Just to help the terminology along, the GM part is the ignition module. It's inside the ignition amplifier



I'm afraid you've been given some misleading info. Nothing in the GM module or the ignition amplifier has a "curve" or calibration.

However, there are many aftermarket versions of the GM ignition module and some are not as reliable as the GM part. Perhaps that's what the mechanic was getting at?

Cheers
DD

 

I just went through this with my '82. It would run fine at idle but when I press the accelerator, it would bog and go nowhere. At first, I could shut the engine off and re-fire and the symptom would temporarily go away. Then I replaced the fuel filter and the symptom went away temporarily. Eventually, even those two remedies did nothing. [fast forward]

I pulled the small plug from the passenger side tank and it dribbled for a minute and stopped. Without the fuel gauge working, I figured that was the fuel that was in the tank. I pulled the big plug and 3 gallons of fuel overflowed my pan drenching the myself and the floor as I frantically tried to put the plug back in. The big plug was FILLED with so much granular rust that it would not pas fuel through the small hole. I removed the screen which had several holes in it, which lead me to the obvious assumption that my pump was similarly full of rust.

My remedy was to add used off road diesel and an agitator. I used a Scotch Bright ball scrubber and welded the mandrel onto a 36" piece of 1/4" filler rod and used it in my cordless drill. Four cycles of scrubbing/agitating and draining as well as vacuuming (shop-vac with semi-ridged hose attached) in between. After which, I took the screen from the suction tube and removed the remaining screen from in between the frame. I dug through the shelf at the auto parts store to find a strainer sock that would suffice for modification (I think it was for a late model chevy truck). I cut the end off of the strainer sock just long enough to slip the original strainer frame inside it with enough left over to fold inward and create a seal. I replaced the strainer and plug. cleaned the crud out of the inlet side of my pump (has it's own screen), and replaced the inline filter.


Almost through a full tank of fuel and she runs awesome!!!!

now for the driver's side...ugh

 

And that, FG, is why I have never even tried using the passenger's side tank on my 87, lol. PO told me one of the solenoids was bad and it wouldn't switch over but the car runs and runs well off the driver's tank. I decided quickly that was good enough for me for now and have avoided the button on the dash like a plague less I suck a bunch of rust into the pump and cause myself problems. One of these days I'll drain that tank and see how it looks but for now, yeah, I've got one 12 gallon tank that works quite well, I don't even want to know what the condition of the other tank is for now.

 

Does anyone know where I can find a brass fitting suitable for replacing the changeover valve in the tank? It just occurred to me that perhaps the return valves and/or changeover valves on the car are not working as they should, and perhaps the changeover valve is allowing the car to suck gas from the wrong tank and sending it to the other tank. I've already had a problem where fuel poured out of the other tank (from the left to the right). I also noticed that in the right tank, I can see plenty of fuel but on the left tank, I see nothing when I look in the hole and push the flap down.

Perhaps it is just out of fuel??

Come to think of it, it DID suddenly die when I started up an uphill section, perhaps when the fuel would've moved to a portion out of reach?

 

Also, I noticed when I got the car to run (see video skip to 2:00 or so) 1983 XJ6 after replacing fuel pump - YouTube

I checked each fuel cap to see if there was any noise coming out of there. There was quite a bit of "sloshing/whooshing" sound with the caps open, indicating that fuel was being moved in some fashion. Now when I jumper the fuel pump to the battery, it runs, but I don't hear any movement at all.

Futhermore, when I look in the right gas tank and push the flap down, I can see plenty of fuel in there--I can see my reflection. In the left tank, I see nothing. Both tanks were drained and filled with exactly 5 gallons of fresh fuel.

I suspect that the left tank is empty and right tank is now filled with 10 gallons of fuel.

The changeover valve is stuck or inoperative, mandating that fuel be drawn from the left tank. The return valves are also, perhaps, stuck, mandating the fuel be returned to the right tank. This has created a situation where the car, trying to draw fuel from the left tank, which is empty. Therefore the fuel lines are filled with air, and the pump can do nothing.

It makes perfect sense! Unfortunately I can't just add a couple gallons of fuel to the left tank to prove my theory. That would result in the right side tank overflowing. The only thing I can do temporarily is to get a tee-fitting and bypass the changeover valve. So where can I get one?

 

https://www.jaguarforums.com/forum/x...at-back-66836/

Following up.