My 96 4.0 I6 with 72k miles cranks about 5 seconds before a cold start. Have owned it for 6 years, always a quick start when cold until now. Starts right up when warm, for about an hour or so after driving. Have replaced fuel pump pressure regulator, fuel filter, and spark plugs. No Joy. Once started the car runs perfectly. Any thoughts on the problem? Thank You, Bob

 

Without knowing much, could be the camshaft position sensor. This sensor is needed at startup only.

This is the hockey puck looking thing at the front of the engine at the passengers side.

What is the tachometer doing during this 5 second startup?

 

Thanks for the reply, Started right up today, no delay, after a few days idle in the garage?? The tach needle raised up very slightly with key to on position then dropped back to off position while cranking until startup. After start tach function normal. I'll try again later to see if the delay is still occurring.

 

Slow start this morning, tach showed about 300 RPM while cranking then to about 1000 when running, Smooth display from 300 to 1000

 

To me, this sounds like the camshaft position sensor then. DBC10603

-Valde

 

Almost certainly the camshaft position sensor. Sounds like it's failing intermittently.. You can completely unplug this sensor (it's the distributor looking thing on the RH front side of the engine) and the car will start and run fine, it' just needs 6-7 seconds of cranking before it'll start.

Basically this sensor tells the ECU which piston is on which stroke, so that the engine can run. If it gets no signal after a few seconds of cranking the ECU just starts guessing (it has two choices) until it gets it right and the engine fires up. Once the engine is running, this sensor isn't used.

 

My big block 3.2 did that.

Before I spent $$, I read about "timing the cam angle sensor", on here, or the other site, memory sucks.

That fixed it, fired up at a simple flick of the starter, Cold or Hot.

It was about 90deg out, thanks to the PO and Freddie Fiddler.

 

Agreed that a failing or badly adjusted Cam Sensor will cause the slow start symptom, but I'd expect that to be consistent whether hot or cold. OP says in first post that it's always OK when hot.


Another possible cause is lose of fuel pressure when cold. A leaky injector or failed non-return valve can cause this when the car sits for some time. A good test for this would be key-on - fuel pump runs for 2 secs, then key off. Repeat this 4 times and then on the fifth time start as normal. Running the pump 4 times would build up pressure again so if this allows car to start quickly then that could be the issue.

 

You are correct about that. A failing cam sensor would certainly be unaffected by cold or hot.

It is not a common failure, so probably not a good idea to blindly purchase one. Ignore my suggestion.

 

I went through the Cam postion sensor ( CMPS ) as P0340 showing and not P0335 for the Crankshaft position sensor ( CKPS )

Ended up being a connector clean

I sourced a replacement CMPS at the local auto parts store ( ordered in ) and was able to return after troubleshooting

I did observe a 600 ohm basic meter reading as a good CMPS , 1300 ohms on the Crankshaft

In the begining ....................................

On key rotation the fuel pump will come on for 3 seconds only then off

This " charges " the fuel line / rail with 43 PSI fuel pressure , different than cylinder " priming "

When the crankshaft position sensor sees engine rotation it will command the fuel pump to turn back on for the duration of the drive , safety design

So you will have 3 clicks on your fingertip on the fuel pump relay , on - off - on

To over ride the fuel pump control jumper between socket 3 ( hot battery power ) to socket 5 ( to the pump )

This will drain the battery with keys in pocket so plan

How your camshaft position sensor comes into play is only on the very beginning than is taken over by the crankshaft position sensor after a certain point , the engine will start with the CMPS connector off

The CMPS has 6 windows inside that can see TDC for each 6 cylinders unlike the CKPS which only sees # 1 , aids initial starting each cylinder firing / injection on the right place and not so much accuracy but serves it's getting cylinder 1 , 2 , 3 and so on combusting to carry on forward

The cams only rotates once for full 4 cycle engine and the crankshaft 2 times so as the timing pickup on the crankshaft comes around it can be TDC #1 combustion firing or the end of the # 1 exhaust piston stroke , 50 / 50

So the ECU tries the first appearance ( CMPS connector removed ) of the # 1 TDC and fires , but could be wrong , so it trys after a bit of cranking to try the 2nd time # 1 TDC comes around , this could be your additional starter rotations

Added note :

The crankshaft position sensor can fail on fuel pump enable ( but still work on other aspects like tach ( 300 starter speed ) and firing ) and not give a code , often seen from others , $ 90 US part and generic part not Jaguar specific so order at local parts store , but.................someone did recently post bad results for generic crankshaft position sensor

You can clean the " face " of the crankshaft sensor of grime that effects signal , different then connector clean , there is no adjustment , just plug and play

Reset the crash / inertia switch as can be fickle

To know your CMPS sensor is adjusted correctly have the engine front geared missing tooth window at the CKPS face ( do not over bend the fans connectors lock levers ) ( 34 mm on the crankshaft bolt ) , cooling fans can be easily pulled up and out of way , the etched circle in the small window should be centered , CMPS hockey puck mounting should not have drifted or come loose but.......................Andy had a way of removing the oil fill cap on feeling the certain # 3 or 4 valves being in open or closed for the true crankshaft rotation position / phase

You can also have plced your cylinders in a bore wash condition to not have good compression for easy start , easy fix but that's a seperate matter other than correct firing timing , caused by short or driveway runs