Ford EDIS issues - Backfiring during cranking

[3fpowered]

Hi all,

Im having some issues with a Ford EDIS setup which I have installed on a 85 Toyota Landcruiser (3F petrol motor). It runs dual fuel (LPG/Petrol).

Basically my problem is this. Whenever the engine is warm it will backfire through the intake while cranking the engine over. It doesn't do it every time, but at least 80% of the time. Doesn't matter if you give it throttle, dont give it throttle etc. As soon as the motors running its perfect; doesn't missfire or even hint of backfiring. Runs smoother than it ever did with the distributor! What is VERY strange is that first thing in the morning when the engine is cold you can crank it over and it will start perfectly, no backfiring or any problems. If you switch it straight off and try starting it again its also fine. As soon as it warms up if you stop the motor, then crank it over again within a few minutes it will backfire, hesitate, then start and run fine. Does this whether the SAW line is connected, disconnected, grounded etc. I am deliberately leaving the SAW disconnected until this issue is resolved.

If I roll start the car (while hot) at a decent pace it wont backfire. If I roll start it very slowly it will. Just thought I would check this in case the starter motor was interfering somehow.

All of these tests were repeated on LPG and Petrol. On petrol its slightly better, but it will still backfire while cranking occasionally.

Here is what I have tried:
- Initially set the base timing to 10 degrees, thought the backfiring was because it was too advanced.
- Set base timing to 5 degrees, no change.
- Went nuts and set base timing to 0 degrees, no change.
- Checked timing marks were correct with a dial gauge (they were).
- Swapped over the EDIS module, no change
- Used coilpacks originally from a car equipped with edis, no change.
- Brand new VR sensor, no change.
- New plug leads, no change.
- Back to the original distributor ignition, starts fine.

Here's a bit of background:

I have retrofitted a large trigger wheel (diameter ~250mm) which I purchased from 'Triggerwheels' the UK and machined to fit the balancer. The VR sensor is from an Australian Ford Falcon, installed ~0.4mm from the trigger wheel. The wheel is perfectly centered, has less than ~0.1mm runout and is machined perfectly. Coils are also from an Australian Ford Falcon (although I tried some original 'EDIS' coils, with no change).

Ive searched and searched the web for people having problems like this. Most are due to the base timing being incorrect, but that the one thing im 100% sure of!

Any help or suggestions would be great!

[pit_celica]

Are you sure your spark plug leads are in the correct firing order? When I was on EDIS, if the spark plug leads arrangement was wrong vs the engine firing order, the engine would backfire loudly. When arrangement was OK, everything was fine. Basically, I was sparking the wrong cylinder at the wrong time.

Sam

[3fpowered]

Yep, leads are all correct. Also tried a different set of leads just in case one of them was faulty.

It runs great... once its started. Its just during starting that it will backfire, stumble a bit then run perfectly. My guess is the Edis is firing at the wrong point at low speeds, then once the engine speed picks up its fine. As for why its doing it I have no idea.

[ashford]

might want to play with cranking timing

[aarc240]

What is providing the 'brains' for the EDIS system?
Are you using an MS of some version?
The EDIS alone won't give you anything other than fixed ignition timing at nominally 10 degrees.

[3fpowered]

At the moment its not running any controller. Im not going to the effort of installing anything until I get the starting issue resolved.

I have tested it with two controllers though (basically hanging the wires out the engine bay as a temp thing). First was a PIC microcontroller based system I designed / prototyped. It worked fine, once the motor was running I could advance/retard the timing using different SAW widths. While cranking the engine it didnt seem to do anything to the timing (no matter what SAW was used) until the engine got up to speed.

Second one I tried was a friends MSII which we re-configured to run the edis. I only borrowed this for a day but it did exactly the same thing as my controller. Ran the EDIS fine once the engine was up to speed (about 1 sec after the engine fires and idles). Did nothing to the cranking timing.

This all makes sense though; according to the EDIS literature the module internally retards the timing when it detects a slow engine speed (i.e. cranking) and ignores and SAW input (until its over 500rpm, or something like that).

Im starting to think the engine must have a burnt valve or something, and running wasted spark is producing some sort of combustion in the exhaust stroke cylinder when the engine is cranking. I have lost count how many times I have searched the internet for a solution to this problem, but noone else seems to have even encountered it.

[Bzltyr]

I am having the same problem. I am running ignition only. It will even start a fire in the carb. Timing is correct doing the same test you did.
It runs great and the timing light says the same thing as MS2.

Cranking timing is at 5 degree BTDC.

Could it be lighting fuel mixture on the "wasted side" and popping through the carb?

[jammy86]

Could you have your wasted spark on the wrong cylinder, so the ignition is igniting the fuel on the intake stroke? When cold it doesn't because of poor atomisation....?

[billr]

Put another way... have you used a strobe light to check timing on every cylinder?

[Bzltyr]

I have not checked each cylinder with a light.

I will give that a try.

[Bzltyr]

The engine runs great after starting. It has plenty of power and no popping or misfiring that I can tell.

[DaveEFI]

I normally set the VR sensor gap to 1mm.
Have you checked the timing using a timing light? An engine will idle with more advance than is ideal for starting. My guess is it is more advanced than the correct 10 BTDC.
Some timing lights don't work with wasted spark - usually 'smart' ones. A basic one is normally OK.

If non of that works, check the battery volts when cranking at the EDIS module. It's possible they are going too low.

[Bzltyr]

Thanks for the help.

I will do some testing today.

Dave, I am not using the EDIS module. I am using Quadspark.

My timing light is a dumb as you can get.

[billr]

You have scabbed-on to an old thread, so we are wandering in the weeds here. Let's regroup, start a new thread and:

[turbo conversion]

Yep, leads are all correct. Also tried a different set of leads just in case one of them was faulty.

It runs great... once its started. Its just during starting that it will backfire, stumble a bit then run perfectly. My guess is the Edis is firing at the wrong point at low speeds, then once the engine speed picks up its fine. As for why its doing it I have no idea.

Is this an MS2 or MS3 system?

If it is MS2 using 3.4.1 firmware this may be your problem, it has a bug.

David