So since my Fuel Pump relay is brand new and there is no visible damage to the relay harness/wires, and the Fuel Pump 25A fuse isn’t blown, and the fuel pump itself is brand new.. I’m assuming the problem is coming from one of these wires in the trunk by the back of the gas tank? Here’s a few photos I took. it seems to me the red/blue and black wire that go to the Purge Valve located on top of the tank are new or at least have been replaced in the past since all the other ones look crusty. Any thoughts that these may need replacing ? If so where would I order them or how could I test them for power? And would these even cause the pump to not even turn on? (pics taken from driver side of gas tank) Thanks again everyone

 

Hi Matt,

One quick test you can try is to remove the fuel pump relay, bend a large paperclip into a U and install it in the relay socket between the terminals that correspond to terminals 30 and 87 of the fuel pump relay. These are the terminals the relay connects to run the pump. Turn the key to position II and you should hear the pump run its priming burst.

If it doesn't run, turn off the key. Remove your paperclip jumper and connect your voltmeter to terminal 30 in the relay socket and a good ground. I can't remember if the '91 battery is in the trunk - if so, the battery negative cable is a convenient ground point. If your battery is in the engine bay, pull up the right trunk carpeted trim panel and find the ground stud below the tail lamp. You should measure battery voltage between terminal 30 of the fuel pump relay socket and ground even with the key out of the ignition switch. The battery power is always hot via Fuse C8 (25A) in the left A-pillar fuse box.

If you don't have battery power on terminal 30, your problem is upstream.

If you have power on terminal 30, test for power on the Blue/Red wire at that black connector between the relay and fuel pump (shown in one of your photos). If you have power there, test for low-resistance (near zero ohms) continuity between the black wire at that connector and chassis ground. You can download the wiring diagrams for your car at the link below:

Jaguar XJ40 Electrical Guide 1991

Did you happen to test the new fuel pump before installing it?

Cheers,

Don

 

Thanks don , I will be doing some testing for power tomorrow after work. Also no I did not test the pump before installing considering I don’t have a volt meter to do any electrical testing but I will get one tomorrow. Fortunately for me all my European cars haven’t had electrical or fuel related issues as confusing as this one. If I can’t figure this out by Wednesday the car will be towed to a British mechanic who is familiar with these older jags. I really want to take care of this myself to save $ and learn a little more since I’m keeping this car but I don’t have the patience like I used to. I’m upset because I just did all new suspension , tires, alignment, radio, speakers , etc etc and haven’t even got to drive it. Anyway I will get back tomorrow to give results.

 

Not a bad idea to get a test light too


Larry

 

I need a quick response if possible, I’ve taken the car to the British mechanic and got a call back this morning in regards to my fuel pump not turning on. He claims that once you install a aftermarket pump that it has to be relocated onto a new mounting bracket somewhere else inside the tank for it to work. I don’t understand how the location of the pump would cause it to not turn on but supposedly he’s the expert and that’s what he’s telling me.. anyone know if this is true?? remind you this is costing me $1100.

 

Hi Matt,

The only reason I can think of that the pump would have to be relocated is if its inlet port is oriented differently than that of the original pump. The inlet of the pump should be mounted in the "swirl chamber" or "swirl pot", which is the area in the bottom of the tank surrounded by a low circular wall to keep a minimum amount of fuel available to the pump at all times so the pump stays primed even while cornering and driving on inclines when the overall fuel level is low.

Cheers,

Don

 

Thanks don. That’s why I’m confused is because my original pump and new pump are 100% identical, I’m not sure if it’s just a easy fix that the mechanic noticed and he’s trying to make money off me or what but I just can’t understand how the location of the pump determines whether or not it turns on . At this point I just want it running again and will pay whatever so I guess we just wait and see.

 

I would strongly recommend that you go to the shop and have the mechanic explain what he means, because it doesn't make sense to me. The fuel pump will run even if it is out of the tank but connected to its power supply.

 

The mechanic sounds like he isn't familiar with the in-tank pump canister system, go elsewhere if possible.

Larry

 

I’m going tomorrow after work to see what he’s talking about. From the phone call we had, he is saying the canister that the pump sits inside of is no longer usable once you put aftermarket pump in, yet the pump I put in was a OEM replacement. Remind you this mechanic owns a shop called Charlie’s British Auto, and claims to have worked on 100s of these xj40s. Maybe I’m misunderstand something. I’ll update tomorrow, thanks again for all the replies!

 

The aftermarket pumps are widely available, branded as Airtex, Bosch, and various other names, but they are all Walbro pumps and they all fit into the canister.
You can even get them on Amazon, they aren't even very expensive.



Larry

 

UPDATE: I called another mechanic today that’s familiar with these older jags, he laughed when I told him that the other mechanic said that the pump needs to be relocated in order for it to work. I had it towed to him today and he will let me know as soon as he starts working on it. He’s also helped me on some troubleshooting before I found these forums so hopefully I hear better news when I get the call. Thanks again everyone.

 

It is a bit tricky to get the pump lined up inside the canister while snapping the lid back on.

 

Might be a bit late for this, but did you happen to look at the link lead inside the tank from the pump to the cap?

In the picture you posted below - did you check the connector with Blue/Red stripe and Black wire??

I ask because when my fuel pump eventually failed, I noticed link lead inside the tank from pump to top cap, pins were burnt. The connector I mentioned just above also had evidence of the pin getting hot.

 

The car is currently sitting at a mechanic in Tampa , he got back to me a couple days ago and said he’s pretty sure it’s either the fuel pressure regulator or my fuel return line is clogged . He hasn’t gotten much time to diagnose it 100% but will let me know within a couple days. Thanks again

 

The tank canister is NOT just a hollow plastic housing, but it does contain a 'jet-pump' to pick up fuel from the tank to keep the canister FULL around the electric pump even when the tank level is lower.

The small seals and diaphragm can be damaged/leak and the mount for the parts can crack/break.

I have had to discard broken canisters and replace with good units to get fuel flowing again.

The design was changed in the X300 to have the pump sitting in a baffled area at the bottom of the tank instead of in the plastic housing. (better design)

 

UPDATE : CAR FIXED
PROBLEM: Burnt ground wire in trunk that connects up to the top canister that sits on top of the tank .

I would’ve never been able to fix this myself considering I would’ve continued to overlook this problem.

$700 in labor and time because the mechanic replaced a fuel hose inside the gas tank and did some other diagnostics.

-So in conclusion, FUEL FAIL 24 code can be various different things, .
I appreciate every person who took time out of their day with this headache, never been more frustrated.