[xj-s] no crank after rebuild

Hi all,

I’ve rebuilt my 88 XJS v12 engine, as well as the interior. Went
to start it up last night, and the car won’t crank (it’s not even
trying). Getting power to the the cabin, but that’s all I can
tell.

Can anyone provide a good diagnostic procedure? Rather than fiddle
with everything, I the group could point me in the most likely
directions first.

Thanks in advance!!

Chris–
cmcclenn
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In reply to a message from cmcclenn sent Wed 28 Jun 2006:

Chris:

There’s a wire that comes off the 12V post on the passenger side of
the car, where the starter feed also comes. This wire is white/red
(? working from memory, here), but disconnects from the harness via
an inline spade connector. If this is loose or intermittent, you
will have the symptoms described: cabin power, no start/no nothing.

Good luck!–
Mike, 1990 5.3 XJS Convertible, ‘Caterwaul’
Lakewood, OH, United States
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In reply to a message from cmcclenn sent Wed 28 Jun 2006:

For initial confirmation that the starter works, check for batt
voltage on one post of the solenoid. If present use jumper cables
and us one clamp to short the two big posts on the solenoid together
(sparks). It should crank. If it doesn’t crank, a simple voltmeter
test or two should find the problem in the power delivery cables.
If it does crank, your circuit from ignition key to solenoid needs
to be traced out. Don’t forget the neutral switch.
Keep us posted.
Noel–
The original message included these comments:

to start it up last night, and the car won’t crank (it’s not even
Can anyone provide a good diagnostic procedure? Rather than fiddle
with everything, I the group could point me in the most likely
directions first.


'92 XJS Conv, '88 XJS Coupe, 1914 &1915 Ford T’s (Forguars)
Edmond, OK, United States
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In reply to a message from Jags+30jugs sent Wed 28 Jun 2006:

Test results:

In summary, no luck.

  • No voltage change from the Red/White wire when trying to crank.

  • Shorting to the starter side of the Red/White to the passenger
    side post, I get life from the starter (guess that’s good, not a
    dead starter).

  • Put the voltmeter on the Yellow/White wire and tried to crank…
    got the smallest twitch on the voltmeter

Does this mean I’ve got a relay problem, or the signal’s not coming
from the ignition to the relay?

Thoughts?

Thanks!!–
cmcclenn
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In a message dated 6/28/2006 6:51:40 PM Eastern Daylight Time, “cmcclenn” chrismcclennen@yahoo.com writes:

  • No voltage change from the Red/White wire when trying to crank.

  • Shorting to the starter side of the Red/White to the passenger
    side post, I get life from the starter (guess that’s good, not a
    dead starter).

Hi Chris:

Yes, your starter & solenoid are OK, you just aren’t getting a signal from the starter relay to the starter solenoid when you turn the key to the start position.

  • Put the voltmeter on the Yellow/White wire and tried to crank…
    got the smallest twitch on the voltmeter

Are you using an analog meter? If so, be careful what you use that on, as it can damage/destroy electronic components.

Does this mean I’ve got a relay problem, or the signal’s not coming
from the ignition to the relay?

If, when you turn the key to the start position, you don’t get 12V (reference to ground) at the WY wire that runs from the ignition switch to the Starter Relay, then your ignition switch or that WY wire has a problem.

George Balthrop, Clifton, VA USA
85 & 89 XJ-S Coupes; 89 XJ40 VDP

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In reply to a message from GBalthropXJS@aol.com sent Thu 29 Jun 2006:

Hi,

I’m using a digital multimeter… hopefully no harm potential there?

Found a bad connection between interior harness and engine wire
harness.

WY is getting 12V! Still no voltage to the WR, though, past the
relay.

Sound like a bad starter relay? It is wired per the wiring diagram.

Thanks again all for your help!!!–
The original message included these comments:

Are you using an analog meter? If so, be careful what you use that on, as it can damage/destroy electronic components.
If, when you turn the key to the start position, you don’t get 12V (reference to ground) at the WY wire that runs from the ignition switch to the Starter Relay, then your ignition switch or that WY wire has a problem.


cmcclenn
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In a message dated 6/29/2006 11:21:00 AM Eastern Daylight Time, “cmcclenn” chrismcclennen@yahoo.com writes:

WY is getting 12V! �Still no voltage to the WR, though, past the
relay. �

Sound like a bad starter relay? �It is wired per the wiring diagram.

