My 1983 XJS fuel injectors not firing. This happened last night while driving home. It was running just fine that night then suddenly it started just slowing down until it quit. It just felt like it was running out of fuel and then just died. I replaced the fuel pump a few weeks ago and the lines with it and it ran fine.
I saw a posting dated 2007 about turning the ignition switch on the turning the throttle pulley. If I hear a clunk of sorts then they are firing. I tried that and if I turn the throttle fast, I hear the clunk sound and can feel it in the fuel rail. If I move it normally as in driving, I get no clunk sound at all. So maybe 2 problems.
The rotor and cap are new. I can’t seem to get an answer from AJ6 as to why my car seemed to come with 2 coils but now only has the one and the single wire cap. Maybe an upgrade with the ECU package.
I checked the plugs and they are dry. Both wires to the injectors are hot with the ignition on. I bypassed the inertia switch just in case but no difference. The ECU is was redone by AJ6 Engineering back in the early 2000’s before I bought it. I had the torque plus package installed by a previous owner.
So, I am dead in the water and would appreciate any help. I am not sure if the injectors get their firing from some other source than the distributor but am looking into that too.
Thanks
Russ
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
2
My 1983 XJS fuel injectors not firing.
I tried that and if I turn the throttle fast, I hear the clunk
sound and can feel it in the fuel rail.
Sounds like the coax wire problem. From the ign amp on the LH intake
manifold, there are two blue/white/gray wires going rearward toward the
firewall. One of them connects to another wire that disappears into a
harness sheath that then goes all the way across the rear of the engine to
the opposite side, where it merges into another harness. Strip the sheathing
off the portion of the harness with only that one wire. It’s white and thin, but
it is in fact a coaxial wire. It’s probably dry and cracked, and one of the
cracks is allowing the shield to short out against the core. If so, the fix is to
strip out that coupla feet of coax wire and replace it. The rest of that line,
which goes all the way to the ECU in the trunk, is usually in good condition.
It’s only the portion directly above the hot engine that gets cooked.
I do see the thin wire you are talking about that comes out if the ign amp. it does enter into a sheathing of sorts. There is a break in that cover but it shows that there are now 2 wires inside that sheathing. One is a now a thicker white wire in good shape and a black wire running next to it. The sheathing is just a fiber type with no coaxial qualities it seems. Not like you would find on a home cable system. I can follow the white wire as it runs into a larger loom and there it looses that initial covering. It is just a plain white wire larger than the one that came out of the ign amp. It seems that the heating from the engine has been addressed with that wire being covered but the sheathing and then entering the larger loom. I just don’t know how and why there is a black wire with it when it gets covered by the sheathing about 3 or 4 inches out of the ign amp.
I tried to take a few photos of it to show you. I am having a hard time forwarding them to me then to you here. But let me know what you think of the slight difference in what I am describing to what you want me to see please.
In the frayed part that is where the black and white wire show in that sheathed portion from the other picture. You can see the blue and white wire and to the right the skinny white wire. Inside that cover the wires are supple still, not brittle like the others that are bare in the same area.
Russ
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
5
One is a now a thicker white wire in good shape and a black wire
running next to it.
The black wire is just a ground for the shield on the coax. Shields should
only be grounded at one end, and I think that shield is grounded at the
other end, so really this ground should be left disconnected.
The sheathing is just a fiber type with no coaxial
qualities it seems.
The sheathing is irrelevant, other than hopefully protecting the wires a little
bit.
It is just a plain white wire larger
than the one that came out of the ign amp.
No, it’s a coax. However, if it’s in good shape, this apparently isn’t your
problem. When it’s shot, it’s pretty obvious.
It seems that the heating
from the engine has been addressed with that wire being covered but
the sheathing and then entering the larger loom.
Yeah, sheathing doesn’t protect wires from heat. It just takes a little longer
for the heat to get to it, but it still does.
If your coax is OK, your problem might be inside the amp itself. I presume
you’ve checked for spark? If you’re getting good spark, there’s still a
possibility that the resistor embedded into the white blob has gone bad
somehow.
There’s also a possibility that your problem is within the ECU itself, or
possibly the relay that powers it. That relay is a tad special, but I believe you
can replace it with a generic relay by adding a diode into the wiring to it.
I have great spark. the coil wire pops nicely and the plug get a good fire too. I am getting fuel to the injectors but the signal to open them is not getting there. I notice that both sides of the injector wires to the injector are hot when the ignition is on. I imagine the pulse must be driven by a grounding in either the ECU, potentiometer or both, or something else.
When I had the potentiometer plugged in and opened the throttle full I get a clunking sound from the injectors. This was a check that one person here said to check to see if the injectors were working and according to that, they are. But even though I tried this method several times and hoping it might let some fuel into the combustion chamber, it did not. Hoping it would fire just a bit.
I open the pressure at the regulators and there is good pressure there too. So, everything seems to be in order except the opening of the injectors. Now I am getting into the “magical” portion of the system. I don’t have the parts to throw at it to see if a different ECU would make a difference or something else that signals the injectors to open. Maybe even the potentiometer has a problem.
I again appreciate your experience and help. My car does have the super enhanced ECU by AJ6 Engineering that comes with the torque package. Something just quit though, worn, broken not sure. ECU’s are not everywhere but I would use one to try it if there were some here that might allow me to try an older Lucas 6cu.
I have written AJ6 engineering for any help but I am sure I would have to send the items they think might cause a problem like that for testing.
One more thing was that my car came with 2 coils. I thought that it must have had the double coil wire dist cap but apparently not. I did disconnect the front coil and it still ran fine. I think I will add it back though even though there is still good spark knowing that it is there for an added boost for the spark. I still need the injectors to open though.
