87 XJS 5.3 has been parked 7 months, installed a new fuel pump, If I jump power to the pump the pump runs fine and sprays fuel at the fuel rail well. When the key is turned to the ON position prior to starting = no pump runnng for 2 seconds to prime. I think cold start injectors have no fuel pressure, and no electrical power. The engine will not start unless I prime with gas in air cleaners, and then it tries to run for about 2-4 seconds, so ignition is working, I disconnected fuel lines from the fuel rail in the engine compartment and flushed old gasoline out when I jumpered the new fuel pump, after I put fresh gasoline in tank. My fuel relay has 12 volt power on terminal 30 but when jumped to terminal 87 the pump will not run. I do not have a 87 wiring diagram but have a 85 diagram. I don't know where the power comes from to energize the pump for priming on a cold start. I need to know what supplies power to the fuel pump relay and what makes the relay send power to the pump, I tried to start by jumpering the fuel pump while cranking the engine but it never fires so it's a fuel problem for sure. Should the engine start if the cold start injectors are inop? Maybe I just need a new fuel pump relay? I would appreciate any thoughts on this problem, Thanks

 

My friends 88 had the same issue, and the problem was in the trunk where the spade connectors to both brown wires were not connected.



Not sure if this is how it was done at the factory or if its custom. Also make sure the inertia switch hasnt popped out.

 

There’s a relay next to the fuel pump relay, same size and shape, one has an orange base and I can’t remember which is which. Anyway, this main relay feeds the pump relay. Make sure all the connectors in the relay bases and in place and in good condition. They can get pushed out the bottom accidentally.

 

An '87 with cold start injectors would be an oddity. They were dropped circa 1984


Wiring fault between the relay and the pump?

Also, the relay has (or should have) two "87" terminals. Did you try jumping both? They're joined internally...so it shouln't make any difference unless there's a fault inside the relay

Should be the same or very close


Terminal 30 is constant voltage
Terminal 86 is key on voltage from the main relay
Terminal 87 (x2) is output to the pump and other things
Terminal 85 is ground from the ECU. This is what triggers the relay

A common fault is that the circuit inside the ECU which triggers the relay goes kaput. To verify, ground the orange wire at the relay. If the relay now works and the pump runs you know you have an ECU fault


Yes. You'd likely have to crank a bit longer on very cold days but that's about it. On warm days there might be no tangible difference.


Maybe. It's easy enough to check. If you do replace it make sure to get a "dual 87" type. Just Google "Dual 87 relay". And this isn't the same as the very common relay with 87 and 87A terminals....which functions entirely differently

Cheers
DD

 

Sounds like the inertial cut off switch to me.
That should be the first thing to check.
It is located on the lower part of the Passenger side "A" pillar.
Press the RED button on it.
If that doesn't work, remove it and check leads for 12V.
If there is 12V just jump the leads.

 

Thank all of you for your suggestions. I have checked the two wires with spade connectors on the positive battery cable- all good. The inertial cut off is in (pulled out and pushed back in) but have not yet checked for continuity thru the switch, but will. Maybe I do NOT have cold start injectors, just thought since the fuel pump used to run for a couple of seconds prior to start it was sending fuel to those, probably I'm incorrect. I did try both 87 terminals and -no pump runs, but relay may be bad or wiring to pump could be bad but all looks well. I will ground the orange wire on the pump relay and see if pump runs. I'll try to find a dual 87 relay and replace. Is the main relay the same as the pump relay? I may buy two relays. I'll add the car had been running well prior to parking. Could the fuel inside the injectors take a while to flush out, I flushed the fuel rail, but with the fuel pump jumpered and running, the engine does not fire at all unless I squirt gasoline into the air cleaners. Maybe my injectors are not operating? Thanks again for all the help, I'll have to work on the car again in a few days, and I'll keep you informed of my progress.

 

The main relay is different in that it has an internal diode.

Do the injectors click when cranking the engine?

I'll add that, besides providing key-on voltage to the fuel pump relay, the main relay provides power to the ECU ....and the ECU operates the injectors. If the injectors are not clicking and the fuel pump is not working, a faulty main relay is something to consider

Cheers
DD

 

Agree with all stated above.

I have that sticky with "Fuel at the front", not the other way around.

Sooooo, at managements demand, and the withholding of Canadian Club until it is posted, HERE YA GO.

If something is out of whack, or makes little sense, let me know and I will sort it.

 

I've ordered a dual 87 relay for the fuel pump and it will be here Monday. I've been unable to work on the car this past week but will follow all the suggestions posted and keep you advised on my progress. Thx.

 

I have not been able to work on the car as planned, I now have a new pump relay but no time to work. I'll try again this weekend if things go right. I'll post any results I get.

