I recently acquired a 1989 VJ-S V12 with 85,000 miles. It is in good shape, runs, but I have no service records. I need advice on a plan of attack to identify issues and optimize performance. My initial plan of attack (in general terms) is:
Ignition system evaluation - distributor evaluation, plugs, and wires - replace/service as needed
Compression check while I have the V area accessible
move injector harness off of block - replace if looks bad - will prob need to do this eventually, but would like to wait if it is OK now
Should I also remove fuel rail and inspect injectors at this point - or put back together and listen to injectors while running to ID issues?
If compression is bad (step back and re-evaluate - ?leak down test?)
ID where oil is leaking… (dye test) -
Attack cooling system…
I realize what I find will change the plan - but would appreciate input.
Thanks!
Hi John and congrats on the the new cat. I’m by no means a Jag mechanic but have been a mechanic for 45 years or so.
Before you dump a dime in the car, do a compression and leak down test. The tooling can be had for next to nothing at HB. Those two tests will lead you in the right direction. If they are poor, dump the car or plan on a major expense of engine rebuild.
I own a 96 Volvo 850 turbo with 145k miles. The Volvo web refers to a “stage 0” for a car with no history. Once the compression/leakdown is positive, pick a system. Be it fuel, ignition, suspension etc. Then restore that system to original condition. I did this with my 850 and it is a most reliable car.
I notice that a lot of guys jump all over the place and replace a bit here and there and not concentrating on a particular system. I think it is a false economy. If you have the coin, do entire system and do it right. You can bit and piece it but I think the reliability will suffer.
Compression check it is - hopefully I won’t need to do a leak down test (for now)
Going system by system makes sense -
The car is in great shape - interior - frame - body - suspension - etc. - It ran smooth when I drove it, and it was driven regularly. leaks oil - no smoke out of the tail - (I actually got two for the price of one - the 89, and a 90 convertible) - the 90 needs help - but one step at a time.
Ok. I may be going off-script here, but I do not advise pulling it apart to make sure it has compression. If it runs on 12 then it does. The injectors are all firing. The ECU does not need to be swapped out. Do not crush the car and move on. Lol.
Check that the fuel lines have been renewed. If not, renew them all. Including those in the rear. The fittings can be heated with a torch and separated for reuse. Use proper care.
Check that all cooling hoses have been renewed. If not, renew them all. Full sets are available as a kit.
Did the compression check (a first for me - so it took a bit of time - not mention retrieving #6A when I dropped it on to the bell housing - 3 hrs of fun …, but I did get a scope camera out of it). Anyway- did them first dry (D)- but had difficulty with good connection on some (threaded connector), and it was a new tester - then did wet (W) - the car hadn’t been running for 2 weeks;
It appears I may need to do some engine work (Leak down test first?) - but I don’t want to to do any major work quite yet (shop is not set up for this right now) - I have friends who swear by oil additives (Restore) - What about -do tune up (ignition) - change oil - do coolant system - do fuel system - and if not too much trouble, attack primary oil leaks. Monitor the compression - if OK - continue on with system approach, if not evaluate engine work.
Again it runs fine - but I haven’t pushed it until I feel a bit more comfortable as to its condition
(I would like to the engine re-build, but not without the right set up).
My dry we’re about 190 across the board. Did you make sure both throttles were wide open? Def makes a difference. I also changed my oil beforehand and ran the engine a bit.
At least you didn’t have any with no compression. I would change the oil a couple times over the next six months, and run some cleaners for carbon build up, then do another reading and decide from there. Clean valves and rings will help.
Yes - the test was with both throttles wide open - I am going to put it back together- and do as you suggest - then check the compression again in a bit -