Working on my Uncle’s XJS. He overheated it, apparently the auxiliary fan did not come on. Had a technician come in remove the heads, I assume everything was inspected, and the necessary repairs were done. The engine reassembled to a point. I now have the car and have been tasked to get it up and running. Compression across the board 140-150 psi, with the exception of 2E at 40psi. Re gapped plugs(Champion), some were still clean, others had a layer of black carbon. Checked fuel pressure(45 psi), had no spark when I got it, cleaned connections at cam position, and engine speed. Now have spark, engine wants to start. I suspect the engine timing is out. There was an aftermarket alarm that has been removed, and I noticed a white wire cut and not connected to anything from the computer below the glove box. Can’t find fuel pressure, or engine timing mark locations anywhere. Thanks in advance. Any input very much appreciated.
Seems to me that sorting out that stuff ^^^^ should come after sorting out this:
Assuming you’re working on a V12 the compression should be around 200 in all the cylinders and, really, that engine is never gonna be right with one cylinder virtually dead at 40
Cheers
DD
Agree with Doug. Compression is low across the board. 2E needs a leakdown test. May have a dropped seat, as the engine overheated…albeit the heads were suppose to be redone. I’d be on the horn with whoever it was that did the head work, for details. If he did the heads, and didn’t bother to clean/gap plugs…Hmmm. FYI…if this is a V12…the correct cylinder numbering is A1 thru A6, and B1 thru B6, A bank on the passenger side…B bank the driver side… if US market. I don’t think any of the V12s had fuel pressure gauges from the factory. SD Faircloth www.jaguarfuelinjectorservice.com
Makes sense, thank you.
Checked my recordings it was A5 that was low.
The person that put it all back together has been MIA, so any info on what he did is not available. Now it’s my task to at least get it running.
Oh boy I think this is going to be a long hard road.
Before getting too deep into it, check the valve clearance. Swapping buckets and shims, grinding valves, or replacing a seat will all affect the shim needed. Even if whoever assembled it put the parts back where they were, the shim thickness will likely need to be adjusted if the has been any head work done. Valve clearances that are too tight will cause low compression.
You may have a cylinder with stuck rings also if it got hot. A leak down test will point you in the correct direction.
You really need to get the compression within spec for it to start and run correctly.
Will do. Thanks for the advice. The older VWs I have worked on had the same type of adjustment.
Cheers
Another thing to try is to blow compressed air down each intake port as you rotate engine to check the valve clearance; not unusual for a bit of gasket or swarf to get trapped under a valve and hold it open slightly. Will show as excessive valve clearance.
Thanks again. Great info.
Just wondering where I could find timing marks on the engine. I see how to align the cams, it would just be the crank. There are three how would I describe them, flattened bent nails on the crank pulley as references for the crank position sensor.
Cheers
Bears
Bears,
I am still a little confused about exactly what engine you have in the Jaguar you are working on. Does it look like the engine and does it have a distributor cap like the one in our 1990 XJ-S convertible with the Jaguar 5.3L V12 engine and Marelli ignition shown in the attached pictures?
If it does, then there are no timing marks and the timing is digitally controlled. There is a minor adjustment possible by rotating the distributor but that is usually not necessary.
Paul
I think that you will need to use a positive stop tool in the #1A spark plug hole. Here’s how I have done it on other engines- use a thin rod to approximate TDC, then rotate engine forward so the rod drops 1/2”. Then install the stop in the plug hole and rotate engine backwards until the stop hits the piston. Mark the damper to a reference point on the timing cover, then rotate the engine forward until the piston hits the stop and mark the damper to the same reference point; TDC is exactly the mid point between the two marks made on the damper.
You can buy a positive stop, or make one by gutting an old spark plug and putting a bolt through the middle.
Do yourself a favor and get the location tool for the camshafts, they will want to rotate from valve spring tension if you loosen the cam chain tensioner and sprockets.
Just be sure both lobes of #1A are pointed up to indicate compression stroke; if not, rotate crank one full turn. You can check that the distributor is installed correctly at this point also, the rotor should be slightly ahead of the tower for #1. You can cut a window in an old cap to see this easier if needed.
GREAT INFO. Sorry for being vague. 1989 XJS convertible V12.
The attached pictures are awesome, and will help tremendously as I received the car in pieces. BTW that engine is beautiful. Looks like a brand new Jag.
Thank you Paul
Robert thank you as well. I will see about acquiring those cam locks and piston stop tool. Maybe they are in one of the many boxes of parts that came with the car.
I will keep posting on my progress.
Cheers
Bears
Removed down to the intakes including the intakes. The heads have definitely had extensive work done. Everything is pristine clean. Checked A5 hole(40psi), its bypassing the piston. Checked the injectors one at a time, all had a good spray, and consistent across the board. Checked the engine timing, it is bang on. Valve adjustments within specs. Reassembled the engine, it started and ran for about 15-20 sec, very rich, lots of smoke so I shut it off. Tried again cold it would run for about 3-5 sec, rich. Installed all the coolant hoses, and put in 19+ litres of G05. No leaks! Checked the temp sensor reading about 75k ohms cold. Jumped the connector to the coolant temp sensor, fixed a broken wire to the throttle linkage, pedal side. Cranked again, started and ran. Warmed it up completely. I will now button it up, and take it from there.
Cheers
Bears
Lots of talk about the idle bypass valve. Tried adjusting it. Ended up wide open. Blocked the line that goes into the left air box from the valve. Runs beautifully, super smooth, perfect idle. Impressed as well at how smooth the ride is. Thanks all for the input.
@RGK20m3 @Paul_M_Novak
Great day
Bears