Hey guys, new on the forum. Trying to get Dad's 87 XJ6 with 100k running it's been sitting in the garage for 8 years. The body and interior are in awesome condition so working on getting the motor to fire. Think I'm having a fuel issue. Have spark on all cylinders and it catches a little but won't really run. From some diagnostic I believe the issue is fuel related. A mouse had chewed a wire to the valve to switch between tanks and I got that fixed. So next I checked for voltage to the fuel pump. Here I think is the issue. Only 4 volts coming out of the wire. I'm assuming it should be 12v, is this correct? New battery in the car, any idea why I would have low voltage and where to start to trouble shoot? Doesn't appear to be a fuse on the fuel pump. Is this correct? Figured old fuel was the issue originally. I am getting fuel up into the rail but thinking pressure to low if voltage at pump is wrong. Probably need to replace that fuel filter as well. Thanks for any suggestions!

 

there is no fuse to the fuel pump.

the fuel system needs to pressurize, place the shifter in 1 or D, turn ignition switch to START and hold it for 4 to 5 seconds, you should hear the pump humming in the trunk as you hold the key in the START position, then back to OFF. (engine will not crank with the shifter in 1 or D, you just want to pressurize the system by doing this).

do this 4 or 5 times, assuming you have plenty gasoline and battery is fully charged.

then place shifter in Park or N and try to start.

Doug will help you further.

 

First bear in mind that the pump gets voltage only when the starter is engaged or when the engine is running. How were you performing the test?

Anyhow....

Remove the fuel pump relay from the socket. The relay is on the firewall and has white, white/green, white/purple, and black wires.

Looking at the now-empty relay socket you'll see (a total of) three white/green wires located in two of the socket cavities. One of those white/green wires goes to the fuel pump.

Using a jumper wire apply 12v from the battery to the white green wires in the relay socket and check your voltage at the pump. If you get a zero voltage reading at the pump apply your jumper wire to the white/green wires in the other cavity. Measure voltage at the pump again.

If you still get only 4 volts at the pump you have a wiring problem between the relay and the pump.

If you now get 12 volts (or whatever prevailing battery voltage is) at the pump you'll know the wiring to the pump is OK and you have a problem at the relay or upstream of the relay. Post back with results.

Fuel filter: yes, replace. Don't just throw the old one away. Empty the contents into a clean jar. If it's gunky you have more work ahead of you.

Cheers
DD

 

As Doug indicated, more work ahead...
I would clean the fuel tanks before running that gunky fuel through the changeover valve, fuel pump, fuel filter, fuel lines, pressure regulator, fuel rail, fuel injectors, return valves and back to the tanks ...if you get my drift.

 

Sounds like it might be too late for that advice.

Nothing that can't be eventually sorted, though. Thankfully.

Cheers
DD

 

thanks so far guys, incredible awesome. Pump works with 12v to it. After running tests I am getting a voltage drop across the diode pack of I think it was 3 volts. All the wiring checks out. So I think I either need a fuel relay or my suspicion the diode pack. Called jag bits (which my dealer told me to call) the diode pack is $175 ugh. It’s just some diodes! The relay is $30. No one local seems to have. Any suggestions? Pay up and buy them?

 

check prices:

SNG Barrat USA store,

Motorcars Ltd.

eBay

 

Yeah, there's a resistor in the diode pack. I've never known why

Voltage to the pump comes from the relay so that would be my guess. But make sure you're getting 12v TO the relay on the white wire.

Voltage from the diode pack just triggers the relay so if your pump relay is being triggered, the diode pack isn't the problem.

Silly, isn't it?

They're DIY repairable if you have a soldering iron, a steady hand, and a dollar's worth of diodes

It's slightly unusual in that is a 'dual 87' terminal configuration. Most common relays have terminal designations of 30-85-86-87-87A. The pump relay (and a couple others) are 30-85-86-87-87

With a bit of Googling you can find one for less than $30 but it's very unlikely you'll find on 'on the self' at any neighborhood parts store

Hella HL87483 Mini Relay, 12V, 40A, SPST, Dual 87 Pin | Rally Lights

https://www.summitracing.com/parts/h...iABEgI54fD_BwE

Cheers
DD

 

Thanks DD. Have a lead on a couple from a local Jag guy and a junkyard that has a few cars. Going to check them out tomorrow. Good with a soldering iron too so might go that route and see what’s going on there.

Based on what you you said I was getting all the right voltages on the relay terminal so maybe it is the relay. The guy at jag bits seemed surprised that I had a Bosch part in there so maybe it was replaced before...

was also quoted $75 for a fuel filter from the dealer, thank goodness for Amazon that dropped to $12. At least to the point of getting it running that will work, restoration time can go better quality.

 

With DIY labor and a bit of shopping around for parts you can run a Series III quite reasonably...as old cars go.

Also, if you need used parts, try David at EverydayXJ

Everyday XJ


Very nice guy, honest, more-than-fair prices. He's almost a hero to a lot of us !

Cheers
DD

 

Scratch the "Almost".


On messing with my Jaguar circa 2001, my "understanding" of relays progressed. Intriguing devices. Amongst what I learned was an easy source for the at "cheap" prices. The parts emporium. A driving light kit.


And, one of my early on trips home on a flat bed was relay related. The FP relay fell off it's mount and on to a hot EGR pipe. I got lucky and replaced it and it's fuse. Fired right up


But, a hole in the relay case revealed the teeny coil and points. Got it.
Much like the ancient "cut out" atop my old generators. Merely, an on/off switch.


But, diodes needed in some circuits. Feed back can be an issue. these prevent that. More intrigue....


Carl

 

Hey Guys,...Regarding the Series 3 fuel pump. Having been around this block a few times, I have a quality question. After sitting for a month or so, my fairly new pump had 12 volts going to it and was dead. I pulled the pump and drained out clean fuel. Bench tested it and it fired up. Re-installed it and all seems OK.
My question,... Out of the 10 or so different priced units sold, I would normally pick the cheap one. Now I have no trust in mine and think I should buy a replacement. Any recommendations?

 

buy the Bosch pump.