Hello, on my 84 xjs I have no spark when cranking eng.I do have 12v going to first coil there are two.im reading 12v to both +and - side of coil with key on is this normal?.there is 12v comming from ecu to power amplifier.Is there a way to test power amp i asume that is what gives volts to dist.
thanks for any help..Ok today i checked coil its good.checked power amplifier with ignition on (not cranking eng) using volt meter.one lead on+ battery post on firewall,other lead on neg side of coil.volts read 0.00 like it should.while cranking eng.volts should read between 2and 3 volts mine is 1.4 so thinkibg power amp no good?? can anyone comfirm this? does anyone know where i can get a good used one.??

 

jagernut,

I've moved your question from General Tech Help to XJS forum. Members here with the same model will be able to help.

Graham

 

You didn't mention whether both coils were receiving a 12volt supply.

"one lead on+ battery post on firewall,other lead on neg side of coil"
Can you re-iterate? I do not follow at all. +side battery post is on the battery in the trunk...
I am also unsure of what you mean by engine volts

• Switch ignition on and check voltage at positive terminal of main coil C.

• The main coil voltage should be 12 volts. If voltage is below 11 volts, check wiring from ignition switch G.

• Disconnect lead from negative terminal of main coil and switch ignition on.

• Negative terminal voltage should be 12 volts. If voltage is zero, replace main coil.

• Measure resistance of all grounds, just to insure they aren't a contributing factor (quick and easy)

 

sorry for confusing,the battery post im reffering to is on firewall.there are two.I do have 12v on main coil.and at secondary coil with switch on.also have 12v on neg side main coil with those wires disconnected.both coils ohm out within specs.but when I have switch on and i measure between neg side of main coil and pos post on firewall I do get 0.0 v but if i turn over motor i only get between .45v and 1.0v my book is saying that out going volts from amplifier should be 2v to 3v when cranking eng. so its saying my ign amplifier is faulty.I check the pick up in distributor by disconnecting leads from amplifier and ohming.it is within specs it measures 3.29 ohms.on 20k setting.now with switch on not cranking eng. i have 12v on wire comming from ecu to ign amplifier.and 6v to tach wire.just wondering. if you think amplifier is faulty according to test i just did?
hope this helps clarify things.
thanks..

 

ok,I disconnected ign amplifier.i opend back plate dont see anything burnt wires all look good.I noticed the pickup kinda crescent shaped black piece has GM stamped on it.I ohmed the two spade terms on it that goes to lead to distributor they ohm out to 12,60 on a scale of 20,000 on my meter,they also ohm to ground on amplifier on 20,000 scale to about 7,000 on smal spade and 17,000 on biger spade.. is this good or bad.if bad is there a GM # replacement on this part?the amplifier number is AB14 and number below that is 48030E is there anything else i should ohm out inside the amplifier?
thanks

 

OK, many, many readings of this to get my head right, and stilll a little confused, so here goes.

The ECU does not supply 12v TO the amp, the amp 12v comes from the WHITE wire of the 1st coil +ve terminal, which comes DIRECT from the ignition switch.

I have a diagram of all that if you want it.

The amp supplies a pulse signal to pin #18 of the ECU for fueling purposes, nothing to do with spark.

The module inside the AB14 is a STANDARD GM item, and also readily available as an aftermarket item.

Based on what you have tested I suspect the module, AND the small capacitor/condensor item inside the AB14, that is screwed to one corner of the casing. It has a bad habit of "leaking" to earth. I remove them at any chance I get.

Those modules are about $30, so worth the few $ to suck and see. Dont forget the white paste on its base, or it will fry quickly.

Those modules are an electronic switching device, replacing the old contact points, and if they dont switch, there is no spark.

 

This thread sounds very very similar to this one, https://www.jaguarforums.com/forum/x...-spark-117909/ Have you had a quick read through to see if anything sounds faniliar or might give you an idea where to look.
Basically I advise like on the thread change your coil system to the new low impedance single coil, solves the coil issue. I would then start looking at your wiring for fried areas or bad earth's, if no change your pick-up module if still no luck look at your amp.

 

Ok Great now that im educated in the correct way I understand the system better now.thanks guys.I have read a few other post and that plus my trusty hanes manual.lol i did the coil test and amp test.ign test and like i said since amp is only putting out .45 to 1v,and the modual contacs ohming out to amp casing.thats my conclusions.
So is there a part number for the condenser/capacitor? is it GM also.
one more thing if I take a test light and touch it to the ground (neg term),on main coil while cranking eng,if all is working correctly,the test light should pulse( flicker) right.

