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Hi all,
My 92 v12 just brought me 850 miles and you may have seen my coolant leak thread. Now the leak is repaired, but the day after we arrived the car would not get down the road. It idles fine at 10k rpm but as soon as you hit the gas it has very limited power, sputters, stumbles, misses… I had lost about a gallon of coolant during the trip. The night I arrived at the very end it had good power and ran fine.
Just prior to the trip we replaced plug wires, plugs with NGK, cleaned up the original marelli cap and placed a new rotor. Ignition has been checked and each plug wire shows they are firing.
I now have the car at a local jag shop where owner has a 86 v12 XJS and he is going to replace fuel filter and check fuel pressure on Monday. Had to order a fitting for the fuel pressure kit as it appears the plumbing is new to him.
I’m having trouble thinking this is unrelated to loss of coolant or somehow related to the 14 hr. trip.
I also discovered upon arrival I was low on oil. Oil removed showed no sign of water in the sump. I drained and measured 6 liters of oil.
Car is now holding coolant and has fresh oil and filter. So it seems we just need to follow normal troubleshooting procedures, but am curious if there are additional suggestions to get back to a smooth running state.
Did the engine overheat as a result of the coolant loss? If so, how badly and for how long?
As for oil, the engine holds about 11-12 litres so if you drained and measured only 6, you were running with significantly low oil quantity.
Stumbling and low power aside, how does the engine sound? Does it sound like it's been damaged? Clattering? Knocking?
If the engine sounds OK and we take the possibility of internal damage out of the mix, the running problem could easily be purely coincidental. These things crop up on used XJSs....most have which have never received the amount of TLC they require.
I'd say your mechanic is taking a reasonable approach. If he hasn't already done so ask him to empty the contents of the fuel filter into a clean glass jar. What you/he sees (or don't see) may well dictate the next steps. Fuel system gunk/rust is common on older XJSs....especially if they've seen little use. Was this this car used very little or in storage ?
Overheated? Not according to the gauge. It read normal throughout. I watched it continuously after I discovered the leak.
No new noises. I know it was pretty low on oil... manual says 10.7 liters including the filter. So it was about half full.
The car did sit sit for a while with the prior owner and I have certainly woken it up on this trip. It lived on an island with no chance of going over 40-50mph since 2004. It saw very little use. Mileage is currently 53k.
My first leg of the trip was 2hrs highway and a bit around town with no issues. Next day was 14 hrs at ~70 mph.
The 'could be' list is long but my gut feeling is fuel tank rust was stirred-up.
Not sure about your '92 but earlier models has a small 'sump tank' in addition to the regular gas tank. These sump tanks are a bit notorious as gunk collection pits.
Never a great idea to rely on the temp gauge when you know you're leaking coolant because as air enters the system the temperature sensor will start reading the air temp as opposed to the water temp which is often much cooler. Not to be the voice of doom but your engine could have been severely overheated and the gauge could have read nominal due to the lack of fluid contact. That being said, if the engine sounds fine, without any clattering or knocking, you probably have gotten away with it.
Starting with the fuel system is the best bet, if that turns up nothing, ask your mechanic to put it on a scope and check for electrical gremlins. Any number of electrical items under the hood could've gotten too wet or too hot.
In addition, I would first dry out all the ignition components. Separate plugs, pull the HT leads and blow out the plug wells, etc etc. I think water in the ignition somewhere is a very likely cause.
Here’s an update after a long spell of inactivity. We got the fuel pressure tested today and it showed a max of 19 psi. Suspected fuel pump failure so we will replace that tomorrow. Hopefully we are back on the road after that.
Here’s an update after a long spell of inactivity. We got the fuel pressure tested today and it showed a max of 19 psi. Suspected fuel pump failure so we will replace that tomorrow. Hopefully we are back on the road after that.
But change the filter too, and check the sump tank, as if that is full of rubbish/sock filter blocked, you will total another pump.
After all the work that you have done, changing the Spark Plugs etc, it would seem that you have left your 'Shop' with the easiest job
As changing the Fuel Pump and Filter is one of the easiest and the cheapest jobs you could do on your Car, on the assumption that She hasn't got one of those In-Tank Fuel Pumps
Easily done in a couple of hours, even if you have never fitted a new one before and since those Pumps are generic and fitted to lots of different Cars, you could get a Brand New one on ebay for around £30 (UK) with a New Filter £10 (UK)
So cheap enough to replace it, just for the hell of it (like you might do an Oil Change)
But the one thing that hasn't been mentioned is the FPR (Fuel Pressure Regulator) on 'B' Bank, as if the diaphragm has gone, that could very easily explain your loss of Fuel Pressure
So ask your 'Shop' to put a Clamp, on the Fuel Return Pipe coming out of the back of that FPR and then if the Fuel Pressure goes up, then it could well be the FPR that's the problem instead of the Fuel Pump
Which could also explain your loss of power
In any event that's gotta be worth a Shot
FPR on 'B' Bank with return pipe at the back and if the diaphragm has gone then that could affect the Fuel Pressure
Last edited by orangeblossom; 10-16-2018 at 01:55 PM.
Oh man this last idea came too late. I just finished removing the fuel pump. It was in the tank, but not the hardest job I’ve done. Someone had been here before me. The old pump system has been slightly “renovated”. The new pump will be a challenge to retrofit into the OEM in-tank system. It will be interesting to see the pressure test result once we have it back together. Will send another update later this week.
Last edited by gccch; 10-16-2018 at 03:35 PM.
Reason: Photos
fuel pump was replaced along with the canister it sits inside the tank. All is well again. I was just reunited with the car after travel and it runs like it did before the long drive and coolant leak. So this was one lousy coincidence.
I’m now on to smalle things like entertainment and comfort (AC)...
09-23-2018 | 09:32 AM
92 v12 loss of power, missing
