Cap & rotor look OK as far as we can see. They are aftermarket, but at least you have the metal sleeve around the carbon brush. Please remove the rotor (two screws), turn it over and post a photo of the underside.
Itās probably an optical illusion but the lower part of the rotor looks clean compared to the upper leg?
The distributor venting
Steven,
There should be two vacuum hoses connected to the distributor for venting purposes. One goes to a plastic elbow on a medium size rubber hose going forward from the Auxiliary Air Valve (AAV) beneath the left side intake manifold. The other one goes to a small air filter located beneath the headlamp relay on the left side of the engine bay. Attached are pictures of both ends.
If your vacuum hose was so fragile that it broke, it bring to question the condition of all the other important components in the engine bay, particularly the fuel injection hoses. Many XJ-S engine fires were caused by old fragile fuel hoses bursting while under pressure with the engine running. Fuel injection hose does not last forever, and if you have no records showing when they were changed, they are all suspect. The fuel hoses with metal fittings on the end connected to the fuel rail have metal date tags on them. If they are original and dated about 1990 they are not safe and should be changed before you have an engine fire.
Paul
also, as an alternative, I plugged up the vacuum tube that goes from AAV rubber elbow to distributor, and use a vacuum port from the top of throttle. So plenty of cooling while driving. I didnāt like the idea of that much vacuum at idle sucking on the distributor. Iāve heard of oil actually being sucked up. And itās just another āvacuum leakā.
Thereās virtually zero vacuum at idle; only the pressure drop from idle airflow through the air filters. But if youāve moved it to a vacuum port on the throttle, NOW it can get a lot of vacuum! Perhaps you might want to rethink that particular mod.
i donāt get that. At idle, vacuum is 17 inHG that is sucking through that AAV elbow, and sucking on the distributor.
On the throttle port, Iām getting 0 inHG at idle. Iām only getting a high vacuum when cruising.
Where do you get the idea that manifold vacuum is applied to the AAV elbow?
AAV attaches one side to intake manifold. Air flows through idle screw, and from the elbow Iām talking about, sucking from the air cleaner. An attachment exists in rubber elbow for distributor, which Iāve plugged up.
Yep, and that side sees intake manifold vacuum. The other side does not, no more than the other side of the butterfly sees manifold vacuum. The elbow sees the same vacuum as the air filter housing.
OK, then that means the vacuum at top of throttle body which Iām currently plugged into, outside of butterfly, sees the same vacuum as if I had it hooked up the original way off the AAV elbow.
No, it doesnāt. The taps on throttle bodies open near the edge of the butterfly so the butterfly passes over them as it opens. In some cases theyāre on the manifold side at idle but atmospheric side at throttle, others the opposite. Lemme make this clear: Under NO circumstances should the distributor vent system be connected to any of those ports!
OKā¦Iāll put it back to the AAV elbow.
I think some of us need these stickers under the hoods of our XJ-Sās!
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If somebody made those, I bet there would be a sufficient demand to buy those stickers.
And it might demand a 20% markup on our cars if we ever sold them!
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I can see it now
āYeah it looks good, but I donāt see the Kirby approval sticker so gonna have to passā
- somebody in the future
Where is that first picture located in trying to find it in my engine but tracing the fuel rail I donāt see anything similar. The metal clamps holding the hose directly onto the fuel injector has the marking ā8-12ā āGermanyā on them not sure if thatās a date or size.
The two screws your talking about are the two Allen heads correct? They seem kind of stuck so want to make sure be fore I break something
EDIT here are the pictures
Steven,
The two attached pictures should help. The first one shows the medium sized hose going forward from the Auxiliary Air Valve (AAV) with a red circle showing where the small plastic elbow comes out of the top and a smaller hose in attached to provide vacuum to eliminate flamable fumes from the distributor. You canāt see that plastic elbow or hose because of the angle that I took the picture at but I took this shot so you can see where it is in the left rear of the engine bay.
That info was just the size of the fuel hose clamp. The second picture shows one of the date tags on one of the four specialty fuel hoses that have metal pipes swaged onto their ends. The tags show the date that the hose was made. If it has a date like 1989 or 1990 on it, the hoses are no longer safe to use due to age. Places like XKS Unlimited, SNG Barratt, and Motorcars LTD sell kits that include all four hoses.
Paul
Your rotor looks fine. Itās apparent, though, that the car suffered a Marelli rotor failure in the past as evidenced by the charring on the top of the distributor shaft. I dunno whether such a failure might have caused other failures so that replacing the rotor didnāt restore proper operation.
Iām also a bit concerned about the location of the slotted holes in the distributor base on the mounting screws. I donāt think theyāre supposed to be all the way at one end. Perhaps others can chime in there.
FYI: Rotating the distributor on the Marelli does not affect the timing; the timing is set by the crank sensor. Locating the distributor waaaay off, though ā as it appears to be in this case ā can cause the spark to crossfire to the wrong spark plugs, usually either at minimum advance (idle) or maximum advance (high RPM, low throttle). It usually makes a complete mess of the running, nothing as consistent as this owner is reporting.