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Trying to start my car after 6 months of sitting. When I started it in July, it fired right up. It now appears that no fuel is coming through the connector to the fuel rail.
I pulled the tank access panel today, and powered the fuel pump directly. Lots of pressure at the fuel rail. So the pump is good.
Turning on the ignition with the gear selector in Drive shows there is no power to the pump. I hotwired the inertia switch. Still no power.
So, my next step is testing the relay and the fuse. My wiring diagrams show me there is a fuel relay directly controlled by the ECU, but it shows the relay on the fuel tank (I suspect a mis-labeling of the chart). There is nothing there but the in-tank connectors.
Nowhere in the manual or the PDFs can I find the location of the relay, or the fuse. Anyone have any idea where they might be?
Any other reasons why the fuel pump would not run or the car would not start?
From what you have said I'm assuming that you have a V12 with an In-Tank Fuel Pump and also I'm not familiar with the Wiring Layout of the 1992 Car
So all I can do is give you some educated guesses of where you might look, as I have a 1990 with external Fuel Pump and a 1995 4.0L with an internal Fuel Pump and your Car falls in between
Where as such the Fuel Pump Fuse and Relay 'Could be' located behind the 'Trim' in the Boot/Trunk just behind the Rear Light Cluster, which on a UK Car is drivers side although yours could be on the other side on a USA Car
If you follow that piece of Steel Trim (on my Car) back in the direction of the Rear Firewall you should be able to find the Relays, which if you look close you can just about see in my Photo where that 'Blue Wire' is
If what you're looking for isn't in there, get back and we'll go to 'Plan 'B' but I wouldn't be in a hurry to put that 'Baffle Plate' back just yet 'in case the Pump is faulty'
Last edited by orangeblossom; 11-20-2018 at 10:27 AM.
Unfortuately, mine is a 1992, with an in-tank pump. I've torn apart the entire rear quarter. There is nothing related to the fuel pump in there. I've exposed the connector/harness to the pump. There is no power to the pump. BUt the pump works when hard wired from the battery. Plenty of pressure at the rail.
The only fuses/relays in the right rear panel are for the power antenna, lights, and the timer for the antenna. So the replay for the fuel pump must be elsewhere.
But it isn't in the luggage compartment. All that's in there are the single fuse for the top pump, and 3 relays for the top and side windows.
The relay must be under the bonnet somewhere, but I am unable to locate it. That's the frustrating part.
However, after some testing in the last hour, I'm led to believe that something else is not enabling the fuel injection. The car has great spark when cranked. If I hard wire the pump, the car still will not fire. My conclusion at this point is that the FI system is not turned on. I'm going back to check to see if I get any voltage at an injector.
So what might cause the FI system not to fire? As I said before, the car cranked right over and fired up in July when I was last stateside. It's been in a frame shop for 2 1/2 years getting repaired. I'm pressing the shop to get the final frame pull done today so I can get the car out of there and back into storage. So of course, the engine refuses to fire up when we go to move it.
Very frustrating. I've only got a week stateside before I have to leave again. This is totally driving me up the wall.
As I gather from several web sites, there is an air flow switch located somewhere in the driver's side air cleaner that will also disable the fuel pump. But I cant find that either. I would love a troubleshooting flow chart to diagnose this.
Do you have any way to test for a pulse at the fuel injectors? I would guess you have no pulse and would probably look at the crank sensor. The fuel pump may not be running because the system is up to pressure but not releasing fuel into the cylinders.
Underneath the Passenger Side Knee Bolster on my 1995 4.0L is a removable panel which undoes with a Coin and inside that panel is a fuse box
With Fuses for the ECU and the ECU Relay: If your layout is the same, it could be one of those Fuses
Also on my 1995 4.0L Car, just to the left of that Fuse Box are a couple of Blue Coloured Relays and the one on the left is the Relay for the ECU (maybe you car is the same?)