Hi Chris:

It may NOT be the starter relay. I’m having a bit of trouble understanding the wiring diagram, but there MAY be a problem with either the Neutral Switch, or the Feedback Inhibit Relay.

If I understand the wiring diagram correctly, the Neutral Switch, when shifter is in Park or Neutral, is supposed to complete a ground to pin 85 of the Feedback Inhibit Relay (just forward of the Starter Relay), via the BG (Black/Green) wire, and the Feedback Inhibit Relay is than supposed to complete a ground to the control side of the Starter relay via the WB (White/Black) wire.

So, if that interpretation is correct, test for continuity to ground at pin 85 (BG wire) of the Feedback inhibit relay when shifter in P/N, and also test for ground at WB wire of Starter relay under same conditions (with key on). I’m no electrical system expert, so if anyone has the 88 Electrical Technical Guide, and interprets Fig 2.1 differently, please advise.

George Balthrop, Clifton, VA USA
85 & 89 XJ-S Coupes; 89 XJ40 VDP

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cmcclenn wrote:

I’m using a digital multimeter… hopefully no harm potential
there?

Nope.

Found a bad connection between interior harness and engine wire
harness.

WY is getting 12V! Still no voltage to the WR, though, past the
relay.

Sound like a bad starter relay? It is wired per the wiring
diagram.

There are several different possibilities. The starter relay
requires 12V to one side of the coil and a ground connection to the
other side before it will engage the starter. There are a couple of
concerns with the ground side; first off, on some of our cars the
ground is closed via yet another relay that in turn is controlled by
the impact switch just inside the driver’s side door. Even when this
relay is closed, the connection from there to an actual ground is
sometimes an issue, since it connects to the bracket itself and the
bracket is screwed to the car with a couple of screws and sometimes
they get corroded or something and don’t provide a good ground.

For a quick test of the starter relay and half the wiring, connect a
ground from the other side of the coil directly to ground and see if
the starter turns the engine over. If it does, you have a ground
problem. If it doesn’t, see if you can have someone else turn the
key while you listen to the starter relay. If you can hear it click
but it still doesn’t make the starter go, it’s probably the relay.

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In reply to a message from Kirbert sent Thu 29 Jun 2006:

Checked the GB wire, and it does seem to have a good ground.
However, it seems to be a ground whether or not the car is in P/N.

Kirbert, I’m not sure I understand… I’ve checked, and the
Red/White isn’t providing any voltage. If I short the hot post to
the R/W, the starter does engage. Wouldn’t that show I’ve got a
good ground?

Also, are you saying that the driver’s side door impact switch has
a cutoff to it, so the car won’t start when the door’s open? I do
know that there is an issue somewhere over there, as cabin lights
don’t come on. Should I resolve that issue first?

Thanks!!–
cmcclenn
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cmcclenn wrote:

Checked the GB wire, and it does seem to have a good ground.
However, it seems to be a ground whether or not the car is in P/N.

Gee, that doesn’t seem right. Maybe I should get off my a$$ and dig
up the wiring diagrams so I can be of more help here – but I’m not
at home right now so I can’t.

Kirbert, I’m not sure I understand… I’ve checked, and the
Red/White isn’t providing any voltage. If I short the hot post to
the R/W, the starter does engage. Wouldn’t that show I’ve got a
good ground?

That shows that the STARTER has a good ground. It doesn’t say
anything about whether the starter relay coil has a good ground –
provided you and I are thinking the same thing about which wires
we’re talking about and what you’re doing with them.

To review: There are two wires on the starter relay that are bigger
than the others. One of these big wires is brown, meaning it is
connected directly to the battery – there aren’t even any fuses in
that circuit. The other big wire goes to the starter, and I believe
that’s the WR wire we’re talking about. If you connect those two
together, you completely omit the starter relay (and everything else
in the starting circuit) from consideration. If the starter works,
you have proven you have a good starter. Nothing else.

To get the starter relay to work, you must have 3 things:

12V to one side of the relay coil
ground to the other side of the relay coil
the starter relay itself must be functional

None of the three questions are trivial. The 12V must come from a
post on the firewall to the ignition switch (which is always flaky)
to here. I’m not sure if there are other things involved, but there
are often problems here.

