Originally Posted by xjrguy

I think I mentioned this before. I'll not be happy until that fusebox by the washer fill neck is substituted. Internal connections in there can get intermittent, especially when hot.



Cheers,

Originally Posted by mike66

I remember reading in Nigel Thorley's book that the rotary switch on the early XK8's transmission can give a lot of trouble with oddball problems and messages. Don't know if there's a way to test it though.

Originally Posted by Spurlee

There are two hoses that heat the Throttle body. They enter and exit the TB on the backside by the firewall. Make sure they are not kinked or collapsed, replace with regular hose, no need to buy $$$ formed hoses, just use enough to make nice round corners.

Make sure coolant is flowing through them.

Also, make absolutely sure that the 4 wire plug on the TB is seated and remains seated while operating. I put a set screw in mine.

Good hunting!

Good luck

Originally Posted by Gus

Are you able to capture the FailSafe code?

Originally Posted by xjrguy

This is what he really needs, the non-generic code or codes that are generated after a no start/engine failsafe incident. The code we are interested in may not be visible to generic scantools sometimes.

For the most part I would discount the trans rotary switch for this, in my experience that throws a 'Restricted Performance' message. That is not concrete though, it still could play a roll.

For some reason oldfart's car is entering 'shutdown mode', which prevents it from running. The attached excerpt of a bulletin helps explain the various faults and messages. When reading it thoroughly you get the idea that he is dealing with a 'multiple failure' situation, which is why I am stuck on that fuse box; or relays actually. I know he says he has moved the relays around, I would like to see them substituted.

Cheers,

Originally Posted by Gus

Steve,

You know we keep dancing around on this project with TB, MAFS, Eng Temp and a host of other stuff but we keep getting a Failsafe and a no start until it cools down. So many things were covered I lost track. I personally keep going back to the TB. Why? I recently had Restricted Performance that did not bring up a code so I plugged in my OBDII and went for a drive RP came up and cleared on the dash but I caught it on the OBDII reader and it was the knock sensor, replaced it and all was good. It seems that every time this car gets up to operating temperature it shuts down and will not start. If this were my car I would plug in the OBDII reader and when it stopped or failed to start I would install a fuel pressure gauge and check for spark on the spot. I went to the onelines briefly and was unable to find anything that would prevent the car from starting that has not been covered. Is it electrical or mechanical? I like your flow chart and might be the answer to the problem. Right now I could not get there because I am overwhelmed with what was done so far. As for the transmission switch I was working with another guy trying to find a problem with his transmission and we found that the wire that is solder in the plug inside the trans was loose, re-soldered and he was up and running…

Originally Posted by OldFart

No. Even when the car is in failsafe, an OBDII reader only picks up the P1111 system check - pass code. I have been considering purchasing a code reader and leaving it hooked up while driving just to see if it will pick anything up.

Thanks,

Originally Posted by oldmots

A common weakness in these cars is the brake light/cruise control switch. If this switch is failing, it can set the failsafe light off in the early models. This part is not expensive but tricky to install. It is related to the cruise control as the brake light switch also houses the cruise control shut off switch. I tried to read some of the comments and did not see any mention of looking at this switch. My other way to deal with this would be when it seems like everything is going wrong at once, be suspicious of the center of everything, the ECM. You can remove this and send it to a rebuilder for $500. Before I did this, I would remove all the plugs on the ECM and clean them with electronics contact cleaner, both male and female sides.

Originally Posted by Gus

From the many posts I have seen I can say the this car has a problem with poor connections and cleaning them is the right thing to do. Every plug I come across I pull it apart and clean both sides and check it to be a tight fit.

Originally Posted by nine7xk8

gus if you were replying to me, the answer is no. when my transmission position switch took a dump the car did not get any spark from the ignition modules. on both banks. but it did have fuel. but you know that brake switch need to be replaced on early models also. i replaced mine as preventive maintenance for just 50 bucks. too bad im having a gearbox fault now. I know its the tranny. I just want to take the tranny and engine out of it and fix every thing like tensioners etc... trans and put it back together right.

Originally Posted by OldFart

Since I've discovered the car will drop the failsafe and actually start when put in neutral, I'm ordering a new switch today.

Can anyone provide me with the manufacturers name for this switch?

Or better yet a part number?

Thanks,

Originally Posted by mike66

New over $500, used at motorcars Ltd about $225. Yikes! Wonder if there's a way of testing yours? Any of you tech guys out there know, or is it substitute and see? Seeing how its a switch, maybe a schematic exists out there where it can be bench tested for continuity?