Help!

I still haven't found the fault with my 1991 Sierra CVH 1.8L engine in my Haynes roadster. It developed an intermittent starting fault. It would start from cold but not after being run and up to temperature.

The Spark plugs are carbonised and I presume the cause is
1. too much fuel (original mechanical fuel pump and Pierburg carb in use, automatic choke working fine)
2. too little air (K&N filter to replace original and plenty of air being sucked in)
3. too little spark
4. compression problem.

As I could not generate a spark from the coil during my diagnostic search I concentrated on ignition problem. I have now replaced ignition coil and rotor arm cover for new and all worked well initially, with all spark plugs firing. So I though I had cured the problem. Then one day it wouldn't start after being run, so problem not solved.

So I conducted a compression test and all cylinders were similar compression dry and wet. However during the test an electrical short jumped from the green wire (which connects ESC II Module to ignition coil) to the frame. The reason for this is initially I erroneously just disconnected the leads to the ignition coil to stop ignition. After the short happened I earthed the HT lead with all wires to boil in place, as I should have done in the first place. Now I am concerned I could have damaged the ESC II module?

However car started first time after the compression test, so presumed no damage done. One day later it won't start at all and there is no spark from my (new) coil.

I checked the ignition coil and primary and secondary winding on coil show normal resistance measurements. I have checked that there isn't a break in the green wire from ESC II to coil, but this is intact. I have checked there is current to coil through black lead and there is. However no spark being generated at all now.

Could the whole problem be with the engine management system not controlling ignition correctly?
Can they produce intermittent problems with ignition?
Or is there another cause and I have just damaged my ECU by shorting the control lead to the coil??

Grateful for experienced advice.
Thanks

One thing I would check is the pick-up sensor that goes to the front toothed crank wheel, see what gap you have it should be around 1mm, no more I think. Check the wires going to it are not intermittent. and contacts clean.

One other thing to check whilst around in that area is that the end is not full or any metal fillings/swarf etc as I think it is slightly magnetic and can attract metal crud, especially if you have been using a grinder at some point.

Other things are make sure the ESC is bolted down as it can get hot.

If you have one of the old style timing light where you can see when a plug is firing that may help in diagnosis.

Adrian

Thanks, I'll recheck the crank position sensor tomorrow.

ESC is well mounted on Aluminium so can loose heat fine.

I was wondering if the ESC II may be blocking ignition at times. The original car has an immobiliser, which I think simply interrupted power feed to ignition coil when immobiliser is on. I have wired the car without an immobiliser and simply connected the Ignition coil power feed straight to key ignition power. Could there be a problem with using a ESC II from a car that had an immobiliser in a car that doesn't have one?

Is it the esc hybrid the one with the vacuum take off in the unit it self or an esc II ?

Adrian

Mine used to do that, but after using it for a while the its "fixed itself". I think what is going on I now pump the accelerator once before starting when warm and she normally starts fine, or it could be stale fuel varnish that is now washed out...

Dan

[Edited on 11/9/16 by Bluemoon]

My ESC module does has a vacuum hose connection. I thought it was the ESC II but it is not very clear in the Sierra Haynes manual. As it has a vacuum, does that mean it is the ESC Hybrid not ESC II?

Would that make a difference to finding the problem?

Do you think the ESC could be source of problem because it is searching for an immobiliser which isn;t there, or is this nonsense?

esch

If the same as above then I believe it is the esc Hybrid

I have removed the immobiliser from mine also without any issues.

Adrian

just a thought do you have the correct plugs?... it's possible that the are to cool causing the carbon build up... getting the idle mixture checked might also be an idea...

[Edited on 11/9/16 by Bluemoon]

Thanks Adrian. Yes mine is the same as your pic, so must be the ESC hybrid. When I wired it, I simply missed out the immobiliser and connected the ignition key feed (Bk/Y) direct to Ignition coil (black lead + supply).

If you could explain how I upload an image I will send my wiring diagram as it would be great if you would check it to see if there is anything there that is causing the problem.

When I tested my engine compression I disconnected black power feed to ignition coil and the green coil lead which comes from the ESC. Then I turned over engine and there was a spark from green lead which shorted to car frame with a loud pop. I now realise this is the opposing current sent from ESC to stop power to coil and collapse the primary circuit. Do you think I could have damaged the ESC by letting this line short? As since then I cannot get any spark from ignition coil.


Dan. I changed plugs for new ones as recommended by Halfords and the new plugs did the same thing developed carbon deposits almost immediately. I have not touched the idle mixture from how the original car was set up and the emissions are fine according to my local garage.

I have a spare esc hybrid unit that does work, so if the worst I could post it off to you for testing, or ask if anyone local has one around.

Here is a picture from the book


cvh3

I have used it just as this and yes the black 12 Volt feed now goes directly to the +ve of the coil.

The green from the ignition module goes to the -ve side of the coil, but also has a connection to go off to the clocks for the tacho, make saure you have the coil in the there feeding off to the tacho, it was a small U shaped thing, it will probably work without it but it saves some of the back emf high volts going to the tacho unit.

Perhaps what you could do to test working operation is put a 12 Volt 5 watt bulb in place rather then the coil pack for the time being.

take the plugs out of the engine to save some load on the starter motor, crank over with the ignition uand see if the bulb flashes on and off when cranking. Gives you an opportunity to mess with out getting zapped by high voltages?

Adrian

One more thing to check is the capacitor that is also across from the _ve terminal to ground, not shown on the picture but should be there.


[Edited on 12-9-16 by AdrianH]

Only one class of problem causes sooted plugs.

I am not sure if the car is on the road yet so I have assumed in my mind that the car is never being run under load for any period of time i.e. it is tending to be run on automatic choke, I had the same sooting issue when building, but fine when used on the road.

Adrian