Ignition coil- 95 Disco I- is a coil a coil a coil...?

[skrufy]

Hi-

have a no start- no spark situation with my 95 3.9l Disco- had a cold start problem that I have dealt with before- fixed with a new fuel temp sensor, but had an ignition miss at high idle thru normal drive rpms....

-so, after having put in new plugs, after market distributor cap, and rotor about a year ago, I put in new LR OEM sparks plug wires and a new fuel temp sensor.....

-so now, no start and no spark...... checked all fuses and all are okay.... all wires appear to be good, new gell cell battery 2 months ago.... haven't checked fuel pressure, but smell gas after attempting to start it- strong fuel smell at tail pipe- replaced the fuel pump about 18 months ago or so.... so don't think it's a fuel issue...

I do have the LR shop manuals- and electric manual- and ordered OEM dist. cap and rotor, and new ignition module (Remote, mounted by the coil on the '95s....) from Brit. Pacific......

-Following the manual Lucas ignition tests-

I get no spark from the coil lead when placed 6mm from the block, the other voltages are within the specs in the various tests (1-5)- and conclusions point to a bad coil...

The Question: since it is a Sunday, and I live in the boonies, is there anything special about the Bosch ignition coil- can I swap out the coil from my Jeep- gasp!! ( relax- it's a 1952 Willys M38A1 Army Jeep- restored- but I switched to 12v. from 24v years ago- installing a coil from the junk yard purchased for probably $4 or so...).....

can I swap it for test purposes- just to see if I can get the Disco to start or try to start- or will I fry some ECM module or something???? don't even know what brand is on the jeep- haven't been out there to check yet......

anybody have an aftermarket part number to choose from- Delco, Mopar, etc....?

thanks-

Tim

 

[skrufy]

Hi-

more info to my post above:

-residual fuel pressure at the fuel rail is 33-34 psi, and when cranking, goes up to 38 psi, so I don't think fuel has anything to do with the no start problem......

-taking the #1 plug out shows it to be wet with fuel.... putting the plug into the empty plug boot and then setting the plug next to the block so that it can ground when cranking- reveals no spark at all, even between the electrode and the center core of the plug.... you can smell the fuel from the open #1 cylinder.....

so, looks like the coil is the bad guy here..... but am having a hard time seeing how the hi and low side of the coil can go so suddenly, but electrical stuff does that sometimes... in coils, I guess the insulating varnish between the coil winding can deteriorate and cause a short internally.......

any thoughts out there would be appreciated!

Tim

 

[Rocky]

Napa has a coil but at $125 (ECHIC442)- Autozone is not much cheaper

ABP prices range from $40 to $99. Lots of choices out there

13 years is more than enough from a coil. Replace it. They can leak as well. Wear gloves when handling

 

[p m]

You can replace your coil with a jeep one, but chances are high that you'll burn the ignition amplifier module. IIRC, the Lucas 14 coil is 12-volt, unlike all pre-EFI Jeep coils that are designed for 6V electrical system, with a ballast resistor.

 

[MUSKYMAN]

the ballast resitor protects the points not the coil.

the rover ignition is a simple square wave trigger that runs at 12 volts.

so a coil is a coil is a coil...as long as its a 12 volt coil

 

[p m]

so a coil is a coil is a coil...as long as its a 12 volt coil

yeah, again, all pre-EFI jeep coils are 6 volt.

 

[ptschram]

Do the rest of the tests before declaring the coil bad. I've seen very few coils go bad on Lucas EMs engines, and when they do go bad, the tests are always definitive.

 

[ptschram]

I put in new LR OEM sparks plug wires and a new fuel temp sensor.....

-so now, no start and no spark......

Gee, do you think the changes you made could have caused your no start condition?

I think I'd go back and start over. Maybe new rotor.

It doesn't make sense that a truck that was running somewhat poorly all of a sudden suffered a coil failure after the replacement of plug wires and fuel temp sensor. Keep looking for the cause, I don't think you've found it.

 

[MUSKYMAN]

yeah, again, all pre-EFI jeep coils are 6 volt.

not really sure where you get this?

STANDARD MOTOR PRODUCTS Part # FD476T

thats about the most common 12 volt coil out there it goes into all kinds of fords, lincolns, IH's and yes just about every jeep made from 1970- 1980 and none have EFI

as I said a coil is a coil is a coil

oh and to bring some tech back to this thread...this coil would have no issues running a 3.9 disco and it about $10 -$12

 

[p m]

not really sure where you get this?

... when I was looking for a coil to use with MSD6A on my jeep (MSD's own coil shorted out and burned the MSD box), I've looked through a bunch of common jeep coils, and found that all of them were six-volt units. All of them were arcing from the center terminal to primary coil terminals or metal case while used with MSD box.
The reason for the ballast resistor is to limit the current through the coil during cranking; when the engine is running, the ballast resistor is by-passed (FWIW, jeeps with electronic ignition also used the ballast resistor, so it's not to protect the points).
I ended up buying a coil spec'd for a Classic, which had reasonable primary coil resistance, and it's been happily under the hood of that jeep ever since.

 

[ptschram]

I've got a lightweight in the shop that keeps burning up the wire from the point to the coil. I've got my fingers crossed that a ballast resistor does the trick.

BTW-Peter, I thought the coil got full voltage during cranking and then the ballast resistor was in the circuit thereafter, not the other way around.

 

[robertf]

BTW-Peter, I thought the coil got full voltage during cranking and then the ballast resistor was in the circuit thereafter, not the other way around.

you are correct, at least that is how the Duraspark setup that Jeep used from 78 to 91 is

 

[MUSKYMAN]

on old points run distributors the ballast resistorwould be bypassed during cranking to put full voltage through the POINTS during cranking then dropped the voltage down to prevent the points from failing.

 

[robertf]

Muskyman there are lots of factory ignitions that use magnetic pickups with electronic ignition modules that use ballast resistors. Its not just to increase the life of points.

 

[MUSKYMAN]

Ballast Resistor: This is an electrical resistor that is switched in and out of the supply voltage to the ignition coil. The ballast resistor lowers voltage after the engine is started to reduce wear on ignition components. It also makes the engine much easier to start by effectively doubling the voltage provided to the ignition coil when the engine is being cranked. Not all car manufacturers used a ballast resistor in their ignition systems So you should check to see if yours does.

well sounds like some did use it to reduce the voltage to the coil as well

 

[Papillon]

Musky,

My research indicates a STANDARD MOTOR PRODUCTS Part # UF312. It retails for about $90 (Ouch!). Where did you get your part number?

 

[robertf]

if you've got the time and know how to make your own coil wire and build a simple bracket, a stock chevy external HEI coil or an EFI Ford 302 coil is a nice upgrade to the old style coils.

Epoxy filled instead of oil, so they are pretty bullet proof. I've done quite a few TBI conversions using junkyard HEI coils and have yet to see one fail. Applications are 87ish to 95 ish 1/2 ton trucks (along with a few dozen other possibilities) for both makes. You can also crank up the spark plug gap with one of these.

 

[MUSKYMAN]

Musky,

My research indicates a STANDARD MOTOR PRODUCTS Part # UF312. It retails for about $90 (Ouch!). Where did you get your part number?

thats not the part number I posted...I posted a $10 coil that ford,jeep and a bunch of others used...it was just a example of a standard canister coil.

you wouldent actually want to use it because it came with clips to attach the wires not threaded studs.

 

[p m]

BTW-Peter, I thought the coil got full voltage during cranking and then the ballast resistor was in the circuit thereafter, not the other way around.

you're right, my bad.

 

[MUSKYMAN]

ok so are we all groggy after a long weekend or what?