XJ40 ( XJ81 ) 1986 - 1994

Cold Start Problems

Old 10-23-2018, 04:14 PM
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Default Cold Start Problems


I have a 1988 XJ40, and have been having issue with starting it for a few months now.

It seems it's getting worse with the cold and humidity. During the summer, when it was very hot, I had no problem with starting the car. It also start sometimes when I switch the key on/off a few times (not enough pressure maybe for the injector to shoot at ignition?). Sometimes is work, something is doesn't. When nothing works, I spray a bit of starting fluid in the intake and it work. When the engine as been running for a while, and I stop it (when the engine is not cold), It usually start back normally without any problem.

The Idle is a bit unstable too. Usually around 600, but sometimes stick to 1000.

What I have checked so far :

Crankshaft sensor - I put a new one.
Temperature sensor - changed it, started perfectly outside, put it back in, same problem.
ECU - Change it, same problem
Main ground near rthe dash - cleaned it
Intake gasket was splitted, I changed it

I also try to put a electric diode at the injectors. I think it should pulse 4 times at cold start, then 1? There's electricity at the injectors but no pulsation at ignition.

I used 91 fuel. I know it could be a lot of things, and some of you gave me a few ideas a couple months ago but i can't find the post back.

You imput would be very much appreciated!


Old 10-23-2018, 04:39 PM
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Default More pertinant infos

I also forgot :

- The battery was changed
- The alternator was rebuilt
- Before Ignition, the battery light, as well as the oil pressure light are sometimes yellow.
- the oil pressure gauge varies a lot.
- The previous owner put some grease in all connectors, but not electric grease. Some kind of bearing grease I think.
Old 10-25-2018, 11:03 PM
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Default ideas

Old 10-25-2018, 11:57 PM
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Try starting the car in total darkness. Look at the ignition system and see if there are any stray sparks or arcing around the plug wires - also, how is the distributor cap and rotor?

Old 10-26-2018, 03:36 PM
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I'd clean as much of that grease as you can. I just went through some electrical issues with my '89 VDP that have gone away since cleaning the grease off the connectors.

Also worth checking is your vacuum lines. I've had idle issues on other cars because of a vacuum leak and there's a possibility there's a small crack that is open when cold but closes up when it's warm out. How does it restart after driving for a bit while the engine is still warm? Also, maybe check your fuel pressure regulator and make sure the diaphragm isn't shot, because that could cause erratic idle.
Old 10-30-2018, 07:36 PM
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If its starting when you cycle it, its because youre able to build up pressure. So your non return valve is not working properly anymore. Not sure if yours is near the fuel filter or built into the pump. My car is from 1994 so the fuel non return valve is inside the tank with the pump. I decided to install a racing inline valve in the engine bay, and have had zero start issues since. Heres a link to my issues when I first acquired the car. Your car is older so you may have the external valve that you can replace with a volvo or bmw unit if the jaguar one is no longer available.

Last edited by Brewtech; 10-30-2018 at 07:41 PM.
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