V12 all new injectors running very ruff? not getting enough air?

Just installed new fuel injectors in V12 that was in not run for 4 years
The car is running very rough–stalls after going a few miles
Any suggestions ?

gsalko,
Welcome. Running problems with a car that sat for years could be due to a lot of things including stale fuel, dying fuel pump, clogged fuel filters, bad EFI sensors, aging wiring harnesses, bad spark plugs/cap/rotor, and much more.

If this happened to me on a car that sat for years I would drain all the old fuel from the tank, add a few gallons of fresh 91 octane fuel, install a fuel pressure gauge at the fuel rail and verify that it is showing a steady 36 PSI or so at idle and slightly more when accelerating. If it does than it is probably not fuel delivery related.

In the meantime you should download Kirby Palm’s excellent “Experience in a Book” from Jag-Lovers (it’s free), and review the section on the engine. You should also rebiew the archives for “rough running V12” to see how many others have dealt with this over the past decades.

BTW, it would help if you identified the year of your XJ-S. The XJ-S was introduced with the V12 in 1975 and there were many changes made to it over the next 20+ years. Knowing what year your car is will help others provide suggestions regarding what to look at.

Paul

Hello Paul

It is a 1991 5.3L convertible

ALL plugs–fuel injectors have been replaced

Engine has 53K on it—new distributor and wiring harness is new

Just installed an Aluminum single flow radiator from e-cool–

all compression test were completed—not a problem getting fuel-

Fuel pump and relays all check out–

any other suggestions??

ECU—EFI wiring–pulling CPS??

Thanks

Greg

Greg – does it happen when the top is down versus up?

Just kidding - - I have convertible envy sometimes. I agree with all Paul said. And search the V12 archives as well.

Assuming you replaced the fuel with new fuel, and all of what you say above, then I would consider maybe vacuum? ECU uses vacuum.

Might as well check the coolant temp sensor on the LH thermostat housing. Your symptoms sound like a bad or disconnected sensor.

Just installed new fuel injectors in V12 that was in not run for 4 years
The car is running very rough–stalls after going a few miles
Any suggestions ?

Did you test the new injectors prior to installing to see if they click ? If not, use a mechanic’s stethoscope (or a long screwdriver held to the ear) and listen to each injector to verify it is clicking. Did installing new plugs and injectors help with the running problems…or said differently—what did the engine run like previously? SD Faircloth

Been working on replacing ALL modules ECU marelli fuel computer–suspension system -exhaust system–
all fuel injectors–wiring harness–ABS–fuel pump filters–all replaced–
water pump–new radiator-all hoses–distributor–ignition coil–all new brakes with calipers and brake drums
and redone gas tank–when the fuel gauge approaches
1/2 tank the motor stalls-after 10 minutes of running
I pull over for 1 minute-turn ignition–car starts right up
goes 1 mile --stalls again–when tank is full–this does not happen

any suggestions?

The fuel gauge signals that there is gasoline, but in reality the tank is almost empty.
In the tank there is a sump that communicates with the rest of the tank through a small opening.
If the small opening is blocked, the sump remains full, the instrument indicates that there is fuel, but in reality the fuel is almost finished.
After a few minutes, the little fuel left goes down into the storage tank and the car restarts.
This is my experience.

In the recently installed tank there is no sump
On the outside of the tank–there is a sending unit–
I always fill the tank–after a 100 mile trip the tank
approached 1/2 full–that is when the
engine stalls after going 3 miles–I pull over–
wait 1 minute–turn on ignition it starts right up-
go 1 mile it stalls when I slow down–does not happen when I fill the tank—Thanks in advance
Greg

Have you tried opening the tank when this happens - any sign of a whoosh of air?

When I fill the tank–and open the fuel cap
there is always a loud “whoosh”"

I had similar issue, it turned out to be my sump tank. I documented the problem here https://foreverjaguar.com/f/your-xj-s-surge-tank

1 Like

Diagnosis confirmed. Fix your fuel tank vent system.

Will get that done ASAP

Thank you for your help
Greg

My whoosh went away when i replaced rochester valve, although i never had driving issues beforehand.

You could have two issues - vent system and clogged sump tank filter as James points out.

Could you please be specific
when you mention
“vent system”

Thanks in advance
greg

Its all in Kirby’s book, about how the tank vents the gas vapors to the charcoal canister and eventually to the intake manifold.

To get started, put the LF of the car up on a stand, remove the LF wheel, and remove whatever panel gets you access to the area just forward of the LF wheel well. Might even take some pics and post them so we can tell you what you’ve got and what to check.

Hello Kirbert

The entire sump tank was removed along with the three hoses
that are connected to the sump tank–IE–coming from the
main tank and from the main Fuel pump to Sump—There was almost
NO debie in the sump and the sump gas strainer was clean–Is rochester
value the only solution to this whoos sound and causing the engine to stall with less that 1/2 tank?

Thanks in advance
greg

For the whoosh sound, you need to either fix the Rochester valve or replace it with a generic equivalent. I recommend plumbing a solenoid valve in parallel with the Rochester valve to ensure the vent is wide open when the ignition is on, but the Rochester or an equivalent 2 psi valve will need to be functional for when the car is parked.

Dunno what that’ll do about the engine stalling with less than 1/2 a tank, though. If you’re pulling enough vacuum to stop the engine, I’d think the fuel tank would be crushed. You might be looking at an unrelated problem there. If you open the gas cap, does the stalling problem go away?