Hello all. I have a 1989 XJS convertible with 69K miles. I am having a problem with the engine (v-12) dying after about 20 min. drive time. I have read every post on this site related to this problem. I see that there are several others that are having or have had this problem. The car acts as if it were out of gas. You can keep the engine running by just slightly feathering the throttle. But it will eventually die and will not refire. After about 10-15 minuets of cranking the engine will fire up and run perfect. From reading past posts I understand that the fuel filter could be the problem. Or the fuel pump. Or the screen in the fuel sump tank. Or the fuel circulating from the engine back to the fuel tank could be to warm causing a vapor lock. Or it could be a combination of some of the above. I have also read Kirby Palm's book concerning fuel delivery. Today I started investigating the problem. My intention was to replace the fuel filter and clean the screen in the surge tank. Do the simplest cheapest things first. I removed the spare tire the battery and the battery box and found a surprise ! Someone in the past has bypassed the surge tank ! The fuel line comes out of the main tank goes to the fuel pump then to the fuel filter then to the engine. There is one small line still connected from the main tank to the surge tank. I assume this to be a vent line. Now what should I do ? Should I leave it like it is and change the filter and maybe the pump ( it whines very loudly)? Or should I re-plumb everything back thru the surge pump and clean the screen replace the filter and maybe the pump ? One other thing, the air conditioner belt has been removed from the compressor so I am assuming the fuel is not being cooled before it is returned to the tank. Thanks for any help/advice. This is my daily driver and I need it to be dependable. Driving this car makes one look forward to going to work ! Thanks again.

 

My assumption...ha ha...assumptions...is that the previous owner found the surge tank so rusty that he went around it.

My advice for "step one" ? Take the fuel filter off and empty the contents into a clean container. What you see will dictate what comes next.

Post back !

Cheers
DD

PS- postings with paragraphs are much easier for old eyes to read :-)

 

Thanks for the reply.

I figured changing the fuel filter would be a good idea no matter what so that

will be my first step.

Your right about the paragraphs. I'm getting kinda old myself (50). My worn

out knees protested loudly while I was crawling around in that trunk today.

Thanks again. I'll post my results.

 

Doug is SPOT ON as usual.

No real harm with the by-pass, EXCEPT that the supply line from the main tank has NO filter in it, that supply filter is in the by-passed tank, so the fitment of a 1/2" filter in that line would be mandatory to save that fuel pump.

The fact the pump is "whining loudly" is usually terminal, so a new pump would be smart.

I have an owner here with a Pre HE XJ-S with that by-pass in place, and it has been that way for 8 odd years, still his daily driver, with NO ill effects. He NEVER lets it get below 1/4 fuel tank reading, just is case. We fitted a Wix brand filter in that line from the main tank to the pump, and he changes it every time he changes the main EFI filter, which is at about the 2 year mark.

 

Forgot something, damn, I do that too much hahaha.

We dont run that fuel cooler here on ANY of our V12's, and even in our 45c+ summers, we have NO fuel vapor issues, or any other issues with fuel for that matter.

Jaguar did drop them later in the V12's life.

Yep, knees and XJ-S get on real well, NOT, I am constantly looking for somewhere to put the crutches, so I can reach them when I want to exit wherever I have crawled in the car/s.

 

Thanks Mr. Francis for your reply.

I'm glad to know that by-passing the surge tank will cause no problems.

Thanks for suggesting that I add a filter up stream from the fuel pump. I

see the logic in this and will add one.

Also thanks for the tip concerning the fuel cooler. That lets me eliminate

the cooler as the culprit to my problem.

In preparation to replacing the fuel filter I was reading my XJS handbook

hoping it would instruct me how to relieve the fuel pressure before I loosen

the fittings. It says 1. Remove the pump relay plug (mounted on the

engine compartment bulkhead) 2. Switch on the ignition and crank the

engine for a few seconds. 3. Reconnect the pump relay plug.

This sound simple and straight forward. But I have no idea what the pump

relay plug looks like. Would you happen to know how I can locate it.

Any help would be appreciated .

Thanks so much.

 

The relay should be in the trunk, near the RH trunk lid hinge, behind a plastic cover. It'll have brown, orange, pink/black, and brown/slate wires.

Cheers
DD

 

Thank you very much.

 

There will be 2 relays in the boot (trunk) and they are behind that carpet panel alongside the battery, simply slide it rearward and jiggle it till it parts companmy with the car.

