I recently bought a '86 xj6 which caught my eye and fell in love with as soon as I saw it. I thought it'd be easy to work on and get it running since all it needed according to the last owner was a bit of maintenance and a paint job. He lied.
Now a new fuel pump,fuel filter,refurbished airflow meter,new ignition module,new coil, now air filter, new cables and spark plugs,new distributor cap and not much patience left later....it dies when switching from park to drive.

It will start as soon as the key is turned. It stays running at idle unless I press the gas pedal then it dies, same if I put it in drive or reverse.

I don't know what to do next if anyone could please point me in the right direction I would be extremely grateful .

 

Good having you with us.



With 30 year old Jags what you've described is pretty typical.

The Series III cars like yours are fabulous....but often need a bit of sorting out.



The 'could be' list in log but you might get lucky and hit pay dirt more sooner than later. A few easy things to begin with....

First clean the throttle body and make sure the throttle blade is set to the proper .002" gap.

Next, what is your idle speed? It might need to be tweaked upward a bit. Even when brand new these engine were set up a bit lean so they barely sustain life under the best of circumstances. With age and miles even less so. Tweaking the idle is often an easy solution. More of a mask than a repair, but often effective. I'd set the idle to 900 RPM in park and see what happens. If you don't know how to set the idle, post back.

Make 101% sure that the ducting from the air flow meter to the throttle body is intact, seated, and leak free.

Does engine temperature come into play? Better/worse/same when the engine is cold/warm/hot?

Cheers
DD

 

Hello Doug, thank you for replying so soon.
There are no problems with the engine temperature and
I did clean the throttle body but have not set the blade gap,
I'll get to that and tweak with the idle as soon as I get the chance.
The ducting from the AFM to the throttle body is in bad shape it looks worn and old I'll see to replace it soon .
Once again thank you for this and I'll post back with updates on the issue.

 

When the engine is hot the problem is worst. As soon as the gas pedal is pressed it dies faster than when it's cold or warm

 

Small update.
The ducting from the AFM to the throttle body looked bad but it was only some cloth material it's wrapped on the inside is good.

The blade gap on the throttle body was set correctly at .002

The RPMs at idle are at 1100 and on drive at 900 ; should I leave it there o lower it to 900 at park?

 

1100 is quite high; I suspect someone has already 'been there' trying to solve (mask) the problem

You'll want to lower to about 900 in "P" at some point

I'll give some more thought to the problem



Cheers
DD

 

When you purchased the car was the running condition exactly the same as it was before you replaced the parts, or did it get better (or worse) with the replacement parts?
Was the fuel pump you purchased an original Lucas unit, or an aftermarket?
Ever tested fuel pressure going into the fuel rail?

Cheers
David
shop.EverydayXJ.com

 

A couple of thoughts:


1. The ills of a worn engine show most at idle speed. Just not enough torque to pull itself and any loads. In addition to the vary valid comments by Doug and David, I would add two.


A. Run a compression check. An engine with poor numbers or unbalanced numbers will never idle well.


B. Get out the vacuum guage. Poor numbers and/or a jumpy needle indicate engine ills.


2. Engine vacuum is used for a lot of things. Leaking hoses or connections create a fast, but a bit weak idle.


3. Dropping the idle from the present 1100 to 900 will make things worse.


4. Are you sure all 6 jugs are firing at idle? Is it smooth or jerky? Each jug needs fuel and spark in the correct amount.


5. Sticky intake valves can create a poor idle. Free them with a very careful injection of water while running. Double care needed. Enough to clear away carbon from unwanted places, but not so much as to "lock" a jug. Unlike air, water does not compress, too much and something will give. Not only not good but very bad.


My cars idle nicely at 500. But neither is a DOHC 6.


Carl

 

To Davidboger ,
when I purchased the car it wasn't running at all and every part replaced was a big improvement. The fuel pump is an original Lucas unit I got on eBay.
I haven't check the fuel pressure because I don't have the necessary equipment.

