Hi Guys

1995 XJS 4.0L AJ16 Engine, still won't start!

Crank Position Sensor replaced and Tacho reads 750 to 1000 when Cranking, so I'm assuming that is not the problem

She will run quite smoothly if a Tea Spoon of Petrol is poured into the Air Intake but otherwise she seems to struggle to get any fuel injected into the Engine, even though there is plenty of fuel at the rail

So because She runs on a Tea Spoon of Petrol if only for a few seconds, I am again assuming that the Spark Plugs are ok

Which seems to leave the Fuel Injection System, as the possible cause of No Start

The ECU seems to be in really good condition, no sign of any dampness or corrosion although I did clean the plugs to be sure

Is there any way of Testing the Injectors without any special equipment?

Is there any Sensor that could be faulty that would stop the Engine from Starting?

She keeps trying to Start but the Engine just won't pick up

Maybe the Injectors are blocked?

They look a bit complicated to take out (compared to a V12)

Any ideas appreciated

No experience working on these engines, so please explain as simply as you can

 

Hello OB,

You now have experience working on these engines, since you replaced of the Crank Position Sensor! No matter how long it took. Countless hours (and threads) have been devoted to the CKPS in the X300 section. Glad that is out of the way of new progress.



Item #6 at the front of your fuel rail (#1) is your Fuel Pressure Regulator. If it has gone South, the injectors will not get the fuel pressure they need to spray enough fuel into the cylinders. Even if the fuel pump is pumping very well, if the FPR is bad, the fuel will mostly just go back to the fuel tank via the return line. Or, it could be leaking through the vacuum line from the FPR to the manifold:

A quick test: Small hose #11 should be connected to the top of the intake manifold. Pull that hose off and smell it. No kidding. It should not look or smell strongly of fuel. It is a suction line from the manifold that acts on the diaphragm inside the FPR. If that diaphragm has split, fuel will get past it and into the intake and/or crankcase, causing low fuel pressure. And we don't want fuel getting in through there!

If the test passes (relatively dry hose), it is still not certain that the FPR is good or bad. But if the test fails (evidence of a fuel leak), for sure you need a new FPR.

 

Hi SleekJag12

I've changed out FPR's before on my XJS V12 which was leaking so bad that it dissolved the Wax in the Thermal Fuel Enrichment Switch that dripped down on top of the Injector underneath it and made me think that the Injector was leaking!

So bad was this that my Car came close to catching on fire!

If it were not for a Chance remark from 'Grant' 'The Wizard of Oz' that the Thermal Fuel Enrichment Switch was filled with Wax inside then I don't think I would have ever managed to sleuth it out

And would probably have ended up replacing all the Injectors but once I removed that Wax Filled Switch and changed the FPR that problem that I had just went away!

Although the 4.0L AJ16 seems a totally different ball game and still a bit of a mystery to me and 'Seems' harder to work on but your diagram is going to help a lot

Are the Injectors Clipped to the Fuel Rail with what looks like 'Sliding Clips' ?

Two other possibilities have also just come to mind:

Maybe 20L of Fuel was nowhere near enough to put in the Fuel Tank, as unlike on a V12 the In-Tank Pump is suspended clear of the bottom of the Fuel Tank

Below is a Link to a Pic of a 'Trial Fit' of the 'NEW' In-Tank Fuel Pump in the Fuel Tank and now wondering if 20L of Fuel is even enough to Cover the Filter on the bottom of the Pump (what do you think guys?)

Is 20L of Fuel enough to cover the Filter on the In-Tank Fuel Pump? (see Pic)

So I will pull out the Fuel Sender and see if the Mesh Filter on the Bottom of the In-Tank Pump is completely immersed in Petrol

Also is there another Fuel Filter apart from the one on the bottom of the In-Tank Fuel Pump?

If so please could someone show me where to find it, as I don't remember seeing one when I was reconnecting the Fuel Pipes to the Fuel Tank

 

I'm sure that 20L of fuel would be plenty to immerse the pick-up mesh.

There is another fuel filter underneath, along the feed line, apparently close to the tank (although I'm not directly familiar with the XJS setup). #7 in the diagram.


When you say "plenty of fuel at the rail" do you mean that fuel flows strongly from the feed pipe into a bottle when the ignition is turned on (or fuel pump is jumped on)? That would be what you want to see when testing for good flow. Do that if you haven't already.

Any sign of fuel leaking at that vacuum hose to the Fuel Pressure Regulator?

