Newcomer XJS V12 - 1988 and some problems ; start, but no crank

XJ-S
21

A long time since I last wrote. I had a lot of work.

I worked on the car yesterday. I check all the wires and connectors, including for the CTS and for the pin 18 ; 5 and 19 in the ECU.
I test with multimeter for ohms values.

On this part everything is OK.

So, very confident, I put the battery back on and put the ignition on start position.

1°) Now, I have the fuel pump running all time. I hear the pump working to put the pression in the rail. The pump stops for a fraction of a second and starts again. Running all time.

2°) I crank the engine and : the starter may have to turn a quarter of a turn and everything stops, no electricity even to the dashboard. Only the lights of the doors and the trunk work.

So I think that unwittingly, when I looked everywhere, I must have touched the wires in connection with the ignition switch…

So I have some work again, maybe under the dashboard… ?

22

Yes, I think you should check your ignition switch.
It could very well be the source of your problem.

23

Check the condition of the battery, sounds like its down on power.

24

Well, at least inspect the fan for any cracks … I still have my doubts about the yellow fan thing, as I have had them on all my other Jags (2 XJ40s, 1 X-300, 4 XJSes) and never had the supposed “explosion” … :thinking: :crossed_fingers:

25

Don’t be impatient… just wait.
It will be great fun, I promise.

26

And also that the connections are clean and tight.

27

Sounds like a corroded battery connection, need to check both positive connections and grounds. I have also experienced internal battery failures causing similar symptoms, which in one case resulted in the battery blowing up. Be careful!

28

I had a fan depart on a different car. 280zx. Not a pretty debris field. suckered. Holes through radiator. Dents in bonnet.
If I had a yellow fan I wouldn’t be rolling the dice…I would be changing that tired old sucker.

2 Likes
29

This cable on my 90 convertible was damaged by heat over the years and would intermittently short out between shield and center conductor near connector on firewall. Cut bad portions out and solder in new. Eliminated all wierd behavior.

30

Battery is OK now.

So, the situation is the following one :

  • I have the fuel coming in the rail
  • I have a spark at the distributor

The engine don’t crank…
The engine turns quickly when I activate the key, but without starting

I checked my timing, but I may have been wrong ?

You must know soemthing :
I removed the connector from the alarm system located in front of the car. It is a volumetric alarm from the late 80s.

I wonder if this alarm does not affect the electricity of the motor ? without being connected maybe I have an electrical issue somewhere ?

31

If the engine “turns quickly when … the key (is activated)” … then it IS “cranking”, correct? :confused:

32

If it has a immobilizer it can get very tricky, it all depends on the amount of botchery of the installation.

Stuck injectors is very possible.
With ignition on, turn the throttle turntable to full throttle by hand, you should hear the injectors click once.
Second, you should verify that your injectors do click while you are cranking the engine.
Also you should verify that the fuel pump keeps running. A small test lamp in parallel with the pump can help.

Do you have spark at the spark plugs though? Take a lead out and check.
Try with some starting fluid again. If it ignites, you know your ignition works good enough for the engine to start.

1 Like
33

Hi there,

I tried again to crank the engine. I have fuel and spark.

I put the timing mark at “0” on the crankshaft, for TDC.
It is correct ??
I was at TDC with valves closed on 1A and exhaust valve (the valve closest to the front of the car) open on 1B.

I put the contact. I hear the fuel pump in the back and some endless “noises of rattles” at the injectors. (what it is ??)

I turn the key (so I start the engine), the starter motor turns the engine fairly freely, but does not crank.

I really don’t know what to do next.

I am correct for the TDC ?
If I have a low fuel level in the tank, is it a problem to crank the engine ? (fuel tank is clean, fuel pump new and little fuel tank cleaned)

Thank you again for your help.

34

I’m just catching up again, and I see you’ve tested some of the wiring, and had some battery problems, but now the car cranks freely but does not start and run.

