I don't think this car has one (er, two). I can see the 6 cylinder has them even earlier than 77 from parts for sale on websites. This car was sold in California originally.

I am not seeing an O2 sensor for the 12 cylinder until 79-ish. Maybe 80?

Given the jag manual does not reference it, and I can't find them on the exhaust manifolds, I have to think they are not on this car.

Odd with cats but I am not sure, but I am thinking no.

 

I believe you are correct.

We got cats down here on some makes of cars in about '74, but O2 came in late '80's.

The old D Jetronic system (purely analogue) would not have the info to deal with those sensors in my opinion.

We got O2 with the P Digital HE in late '87. They were a single wire sensor, and notoriously unreliable on any car with them.

 

Thank you, Grant. That makes some sense to me.

Update on overall progress. Fuel leak in trunk was killing residual pressure. Starts first turn of key just reaching in with no feathering of gas pedal. Still rich with slight backfire on right bank when warmed. I ain't skeered. Just have to apply the resource.

 

If it has o2 sensor/s they should be down stream of the manifold to exhaust joint.
A device that looks like a plumbing plug with one or two or more wires attached.
Mine was loose when my car was DOHC powered. I had strong doubts as to what it contributed.

As a lump, it has two O2 sensors down stream of the joint and my scan tool easily reads their function.

Just my two bits!!

Carl

 

If its still a tad rich at idle, adjust the mixture screw on the MAF sensor on the LH side of the radiator top panel. It is under a largish plastic cover thingy, and a dob of Yellow paint tells the authorities you have messed with it, and are a bad, bad boy. It has extremely coarse threads, soooooo, a small rotation will make HUGE variations. It is a 1/4"?? allen key.

I THINK, from memory (haha), inwards for lean and outwards for rich. However, with the engine running at idle, and turning that plug will have a different "sound" to the engine, and a keen ear will pick the "sweet spot" very quickly.

Also the fuel pressure in the twin rail set up is critical that it is identical in both rails or havoc reigns supreme. Very time consuming to get it spot on, so much so that a lot of PreHE engines have been fitted with the HE rail, and a single PreHE regulator on the outlet (LH) only, and quite successful.

Then comes the parentage of the PreHE. It was/is designed to be DRIVEN. Both ours would get quite hissy with our stupid 50kph speed limits, so a regular blast up the country road for a 100kms or so sorted many ills.

I maintain the encouragement of alternative fuels, so buy another PreHE and hurry the greenies up HAHA.

:icon_b eerchug:

 

Thanks Carl, I know where they ought to be on the original engine exhaust manifolds, but they ain't there. On your newer non jag engine, you have an upstream and downstream (of cat) conv O2 sensors. Upstream one is probably slightly beyond the cast iron manifold. Front one is the control and rear one sniffs if the cat is doing it's job.

I never disable an O2 sensor as they are shut off under WOT. The rest of the time they save gas.

Don't I have a manifold vacuum thingie, not a MAF sensor? See pic.

Regarding fuel pressure, I only put the gauge on one side so more analysis is required. That may be the issue.

 

Yep thats it. Different language down here, mmmm.

The end that faces away from the engine has an allen key threaded adjuster in it. Yours has the plastic "thingy" missing, common.

That may be the issue, so time to set both rails will need to allocated. I bit the bullet and got 2 fuel pressure gauges, and attached both, and set them that way. The book claims 31psi +/- 2psi, but I found both ours were sweet (that word again) at 29psi. By changing the pressure as little as 1psi made things just "unsweet".

 

Bob:

Not that it matters, because it doesn't as to the original Jaguar system, my PCM is mid 94. The data port is OBD II shaped, but the system is OBDI. OBD II has the 4 O2's as you describe, while OBD I relies on merely two, one per bank, just aft the manifold to pipe joints. It took a tussle with the SMOG referee to clear that up and get a pass. His scanner could not handle it. So, kindly or embarrassed, he accepted the readings my scanner provided.

I refered to the loose O2 when my car was DOHC powered. I doubt that it functioned at all.

But, I agree, O2 sensors are on board sniffers and definitely should work. Or be replaced.

Side bar: My after market harness maker reversed the leads on one O2, much travail to find and fix that!!

