Injectors won't spray fuel
#1
04-03-2014, 05:17 PM
Injectors won't spray fuel
Hi! I am a brand new member who owns two Jags. A 76 XJS that is running fine, though the V-12 is scarey complicated. And a 1982 series three XJ6 which will not start after this winters rest. It has spark and fuel up to the injectors. It stumbles and fires a little from the cold start injector or a spray of ether. I pulled out an injector and can see that it does not spray. Based on what others have said I checked for voltage at the two brown/slate wires on the plug going into the injector resistor box (cigarette pack shaped box forward on inner right fender) and found no power reaching it. Any ideas about where to go back from here?
#2
04-03-2014, 06:08 PM
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Hi! I am a brand new member who owns two Jags. A 76 XJS that is running fine, though the V-12 is scarey complicated. And a 1982 series three XJ6 which will not start after this winters rest. It has spark and fuel up to the injectors. It stumbles and fires a little from the cold start injector or a spray of ether. I pulled out an injector and can see that it does not spray. Based on what others have said I checked for voltage at the two brown/slate wires on the plug going into the injector resistor box (cigarette pack shaped box forward on inner right fender) and found no power reaching it. Any ideas about where to go back from here?
Power for the two brown/slate wires comes from the "main relay" on the firewall. It's next to the fuel pump relay. Swap the two. If your fuel pump doesn't work and your injectors do, then you've found your problem.
These two relays should be between the red diode pack and the larger starter relay.
Cheers
DD
Cheers
DD
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Jagart2 (04-05-2014)
#3
04-03-2014, 06:15 PM
Hi there,
The first place ide go is the fuse panels and with the ignition on make sure if there is power at one side of a fuse, there is power at the other. A visual inspection is no good. I and many others have had issues from loose and corroded fuse holders. The best thing to do first is remove all the fuses one by one, clean the contacts with some sandpaper and bend the contacts together a little so it grips the fuse tight.
If there is still no power ide start looking at the relay's at the top of the fire wall. There is also a diode pack, (the red one) but im pretty sure that has more to do with the fuel pump interlocks. I don't have the book in front of me to tell you which one is which. Ide say relays as after sitting one may have frozen and wont give power to the ecu if the thing drove fine before sitting.
Otherwise have a look at the wiring in the area, it is often brittle and corroded by this stage and family's of mice may have seen it as a warm place to nest. I had two issues of my own that stooped the injection pulse, 1 was the trigger wire that goes from the negative side of the coil to the ecu. this is basically the lifeline of the injection in these cars as if its not connected nothing will happen. It runs across the top of the water rail and mine was very crusty and had broken in the middle. It does also have a connector that I would hold suspect. Another time i lost injection pulse was when the earth connection of the ignition amplifier was compromised. The amplifier relies on it being bolted to the manifold with a good connection to work. If the connection goes south then so does the spark and injector pulse. The best way to fix this is taking it off completely and sanding its feet and the manifold to ensure good connection. Probably another place to look would be where all the earth wires come together on the end of the water rail. Ide take the bolt out and sand all the terminals and mounting points here too.
Also worth noting is these old beasts are pretty particular about battery voltage. If you dont have a good strong battery then often under cranking the drop in voltage will be enough that the ecu will simply stop.
As to the v12's they look horrible but arnt all that bad, ive worked on some pretty horrible ones at work that seem to keep running. I think the key is to keep the cooling system in good order and make sure the distributor advance is not gummy or frozen. Some have big issues on the wiring loom where is snakes into the the valley under the compressor. Ive seen horrible things here as the heat makes the insulation brittle, eventually falling off and leaving the wires to short out.
Anyway, I always seem to ramble on allot more then is necessary,
Regards,
Jay
The first place ide go is the fuse panels and with the ignition on make sure if there is power at one side of a fuse, there is power at the other. A visual inspection is no good. I and many others have had issues from loose and corroded fuse holders. The best thing to do first is remove all the fuses one by one, clean the contacts with some sandpaper and bend the contacts together a little so it grips the fuse tight.
If there is still no power ide start looking at the relay's at the top of the fire wall. There is also a diode pack, (the red one) but im pretty sure that has more to do with the fuel pump interlocks. I don't have the book in front of me to tell you which one is which. Ide say relays as after sitting one may have frozen and wont give power to the ecu if the thing drove fine before sitting.
Otherwise have a look at the wiring in the area, it is often brittle and corroded by this stage and family's of mice may have seen it as a warm place to nest. I had two issues of my own that stooped the injection pulse, 1 was the trigger wire that goes from the negative side of the coil to the ecu. this is basically the lifeline of the injection in these cars as if its not connected nothing will happen. It runs across the top of the water rail and mine was very crusty and had broken in the middle. It does also have a connector that I would hold suspect. Another time i lost injection pulse was when the earth connection of the ignition amplifier was compromised. The amplifier relies on it being bolted to the manifold with a good connection to work. If the connection goes south then so does the spark and injector pulse. The best way to fix this is taking it off completely and sanding its feet and the manifold to ensure good connection. Probably another place to look would be where all the earth wires come together on the end of the water rail. Ide take the bolt out and sand all the terminals and mounting points here too.
Also worth noting is these old beasts are pretty particular about battery voltage. If you dont have a good strong battery then often under cranking the drop in voltage will be enough that the ecu will simply stop.
As to the v12's they look horrible but arnt all that bad, ive worked on some pretty horrible ones at work that seem to keep running. I think the key is to keep the cooling system in good order and make sure the distributor advance is not gummy or frozen. Some have big issues on the wiring loom where is snakes into the the valley under the compressor. Ive seen horrible things here as the heat makes the insulation brittle, eventually falling off and leaving the wires to short out.
Anyway, I always seem to ramble on allot more then is necessary,
Regards,
Jay
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Jagart2 (04-05-2014)
#4
04-05-2014, 11:14 AM
It runs!
Thanks to Doug and Jay. It turned out to be the ground wires at top rear of water tube. They did not look bad but cleaning them off did it. I once had a 3.1 V6 chevy "plastic" minivan with a starter that had a fussy ground. I will keep checking back to this forum and maybe I can help someone sometime. I am pretty good with brakes, clutches, and mechanicals. Even have swapped a few engines. My fork truck makes an excellent engine hoist.
Enjoy your Jags! Art
Enjoy your Jags! Art
#5
04-05-2014, 11:25 AM
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