1987 XJ12 HE Engine won't crank

(Gregor Eichenberger) #1

Hi Jaglovers

I had troubles with my old starter
which made only solenoid clicks
when trying to start the engine.

So I pulled the starter and
it showd that the old starter
was weak while I put it in
a V12 Engine without heads/
camshafts. The old starter was
not able to turn the engine.

So I bought a reduction gear
starter and tested it before
I installed it.
Now, while I tried to start
the engine with the new starter
I have the same Problem.
The solenoid only clicks and the
starter does’nt crank the engine.

So I took the battery out and tried
directly by putting - on the starter
and + to the port of the starter and
to the solenoid and nothing, only
the solenoid is working.

I then tried to turn the engine with
a 30cm (11.81") fork key (while I was
under the car) on the pully and the
engine turned very very hard but it turned
(annotation: i did not take the sparks
out…), so the engine is not seized.

I don’t know what’s the problem now.
The battery is fine, is working in my
XJ40 and was fully loaded.

What else could be wrong? Does someone
has an idea?

Best regards, Gregor

(Paul M. Novak) #2


There is an excellent resource for Frequently Asked Questions (FAQs) on the Series I, II, and III XJ6s and XJ12s on the old Jag-Lovers site. The URL is http:// www.jag-lovers.org/xjlovers/xjfaq

Once there, scoll down to the “ENGINE” section and click on the first one titled “Engine Will Not Crank Checklist” written by Doug Dwyer. This FAQ is an excellent guide to getting your Series III 1987 XJ12 running again. Having the engine not crank is a somewhat common problem in the XJ6s and XJ12s, especially due to their age, and a variety of faults can cause that fault (starter, battery, starter relay, ignition switch, battery cables, ground straps, etc)

While you are on the FAQ page, please take a look at the extensive list of FAQs put together by XJ List members over the years before Jag-Lovers migrated to the new site. It is quite likely that other FAQs listed there may be helpful to you as well.

BTW, the “Old Site” is still accessible by going to the new site home page and clicking on “Old Site” located at the top. That is how I usually access it.

I refer to the “Old Site” regularly while working on my two Series III XJ6s and my 1990 V12 Vanden Plas (a Canadian market 1990 XJ12).

I hope this helps.


(Gregor Eichenberger) #3

Dear Paul

Thank you for your advice and reference but I know this site already (http://www.jag-lovers.org/xjlovers/xjfaq/nocrank.htm).
The Problem is not the contact to the starter or the starter relay. Also is the
new Starter running fine when I took it out the car.
While in the car and connected directly to the battery poles (the starter) it
won’t turn the engine. The solenoid works fine but turns the engine only
a few millimeters.
Probably I have a seized engine :frowning:

(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #4

Have you checked the ground straps between engine block and chassis?

(Gregor Eichenberger) #5

Yes, while I had the trouble with my old starter I checked all the points (starter relay, in the site above.
While I took out the old starter I used to losen the connection to the chassis and cleaned the connectionpoints from rust and dirt. Also on the plus pole distribution point on the firewall to the starter.

i would also think it’s a short circuit. But I am irritated, however, that the starter is equally slow when I give mass directly to the starter (from battery) and plus directly to the positive pole of the starter (from battery) and the solenoid bridge.

(Paul M. Novak) #6

If I were you I would remove all the spark plugs, pour a small amount of lubricant into each cylinder through the spark plug hole and see if you can get the engine to turn using the starter. With the plugs removed there will be a lot less resistance to the engine turning. In your previous email you said that you could turn the engine a small amount by hand. With the plugs out, and the cylinders properly lubricated, the new reduction starter should be able to turn the engine, unless there is something seriously wrong.

For the lubricant you should use something that might break down any rust or corrosion that might be there if that is what is preventing engine rotation. Although I have never encountered a problem exactly like yours, I have used Marvel Mystery Oil to prelubricate cylinder walls and rings after a cylinder head change. I have read on Jag-Lovers about others using a combination of kerosene and Automatic Transmission Fluid (ATF) inside the cylinders to soak it over a period of days to loosen things up, but I have never done that myself

Do you have any evidence of overheating or a failed head gasket like coolant in the oil or oil in the coolant?


(David Jauch) #7

It could be than an injector failed open or leaks and filled a cylinder with fuel, or the head gasket did the same thing with coolant. Or that long sitting just seized the engine.
Given it is a V12 try to only remove all accessible plugs and try to crank it by hand. A 30cm Gabelschlüssel might be a little weak, if you have a large ring spanner or big enough tube try that… and add a little bit of ATF or some WD40, Diesel etc. into the bores beforehand. Oil preferable because it won’t make an oil change absolutely neccessary. Should you now be able to turn the engine, make one revolution by the hand, then try the starter which you know works well and then replace the plugs and try again. Should it still not turn I’d remove all plugs and inspect the cylinders via a Boroscope / endoscope if possible.
Maybe you burned the old starter by trying, but that surely indicates it being on the way out anyways…
Good luck!

(Gregor Eichenberger) #8

Yesterday I took all spark plugs out and tried to turn the engine by hand.
Works lot better but I hear a squieking noise in the middle of the B bank. Sounds just like
the pistonrings are making this noise => that’s new and was never before.

Now I’ll give it a try with some Dexron. Will wait a day or two and then turn the engine by hand again.
@davidsxj6 The combustion chambers are dry, there’s no gas or antifreeze inside, so I had luck with that.
Let’s just hope that it’ll be fixed now…

@Paul_M_Novak2 about the engine…
I changed the Headgaskets in 2017 and hat lot of other things to restore on the car (Kirby’s Book had a lot of
advices like distributor, injector harness etc…).
So the Motor did not run since before the headgasket broke (but the car is in a dry garage) It used to run for a short time to adjust the ignition. So when I tried to start the engine, the old starter didn’t it anymore. But also before, the old starter was always weak and had a strage sound.

I’ll let you know…

Best regards,

(Gregor Eichenberger) #9

So, yesterday evening after work was the day…
Tried to start after I took all sparkplugs off and put some dexron
in the chambers…
Turned extreme fast and the squieking sound on the B bank is gone :slight_smile:

So seems to me it was rust on the piston ring(s). Newer thougt one or two cylinders
with some rust on the rings could do such a mess…

best regards and tank you, Gregor

(Paul M. Novak) #10


That is very encouraging news that the engine turns now and the noise is gone. Please write back when you get the engine running. I will be curious to see how things work out.


(Gregor Eichenberger) #11

Hi Guys

Now, after the big joy the starter wouldn’t start anymore. The starter relay is fine, but I have a Problem with the Voltage of the W1 cable.
Posted it in the XJ section => Canadian XJ12 1987 Inhibit Relay
Maybe someone knows the awnser about the inhibit relay for my canadian XJ12?