 

ok,I have now,come to the conclusion that when you buy a car like the xjs.it should come with course in lukas wiring.I wouldnt do a bondfire,Il get fined where i live but an 80' cliff will do..even thiugh thats my thats my thoughts at moment.Im determined to not give up.I just love this body style.and i do like a challenge.If I have to tear this car,apart to see how it works so be it.
Ok,got that out of my system..Im going to start from the beginnig.
I have no spark eng turns.I noticed the two outside wires on the four white wires where not hooked up.with help from doug i hooked them up the two middle wires go to main coil,solid white to +side and wht with black stripe to neg.now the wire i found that looks like a small coax cable,I cut back the outer shielding and spliced the inner wire only to the white wire with gray or blue( hard to tell) the far right one of the four white wires.as looking down from above amp leaning over (drivers side fender)in that,same loom where coax wire came out of there is another wire black not hooked up where does that go?also the far left of the four white wires i hook up to the tach wire.the two wires comming out of the side of amp.that go to the distributor pick upare hooked up when i dusconbect the plug from amp and ohm it it it is with in specs 3.78 ohms.with ign on i have 12v to both ign coils +and - now when I disconnect all wires from both coils,I ohm both the primary +and- sides of each coil and secondary (the middle connector on coil that goes to distributor.and thay are all within specs.I then hooked all wires back up on coils,exept for neg-side on main coil.put my neg lead from volt tester on that neg side of coil(not hooked up) and my pos lead from volt tester to the pos + post on firewall(tgat cones from post side of battery)with ign on I have 12v now when I hook the wires back to neg side of main coil and leave my volt tester hooked up the same way with ign on i have 0.00 v as i crank eng I only have .45v on my meter.my haynes manual says I should be reading 2 to 3 volts comming out of amplifier.says amplifier is faulty? heres the kicker,my ign amplifier has no ground wire I took it off looks like it never came with one.and when I ohm the modual in amp the terms going to plug on side of amp to distributor they ohm out at 12,600 on 20k setting.now when I go from terms on modual to ground (the amp casing) there is ohms.about 17,000 on same setting.but going down scale on my tester (10k,2k,200) its infinity.does that mean my problem lies in a faulty modual? im thinking it shouldnt ohm to ground on any setting correct? and is it possable my ign amp could be internally ground?

 

I noticed the two outside wires on the four white wires where not hooked up.with help from doug i hooked them up the two middle wires go to main coil,solid white to +side and wht with black stripe to neg.


Sounds right


now the wire i found that looks like a small coax cable,I cut back the outer shielding and spliced the inner wire only to the white wire with gray or blue( hard to tell) the far right one of the four white wires.as looking down from above amp leaning over (drivers side fender)


Sounds right


in that,same loom where coax wire came out of there is another wire black not hooked up where does that go


I connected the shielding for the coax wire to the black wire and taped it back making sure it made contact with nothing else.


also the far left of the four white wires i hook up to the tach wire


Sounds right




the two wires comming out of the side of amp.that go to the distributor pick upare hooked up when i dusconbect the plug from amp and ohm it it it is with in specs 3.78 ohms


Sounds right


with ign on i have 12v to both ign coils +and - now when I disconnect all wires from both coils,I ohm both the primary +and- sides of each coil and secondary (the middle connector on coil that goes to distributor.and thay are all within specs.I then hooked all wires back up on coils,exept for neg-side on main coil.put my neg lead from volt tester on that neg side of coil(not hooked up) and my pos lead from volt tester to the pos + post on firewall(tgat cones from post side of battery)with ign on I have 12v now when I hook the wires back to neg side of main coil and leave my volt tester hooked up the same way with ign on i have 0.00 v as i crank eng I only have .45v on my meter.my haynes manual says I should be reading 2 to 3 volts comming out of amplifier.says amplifier is faulty?


More than likely it is the ignition module inside the amplifier that is faulty


heres the kicker,my ign amplifier has no ground wire I took it off looks like it never came with one.


Amplifier box doesn't have a ground cable. The shielding mesh cable for the 2 signal wires in the harness from the distributor to the amplifier is usually connected to one of the amplifier mounting bolts.




and when I ohm the modual in amp the terms going to plug on side of amp to distributor they ohm out at 12,600 on 20k setting.now when I go from terms on modual to ground (the amp casing) there is ohms.about 17,000 on same setting.but going down scale on my tester (10k,2k,200) its infinity.does that mean my problem lies in a faulty modual? im thinking it shouldnt ohm to ground on any setting correct? and is it possable my ign amp could be internally ground?


