently ressembles a large paperweight - looks pretty, but doesn't move.

For whatever reason the engine will not fire up.

Turns over on the key, ignition lights all come on, oil and fuel in the right places but no magical purr of the flat four.

Everthing has run before, and the car has moved under its own steam. only changes since the last run are the engine has been out and in once through the respray and the exhaust has been cut and welded (tail pipe angles changed)

I am no engine expert, despite having had various vws over the years, and am struggling on where to start. Following my posts re the fuel pipes I have turned the engine over with the fuel line to the carb disconnected - this is delivering fuel.

I have changed the coil for a new unit as I know I left the ignition on for a day during refiitng and feared I had burnt it out - this has made no difference. I haven't changed the condenser - would a faulty one stop the car starting altogether?

I have a positive feed to the coil (terminal 15) - can I test that it is outputting to the dizzy?

Any thoughts/hints gratefully received

letterman7
27-03-2008, 11:10 PM
Pretty basic Jim, start simple. Engines need gas, air and spark. You've determined you are receiving gas, I can't imagine it's not getting air, so only spark is left. Pull the plug leads off the plugs (one at a time), put a spare plug in that lead, and have someone turn the engine over while you hold the lead with insulated pliers to the block somewhere. If the coil and condensor are working, you should have a nice fat spark. Weak spark - you'll be able to tell, it looks like a small static shock spark - won't fire the engine.
If you have a good spark on all cylinders, try changing the plugs. Once they foul with gas, it's over. You'll need new ones.

Keep us posted!

Kym
27-03-2008, 11:32 PM
Jim,

Take of a plug lead, stick a No2 Phillips head screw driver up the lead. While holding the screw driver handle position the shaft of the screw driver between the handle and the plug lead within a couple of mill of a good engine earth. Now crank the engine and see that you have a nice healthy looking spark. If you have a good spark, you have a good supply of fuel and the engine has compression, check that your ignition timing has not moved i.e. your distributor has not been turned when removing or replacing the engine. Next if you have a good spark but no ignition check your valve timing, however we will come back to that if all else fails.

If you have no spark, first check the air gap on your points in your distributor unless you have an electronic ignition module. Take the distributor cap off. Turn the engine over slowly by hand and as the cam in the distributor turns the points will open and close with a gap at the points that should resemble the thickness of a hacksaw blade. If there is a gap and the points are clean not pitted, turn the engine again by hand until the points close. Now turn the ignition to on and using a common screwdriver and not touching anything else, push open the points and let them close again. Each time you crack the points open you should see a small spark at the points. While you have the dissy cap off check the contacts in the cap and clean them if necessary (scrape with a common screwdriver) check the cap for cracks, check the rotor button in the centre of the distributor to make sure it sits firmly in its resesss. Check the condition of your HT leads with a focus on the main from coil to cap. Put the distributor cap back on and if still no spark, try hot wiring the coil and see if you then have spark. I have had a situation before when I replaced a faulty coil with a brand new coil and then after many frustrating hours discovered the new coil was also faulty. Easiest with your battery up front is to clip a wire to your main terminal lead on your starter motor. Quickly scratch the wire across an engine earth and see that it sparks. Don't leave it long or it will get hot or melt, no fuse on this sucker. Just before you are ready to crank it, hook the wire to your + terminal on your coil. Using the Phillips head check for spark. If there is good spark now the engine may even start on three cylinders.

Ric you beat me to it.

letterman7
28-03-2008, 01:59 AM
Yeah, but your descriptions are much better :clapping: !

Spacenut
28-03-2008, 08:25 AM
Yep, I had exactly the same problem on the Banana heading into work one day - I had replaced the 1978 Alfa coil with a new one, and my ignition failed! Fortunately I was on a hill at the time and demonstrated the HPF aerodynamics by coasting along to the next exit (1 mile) and even rolling up the slip road. I did a series of quick diagnostic tests (same as recommended above, but with the kind of tools you have by the side of the road - keys and stuff...) and determined that the new coil had failed.

I walked down into Hordean where there is a small garage and asked for an ignition coil and the technician pointed to a pile of old bits in the yard. I found a scrap Ford coil and swapped the wires over, brooom!

I ran around for a week with the Ford coil tie-wrapped to the dud before I put the Alfa coil back on. It's still on the car as far as I know!

I can't add anything more to the above tests, other than to say that condensers (which is the old-fashioned word for a capacitor) normally fail open-circuit, so you should still get a spark at the plugs, but probably a weak one. There will be a large flash-over across the points when you flick them open.

Test that you are getting a switched ignition feed to the coil (on the "+" terminal), and don't forget the engine earthing as without it there will be no potential difference between the HT and the engine block (which is what makes sparks).