The relay in the BLACK socket (base) is the fuel pump relay.

 

Thanks. I looked at these relays during my search and suspected that one

would be what I was looking for. Also the wiring from the fuel pump

seems to lead into one of them. But then I read the manuel that came

with the car when new and thought surely the person that wrote the

manuel would know what he was writting about. I guess I shouldn't think

so much. Thanks again for the information. I will not be working on the car

until I get another off day (next Tuesday). Gotta work to support the Jag.

 

Yesterday I replaced the fuel filter on the Jag. All went well except the auto parts store gave me the wrong filter. I also completely removed the serge tank and all it's plumbing. The old filter was packed with liquid sand. The serge tank was all rust inside. Today I filled the car with premium fuel and took it out on the highway and put the peddle to the floor ! Pure smooth acceleration ! No sputters and no missing. I will replace the fuel pump and install a filter between the tank and the pump next. Thanks everyone for your help.

 

I have noticed from reading others forums that when a repair is made to

an older model Jag that it will often create a new problem. That has

happened to me. As you know from my previouse posts I replaced the

fuel filter and removed the surge tank from my 89 XJS. Now I find that the

signal lights have stopped working. How could replacing the fuel filter

cause the signal lights to stop working. During the filter replacement I

disconnected the battery and the fuel pump reley. Could this be the

cause ?

 

In *this* case it's probably just coincidence.

However there IS a true "fiddle factor" on the electrics of these old Jags. Weak/dirty/corroded connections can be sensitive to even the slightest jiggling about. Been there, done that...many times. Almost impossible to avoid at atimes.

It's good practice to check/clean/tighten any electrical connections (and grounds!) that you come across during the course of other work.

Cheers
DD

 

I have been thinking about what I may have done in the last few days

that would have caused the signal lights to stop working. As I was

backing the car out of the garage this morning I rememberd that a couple

of days ago, when the clogged fuel filter caused me to be stranded in the

middle of the road ,that I had turned the emergency flashers on. So as I

was leaving the drive way this morning I turned on the flahers for a few

seconds then turned them off. Then I tried the signal lights and they

worked ! This car is gonna drive me crazy.

 

Power for the turn signals comes from the hazard light switch...which probably has dirty contacts. Operating the switch cleaned them a bit.

Cheers
DD

 

On my xjs every once in awhile my blinkers quit working and after trying to figure and figure it out. I just slide my fuse a lil bit and I got blinkers again

 

Do yourself a favor and clean the corrosion from all fuses and fuse clips and then go around the car and clean every connection and ground point you can find. Make a full Saturday of it. It'll go a long way towards preventing the oft ballyhooed "Prince of Darkness" situations.

Cheers
DD

 

Friends,

If I remove the surge tank, which I have done...(it is filled with rust debris) what do I do with third line that comes out of the tank? The lowest line out of tank goes to prefilter then to my fuel pump. The line to engine comes from my post fuel pump filter and I have a third line that went into surge tank that I don't know what to do with....this isn't the return line is it? So do I need to put in a T so it goes back to fuel pump? Any help would be great!

 

The third line goes back to an inlet at the RH side of the tank, about 1/3 of the way up. Pic here, see the hose next to the RH tank strap:



I think it is to prevent any undue pressure differences building up in the surge tank. If you have removed your surge tank permanently from the system, you can just plug this line at the tank end.

Greg

 

Hi Greg,

Thanks for the pick...so a couple of things. The line on the left side bottom of the tank is I presume the return line from excess fuel. The low center one is the main line which should head to filters and fuel pump and eventually out to the hose/pipe on the very right side of car to the right side of battery back to fuel rails/regulators correct? I''ll need to check my hook-ups again because I had a little bit of fuel coming out of the line that is a 1/3 way up on the tank on the right side (just left of battery). I did have it plugged but my plug was temporary and I noticed fuel dripping out of it so I unplugged it while I had my fuel pump running and some fuel came out. It eventually stopped while the fuel pump was still running however. Could this be indicative of pressure building up in the main tank? When I take the middle main line off the fuel pump, I only get a trickle of fuel, not a tremendous amount of flow. I would expect this to flow pretty well since it is gravity fed correct? I fill the tank with fuel and will do so with more to ensure that isn't the case. Thanks again for your help!!!https://www.jaguarforums.com/forum/i...s/icon_lol.gif