Ok, always thankful for the help and today I have posted more than I do in a month. Heres the story: I bought my US87 928S4 Auto (161K) a few years back (physically unseen) from a guy in NY and had it shipped to NC. It ran, but after it go warm, it would shut off. I found some perished breather hoses and disconnected vacuum (or missing) lines and decided to do an intake/valve cover refresh (engine bay was a tar pit due to the hoses being perished). I replaced all the hoses (oil, coolant, fuel), seals, vacuum lines, fuel pump, tank strainer, fuel filter and knock sensors. I turned the key for the first time in a year today and it started (big relief for me) and then, after if got warm (about 10 mins), it died. It will crank strong (unitl the battery dies), but will not fire up. I tried pumping the gas when cranking and no help, just a lot of turning. I tried disconnecting the main ground for a min and reconnecting-no help. I have also cleaned all grounds. I know that some may be thinking this in TBF (maybe it is), I have tried to measure it (crank play), but each measure gives a different reading on my caliper (hard to place this thing in the same place to make the measurement). I also changed the left sensor (passenger side) on the water bridge. What would you do next? I will replace the fuel pump relay as I read a post about it fixing a similar issue yesterday. Could it be a sensor telling the car not to start because of heat? Does this sound like TBF (it turns strong (until I drain the battery in frustration). Anyone near east NC like doing crank play measurements? I have had this car for almost 3 years and have driven it .25 miles-very disheartening. Thank you for all replies.

 

When the engine runs for 10 mins does it run well? Can you drive the car?

The obvious is you have all you need for it to run and something quits.............does it die immediatley or does it splutter?

How is the O2 sensor or the TempII sensor?

Did you change the oil? if so was there lots of sparkly bits?

If the car was in front of me I'd be looking at the fuel system.

 

it runs ok (not awesome though ). It will drive and will leave rubber behind. What I have noticed is that everytime I start it, the power (not electical) is not the same. One time it will burn out and the next time, when floored, it just goes like my Audi. Then I park, let it idle, and then off. No sputtering, it just quits. All the lights are still on though. Where is the temp 2 sensor located. I changed one temp sensor on the water bridge (left one-passenger side). The O2 sensor may be original. It has also had the smog pump delete (I think) if that helps.

 

You need to follow a good diagnostic tree. The workshop manual has a lot of good diagnostics information. The easiest and fastest test is for relays.

a) Do you have spark? If no, start with the EZK relay testing. Is there 12V at relay socket 30? If no, that needs to be fixed. Next jumper EZK relay socket 30 and 87. If still no spark, go to the workshop manual for specific tests.

b) If you have spark, start with the LH relay testing. Remove the LH relay. Is there 12V at LH relay socket 30? If no, that needs to be fixed. Next jumper LH relay socket 30 and 87. If still no start, go to fuel pump relay test.

c) Remove the Fuel Pump relay. Is there 12V at fuel pump relay socket 30? If no, that needs to be fixed. Next jumper fuel pump relay socket 30 and 87. Do you hear the fuel pump running? if you have a fuel pressure gauge, confirm the pressure is to spec and that after turning off the pump it holds pressure to spec. If still no start, go to further diagnostics in the workshop manual.

 

My initial thought is, "what would malfunction when engine got warm (or hot)"? Certainly, some electrical parts/sensors might do that. Is it related to the water temperature, oil temperature or the engine block's temp?

Maybe that is the delay, IE that things don't all warm up at the same time.

Just a thought.

Joe

 

Thank you Rich, I will try your instructions tomorrow. Dumb question, is the key turned to accy during these checks or does it need to be in at all?

 

I'm with you on the senor Joe, just which one? I could try disconnecting them one at a time when it stalls and see if it starts then-would that work. Could it be the MAF (read a post on that one). If it was TBF, what would I notice?

 

The 30 circuit should always have battery voltage. Jumping 30 to 87 accomplishes what the relay does, turn on the circuit.

You crank the engine to see if it starts and if it will stay running with the relay position jumpered.

One of the relay failure modes is not conducting current as they heat up. This test will find out of that is your problem.

