bad starter

[timpengilley]

hi everyone, can anyone advise me as to why my car turns over for about 10-15 seconds before it starts most of the time?
thanks

[ptjs1]

Tim,

there are a number of things that could be causing the problem. There are a few XJS foibles that can cause starting problems, but they differ depending which car you have. Your signature or post doesn't indicate what year XJS you have or what size engine it is.

If you can give some more details and also other factors such as whether the problem is worse if the car is cold or hot, then i suspect you may get some responses.

And remember you can just contact the clubs paid technical XJS adviser for thoughts.

Good luck

Paul

[davidr]

Tim - I remember reading somewhere that some engine management systems do this to allow oil pressure to build up before the engine fires up so maybe it's meant to do that. I think your car is an XJR-S? I think that has a different engine management system to standard cars?
Does it always do that? Does it only do it when the engine is hot? Does it run normally once it starts? Does it run normally under full throttle?

[timpengilley]

oh dear, turns out i have to wait about 10 seconds before a relay can be heard coming in, a red light then flashes on the dash which must go out before the car can be started! LOL. i guess there must have been an immobiler or something fitted in the past which is now removed, dont think this is a standard feature?. thanks for your help on this.

[ptjs1]

Tim,

As mentioned, if you advise us what car you've got, engine size, year etc, it's much more likely that members can offer advice.

You refer to a red light flashing on the dashboard; whereabouts is the light? Does it flash when the ignition is off or does it come on when the ignition is turned to position 2. I don't think it will be a relay that you can hear, it's more likely to be a fuel pump or even something like the abs pump. The more specific that you can be about the order of events, the easier it will be to pin down the issue. The key thing is knowing if we're dealing with a V12 or a six-cylinder. V12s are more likely to have fuel pressure buildup issues whereas a six cylinder could be suffering from a crank position sensor failing.

Paul

[timpengilley]

sorry, its a 1989 6.0L xjrs.
thanks for your help

[timpengilley]

starting - turn to position 2, wait approximately 15 seconds, red led flashes simultaneously with pump/relay sound, somewhere towards rear of car, turn key, car starts normally.
led is positioned on top on left of steering column, in front of rev counter.

[davidr]

Tim - I think the noise you can hear behind you is the fuel pump. It may be that the pump is struggling a bit and takes a while to get up to pressure. This can be for a number of reasons such as a blocked fuel filter, crud in the bottom of the tank or the swirl pot, dodgy fuel pressure regulator etc. I'm sure that other people will have other ideas.
It may be that the flashing lights etc are a red herring.
Does the car run normally once it's going?

[timpengilley]

yes runs fine? it was just the wait starting that was a worry

[AlastairCM]

Sounds like the noise is the fuel pump pressurizing the fuel rail prior to start. It takes around five seconds to pressurize on my 87 5.3 V12 before it shuts off to prevent over fueling/flooding. It won't start if I try and turn the ignition before it fully pressurizes. The pump is switched via a relay in the boot, which could be the relay click you are hearing as the pump goes on and off (there are two relays close together in the boot, one for the fuel pump and a master relay for switching the ECU) .

I think from memory the ECU switches the pump relay via a circuit that includes the inertia cutoff switch. If your pump is firing up then it doesn't sound like its a problem with the inertia switch needing resetting or the pump relay switching.

I seem to vaguely recall the 6L XJR-S has a different fuel pressure regulator than a standard 5.3 V12, but not sure whether it takes longer to pressurize the system? But 10 seconds seems a long time.

You could always check the voltage at the fuel pump to see if the pump itself is getting low voltage which reduces its operation. Alternative could be a fuel filter that needs changing or the gauze filter in the swirl tank getting blocked which is restricting fuel flow. But all these things should also manifest themselves more when the engine is under load and calling for more fuel.

[AlastairCM]

I had a quick look at a US 1993 MY product support guide for the XJRS. It mentions the 6L XJRS having two downrated fuel pump modules to cope with the demands of the 6L engine. Both are controlled by a single relay and the wiring layout looks otherwise the same. There is a Jaguarsport part number for the twin pumps, SPC 1312, but I can't find any further details about the specification. There is nothing in there which talks about the how long the pumps operate pre-ignition before the cut out.

If there was a problem with the pump relay not responding to the ECU the Zetec magement system would flag DTC code 22. However, it makes it clear that it won't flag DTC code 22 if the relay is responding fine but there is a problem with one of the pumps itself. The ECU only measures relay response.

If the car is running fine otherwise, is it possible you have a voltage drop for the first 10 seconds at the pumps which is causing them to take longer to pressurise the system then they should? Perhaps it is linked to whatever the mystery led is responding to?

Perhaps only one of the pump modules has a problem which is being masked by the other one, although agin I would assume you would notice an impact when driving?

I would check the voltage across the pumps during that first 10 seconds to see what it is doing and whether the supply is fluctuating.

[PaulGover]

starting - turn to position 2, wait approximately 15 seconds, red led flashes simultaneously with pump/relay sound, somewhere towards rear of car, turn key, car starts normally.
led is positioned on top on left of steering column, in front of rev counter.

I don't know the 6.0 litre cars, but my '91 5.3 has an aftermarket immobilizer, and acts a bit like yours. The flashing LED suggests you too may have one. In my case, the delay seems to be for the fuel pump to come on - there's an audible click behind the dashboard after a couple of seconds, and only thereafter will the engine start.

I've no idea why it works that way, but somehow the immobilizer got Thatcham 1 rating despite being one of the old style ones with a fairly simple keyfob pushbutton. It seems to be they restricted the range of the transmitter by fitting a lousy aerial, and interlocked all sorts of things (doors, boot lid, gear selector, etc.) and used short timeouts. As a result, it can be a real struggle to start if it's in a bad mood, which is reassuring