Rick is right about the fouled plugs, but you should be able to dry wet plugs and re-use them, at least to initially start the engine. Cranking a cold engine takes a lot out of the battery, and it has to make sparks at the same time, so make sure there is plenty of charge.

Do you have carbs with sonic idle cut-out solenoids fitted? If so, you need to connect these to the ignition feed or the plunger won't retract from the main idle jets. I had this issue with my old (Solex?) single chokes on the 1.7. It can be overcome by winding out the mixture adjusters so the carbs run on the main jets instead of the idle jets, but starting from cold is very difficult under these circumstances.

For initial starting it might help to advance the ignition a bit (I think the stock setting is 9° BTDC), as this helps the engine to "catch" easier.

Good luck!

Lauren

bushboy
28-03-2008, 10:28 AM
Jim,
Be brave, just grab hold of the plug lead with a wet hand & turn the engine over. You will soon know if you have spark or not :laugh: :laugh:

Well actually what the others said is correct :sorry: :sorry: couldn't help my self

bushoy

Big Birds Car
28-03-2008, 12:36 PM
Can you see into the carb chokes if you take the air filter off? If so look into them and operate the throttle by hand and see if the accelerator jets are working, (squirt of petrol into the choke)this will prove that there is fuel in the carbs if nothing else.
If you have a spark you could always continue with the BB school of health and safety and tip a bit of fuel down the carb and try to start the engine, again if it is a fuel issue this will show up as the engine should try to fire if not run for a short burst.

Disclaimer ANY damage to persons or property from doing the later is entirely at your own stupid risk :bleh: (well it's worked for me on a fair few occassions :clapping: ).

But check the earthing straps first or even use a jump lead from the battery to the engine direct to make sure you have an earth. Good luck.

jim73vw
28-03-2008, 07:18 PM
Ok, a little update,

Thank you to everyone for the useful response - was back to work today so no major work done, and having some relaxation tomorrow at the Volksworld show !

Did a few checks tonight, but waiting on Sarah to turn the key tomorrow afternoon for the rest !

Turning engine by hand the points appear to be gapping fine - I did change these last March and she has only done 2 or 3 road tests since then. I think I also changed the condenser then but cannot be sure so will pick up a replacement tomorrow to be safe.

I popped the plugs out, as I intend to put a new set in tomorrow anyway and they are very black, and sticky wet, with a heavy fuel smell. Is this caused from the turning over of the engine when the coil feed was not connected? and if so could this be enought to stop firing up now ?? Again these plugs were new last March, and haven't seen much road use. I would expect them to be a bit nasty as she has only been used for testing, but not completely black (photos below)

Will check the spark on the leads tomorrow. Engine block seems well earthed. Hefty earth cable to axle beam and a chassis bolt, and earth strap from frame horn to gearbox.

http://farm3.static.flickr.com/2158/2369544720_7f061099b3_b.jpg

http://farm4.static.flickr.com/3069/2368711955_c2773683eb_b.jpg

Alzax3
28-03-2008, 07:33 PM
'Sticky wet' and 'black' doesn't sound too healthy, and the sticky and black bit shouldn't be occurring through turning over without a spark. Sounds more like oil fouling - though the black may just be from running with an over-rich mixture. More investigation needed!

letterman7
28-03-2008, 08:05 PM
Agreed. It sound like it was running rich before, hence the black soot (and I think you mentioned it was running that way at some point). The wetness is from the fuel being dumped into the engine. Even though it isn't firing, turning the engine over is still forcing fuel through the pump, and since you couldn't get it started and were no doubt pumping the pedal, raw fuel is squirted into the cylinders. Either way, time for new plugs. Sounds very strange, but when the porcelain gets wet with gas, and stays that way for a while, the plug gets rightfully fouled and won't fire properly. I didni't believe it until it happened to me a number of times, and my mechanic kept telling me - change the plugs!

Ben
29-03-2008, 12:14 AM
Hi jim73vw

The olney thing I can think of is Petrol can with water in it. you have wet plugs that smell of petrol diluted by water?


Ben

jimcub
29-03-2008, 01:06 AM
I did the static timing bit when I first put the engine in and it fired instantly, put new carbs, coil and dizzy on and it would not fire. I had petrol and spark but still nothing apart from a few blow backs through the air filters, I had to reset the timing as it was out and in the end it fired up but ran rough. until I set it with a strobe, then I reset it by ear. I now have to balance the carbs, but it does pull miles better and power is instant.

jim73vw
29-03-2008, 08:00 PM
:clapping: :groupwave: :crylol: :laugh: :groupwave: :clapping: :groupwave:

Had a good day at the Volksworld show today and came away with some goodies

Bought some replacement plugs and condenser, and fitted those this evening.

Checked engine block earth - big spark -fine.