 

Fuel Pressure is pretty critical to these cars, though I wouldn't expect it to cause a shutdown purely by putting it in gear.
I asked because I've seen the same scenario in cars with aftermarket fuel pumps that were supplying too great a fuel pressure...
I've also seen good sounding Lucas pumps that would do fine at idle, but die off once the car was under load.
Typically I'd run a long fuel hose from the CSI spigot on the fuel rail to a cheap Pressure gauge that I got at Harbor Freight. At idle I'd have the correct 33psi, but under load I've seen them drop as low as 8 psi. (Picture me driving down the road, bonnet popped with the hose sitting just at the driver side wiper blade so I could monitor it under load)...
It may not be the cause of your problem, but may be something to look at since you got a second hand (?) fuel pump....

David
shop.EverydayXJ.com

 

After tweeting with the idle to get it at 900rpm in Park now I can press the gas up to 4300 rpm before it dies (huge improvement) haven't test it on drive yet.

To davidboger,
It is a second hand fuel pump and I'll get the pressure gauge to test it later today probably. Should the pressure stay at 33psi at all times?


To JagCad,
I will run the compression test and look for vacuum issues although the engine runs smooth and sound very good as if nothing was wrong.
Lastly ,where do I inject the water while running? The air intake? And would something like sea foam or similar work as well?

 

Once the engine warms up rpms wont go past 3000

 

UPDATE: might have found the problem or problems.
I got the fuel pressure testing kit and did just that. (Watched a YouTube video on how to do it) turns out fuel pressure was at 20-25 psi and as I accelerate it dropped to 0 and died.
It was suggested that I cleaned the pressure regulator and did that;next I had to bring the pressure up by turning the key on drive until it hit 30psi to turn on the engine. I accelerated and nothing happened ,no stalling no nothing ( all this on Park) I thought it was too good to be true..and it was. Pressure started dropping slowly until it was struggling at 20ish psi.
It was suggested that I disconnected the vacuum hose from the regulator and the psi was supposed to go up..it didn't and the car died.
Now I can't get the fuel pressure up past 10psi. And the pump barely makes the humming noise.

So did I ruin the fuel pump or was it already faulty and needed another one??
And is the regulator also faulty and needs replacement??

 

How did you clean it?



Run a 'deadhead' fuel pressure test. Remove the fuel supply hose from the fuel rail and attach your pressure gauge and use the 'turn to start in drive' trick to run the fuel pump. You should get at least 50 psi pressure from the pump, maybe a lot more (make sure your connection to the supply hose is good!). If you don't, then the pump is weak or the flow is blocked.

If your deadhead pressure is good then replace the pressure regulator

Good sleuthing so far !

Cheers
DD

 

I've got a feeling that it's likely in the fuel pump.. Though the pressure regulator is certainly suspect too...
I said above the pressure should be 33, but I think it's 36....Either way, dropping off to 20 or less certainly isn't going to make it run...
Only thing to do now is the test that Doug suggests.. If it turns out it's the pressure regulator, I can help with sourcing that...
In the meantime, here's some extra reading material for ya......

Cheers
David
shop.EverydayXJ.com

 

Slick. David and Doug on the case. As good as it gets. Instruction to a willing student. Also great.


It is indeed a fuel issue. Far better than a worn out engine issue.


Issues reduced to pump or regulator or both. Perfect execution of "process of elimination". Sweet running Jaguar and happy steward in sight.


Carl

 

Just did the deadhead fuel pressure test. It went up to 70psi. Therefore fuel pump is good i supposed. Is there a test i can do to make sure it is the pressure regulator? And would you recommend a certain one?

 

If you're getting 70 psi deadhead but 0 or 20 at the rail, I don't see how it can be anything except the regulator.

If the pressure was too high at the rail then you could look for a restriction downstream before condemning the regulator....but that scenario isn't what you have.

David can fix you up with a good used one. If you want new, I think any of the name brands would be OK. Bosch, Standard Motor Parts, Beck Arnley, etc. With all the global manufacturing and label engineering going on it's hard to rely too much on brand names these days, IMO.

Cheers
DD

 

Yeah, My bet would be David's good used one. He might just have a proper NOS.


Forget the "water injection" for now. Not needed. It is introduced slowly through the air intake, ie throttle butterfly valves. I'm not familiar with Seafoam.


Carl

 

As you all can tell I'm exited and very eager to get this car running so I went to autozone last night after reading the replys and purchased a new one....

Installed it and Magic happened, the car didn't stall. I rev up to 5000rpm and it was beautiful. I'm about to take it on a test drive.