Hello, I am new to the forum, this is my first thread.
I have a 1986 XJS that will not start. It was working a year ago, then it started but died right away as if it did not have gas. After a few attempts, it did not start again, it turns over, but nothing else. I started checking, have been reading manuals and forums.

The gas pump works well, it turns on for a few seconds when the ignition is set to ON and stops.

I removed the gas pressure regulator in the right side of the engine and placed a pressure gage with two pieces of gasoline hose and the pressure is around 36 PSI.

I removed the injector rail and injectors, suspecting they were plugged, but found them to be OK, I opened and closed them with a 1.5 V battery and saw gas flow through. Placed new rings and reinstalled the injectors and rail.
Removed the power resistors, cleaned the connector and reinstalled.

Verified the cable that goes from the Ignition amplifier to the EFI (6CU in my Jag) it is not grounded and it has continuity to the ECU.

Installed a noid light in some of the injector connectors and every time the light indicated there is signal from the EFI. I can also hear the injectors working (using a hose).

Verified spark from the coil to the distributor (cable that goes to the centre of the distributor), there is spark, verified spark at two different outputs of the distributor and there is spark too.

The cooling fluid temperature sensor is not good (totally rusted connector, spades gone) I will temporarily install a 3.3 KOHM resistor to simulate a temperature between +10 and +20 degC.

The air temperature sensor is also faulty, it has a high resistance (3.4 KOHM) I will temporarily install a 470 OHM resistor to simulate a temperature between +10 and +20 degC.

The engine turns over, the ignition seems to work fine, the gas rail has pressure, the injectors work. Yet the engine does not start ! There is my problem. If any one has any ideas I would really appreciate to hear them. Thanks.

 

I forgot to write that the first thing I did was to clean the gas tank and the gas filter and flush the gas lines.

 

Check the crank position sensor, bottom front of the engine, 2 spade connectors.
Had the same problem today.
Coolant sensor will stop the engine running.

 

Your car is an 1986 it won't have a crank sensor.

When you turn the ignition on do you hear the fuel pump run, if not. There is a inertia switch on the drivers door pillar near your feet as you get out, check this is not popped and has continuity.

Crank the engine then pull a spark plug out and check if its wet with fuel.

 

Does it even give a cough or hiccup?

Have you tried cracking the throttle open bit?

I know you've checked for spark but, just to cover bases, is the distributor rotor spinning as you crank the engine?

Have you checked compression?

Cheers
DD

 

have you renewed the HT leads, especially the one from the coil to the dizzy, renewed the dizzy cap, rotor and spark plugs. If not, I would.
Greg

 

Read all your first post a few times, oh boy you have been thorough and busy.

Is the spark you see at the HT leads AT the plugs, a "Blue Crack" of a spark. If it is OK. If its a half hearted Yellowish affair, no good.

You have 11:1 comp there and weak spark will not cut it in that combustion pressure.

We got 12.5:1 and if we dont get a fat crack of a spark that thing will crank forever.

Recheck that shielded lead from the amp to the ECU, in particular pin #18 of the ECU MUST have a continuity in that very thin inner wire.

The CTS being crappy you have in hand, but just for giggles, and to satify the OLD guy (me), check the continuity of the 2 wires to the ECU from that CTS. Those wires are well known to breakage anywhere along the LH side of the inlet manifold, and bridging the terminals in the plug will do "bugger all" if the wires are broken. The CTS uses pins #5 and #19 of the ECU.

I would not be too worried about the ATS at this time, it is only a trimmer, and will NOT stop the engine running.

Next, the TPS is out of range, thus confusing the ECU. The TPS MUST be at 0.32 to 0.36 volts at idle. If it is out of this range, the ECU cuts the injector circuits during cranking.

 

I have rechecked the wire from the Ign amp to the ECU it is OK, also rechecked resistance between pins 19 and 5 of the ECU connector, it is 3.2 Kohm. (CTS). What is the TPS?.
Yes I believe have a fairly good spark. Have not remover a spark plug yet, to check if it is wet after cranking.

 

I also just rechecked the throttle pot at the connector to the ECU, it seems OK, also the microswitch is OK.

 

It does not give a cough or hiccups, nothing, it just turns over.
The injectors are working when cranking, there is clicking noise at many of them, have not checked all but at least 8 of them.

 

Just realized do not have the right dice to remove spark plugs, have to get one so I can remove one and see if it is wet.

 

Pull a plug lead and get a friend to crank the car while you hold the end about 5mm from the metal of the engine, see if there is a fat blue spark, or indeed any spark, as Grant suggested above. Good to change the plugs, obviously, but seeing if there is a decent spark going into the plugs is a very important test.
Greg

 

I pulled out a spark plug, it did not look good, dirty and the opening is too wide.
I cleaned and without changing the calibration checked the spark while turning the engine, there is a spark, but I would say it is a weak spark. I did test the sparks at the outputs of the distributor cover (where cables to spark plugs are connected) and it looked OK, I will replace all spark plugs. It will take me a week or so, too many things to do. By the way, I did crank the engine and removed again the spark plug, it did not look wet, it was dry.

 

1) Have you changed the leads and tested the LEAD end at the plug end of the lead to the metal for a big spark?
2) The ECU is "told" to keep fuelling during cranking by a signal from the starter solenoid. This needs to be checked too, or it will not start if no signal being sent/not received by the ECU.
Greg

 

There is good spark between the lead that comes from the HT coil to the centre of the distributor, testing the end of the lead to GND, space about 1/4". The spark is good.
Going out of the distributor it is algo good, so it seems the rotor and distributor cap are working well.

 

I have re-confirmed the ECU sends signal to the injectors while cranking, both with a noid light and listening with a hose, the injector clicking noise. The injectors are working while cranking

 

Hi Febres,

Having read all of your post it sounds like you have all of the ingredients for a running engine but its still not working.

Here is my suggestion...go get yourself a can of Starting Fluid. Squirt a little into each throttle body (open the blades first so you can squirt into the intake..not too much, just a quick squirt).

Try to start the engine. If your plugs have spark then the engine will try to run or at least cough on the starting fluid. If the engine only turns without any cough or trying to run then the ignition is your problem.

If the fuel injectors are truly opening as you said then the engine is probably flooded from all of the cranking you have been doing. You should have a strong smell of fuel form the cranking.

Try the starting fluid and let us know the results.

Mark

 

Hello Mark,
I already have the starting fluid, but have been hesitant about using it. This engine is a multi-port EFI, there is no throttle body that I know of. I guess I can spray some starter fluid in the air intake, but I am not sure, If any one knows where to use the starting fluid, please let me know.

 

Hello Grant Francis,
Still I am not sure what the TPS is, maybe the Throttle Potentiometer ? I verified variation of resistance between pins 7 and 20, and between pins 7 and 19 in the ECU connector when throttle changes, but have not measured voltages. Please confirm what the TPS is, thanks Grant

 

If you have an '86 XJS then it has a V12. It has a throttle body on each side of the engine. Take off the air cleaner covers and remove the air filters. You will then have access to the throttle bodies. Open the throttle and spray in a bit of fluid. No need to replace the filters and covers...just try to start the engine and let us know what happens.