 

I FOUND TIME TO GROUND THE ORANGE WIRE ON THE FUEL PUMP RELAY AND IT MADE NO DIFFERENCE. Pump is inop. with key on and in start . I hot wired the pump and the pump ran well. Engine would not fire at all with the pump running. I have a new fuel pump relay installed. I have 12 volt power to terminal 30 on fuel pump relay. It seems there was power on another terminal but I've forgotten which terminal and I must stop working now on it. Is there a good wiring diagram that shows the fuel pump system. I think the ignition switch must send power somehow to turn on the pump for 2 seconds and then perhaps the ecu keeps the pump grounded to continue running after start. I appreciate all your help. I can't spend as much time on this as I should, just a hour or so every few days. I"LL next get someone to help me and try to determine if injectors are getting any power. All suggestions are welcome. Is there a good wiring diagram on this site anywhere? If the main relay sends power to the pump relay which terminal? It may be possible the main relay is bad?

 

OK, step #1 done and dusted.

With the pump hotwired and running, I will assume you do have actual "bang juice" at the engine bay?
My reasoning is simple, the pumps have a +ve and -ve terminal, duh Grant, and some pumps have the larger terminal as +ve and some have that larger as the -ve. The pump will spin whichever way is is wired, but only pump fuel the correct way. That one caught me out way back in the '80's, and took days to find, and many, many beers.

The inertia switch only cuts the fuel pump relay circuit, tick, and you have by passed that with the hot wire, tick.

The no running still needs more steps.

Is there spark?, does it cough and splutter with Starter Fluid sprayed up the snout?

If it does something with Starter Fluid, you have confirmed spark, then Injector Pulse is lost, and that is another list to work through, and covered in my sticky at the top.

I suggest bridging the 2 terminals in the Coolant Temp Sensor (rearward of the B Bank thermostat housing). Those sensors can reek havoc, so a quick bridge in the plug for the duration of sorting, is removing that CTS from the system. It basically "fools" the ECU to a Hot engine, and Injector Pulse takes place. Without that bridge, or sensor sending feedback, Injector Pulse is missing.

I will keep thinking.

 

Another item on that list.

You will need a helper, or very long arms.

Place your finger ON the Main Relay casing, have the helper turn the Ign switch to ON.

You should :feel" that relay CLICK. If so, it is working mechanically, but is it passing electrickery, no idea, probing wires is the only way. The fact the Pump Relay is still dead with the Orange Earthed, has me doubting that area seriously.

The reason for that suggestion is the Main Relay "powers up" the Pump Relay, and other things, including the ECU, hence the 2 X 87 terminals of the Main Relay.

Reading your 1st post, good on ya Grant, you have fuel to the engine bay, so pump wiring is OK, oops from my part.

 

Thank you for helping me with the XJS. I found today the main relay is inoperative. Sending no power to the fuel pump relay. I installed a new pump relay in the main relay position and the pump ran about 2 seconds and shut off. I'm certain if I can find a new relay for the main relay all will be good. Any idea on where best place to find a main relay? I understand it has a diode in it the pump relay doesn't have. Could the pump relay serve without the diode? Thx again for all the really good info everyone gave me. I found a main relay a few days ago somewhere on the internet but it was priced $80-$90 or so and that seems high since the fuel pump relay was less than $10.

 

Search the archives using "AGU1070 relay" for discussion, such as, for just one example

https://www.jaguarforums.com/forum/x...-relay-187285/

I'll try to remember (or find notes) on what I ended up using

Cheers
DD

 

Doug thx. I found the exact same relay that my XJS had on the internet at Ebay and ordered. The price was $12. Part # 332014112 Bosch has the red stripe on the relay just as the original. Thanks for your help though.

 

Bit late as usual, maybe the time zones, or just plain Old Age.

Mine ran a simple 5 pin, 30Amp, Double 87, relay as a Main, NO Diode. Duplicated in the Pump position.

Reasons being, waaaay back, before Computers, no one had a conclusive reason for the Diode. I made a management decision and went Grant's way. I have had no issues for a very long time, so I got it right I reckon.

Glad you found the issue, and I say again, SIMPLE cars these Jags.

 

89 XJS V12. In my case both wires going to the fuel pump are going to ground with the ignition off or on. I think it's OK for the black ve+ wire but not the brown/white ve- wire that goes to the black main fuel pump relay. The wire is in the #87 spot with another brn/white wire. The other brown/white wire heads toward the front of the car but I'm lost as to where it comes out. I'm also guessing that it is shorted somewhere but don't know where to look. My wiring diagram is blurry but I think it goes to the cold start relay. But my diagram may be old. Any suggestions as where to look?

It's running after I played with and reset the roll-over switch a few times.!!!!!! Not sure about the wiring but it's running.

 

AHA,

As Doug states regularly, "the fiddle factor fix". Might last a day,week, decade, the joys of motoring.

You have a wiring issue around where you "fiddled".

Also, that Inertia (roll over) switch is dicky at best.

 

Thanks Grant. I've also fiddled in that area when the power brakes failed. Looks like a wiring harness passes through the inside fender wall into the driver's leg area. Maybe there's a short there but don't think I will open that can of worms right now.. It's running and I know where to jiggle a few wires.