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Oh thanks Paul, l didn't know that. I will try the 2 sec thing later. My feeling is that the pump didn't run with direct power it most probably means pump out......
I think unfortunately you may be correct. And the time control element seems to make it more challenging to test the FP Relay, unless you hook it up independently of the ignition feed / ecu input.
This is how you Test the Fuel Pump Relay independently of the Fuel Pump that takes only a 'Minute' or Should that be 'Moment' to do
(1) Get yourself a Test Light (or you could use a DVM)
(2) Ideally the Test Light should have a very long Wire, or at least it should be Long Enough to be able to See The Test Light, while you Turn the Key in the Ignition to Position (1) If not you could ask a Mate to keep an eye on the Test Light and then report back as you do the Test
(3) Remove the Two Wires from the Fuel Pump
(4) Connect the Two Wires from the Test Light to the Two Wires you Took off the Fuel Pump
(5) Turn the Ignition Key to Position (1) (or maybe its position (2) can't remember that far back!)
(6) The Test Light Should Light up for about 2 Seconds and then go OFF on its own
(7) Do this Test a Couple of Times, just to make sure that it wasn't a Fluke
(8) If the Light comes on for a Couple of Seconds and then goes off again (As it Should) Then you will know that the Relay is Good and that the Fuel Pump may need replacing or maybe the Main Relay next to the Fuel Pump Relay may need replacing, as Both Relays need to be Working for the Fuel Pump Relay to Work
(9) If you need a New Fuel Pump, get an El-Cheapo one off ebay ($30) as they are Generic and Fitted to many Cars
Ok.. tested relays with test light and worked as they should. Thanks Paul OB.
Now to try to get to the fuel pump...Oh joy...
The "getting to the pump" video worked well on the Facelift coupe but i'm looking at that cage on the convertible and already finding excuses not to touch it...wtf
Just tackling this issue now with my '92 XJS V12 convertible. The circumstance is the same. Car was driving perfectly fine. Parked it for a month. Engine cranks but no start. After reading this thread, I was able to locate the main and fuel pump relays. After removing the carpet trim (by sliding it out at an angle), there is ample access to the space behind the metal plate. You can reach in with your hands to remove the two relays without undoing the metal plate.
These relays are quite cheap. I plan to just replace them both. I ordered from https://www.autohausaz.com/. Part #s are as follows:
Main relay: 0332014112 (Equivalent to OEM # AGU1070)
Fuel pump relay: 0332019151 (Supersedes 0332014113; equivalent to OEM # AGU1068)
The fuel pump relay is the one in front; the main relay is the one closer to the back of the car. Attached are a few photos I took.
Although you MAY have a problem with either the Main or Fuel Pump relays, I wouldn't start by initially replacing them. Perhaps just remove them and bridge the input and output terminals in the holder and see if the fuel pump runs when the ignition is turned on? At least then you'll establish if it's a relay problem, or the power feed to the relay holder, the pump & wiring itself, or something else.
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.
Cheers
On my 1990, the fuel pump relay is in the boot on the right side under a black plastic cover. There are several relays there. I know this because years ago on a trip home from a car show in Wilmington NC (Brits at the Beach), I had a right rear tire blow out from dry rot. The car attempted to start after I replaced the tire with the spare, but then nothing. I had it flat-bedded home by AAA (fortunately just under the 100 mile free limit). The next day I started to chase the problem. When I removed the plastic cover, I found the fuel pump relay had popped out of its slot, apparently from the impact of the tire blowing out. Don't ask me how, but as soon as I replaced it in its slot, the car started immediately and has since.
Last edited by 3Jagsplusothers; Dec 29, 2025 at 07:49 AM.
