XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

5.3 V12 takes a while to start...

Old Oct 9, 2020 | 04:26 AM
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Default 5.3 V12 takes a while to start...

Hi all,

I have a 1993 5.3 V12.

Recently it has needed a fair bit of cranking before it kicks into life, especially if it has not been started for a while.

It just whirs away for maybe 20-30 seconds then starts up.

Feels like there is no fuel.

Any ideas?

Cheers
Richard
 
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Old Oct 9, 2020 | 05:28 AM
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Hi Richard

Maybe the Fuel Filter is Blocked and needs replacing, less than a Tenner on ebay, so that is what I would do first, as its sounds like fuel starvation could be the problem
 
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Old Oct 9, 2020 | 08:21 AM
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Continuing with the 'no fuel' thoughts......

Turn the key 'on' without trying to start the engine. You should hear the fuel pump hum for 2-3 seconds. This primes the fuel rail at the engine.

Do you?

Next (and assuming you hear the hum), turn the key 'on', smartly jab the throttle a couple time, and then turn the key to 'start'. Any difference? The throttle jab should energize the fuel injectors, thus giving squirt of raw fuel into the cylinders. If this improves the situation then it sorta confirms a lack-of-fuel problem.

Also, when you change the fuel filter, empty the contents into a clear container. What you see might dictate your next steps.

Cheers
DD
 
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Old Oct 9, 2020 | 08:52 AM
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Originally Posted by Doug
Continuing with the 'no fuel' thoughts......

Turn the key 'on' without trying to start the engine. You should hear the fuel pump hum for 2-3 seconds. This primes the fuel rail at the engine.

Do you?

Next (and assuming you hear the hum), turn the key 'on', smartly jab the throttle a couple time, and then turn the key to 'start'. Any difference? The throttle jab should energize the fuel injectors, thus giving squirt of raw fuel into the cylinders. If this improves the situation then it sorta confirms a lack-of-fuel problem.

Also, when you change the fuel filter, empty the contents into a clear container. What you see might dictate your next steps.

Cheers
DD
Hi, I just tried what you suggested.

Turn ignition on - yes I could hear the fuel pump prime
Jabbed the throttle a couple of times
Tried to start it... no was the same just turned over quite a bit before it started
 
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Old Oct 9, 2020 | 10:44 AM
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Verify that you have spark during the starter-churning phase.
 
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Old Oct 10, 2020 | 05:26 AM
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Originally Posted by Greg in France
Verify that you have spark during the starter-churning phase.
Hi,

There was no spark! Then started to spark and it started.
The spark looked quite weak
 

Last edited by lambo911; Oct 10, 2020 at 05:51 AM.
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Old Oct 10, 2020 | 06:01 AM
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Hi Lambo911

Test the Spark on Both Banks and see if the Spark on one Bank is better than the other

That might narrow things down a little bit
 
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Old Oct 11, 2020 | 10:40 AM
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I have found that the battery voltage has an influence..
The engine was turning over ok but the voltmeter was half way between 9 and 13
So I fully charged the battery and it fired up straight away.

My car has the two ignition amplifier units mounted on the front panel.

A while ago I was doing some work on the AC and I unplugged the front ignition coil. I forgot to reconnect it, started it up (started fine) and drove a few yards before realising something was up and the engine light also came on. I reconnected it and all was ok, but I think it is since then I have had this starting issue.

I wonder if running the engine with the coil disconnected damaged something ?

Cheers



 

Last edited by lambo911; Oct 12, 2020 at 03:48 AM.
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