The ground involves another relay, the impact switch, and I think
the Park/Neutral Safety Switch (I know it’s involved, I’m just not
sure it’s here). Making sure each of these things is working
properly is simply a matter of chugging through it.

The starter relay itself is an unreliable item, and it often gets
intermittent before it fails altogether. The Lucas part is
expensive, I recommend replacing with a Chrysler starter relay which
is electrically identical but a lot cheaper, cheap enough you could
arguably just replace it as a test to see what happens.

It often is very helpful to isolate a problem to one of these three
areas. For example, if you install a jumper to provide a direct
ground and it starts working, you know the starter relay itself and
the 12V circuit are good, your problem is in the ground circuit. If
you provide 12V directly to the relay coil (there’s 12V right next to
it on the big brown wire, remember) and the starter engages, you know
the starter relay and the ground circuit is OK and there’s a problem
getting 12V through the ignition switch to the starter relay. Either
of these is a big step towards isolating the problem.

Also, are you saying that the driver’s side door impact switch has
a cutoff to it, so the car won’t start when the door’s open?

No, the car won’t start when the impact switch has been tripped. It
just happens to be located right next to the driver’s side door. You
bump it with your foot when getting in. The little button sticking
out the bottom must be up for the starter to work.

I do
know that there is an issue somewhere over there, as cabin lights
don’t come on. Should I resolve that issue first?

Cabin lights are a completely different issue – unless the problem
happens to be a major disconnection of 12V power from a post on the
firewall that has taken both circuits out at once.

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In reply to a message from Kirbert sent Thu 29 Jun 2006:

I wanted to say again how much I appreciate the help… would be
out of luck without you guys!

than the others. One of these big wires is brown, meaning it is
connected directly to the battery – there aren’t even any fuses
in
that circuit. The other big wire goes to the starter, and I
believe
that’s the WR wire we’re talking about. If you connect those two
together, you completely omit the starter relay (and everything
else
in the starting circuit) from consideration. If the starter works,
you have proven you have a good starter. Nothing else.

Yep, it’s the WR that goes to the starter-- shorting that to the
live post shows the starter is good.

I am getting 12V off of the White/Yellow when I turn the ignition,
but that’s just for the relay, and not the direct power to the
starter.

Should the brown be hot all of the time? I just checked it again,
and it’s not live (thought I checked it before… one of the first
things I tried, but I guess I made a mistake… or I’ve tripped
something while messing around). Perhaps that’s the problem?

I’ve checked the impact switch (thought you were talking about
something else, sorry!), and it’s in the right position.

Thanks again!

Chris–
cmcclenn
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In reply to a message from cmcclenn sent Thu 29 Jun 2006:

Ok, I’m an idiot.

While putzing around w/ other things (replacing balance pipe hose),
I disconnected the contact to the post b/c the wire was in my way.

That explains why, even after I fixed the YW wire, it still
wouldn’t start.

So, originally it was the WY wire. After that, it was my stupidity.

It cranks! No start yet, hopefully b/c of a low battery, but it’s
on the trickle charger now.

More to come! This project has been going two years… full tear
down and rebuilt, engine (and compartment) and interior. I’m
excited to be nearing the end!

Thanks again for all of your help… if you’re ever in the
Charlotte, NC area, please let me know. Beer’s on me!–
cmcclenn
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cmcclenn wrote:

Yep, it’s the WR that goes to the starter-- shorting that to the
live post shows the starter is good.

I am getting 12V off of the White/Yellow when I turn the ignition,
but that’s just for the relay, and not the direct power to the
starter.

You have tested the direct power to the starter. It’s fine.

Should the brown be hot all of the time?

Yes. A brown wire ANYWHERE on a Jaguar is connected directly to the
battery + terminal.

I just checked it again,
and it’s not live (thought I checked it before… one of the first
things I tried, but I guess I made a mistake… or I’ve tripped
something while messing around). Perhaps that’s the problem?

Might as well look into it. The easy way would be to short the WR
wire to it AGAIN and see if the starter turns. If so, it’s hot, and
you just are having difficulties using a VOM or whatever.

I’ve checked the impact switch (thought you were talking about
something else, sorry!), and it’s in the right position.

That’s good, but it doesn’t mean it’s working properly. Again, you
need to verify whether the problem is the starter relay itself, the
ground circuit, or the 12V circuit. Once you’ve done that, then we
can look into the details that might be the problem.

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