Hello everyone,

My XJS has been running fine up until a couple weeks ago, about the same time it started getting cold, but I don't think that is necessarily my issue.

Once I get it started, it runs fine. I initially thought it was the battery so I got a tender and check it before I go to start the car and it's at a perfect 13.5 volts, so no problems there. I think that my problem is fuel.

I can crank it for about 5 seconds and it will sputter a bit. If I give it a couple pumps of the gas pedal and crank it then it will fire and run for a couple seconds, then die.

Every time I have tried it, it takes me about 20-30 seconds total. I give it some gas, crank for a bit, give it more, etc. until I eventually get it running, If I try to give it more gas once it's in a rough idle it will die, so I have to kind of "pump" the pedal up to 2K to get the alternator kicked on (not sure if this helps but it seems to, even if it's to get some fuel in there) and it will run fine. I can drive it at this point without any issues that I can detect. If I stop it and start it again within a couple minutes (haven't tested any longer duration than that) It will start without issue.

Another odd symptom, when I idle at a light it has what sounds (and feels like) a random miss, but if I give it gas it will go away. It did this a little bit before the fuel issue, however. I think I need a new distributor cap for that. I've got one, I just haven't installed it yet.

Some additional information, all of this done a few months ago with a couple hundred miles on the car since then:

• My car sat for a while (long story), so I had both tanks (main and sump) cleaned and coated with rustproofer.
• I replaced the fuel filter with a brand new Bosch unit
• Fuel pump is original
• Plugs and wires were replaced
• Ignition harness short between the V was the cause of the original problem, so I rewired that. Ignition (wiring at least) is assumed to be good at this point.
• Regulators and Pump are assumed to be OEM, or at least very old.

I'm armed with a fuel pressure gauge and will go home and test it. Upon looking at a couple other threads it looks like I'm looking for 35-40ish PSI? If someone who has done this before could pick a picture from the internet and draw a quick paint circle to where I should measure from, I would appreciate it. Wiring I can do, but chasing fuel issues is not something I've tried before. I saw another thread where the gentleman was measuring at the wrong place, and I'd like to try and avoid that if possible.

I was just going to go ahead and replace the fuel pump, but I'd rather not waste the cash if that isn't the issue. Any help would be appreciated, thanks!

 

Sounds like you don't have enough fuel. Perhaps low pressure from filter, pump, or regulator, or perhaps clogged injectors. Could be an electrical issue with the injectors too.

Additionally, you could have enough fuel, but too much air. I would do a vacuum leak test, or at least get it running and do some hunting with some wd40 for leaks.

 

I would check your AAV (aka the Cold Start Valve) before anything else if it runs fine after warm up.

 

Good points on both accounts, thanks guys. The Auxiliary air valve is a great point, I hadn't thought of that. I went outside and found it:



I'm guessing the connection on the bottom left isn't supposed to be like that? It's completely open to ambient air. Whatever seal was there has dried and gone. Could this be hindering my cold starts?

Also, this blue solenoid-looking thing is by the AAV, should that tube be hooked up to something?

 

On a hunch, I taped that joint up with duct tape to give it a rudimentary seal, along with this thing:



Because it was laying next to a hole in the airbox.

It fired right up! I can hardly believe it, I never get the easy fix! Mac, thank you so much! I never would have thought of that as the cause of the problem. "the cold start valve" was the source of my cold start issues. Go figure.

Can anyone tell me what the second thing I did an excellent tape up job on is so that I can find the little boot for it? Mine has gone missing.

I love this forum!

 

OK, I'm getting a little too much credit because I was thinking about the AAV (Auxiliary Air Valve) which is part of the cold start system because it controls how much air is let in during idle (it's on the other side of the engine from what you have pictured).

What exactly did you tape up?

I think your first picture is of the Air Switching Valve not the AAV.

EDIT: I think the blue thing is the EGR Vacuum Solenoid

 

I think if I look closely at one of the pictures, you duct taped the Supplementary Air Valve into where it belongs in the air box...?

There is supposed to be a rubber grommet that holds it in place and also makes the connection more air tight. I'm guessing that if that were missing and the valve fell out, you would be getting excess air under cold start conditions (think of an old fashioned choke that doesn't close).

So it might be a super easy fix, just not at all the one I was pointing you too originally.

Hopefully the more expert folks will chime in, because I'm just thinking out loud.

 

I can't open any of the pictures.

Anyhow, glad it all got sorted out !


Cheers
DD