Stinkin Jag..

Okay, I found the answer to the trim piece problem (thanks, everyone!!), but now I've got a bigger one.

Just the facts: Jaguar XJ40, 1993. 4.0ltr straight 6. Runs fantastic..once we get it to start. XJ40 guys over at jaguarfourums.com recommended a "grassroots" fuel pressure test. Click the ignition on and off (on a hot engine) four or five times (listen for the fuel pump to run up each time) without tripping the starter..if it starts properly after that, it's a fuel pressure problem. Sure enough, that's what happened.

Problem is, I don't have a fuel pressure gauge. I look at the cheap ones, but they don't have different fittings to inspect different fuel rails. Anybody know what fitting I need to inspect this thing? I'd hate to just replace the pressure regulator just because I don't want to dive into the tank for the fuel pump..

Gasoline can leak forward, through the regulator, or backwards, through the pump or check valve. So I'd be less than inclined to just replace a regulator because the car leaks down pressure after it sits for a bit.

I'd rather spend $2 for a push button switch and wire that to the fuel pump. Then when I get in the car push the button for a few seconds, and fire the car up.

I could even rationalize it as a security device!

You could see what an independent shop whould charge just to check fuel pressure.

Go to Harbor Freight and look at what they offer for a tester with multiple fittings. YES, you may use it only a couple of times a year, but, it's like a compression gauge: when you need it, you need IT. And it does the job. Consider it a minor investment in your jag.

The gauge isn't really going to tell you anything more than you already know. Residual pressure is going away. Possibilities are fuel pump check valve, pressure regulator, dripping injectors, or an external leak. External leak is pretty obvious, dripping injectors give you a misfire and black smoke on startup. To isolate whether the fuel is going ahead through the regulator or back through the pump, you've got to run the car, then shut it off and quickly block either the pressure line or the return line. Let it sit for however long it takes to be difficult to restart, then unclamp and restart. If the car restarts properly with the pressure line blocked, its the pump. Return line, its the regulator. The gauge will make things easier, but I can't tell you how many times I have connected a pressure gauge just to have the car start fine repeatedly.

I'd be betting on the fuel pump check valve, myself.

foxtrapper wrote: I'd rather spend $2 for a push button switch and wire that to the fuel pump. Then when I get in the car push the button for a few seconds, and fire the car up.

As a short term bodge yeah.... I can see that but for the long term on a "luxury" car? I mean as little as I care for Jaguars even I think that they deserve a bit more than that......even a Yugo deserves better than that.

It just screams "beater".

ditchdigger wrote:

foxtrapper wrote: I'd rather spend $2 for a push button switch and wire that to the fuel pump. Then when I get in the car push the button for a few seconds, and fire the car up.

As a short term bodge yeah.... I can see that but for the long term on a "luxury" car? I mean as little as I care for Jaguars even I think that they deserve a bit more than that......even a Yugo deserves better than that. It just screams "beater".

Especially on a car that, IIRC, is his wife's...

Streetwiseguy wrote: If the car restarts properly with the pressure line blocked, its the pump. Return line, its the regulator.

Thanks, that sounds like a way to get it done without having to buy/borrow a gauge. And I hear you on the check valve..I'll have to break out the manual and see if it tells me where it is. It's a weird book-evidently the official shop manual is 7 volumes, so they've printed some of the basics in an "owners version". I've discovered some stuff's in it, and some's not.

Thankx for the advice, everybody. Best car forum on the net!

EDIT: aside to pigeon: Yup. She's kind of warming up to the driving thing, but doesn't want anything to do with working on em. I've tried.