  1. Before you doo too much more cranking, it may be worth putting a squirt of oil into each spark plug hole so that the rings remain lubricated. There is at least one instance of an engine being ruined in cool-air high humidity environment because the low pressure created in each cylinder dry-cranking caused the humidity in the air to fall out in the cylinder, and create enough light surface rust that it ruined the rings with repeated cranking (as the problem was being chased down.).

Re Timing… have you touched or adjusted anything? or were you just looking? Usually timing is one of the last things we’d move on to. But at 0deg on the timing marker (assuming no shifting in the balancer due to rubber deterioration) the engine is either 10 degrees past an ignition event, or 360 out from that. That means both the intake and exhaust valve should be closed.

How are you seeing the exhaust valve? Are the exhaust manifolds off the car?

Low fuel in a clean tank is not a problem as long as it fills the sump and maybe a few gallons. There has to be enough to keep the fuel pickup sock in the sump under gas at all times.

You checked the Om value across 5 & 19 to the CTS, and how did you do the test for continuity on 18? Ran a loop in the engine bay?

You have spark (assuming it’s correct) and air, which suggest you have no fuel for as of yet unknown reasons. And you have a fuel pump that continuously stays on? (a problem we may have to deal with later).

Regarding the fuel injectors. It might be worth buying a NOID light.
NOID LITE (BOSCH 2) | OTC Tools
You can get them in small kits on Amazon or Harbor Freight or other auto-parts tool stores.

image
image640×640 33.9 KB

Another option: use a test light:
image

The light plugs into one of the fuel injector plugs and blinks as the ECU pulses the fuel injector… OR… does nothing… if the ECU is either not firing the injectors, or the injectors have no power or no connection to the ECU.

At this point, we need to know if the injectors are firing, and are capable of being fired by the ECU.

As smartly noted by Aristides above, the ECU will fire ALL the injectors as a single burst when, with key-on, you turn the turnstyle to WOT engaging the WOT switch (assuming that’s working.) IF you hear all injectors audibly click, then the ECU is capable of firing the injectors, and the problem really likely goes back to checking the pin 18 shielded RPM wire again.

IF on the other hand, there is NO audible burst, then:

  1. The switch is broken (check)
  2. The injectors are stuck. (Get a cheap Amazon/Ebay connector and make a pigtail to a 9 volt battery and try it on each injector tap tap tap tap ing the connection VERY BRIEFLY to see if you can get them to work. ABSOLUTLY DO NOT HOLD THE CONNECTION)
  3. There is no power to the injectors (check)
  4. There is a broken connection to the injectors (we’ll address that if the other tests don’t work)
  5. The ECU has a failure.

~Paul K.

35

That is an amazing and normative write up jagguy. I have a very similar problem 1987 v12 xjsc. I took the injectors out to get them professionally cleaned. I also took the manifolds off to spray them. I put the injectors back in and started but ran awful. So took them back out and fired them with an injector pulser and now all firing well.
I put them back on and at present I the car will not start. I have spark, node light shows the injectors fire on crank (flashing node) I have fuel, I couldn’t get a pressure connector to fit the rail so I resricted the flow back out on the amp side to build pressure and still nothing.
I have tested the wiring pin 18,5 and 19 and no grounds or shorts in 18s coax.

Now the strange bit when I crank my rev counter is going crazy and can jump to the red and the odometer is going round so mileage is going up when stationary.

I can see the rev counter gets fed from amp so disconnected the wire from amp and sit still goes crazy.

What I have found is the amp is leaking to the shell of it and the injectors don’t fire if the shell is not ground to earth. But if I ground the shell to earth the injectors fire.

Looking at your amp photos the second one has the white resistor and the bit it’s linked to fixed to the shell removed. I have read you can remove parts in there as can be an issue. Is this what should be removed and re-wire to bypass? If the injectors are firing if its grounded is the amp still the issue though. I also notice on that second amp you have a ground to where I tested 12v on the actual amp locating pins so would that be expected to have 12v there?
I have a spare GM amp (just the inner black piece) which I hooked up but no difference.