Apparently this Blue Relay has a bit of a reputation for not making very good contact in its holder, so definitely worth taking out and putting back again, or even swapping it over for the other Blue Relay which is next to it
Having tried every trick in the book and then some! this was what eventually got my Car Started
Check the Blue Relay on the left to make sure its making proper contact or even swap it over for the other one
If that doesn't work, then I've got 'Plan 'C'
Have you got any engine Photos, that might give one of us a better Clue?
Last edited by orangeblossom; 11-20-2018 at 11:33 AM.
Plan B sounds good. I was just on my way over to the shop to check for injector pulse.
Was just readying through threads, and am now thinking it's the main relay or fuse that's giving me problems. I know where that panel is. I'll head over now (it's 300 feet away from the apartments I'm rehabbing.
If you cannot find the Relay underneath the Passenger Knee Bolster, then maybe your Relays could be where they are hidden away on my 1990 V12
Which is in the Boot/Trunk inside a Plastic Box near the rear Firewall as shown in this Photo
The Main Relay on a 1990 V12 is the Red one with the Stripe and the Silver one in the Black Holder is the Fuel Pump Relay
These Relays are Not interchangeable as the one with the Stripe has a diode
Have you tried Starting the Engine while 12 volts is connected directly to the Fuel Pump?
Where in the event that She doesn't start then that would narrow the causes of her not starting quite a little bit, as although you've got plenty of fuel going in, that doesn't equate to fuel pressure
Where maybe the diaphragm on the FPR (Fuel Pressure Regulator) on 'B' Bank is either ruptured or may be leaking, in which case She won't Start
You may even have a Schrader Valve on your Fuel Rail, where a Shop could easily Test the Fuel Pressure for you
Or it might be the Air Temperature Sensor (see photo)
XJS Air Temperature Sensor
Get back as there's still a lot of other stuff you can try
Last edited by orangeblossom; 11-20-2018 at 01:06 PM.
Incredible. It was hidden behind the metal support bracket for the lift for the boot lid. No labels, no markings, anything. One I stuck my arm in the recess above the ECU to trace the harness, I noticed two relays. The 1070 was in a red socket holder. I'm taking it home to test it now
What you want to do now is to Test the Fuel Pump Relay on the Car, as both relays need to be working for the Fuel Pump Relay to work and Testing it is dead easy, as you will see from the short Video I made
The Fuel Pump Relay only operates for about 3 Seconds at every actuation (on/off) of the Ignition Key and you can either uses a Test Light or a DVM Meter
Testing the Fuel Pump Relay is on Page: 46 of my 'Cherry Blossom' restoration thread and here is a link to that page
Just a reminder that the Fuel Pump Relay is Silver Relay in the Black Holder, as that's the one more likely to be the cause of the problem
It turned out the main relay was not working. Funny, as it was sitting in a garage since July.
I still cannot believe that Jag would have hidden the 2 most important relays in the car behind the support metal work. No labels, no indication. When I first started digging in there, I thought about removing the panel. But then I thought: 'What sort of morons would hide the fuel pump relay behind this piece'?
Now I know.
I've re-routed the two relays so they are on the front side of the metalwork. So now they are both accessible. I've sourced a new Bosch, and will add the damping diode to it.
Thanks so much for the help. Now the frame guy promises me the car will roll out of the shop tomorrow. Then all I have to do is to replace the front subframe and get it to a paint shop in the two weeks before I head back to Africa for the winter.
I still cannot believe that Jag would have hidden the 2 most important relays in the car behind the support metal work. No labels, no indication. When I first started digging in there, I thought about removing the panel. But then I thought: 'What sort of morons would hide the fuel pump relay behind this piece'?
Now I know.
Remember, there are no engineering flaws on a Jaguar. Anything that appears to be an engineering flaw is actually "An interesting design feature"
11-20-2018, 09:42 AM
1992 V12 convertible fuel pump relay location