Tried spark test with a plug - nothing.

Put clear dizzy cap on to see spark inside dizzy - nothing.

Ran temporary wire from alternator positive to coil, and discarded switched feed - turned key, and the sweet sound of a flat 4 !!! :clapping:

The original switched feed had failed, and the new one clearly didn't have enough juice ! Will trace them both back and remove - to avoid any nasties and run a new one !

Will check the wiring diagrams tonight but anyone any idea what fuse and cable to use?

Thanks to everyone that pointed me in the right direction - have re-examined the plugs I removed last night - they are dry now - wet was just fuel and are simply sooty, so should clean up. I compared them to a chart I have and the ressemble the fuel rich example photographed !!

I never thought Sarah would be so pleased to hear Nena ! I am a happy man again.

Now to fit the new gearknob, gaiter, sunroof, fire extinguisher, headlight covers, side windows, stereo, speakers, steering wheel and get the MOT done !

Cheers again all,

letterman7
29-03-2008, 10:43 PM
:clapping: Yaaahh! Run the largest wire you can, Jim, preferable not smaller than 12g.

jimcub
29-03-2008, 11:33 PM
I put 4 new plugs in and it ran fine, then all of a sudden one gave up on number 2 causing very bad starting problems. changed it and it ran fine.

jim73vw
30-03-2008, 08:44 AM
Dumb question - does the feed to the coil go through a fuse.

The wiring diagram I have infers it spurs from the switched feed into the fuse box, on the non fused side. The manual (Volkswagen official service manual) also states that all electrical circuits other than those needed for starting and operatig the engine are protected by fuses.

Could this be where I have been going wrong?

jimcub
30-03-2008, 05:55 PM
Mine does go through a fuse, it turns over but no live to coil.

MicksRedNova
30-03-2008, 11:01 PM
Dumb question - does the feed to the coil go through a fuse.

The wiring diagram I have infers it spurs from the switched feed into the fuse box, on the non fused side. The manual (Volkswagen official service manual) also states that all electrical circuits other than those needed for starting and operatig the engine are protected by fuses.

Could this be where I have been going wrong?

Jim

The only thing in the circuit between the Battery +12v and the coil (hot-side) is the ignition switch, not normally fused!

For convenience (and cost saving probably) the wire from the ignition switch goes to the fuse panel, but only to provide a fused feed to things like windscreen-wipers, indicators and headlights - 'cos you want those things to be switched off when you turn off the ignition and take the key out.

The wire should be 2mm (which is about 15 Amps I think) because the coil will draw about 7 - 8 Amps when the points are closed (Note: It's not a good idea to leave the ignition on with the engine not running because if the engine is stopped, with the points closed, it doesn't take long for the coil to overheat, and possibly burn out, at that sort of current.) In normal operation the points are only closed for very short time.

If you did decide to put a fuse in the line between ignition switch and coil (which is up to you, you don't have to follow the VW penny-pinching method) it needs to be 10 -15 Amps (worth checking across an empty fuse holder with the points closed to confirm the current flow and hence fuse size) (and quite easily accessible) otherwise it will blow easily and be a pig to change.

Note: Fuses have a 50% margin - so a 10 Amp fuse won't blow 'till about 15 Amps is flowing, but normally you err on the side of caution and select the next standard sized fuse up from the current flowing (e.g. If you measure 8 Amps flowing then a 10A fuse is good, if you measure 10Amps then you would normally use a 15A fuse. Provided you wired it up with 15Amp wire.) But don't stick a 30Amp in there as this would cause the wire to melt before the fuse blew in the event of a dead short!

Mick

jim73vw
02-04-2008, 10:17 AM
Thanks Mick,

You have reassred me that I was reading the wiring diagrams correctly !

I have now fully traced the original wiring to the coil and have a confession :oops2:

I had the correct guage wire running to the engine bay but when removing engine for paint I tied them all up and labelled incorrectly.

The wire I had connected to the coil was my spare for future rev counter use, the hefty coil feed was tied up inside the engine bay still - so whole missed MOT and wiing/engine panic was avoidable :sorry:

Cheers all for your patience !

letterman7
02-04-2008, 03:47 PM
:D It happens to all of us Jim! Don't feel bad - feel part of the community!

vpogv
02-04-2008, 05:45 PM
Patience? :laugh: Just wait until I start my wiring job. It will make your posts look like nothing. :)

MicksRedNova
02-04-2008, 11:01 PM
Thanks Mick,

You have reassred me that I was reading the wiring diagrams correctly !

Jim, no problem. It's good to use my 30 years of electronics experience and countless training courses during that time for some benefit once in a while. Now that I sit in front of a PC or in meeting rooms all day :nonono: it's almost a pleasure to apply some deep thought to an electrical problem.

Mick