I couldn't find any solid info on how to test the ignition module with a multi meter. I would start with attaching the shielding from the coax wire for the ecu to the black wire in that harness. If that does not work I would probably replace the module.


Hope this helps!

 

ok thats what that black wire is ok ill hook it to the outer mesh on white coax wire to ecu.
also my dist only has the two wire that go up to modular it never had it..I put pics on my garage.but I do have the pulse at neg side of cable with test light when i crank eng.so thats working at least.thanks capriceguy.

 

update,well i cleand secondary coil wire that goes to dist.disconnected it from dist and held it to ground.good spark.pluged it back into dist,and checked spark on one of the plug wires to spark plugs.grounded it with screwdriver to ground.I now have spark.I did strip black wire thats with ecu coax wire and connected it to outer mesh part of coax wire from ecu to amp insulated it good,like caprice guy said.so that im sure helped.I have new fuel pump installed.I can hear fuel rails preassurizing for 3 seconds when i turn on ign,so im sure pump is working fine.it is still not starting after cranking for a good 20 seconds.so i turned ign off pulled a spark plug and its not soaked with gas it just has a little barley wet at base of electrod and smells a little like gas.Im assuming thats good.the distributor is loose and turns so not sure where it should be.The car has been setting for a nunber of years,im just wondering if it will take a while to start? or is something else wrong?while i was cranking it for a second it did barley catch and that was it.any ideas anyone??

 

Better get this sorted out! At this point the only problem might be that the timing is way outta whack.

Do you think the distributor has actually been removed? Or is it just loose?

Turn the engine until cylinder 1A is at TDC on compression stroke. Is the distributor rotor pointing at the #1A position of the distributor cap?

Cheers
DD

PS- your posts are hard to read, at least for old eyes! Some spaces, paragraphs, and capital letters would really help. Not trying to a pain in the butt here. Just giving a little nudge

 

Sorry about that,Im use to texting so fast,I forget alot of punctuation.Ill be slower and more accurate.
Ok, I haven't checked timming,but that is my next step.Distributor turns like it is loose.Not sure if it has ever been taken out.
So plug 1A,is that front of eng right bank plug,as looking from inside of car out.?
And I believe a little contsructive correction goes a long way.

 

Correct !


Cheers
DD

 

Ok,I checked timming by taking out 1A spark plug.putting my thumb over spark plug hole.Turnnig over eng,till my thumb blew off hole.The rotor on distributor was pointing right at number one spark plug on cap.so i went down under car to see where the timming mark on crank pully,dampner was.It was not lined up.So I turned eng over again,till rotor on distributor was 180 degrees around.(oposite of where rotor was before on disttibutor).I then went back under car and timming mark on crank pully 1A was basically lined up .So im thinking distributor must have been out at one time,and is 180 off.what do you think?also how does distributor come out? I see no hold down bolt

 

You are definitely 180 out from what you describe. to remove the distributor, simply remove the cap and the rotor button, you find a plastic cover guard with 3 slots cut in from the top. Use an Allan key I'm not sure on size down through the slots and and remove the three Allan key bolts that hold down the dizzy. Mind you as these bolts come out they hit the dizzy so you have to lift and turn the bolts at the same time equally. Make sure to replace the oil seal o ring when you put it in the car again.
While its out do a full service on it make sure your advance works both vacuum and mechanical, oil them up. Also check the sender unit, the gap should be 0.1mm.
Good luck.

 

Thanks,I thought it was out 180.I will start on it tommarow.Thanks again for info.

 

Update,I checked timming.I took Front right spark plug out 1A.removed dist cap,turned eng over till timming mark 1A on dampner is exactly at 0° on timming scale.(TDC).I checked 1A spark plug hole with long screw driver and flashlight.piston is up.This should be compression stroke, exhaust valve closed.I then checked rotor on distributor.It is pointing at aprox 7:30,using a/c compressor as 12:00 looking from above.I was told rotor should be pointing at the 11:00 position.So if I leave eng at 0° on dampner and take out distributor.Then reinstall distributor so rotor is at 11:00,again looking from above using a/c compressor as 12:00 mark,then arrange plug wires starting at #1 mark on cap. going counter clock wise in correct order.I should be right on with timming correct?Ofcourse ill need timming light to adjust to 10° before TDC.The finall adjustment.

 

yes please on the diagram.