I recently installed clear coolant filters from Summit Racing on my 89 HE V12.



When checking for leaks, I ran the engine for a about 10 minutes and cycled the throttle between 1,000 and 2,000 RPMs.

Eventually I could see indications that coolant was through the B bank filter into the radiator. But I never saw any sign that coolant was flowing through the A bank filter. And the temperature gauge on the dash never got higher than midway between C and N.

So my hypothesis is that my A bank thermostat is not closing off the bypass to send coolant to the radiator. But that would imply that the entire engine is being cooled by only the flow from the B bank through the radiator and out the lower pipe to the water pump which feeds both banks.

Given the reputation for overheating, I’m surprised this would be sufficient to keep the temperature on the A bank (where the sensor for the dashboard is located) at what appears to be a normal operating range.

Or since the B bank tends to run hotter, that thermostat should open first. Did I just not stress the engine enough for the A bank thermostat to open? Prior to this, readings on the dash gauge have not gone above N, even when driving the car hard on a summer day.

I am reluctant to push the engine harder until I have a better sense of what might be happening…

 

When I shut the engine off, the Aux fan did not come on — which it usually does when driving around

 

My first thought is "air pocket"

Did you bleed the system after installing the filters?

Cheers
DD

 

I filled the system using the “jack up the LH front” method which has worked for me in the past. But this time, after filling the system I had to drain and refill the Expansion Tank after I realized that I had forgotten to torque a jubilee clamp. Not sure if that would cause the air pocket but can try draining and refilling the whole system later tonight...

Thanks for the suggestion

 

Decided to take the car out to see if a short drive would cause the A bank thermostat to open vs. just idling in the garage.

The car felt very sluggish and transmission had difficulty shifting gears. Immediately turned around and pulled back in the garage and shut it off.

Popped the bonnet and restarted it. Quickly determined the B bank air intake trumpet was sucking in air but the A bank was not. Manifold on the B bank was hot but A bank was only warm.

Decided to call it a day and ponder it further over an adult beverage.

Think I have the dreaded Marelli distributor short. If so, lucky it happened at the outset when the cats were cold so I didn’t immolate myself and the car.

Will remove the distributor tomorrow and have a look. Is it possible to buy a replacement Marelli distributor anywhere? Or can I get buy with the silicon goop fix?

 

You must also check to see if the catalyst on the duff side has melted and blocked the exhaust. Also, you must change all the plugs, and HT leads if not recently new, as Baxtor in Australia has experience that proves that poor plugs and or leads are often the root cause of a Marelli failure.

 

Greg, how do I check for a melted cat? Observation at tailpipe, or do I need to remove the cat from the the car, which sounds like a big job.

Fortunately, plugs and leads were replaced a few months ago...

 

This sounds a little off to me for the normal Marelli problems. Both sides should be drawing air, but one side isn't getting spark, and isn't its usually the B bank? If the A bank isn't getting any air I'd investigate that first. Is the throttle plate opening?

 

Both sides should be drawing air but the left draws a lot more than the right at low rpm, which is perfectly normal and, in and of itself, is no cause for concern.

Cheers
DD

 

Clearly I am repaying some sins from a previous life...

Removed the distributor. Delighted to see no scorching or other signs of a short.



No scorching here

Or here

Or here either

Proceeded to cut off the post using a rotary tool. Took longer than expected and went through several disks.



Pausing work for a glamour shot

The finished product, stub removed is sitting on the bottom wing of rotor for dramatic effect

Put the silicone sealant in the asterisk shaped hole, waited 30 minutes and reassembled everything. Checked the photos I took during disassembly to make sure I put the rotor back on with the proper orientation. I am 99% sure I put it back on correctly.

But now the car won’t start. Cracks fine, but never catches.

Not in a happy place, so postponing removing it all to check orientation of the rotor until tomorrow.

Until then, does anyone have any bright ideas? If I put the rotor back in 180 degrees backward would it cause the above symptoms, or would it instead run roughly?

 

Just a thought. Have you got the coils connected to the correct terminals on the distributor cap. I managed to twice to get this wrong. Engine spins but won’t run.
Rob.

 

Or, have you checked that in replacing coil plugs tangs on the receiving coil end didn't get bent out of line,,, not going into the receptors of the plugs...

