Loss of power, missing

(Greg Heitman) #1

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.

(equiprx) #2

First thing I would do is pressure-check the coolant system.
You said the leak was repaired, but what did the repair involve?
Was the thermostat checked, replaced or what?
How about the cooling fan and thermal switch/relay?
Just because the coolant is not getting into the crank case or leaking out when idling or static, doesn’t mean it’s OK.
Loss of coolant could be an effect or a cause of head gasket failure.
Are you getting any exhaust smoke? Blue, white or black?

(Aristides Balanos) #3


When was it the last time that you’ve checked the oil before that ?
What I mean is, in how many Km your engine loose 6 (!!!) out of it’s 12 litters of oil ?
If you don’t have a MASSIVE oil leak the answer is obvious…
And plus the overheated long drive…
I think only a compression check will answer all these questions.

I hope for the best.

(Greg Heitman) #4

I checked the oil mid way on my long trip, so with about 400 miles to go. At that time it was reading low and having been just run perhaps more was draining into the sump. This is definitely on my mind as a concern…

(Greg Heitman) #5

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.

(Greg Heitman) #6

Been out of town for a month. Car is back together with a new fuel pump assembly in the tank. It’s all good. Even my check engine light is off!

Now for some radio and brake work.