 

Hi SleekJag

You and me both! as I also thought that 20Litres of Petrol would be more than enough to try and get her Started but its looking like not so!

Because the Fuel Tank as you may probably know, is a totally different set up to that on a V12

Where for those who may not know, the V12 feeds off a 'Sump Tank' which is 'Gravity Fed' from the Main Tank and so as long as the Sump Tank stays Full, then you should have enough to run the Engine

And while I'm not exactly sure how much the 'Sump Tank' on a V12 holds, it doesn't look more than about a Gallon

But on a 4.0L Facelift with an In-Tank Fuel Pump, it's a totally different Story as that Fuel Tank doesn't have a 'Sump Tank' but instead suspends the In-Tank Fuel Pump off the bottom of the Tank on a vertical bracket

So up to the point where the Petrol is just below the Filter on the In-Tank Fuel Pump, that part is then in effect what is used instead of a 'Sump Tank' to try and keep any debris away from the Filter

Where unlike on a V12 Tank, the 20Litres of Fuel I put in, once spread all over the Floor of the Tank, seems to be hardly enough to cover the Filter on the bottom of the In-Tank Fuel Pump

So while there 'APPEARS' to be enough Petrol getting to the Fuel Rail

Because the Pump is unable to replenish itself fast enough (20Litres = Not enough Fuel in the Tank?)

It looks as though the Engine is experiencing Fuel Starvation (Almost enough to Start her but Not Quite)

Hence the possible reason why She is trying to Start but won't 'pick up' 'if you see what I mean'

Of course I could be totally wrong but I honestly think its down to a lack of Petrol, where far more may be needed than would be in a V12 where of course the Sump Tank only needs enough to be kept Full

In which case there is really only one way to find out, before the 'Nuclear Option' of taking out all the Plugs and the Injectors

 

Do you have a multimeter that shows frequency or dwell? If so, you can measure for a trigger voltage at the injector. You could also unplug an injector and put an led into the plug to see if you get a pulse (it will need to be the correct way around) .

There is no way on Earth that Jaguar designed a car to have 20 litres of fuel in the tank that can't be accessed by the pump - what would be the point? If you think there's no fuel getting to the engine bay, undo the fuel feed pipe from the fuel rail, stick it in a bottle and turn on the ignition.

 

Hi Bladerunner

The In-Tank Fuel Pump Filter, sits about an inch high up from the bottom of the Tank and as such seems to need to have Petrol to a depth of about 1.5 inches to cover the Filter completely

Where 20Litres of Petrol when spread over the base of the Tank, seems to be only just enough to do that, as unlike the V12 Prefacelift the 4.0L Facelift (with the In-Tank Fuel Pump) doesn't have a 'Sump Tank' it can feed off

So in effect the space from the Filter (of the In-Tank Fuel Pump) to the Bottom of the Tank, takes the place of the Sump Tank and as such it appears that the Fuel I've put in just makes up the distance from the bottom of the Fuel Tank to the Filter

Which needs to be completely immersed in Fuel, or else it would seem that you would get Fuel Starvation, which is what I think I'm getting now and so the only way to know for sure one way or the other, is to put more fuel in and then see what happens

As for the Meter to measure the Dwell, unfortunately I don't have one and hopefully may not need one if more Fuel solves the problem and although I've got the Petrol already to go in

This isn't the day to do it, as its chucking it down with rain

 

I'm not familiar with I6 but all injected cars (petrol that is) initiate a priming pulse before starting, can you hear the injectors click when you turn the ignition on? I also would expect the I6 to be the same as the V12 in that once it starts to crank the injectors should fire 2 - 4 pulses per engine cycle.

You could pull the injectors and test them on the bench with carburetor cleaner, a syringe and a 9v battery.

 

I'm still confused by the 20 litres of fuel not being enough for the pickup. That's nearly a quarter of a tank (tank capacity is 89 litres, I believe)?

 

Maybe too much water in the tank

 

If only She ran on Water I'd be driving her Night and Day!

 

Hi Bladerunner

I've just found out the Fuel Sender isn't working! and there is no power getting to it

I'm totally lost on this one, any ideas?

 

Do you mean the sender for the level gauge?

 

Hi Bladerunner

I thought the Sender was the Level Gauge

Its the Float that goes in the hole in the Tank which can then be read off the Gauge on the Dash

Neither one is working (Nothing Showing On My Voltmeter) maybe that's one of the reasons why I thought that I was very low on Fuel to get her to Start

 

Here a TSB covering AJ6 & AJ16 injectors