 

My hat is off to you for finding that one, Carl. I can figure out the wires on the newer ones (with the web) but I still do not have a system down to test them. I think you can buy or make back-pin setups that help.

I really need to spring for a real scanner. Although, used. O2 sensors and ABS problems are really a crap shoot without them.

Can you use the OBD2 in the OBD1 port on your car? My sister's 94 Ford F-150 still requires a paper clip jumper under the hood. I remember doing the same paper clip thing under the dash of my wife's 84 Chevette. But not sure if that was OBD 1. At least it was a Chevy OBD. :-)

I will not adjust the unit until I confirm that the two regulators are in sync. There is a black plastic cap on the outboard side. That is a good thing, as I will be tempted to mess with the adjustment if I can see it.

I did note the pressure was around 29 on the side I checked and when I plugged the air sensor back on the left side air snorkel, it jumped to 37-ish. That is the bank that is rich. Manual says 2.1 bar - constant. Seems to be too high, on the single side I checked. Making headway.

Thank you.

 

What a slave driver.

OK, so I do it. My 80 year old father-in-law, is making sure the hose joint ain't leaking and has a fire extinguisher in hand.

Driver's side, dead nuts at 30 psi cold and after warmup. Rev the engine, rock solid. Bleed the fuel pressure tester into a pan and a little spritz comes out and residual pressure is gone. Sweet (sorry).

Passenger side, 32psi (average) and the gauge is fluctuating rapidly 5psi high and low. Rev it up, fluctuates from 20-40 wildly. We adjust it down to average 29 based on your input, pretty much for fun to check how the adjuster works. Before I adjust anything, I state "The dude from Australia says....." The old man is tickled that I have these exotic contacts.

Shut it off, and bleed fuel and it won't quit coming out. I am thinking a good half pint. The regulator is not sealing off system pressure from the right bank.

I think I needs a new regulator. :-)

 

AHA.

You. sir, have found 90% of your issues. Fear not, that is a common failure of the PreHE FPR's.

Sometimes, poking a slim blunt rod (screwdriver with the end ground flat) up the spigot, and pushing against the tapered rod a few times might just clear the rusty scale that is more than likely giving you the grief. I would unwind the adjuster all the way, thus reducing the spring tension, and generally making the rod easier to push.

I needed 2 for one of ours a loooooong time ago, and Jaguar was serious $$, so I got 2 from Mercedes, changed the bracket, and still running sweet, car has NO idea they are Merc parts HAHA.

The were/are Bosch FPR's, and used on many, many cars of the period using the D Jetronic fuel injection system.

 

I thinks its a MAP thingy (manifold absolute pressure)

 

Yes - vacuum is not the correct term, let alone thingie.

I don't quite understand the term "absolute" but Jaguar uses the term manifold depression vs vacuum. Perhaps it has to do with more fuel being introduced when the manifold depression is less - therefore pressure has been added to a baseline (high) manifold depression and this increment is what is the measure of engine load is.

 

Bob:

The paper clip thing to me is new?

Althought my connector is shaped ala OBD II, it is wired OBD1. Kind of a mid year transition thing. I bought a device that i thought was a scanner. alas, it was a mere code reader. so, I upgraded, more bucks of course. Around 350 then. probably less now. It has cables for other ports. and, a cable to fit the OBD II shaped port to read OBD I. Really slick. Just set it up. follow the instructionsand data flows!

I've never used it again since it helped me get past the SMOG referee.

It would probably read my Jeep as well with the right cable. which may well be included.

As long as the check engine lights perform, I don't figure to need it. But, if i do get one, it will n ot only read the code but the data and the ranges for that data.

Carl

 

What is the name of the scanner tool? Sounds interesting.

I know you can buy scanner emulators for VW's -a VAG-COM emulator - in that $$ range.

Re paper clip. You connect between two ports on a female diagnostic connector and one of the dash "idiot lights" flashed a code sequence that you reference against a list. A basic code reader. Dealer probably has a real diagnostic tool that plugs into the the entire connector.

 

Cool!

Both units are Bosch. The working one is newer looking than the failed one. They are well under $100 but will try the refresh for fun, if I can locate the largest phillips screwdriver ever made to pull the fastening strap off. :-)

Thanks for the help.