[silver_pilate]

I've been having an intermittant dying problem with my 91 GT, and I just pulled the codes on my car. Here's what I came up with:

Hard codes: -85 : canister purge solenoid circuit failure (had that
one for a while)

Stored codes: -87 : fuel pump primary circuit fault
-96 : fuel pump secondary circuit fault / high speed
fuel pump relay open

Anyone have an idea what this translates to? A buddy had the same codes come up and said that his EFI book talked about the code 96 referring to a secondary relay which increases voltage to the pump under loads. Mustangs only have one relay (under the seat) and don't use a secondary relay.

Could the relay cutting out when it gets hot cause both of the stored codes?


Here's the history:

It's happened 4 times both before and after I changed fuel pumps (from stock to a 190lph). It happens after extended drives, usually at least 60 minutes or so. Amount of fuel in the tank doesn't make a difference that I can tell.

I will drive the car for a while on the highway (as I said, usually about an hour) and then the car will stumble very briefly and/or just cut off (has always happend after I slow down and come to idle speeds or get in traffic). Usually, you can then start it and make it run for a block or two, the engine stumbling the whole while. Then it dies for good. It will usually start, but won't stay running more than 5-10 seconds. After letting the car cool off for 45 minutes to a couple of hours, it will start right up and run just fine.

So, here's what I was thinking:

-Possibly the TFI module is crapping out on me. It's the original unit with 140,000 or so miles on it.

-Also, could possibly be the fuel pump relay getting hot and flickering out on me (possibly confirmed with the above codes)

-Also could be the fuel pump overheating and crapping out on me.

I've hooked up a fuel pressure guage to see what the pressure's doing when it cuts out. Fuel pressure looks fine at 37-38 psi, dorpping a little with light throttle blips. So far, after dogging the crap out of my car, I haven't been able to make the thing die. I figgured if fuel pressure looked ok, I would just replace the module, and if fuel pressure dropped, I would replace the relay and see if it cured the problem. I've got both parts in the tool box in my car so I can do the repair immediately.

Anyway, does anyone have any thoughts? I'm going to go ahead and replace the TFI module and keep the original as a spare, but I don't want to replace the module until I'm sure it's the problem (i.e. it dies, I repalce the module immediately and it runs fine). I just want to narrow it down and make sure I have the right problem.

Thanks for any ideas!

--nathan