Hello all.
I am a forum member on the Series 3 section of the forum.
I recently purchased a 1990 Jaguar Sovereign (XJ40) with the intention of using the wheels and outboard setup for on of my Series 3 cars. I decided to see how the car works and by just putting some fresh premium fuel and a bottle of Octane booster (because the car was sitting for about 18 months with a 1/4 tank of fuel), the car started right up. Pushing the envelope I checked all of the fluids and decided to drive the car as far as I could go with my other vehicle and trailer following. Result drove 80 nervous miles to my home. During the trip I noticed a few minor issues, nothing to brag about.
Yesterday, I washed the very grimy engine bay and air dried all of my connections, with the sun beating down on the engine. When all was said and done, I cranked up the engine and it started right up.

While doing the cleanup I found a broken valve that connects a large host that goes under the battery tray and connected to a small vacuum line that runs to the intake manifold (pic1) I did a temporary connection (pic 2) since there was vacuum at the small line.

I also found a vacuum line that is disconnected on both ends. It clips on to the battery tray (pic 3)

Lastly, I now have a check engine light on. VCM display Fuel 24. Failure 24.
I cleared the code and the CEL comes back on with the same code.
What does code 24 mean?
On the drive, there was no CEL. This only happened after I cleaned the engine bay.
Thank you all for your help.

 

Never had that particular code before but fronm what I understand it's the Ignition amplifier circuit (small black component near the coil) - try unplugging it and drying it off and replugging then clear the code by disconnecting the battery - make sure you have the radio code first though!!

here's all the codes and the whole nine yards of electrical info for the 40 in PDF ...

http://www.mediafire.com/file/36ldvy...Management.pdf

Welcome to the XJ40!

Larry

 

@ Lawrence: Thank you for your prompt response. It is possible that the area where the ignition module is and the way it sits flat, water may have gotten into the connector. I will attend to that tomorrow. That link you sent me is exactly what I need to have in order to check out the system. Thanks again.
Anyone knows what the broken vacuum valve is for, and a part number?

 

Hi sanchez,

If the vacuum line that valve was in runs through the firewall/bulkhead, it may supply vacuum to the HVAC vent flap system that controls the flow of air from the various vents in the dash panel.

The hose that is not connected on either end may very well be the vent line for battery gasses, that should connect to a port on the end of the battery and direct fumes down to the underside of the vehicle where they will be carried away without accumulating in the engine compartment.

Regarding the ignition amplifier or module, I agree with Larry's suspicion that the connector is wet. Another thing to be aware of is that the flat piece of metal below the module is a heat sink, and there should be a thin layer of thermal compound between the module and heat sink. If you disconnect the module from the heat sink, you should replace this thermal compound, which increases the transfer of heat from the module to the sink and reduces the possibility of module failure due to overheating. Hopefully you'll be able to simply disconnect the module electrical connector and dry it out (some zero-residue electrical contact cleaner will help expell moisture and completely evaporate, leaving dry, clean terminals).

Cheers,

Don

 

I am still looking for the part number for the vacuum valve as shown in Pic 1 in Post 1. Does anyone know the Part # ? I searched to no avail.
I remove the ignition module connector and dried it out. The CEL is now off. Thank you all.
Continuing on the engine bay servicing, I removed the plate (on the TB) that the large bellows is attached to. In turn the plate is held by 4 bolts to the throttle body.
I did this to access the throttle body bolts.
I purchased a throttle body gasket and it came with an O-ring(approx 3 1/4 inch diameter), but no install instructions.
When I removed the throttle body plate and throttle body, there was silicone between the plate and the throttle body, no O-ring. Is this where the O-ring goes? If not
Where does the O-ring go? Anyone?
I installed it without the O-ring and now if I accelerate gently the car gets up to speed.
However, If I punch the accelerator, the car does not speed up. It's acting as if I have a bad MAF sensor except that it does not stall out.
Could it be that missing O-ring?
I did not notice this problem before I cleaned the throttle body, which was full of carbon deposit.
Thanks

 

The throttle body is supposed to mount directly to the intake manifold with no sealant or gasket of any kind, so the two surfaces must be completely clean and free of scratches. If the surfaces are scratched, you can use a very thin application of silicone sealant, but be absolutely certain the sealant you use is safe for oxygen sensors, because not all of them are.

One common problem is that if the large hose clamp that connects the bellows or accordion hose to the plastic air intake elbow is overtightened, the plastic elbow can partially collapse on its lower edge, creating a leak that is not visible from above.

When you cleaned the throttle body, if you sprayed cleaner into the throat, the cleaner may have drained down the butterfly valve shaft into the Throttle Position Sensor (TPS), which could be causing problems. The TPS tends to become contaminated with oil that is drawn into the throttle via the crankcase breathing system and drains down the shaft into the valve, so many of us have drilled a couple of drain holes in the plastic case of the TPS so we can easily flush out the old gunk with zero-residue electrical contact cleaner, and so future oil drainage can drip out of the TPS instead of accumulating inside.

Beyond that, check all your air intake hose connections, breather hose connections, and electrical connections.

Cheers,

Don

 

Thank you Don. I will remove the throttle body again and clean up the TPS.
Anything on the O-ring?

 

I have never seen an XJ40 throttle body that used an O-ring, but I haven't seen them all yet....

I just checked the parts diagrams at jaguarclassicparts.com and it does appear that up to engine number 113727 (engine number, not VIN), a gasket was used between the throttle body and intake manifold, but no O-ring is shown in the diagram. Here's the exploded view of the throttle body from the listings through model year 1992. Part 6 may look like an O-ring but it's the butterfly plate:



And here's the exploded view of the MAF and air intake plumbing:



Cheers,

Don

 

Thank you. I will try to sort it out.

 

Was at the auto part store where I purchased the throttle body gasket set and had the rep look up a diagram of the gasket set I purchased. Well, lo and behold, there was no o-ring.
I seemed that the box I was given was a return from another customer who 'maybe' inadvertently included the o-ring in the returned box. The rep brought out another box and of course there was no o-ring in it.
I wonder whether the returnee is going crazy looking for that o-ring.
On a better note, the acceleration issue went away on its own. I guess that all of the moisture introduced by me when washing the engine bay finally dried up.