My 87 XJ6 Series III has always run well, idled OK but for a long time now has been very cranky on cold and hot startup.

Recently, I read about someone with a cold start problem and to get around it, they would try shifting to 1st gear, turning the ignition to the start position several times and then they were able to start the engine, usually on the first try. I tried the same with a cold engine and it worked like a charm -- started up right away!. The funny thing is I tried on the same technique on a warm engine and while it didn't work instantly, it definitely got the engine to start much more quickly.

My question is: Given these observations, what is the underlying cold and hot starting problem that I have? They seem to be related. I should also mention to I have a fairly new battery in the car and I have also replaced the fuel pump with a Japanese model about a year ago and it has given me no driving problems thus far.

Thanks,

 

By turning the key to the start position with the gear selector in anything other than P or N, the starter is inhibited but the fuel pump will run (you should be just about able to hear the whine of the fuel pump while holding the key in Start). So this primes the fuel circuit.

As your car is difficult to start unless you do this first, it implies that you are losing fuel pressure when the engine is off. So you should check for any leaks on the fuel rail, feed and return lines. If there are no leaks, you might need to replace the fuel pressure regulator as it could be failing to hold the required pressure when the pump is not running.

 

I understand the issue is the check valve located in the trunk after the fuel filter in the aluminum block.
This check valve is not available.

In my '84 I have been thinking about removing it and cleaning it, but never get it done !

 

As Jose says the check valve is in the air bleed block, item #5 in this illustration:

https://parts.jaguarlandroverclassic...3NDgwNzYzNw../

If you Google "Fuel line check valve" you'll find a slew of choices for a generic replacement which can be spliced-in

Cheers
DD

 

Thanks Doug.

 

You may want to buy several different check valves and check them for leakage, I've not had good luck with them. Got a new one on a bmw leaking as we speak. Also, the fuel pump generally has a better working check valve built in if I'm not mistaken (most elec pumps do), may be worth disconnecting and running the pump backwards to try and clear it or try a different pump. A pressure guage near the fuel rail helps diagnose, I just splice one in on most of my cars and leave 'em.

 

CAC2028 is the part number for the check valve. I wonder why nobody is reproducing it.

 

Probably just a matter of weighing consumer demand and potential sales against production costs and profitability.

Cheers
DD

 

I should have mentioned that when replacing the fuel pump in the recent past, I also added am inline check valve directly after the fuel pump as per someone's suggestion.

Neither the new fuel pump nor the check valve have given me any problems however the underlying issue which seems to be lack of fuel pressure when the engine is shut off has persisted before and after the fuel pump replacement. It makes me think the poster who mentioned as fuel leak somewhere is probably correct.

Is there a convenient place to hook up a fuel pressure gauge on the SIII?. I have a feeling I should be able to watch the fuel pressure drop as I shutoff of the motor. Are there any common spots for fuel leaks in the SIII. I know I don't see any fuel under the car but somehow the fuel may be returning to the tank.

 

Mine is at the rear of the fuel rail, easy enough to splice one inline there. 5/16 hose iirc...

 

The common place to attach a fuel pressure gauge is at the fuel rail itself. Disconnect the hose for the cold start injector and use that nipple on the fuel rail for your pressure gauge.

An external fuel leak will naturally leave a strong odor. However, if the previously mentioned fuel pressure regulator is leaking you wouldn't smell a thing. In this case "leaking" isn't perhaps the best word; what would be happening is that the FPR is opening and allowing fuel to escape into the return line, thus dropping the fuel pressure.

Of course the FPR can develop an actual leak through the diaphragm as well. Pull the vacuum hose and see if it looks wet inside. A leaky diaphragm would allow raw fuel to be drawn into the engine and you'd have an over-fueling condition.

Cheers
DD