Can't really complain too much about my 1987 4.2 Series III as it runs and drives fine and never stalls on me. Only issue is that it spends about 3 times longer cranking to start it than any other Series III I have ever heard start.

This is true whether it is a hot or a cold start and, it is running with many new tune-up parts and filters -- still no change in the long cranking.

Recently, especially when warm starting, I began to very lightly depress the accelerator when cranking and I noticed that it seems to start in half the time. I know this is a clue as to what the problem might be but I am not sure how to translate this observation into a fix. Has anyone experienced this long cranking problem on a Series III and found a fix for it?

 

Not sure if this is a "fix".
I regularly put the drive selector into a position where the starter doesn't work. eg R, D etc.
I give it 15 to 20 seconds with the ignition key turned to "start"
This allows the fuel pump and fuel rail to come to full pressure. It also moves hot fuel out of the fuel rail if parked on a hot day.
This does not explain the accelerator pedal query.
cheers

 

from another forum not Jaguar related, but the same issue in a Ford 4.0 liter:

1 poster says it's a lazy old Fuel regulator;

1 poster says forget the Fuel regulator, it's a check valve right after the fuel PUMP..

Please note these comments deal with a Ford fuel injection system, not a Jaguar XJ-6.

in my 1984 XJ-6, which sits a lot in the garage, I prime the fuel system the same way as Bill Mac does, place the shifter in D, or 1 or 2, then crank the ignition switch to START and hold it there listening for the fuel pump "humming" or "whinning" to "charge" or prime the fuel system.
the only difference between the way I do it, is that I hold the switch in the START posittion for only 5 to 6 seconds, and then repeat this 4 to 6 times depending how long it has been since the engine was started.

let's see what Doug says.

 

I'd certainly try to prime-the-fuel-rail trick as mentioned above and see if anything changes. If there's an improvement then the pressure regulator and/or pump might be weak, just as Jose mentioned.

Depressing the throttle while starting opens the throttle blade which, in turn, reduces vacuum. The fuel pressure regulator, which is vacuum operated, will respond to lower vacuum by increasing the fuel pressure a bit. Tricking the system this way further suggests that you have a fuel supply/fuel pressure problem. An actual fuel pressure test would be very useful here but replacing the pump and/or regulator is not difficult nor horribly expensive so, as guesses go, not too hateful.

Cheers
DD

 

Thanks for the prompt responses and interest. I should have mentioned that I changed the fuel pump last year because it simply stopped working! I put in a new pump and new fuel filter as well and the pressure regulator was replaced about a year prior.

The interesting thing is I had the exact same over cranking start up problem before and after the new fuel pump.

The idea of lowering pressure and increasing fuel flow is an interesting one. What happens with the air flow when cracking the throttle plates slightly more open?

 

Add a racing style check valve to the hose that feeds the rail. I did the same thing to my old XJ40. Cured my hard start issues.
XJ40 fuel check valve, Post #21 and #23

 

This would be a one-way valve that maintains pressure in the fuel rail while the fuel pump is not running? Sounds like an interesting idea. Always got to be careful when messing with fuel. I'm a long away from the car right now. Any recommendation on a quality check valve of the right size that will work on my Series III fuel rail?

 

Am I right that the hose that feeds the fuel rail is a 5/16" hose or is it bigger than that?

 

Call these guys, theyre the best I know.
DMP Racing
They only carry Made In Usa parts. No china crap. Im not sure about the size of the hose, I’ll call my local jag shop and ask them, since they replaced my feed hose not long ago. You can put the check valve anywhere on the hose past the fuel pump. The point is for fuel not to return to the tank so easily. All cars have a built in check valve in the tank or near the fuel rail from factory. If its in the tank like most Jags, I just install a new one directly into the fuel hose and problem solved. Try it. Or have a mechanic install one. Make sure not to install it backwards or you will never get fuel past it😆

 

Thanks for the tips. I called the guys at DMP and they have a quality check valve on the way with the right barbed fittings for the 5/16" line on my XJ6. Even if it doesn't completely solve my problem, it seems like a good idea anyway.

 

It should solve your issue since spark, and air are not a problem from your description of things. Your car will start, its just taking a while for fuel to reach the injectors. Keep us posted and add some pics of your installation. For added safety I added fuel injection hose clamps to the hose ends. The barbs do a great job, but I like the added peace of mind knowing theyre also clamped

 

Yes, I would not want fuel dripping in the engine compartment!

 

A healthy pump will re-pressurize the fuel rail in 2-3 seconds so if you're having to crank the engine for longer than that (not unusual on these cars) it probably isn't a fuel drain-back problem. But, still, the check valve is a good idea as the originals are known to fail.

Decades ago I had an extended-cranking issue. Long story short, a borderline battery was the problem. The F.I. system really wants full voltage.... and the starter uses gobs of power. The voltage drop at the F.I. system was causing the problem.

Cheers
DD

 

This is an interesting story. I could put a volt meter across the battery while cranking. Or maybe I should put it across the terminals of the FI system. Where would that be exactly? I did replace the FI harness two years ago that runs over the engine thinking that would address any FI electrical issues. However, you have brought up something completely different.

I wonder how you corrected this? Maybe a more efficient starter perhaps? I recently put in a new battery but it had no effect on the cranking issue.

 

The main voltage feed to the ECU is on Pin 10. A brown/slate wire. You could remove the big connector and check voltage at Pin 10 while cranking.

I don't know what the magic "too low" voltage would be. I'd think anything below 12v would be suspect but others will chime in

A voltage drop problem could be any number of poor connections or poor grounds along the path.

How does the starter itself sound? With age and wear they tend to draw more power....sometimes accompanied by unusual sounds. Another clue here, tho not precise, is excessive dimming of your interior pillar lights while cranking.

You could try adding a jumper battery next time you start. If the car starts more easily with the added amperage, that's a good clue. But, if there's no change, nothing is really proven or disproven

Cheers
DD

 

I think the starter was rebuilt about 5 years ago but it is still the original starter. Maybe there is a gear reduction starter out there that starts faster and draws less amps. I don't have an extra battery but I could try having another vehicle running with jumper cables attached to see if that starts with less cranking.

I believe the ECU is in the trunk. I should ground the voltmeter to the ground wire the ECU is using to really see what voltage pin 10 is at during cranking. What pin is the ground pin for the ECU?

 

How about you just link up another battery to the car and see what happens first? If it starts right up, then its a weak battery. If it still keeps cranking its not a voltage issue I think. Im not sure how bad cranking can get on the 4.2 with low voltage, but the XJ40 will not fire up if voltage is too low. The more you crank the less of a chance to fire up you have, due to voltage drop during this process. I still think your factory fuel check valve has failed and now youre left with the need to re pressurize the system.

 

Hi, in the XJ-6 4.2, where exactly is this check valve located ?

 

I think the return valves are what the Series 3 cars had, and there are two. But I believe that check valves are built into the pump within. 4.0 XJ6 cars have a submerged pump with an incorporated valve, so its a real pain to replace it. OP could try switching from L to R tanks to see if theres any change to the length of cranking times to see if it makes a difference. But I doubt it. Either get a new pump or add an inline check valve

 

The original check valve is screwed into the air bleed assembly. In the spare tire well, RH side, forward. Look like a simple fuel hose nipple but there is a check valve built in

Part numbr CAC2027



Cheers
DD