Any ideas greatly appreciated I am totally stuck now.
Oh and coolant sensor I have tried a new one and also linked out sensor and still no joy.

36

when I lumped my 83 XJ wuzza six, I sold off a lot of the parts. I had a buyer for the fan. but, on cleaning it up to pack, i saw all the cracks at the hub in the yellow plastic!!! No, sir, In to the waste can. I sent the guy the brand new black fan i was given by a work colleague… SOG stiffed me!!!

On topic. No start. Use the meter, check battery voltage at it’s posts. Remove and clean all battery cables at each end.

Jump carefully, 12v to the small post on the starter. it should crank with vigor.

1.If yes, work back on the circuitry to the ignition switch.

2 if no, there is starter motor or solenoid issue!!!

Quyick check/fix??? Jump 12v to coil +

Crank. In many cases, the engine will start. next is why?

Carl

Carl

37

Usually this means you Ignition Amp is acting up.

Now, that’s a new one ! You lost me there…
In order for the odometer to work it needs a pulse from the transducer.
Did you connect / disconnect anything related to the odometer and connected an ignition related cable to the wrong instrument?

Also very strange… revise your connections. Something is wrong.

What do you mean by that?

Of cource they don’t…

Check your connections.

Maybe these will help:

Ab14 amp
Ab14 amp928×459 13.8 KB

v12 ign1

GM Ignition Module Test

38

Thanks I was looking for that bottom test one for amp as seen it before.

So by leak I wasn’t sure if amp shell should be 12v until grounded but from what you commented on about the injectors won’t fire until amp grounded I am assuming it should be like that then? It uses the shell as it earth return?

No not that I know of disconnecting something related to transducer although not sure where that lives? That’s not the bit that goes in the side of the gearbox is it? If it is that was replaced recently as speedo wasn’t working but that was when car was fine havnt unplugged it since.

Must have something grounding somewhere but I have been through all the wiring I touched and more.

The injector harness is fine also. I am leaning towards amp or ecu. Although the ecu is firing the injectors so maybe more amp.

As say I have a spare actual amp inside. But I have seen posts in the past that say you can remove something in there that can fail. Possibly the capacitor, lookingat the second amp in those images it looks like the white resistor blob and the round bit that has one wire going to it have been removed. Just wondering if that’s the mod?

But the odometer is the strange bit. I’ll have to run a spare coax down the side of the car I have bellied it and all fine but maybe somehow the pulse is grounding and coming back up the transducer path. As say because I havnt touched that as far as I’m aware.

39

@ Paul V12JagGuy :
So, for the timing, yes.
I moved out the distribuitor unit, because I changed the pinion at the bottom of the distribuitor and I changed the shaft that drives the distribuitor.
Then when I put back the distribuitor unit, I check the timing.
Now, I must be at “0” or at “10” before TDC on the crankshaft ?

I checked the valves because I took off the spark plug and look inside. I presume I’m not at 360 °
Valves at 1A closed and the front valve at 1B open, the other one closed.

I checked pin 19 and 5 with Ohms, it was OK (but I didn’t remembers the values) and I make a loop in the engine bay for pin 18

I have spark at the plugs, and I have fuel at the fuel hose before rail.

After I cleaned the injectors, I try each injector on the banch, with a 9V battery, everything was fine.

When I put the key on, I hear audibly all the injectors, but they don’t stop making noise when key on.

What I have to do now ?
I have to make again the test with PIN 18 ?

40

In regards to your injectors when you key on, do you mean not cranking but just switched on so fuel pump works and they continue firing instead off just once?

Sounds like you have a ground on your injector loom or have you tried unplugging the tdc. It’s a 3 pin connector at the back centre of your engine bay.

The other thing I found on mine was if the amp is not grounded properly the injectors would chatter