More,,, that the upper and lower coil plugs are on the right coil...

This car has taught me to be very careful about getting into and doing 4 things at once.

Did something come undone when you were working in the upper corners of the radiator working on the hoses? Spill water into the resistor pack,,, anything? Disturb grounding points on the RH or LH upper rad earth points?

I'd bet it's something painful but simple.

 

This was bugging me enough that I couldn’t let it go. So I disassembled the distributor and tried putting the rotor on backwards. It won’t go — the two mounting holes are aligned in such a way that it only fits one way. Pretty clever of someone in Jaguar engineering to think of that.

I reconfirmed that A and B bank coils are connected to the correct terminals in the distributor cap. I reconfirmed all the HT leads are connected to the right terminals. I doubled checked that all the connections are secure.

I’ve gone back over the whole engine bay looking for wires or vacuum hoses I might have displaced when changing the cooling hoses. Nothing looks amiss.

I didn’t spill any fluid on the power packs when draining the rad since I used a vacuum extractor (which works quite well, by the way).

Is there a way I can check if the HT leads are getting power? If so, than I can try to rule out the spark side of the equation (plugs are relatively new) and move on to the fuel side...

 

I double checked the A bank throttle body. The butterfly valve opens and closes normally with the air filters out. I replaced the filters with new Wix filters of the same model, so I don’t think they would be causing any obstruction.

 

Remove an HT lead from a plug, expose the connector by pushing back the boot (or unplug the lead from the dizzy and use a spare piece of HT lead with no boot) ask a helper to turn over the engine on the starter, while using an insulated pair of pliers, hold the lead about 4mm from the engine (eg the manifold) and look for a fat blue spark.
Test one each side. I feel you have no spark.

 

I agree with Greg, and believe your first step is to test that you have spark on both banks A & B. I suspect you won't it have it on Bank A.

Each bank has separate Power Modules and Coils so that is 2 potential points of failure for just Bank A. You might find the official Jaguar Marelli Supplement helpful which I'll add below.

 

I ran a version of Greg’s test using an old VW spark plug I had lying around. I connected this loose spark plug to the HT lead for the 2A cylinder and cranked the engine. I repeated the process for the 2B cylinder. I had spark for both banks.

So I guess it’s a fuel issue. The fuel injectors were recently serviced and confirmed to be operating properly.

But when I was performing my radiator hose leak test, the car was very low on fuel. I also ran the car for some of this test with the front end jacked up. So is it possible that part of the fuel supply has run dry and has an air pocket in it?

I read somewhere on the forum about “priming” the system by cycling the ignition between on and off a few times, but that didn’t make a difference.

For lack of a better idea, I am considering removing the extraneous fuel supply regulator to see if that does anything.

Suggestions?

 

I've opened the fuel lines on my ol lady more times than I can count and I've never had to prime the fueling system,,, certainly not one side/bank over the other. I have a hard time thinking that one entire bank of injectors stopped functioning properly and aren't getting fuel, and not the other, because of a an air bubble. But I have been WAY wrong before.

Are you sure that your AIMs and tentative conclusions in diagnosis for the rough running and stall/no start is on the mark,,, in the first place?

-Can you hear the fuel pump?
-Can you remove the fuel line from the RH regulator or rail to test for fuel using a bucket during the 2 second prime when you turn the key...

Are you out of gas?

 

I can at least rule this one out! I poured in 2 gallons of fresh fuel from a can.

I have no confidence in my prior diagnosis of no power and now no start. After replacing the radiator hoses I ran the car for about 10 minutes in the garage and it seemed to be running fine.

It was only when I tried to drive it that there was a noticeable loss of power and difficulty changing gears. Those symptoms coincidentally matched what I had been reading over the weekend about the dreaded Marelli. So I did the silicone goop fix as a something I had planned to do any way.

I’ll check the fuel pump for sound when I have a willing helper, but the wife is annoyed with all the time I spent in the garage over the weekend, so it’s going to take some charm!

In the meantime, I had previously had a check valve installed on the B bank fuel line when it was serviced, so I may see if my local parts store has a loaner tool I can use to check the pressure...

 

Have you changed the fuel filter? That is classic symptoms of a restricted fuel supply and when you ask for more power it goes lean and had no power. Could also be caused by a pressure regulator sticking open and you have low fuel pressure.