The temp II sensor could also cause problems. It is the sensor at the front center of the engine that has two wires plugged into it.

If the ECU doesn't know that the engine is cold, it does not provide cold start enrichment and it will not start. Eventually after cranking enough, there may be enough “raw” fuel sprayed into the intake to start the engine. You would see smoke after starting because the fuel wasn’t metered properly.

The Temperature Switch II is located in the front center of the engine just to the right of the fuel pressure damper.

1. Check the plug to the sensor, is it on tight? Are the contacts clean? If not, clean the connectors and clip it on tightly. Check engine starting now. If it does, you’re done. If not got to step 2.

2. To check the temperature II sensor, you’ll need an ohm meter. Remove the connector from the LH control unit. Connect the ohm meter to LH connector pins 13 and 5 for 1987 and newer 928s, and pins 2 and 5 for 1984 – 1986 LH equipped 928s (not to the pins on the module itself). The correct value ranges are:

0 C / 32 F: 4.4 - 6.0 k-ohm
15 – 30 C / 59 - 86 F: 1.4 to 3.6 k-ohm
40 C / 104 F: 0.9 – 1.3 k-ohm
60 C / 140 F: 480 – 720 ohm
80 C / 176 F: 250 – 390 ohm

Since your problem is a stall after starting, you could just look for the proper resistance range for the engine when it stalls. If the sensor is shorted (zero ohms resistance) the mixture will be too lean and the engine will not start when cold. For problems at other engine temperatures, I’m including all of the resistance ranges for higher engine temperatures. If the sensor has an open circuit (infinite resistance) or the plug is not connected to the sensor, the LH module logs an error code and uses an 80C / 176 F engine temperature “limp home” value. This would cause hard starting, the gas pedal would have to be pressed to enrichen the mixture for starting.

If the values aren’t correct, measure them directly at the Temperature Sensor II. You’ll see that there are two prongs on the sensor. There are two separate temperature sensors housed in the one sensor body, one for the LH and the other for the EZK module. Note the orientation of the protruding alignment notch on the outside of the sensor. If you are viewing the alignment notch orientated to the left side, the prong closest to you is the prong for the LH controller and the prong further away is for the spark control module. Clip one of the ohm meter leads to the prong closest to you (LH) and clip the other lead to a ground point [Do NOT connect the ohm meter leads between the two prongs of the sensor]. Repeat the resistance measurements.

 

Wow Rich, I know that took you some time to type out. Thank you for your time and patience. I will try that out tomorrow after work.

 

Check the wiring at the MAF connector along with the wiring at the O2 connector.

 

When I hooked up the MAF yesterday it looked good as well as the 02 sensor wiring (initally-while I was hooking up that POS vacuum line to the trans). I will follow it back to see how it looks after the checks Rich recommended. Soooo, I assume this does not sound like TBF so far? If it was TBF it would have a hard time turning right?

 

Hey CJ,

I think its interesting that while the engine warms up, everything seems to run great.

It's when the engine is warmed up, you have problems. It sounds like the ECU (or car puter) is getting or giving out some bad signals.

The fact that it runs, rules a lot of things out. You are getting fuel, fire (spark) and air during the warm up. Its just which one of those stops when the engine is warm.

I am like you, first thing I would do is check the obvious, check for loose, corroded or worn electrical connections and wires on all the sensors, etc. around the engine. Things that would tell the ECU to shut down fuel or fire.

In general, a lot of problems are just bad connections, IE the "bang the TV" fix that worked in the analog days!

Joe

 

Id be looking at a connection that has high resistance, and once it gets warm..shifts, doesnt connect well anymore.


O2 heater/fule pump fuse, or fuel pump relay.

You could...start it, let run till it dies, then check for 12v across the two pins on the O2 sensor..unplug it below the CE panel, and the two pins you wanna check for 12v across are the two of the three..of the same gender in the plug. The odd pin out is the O2 sensor voltage return itself..so not that one.

That'll tell you the condition of the FP fuse part of the panel...itself.

Then go to relay, bypass it, see if it starts right up.

 

Isn't thrust bearing failure characterized by a car that dies when it is warm and runs fine when it is cool... Man I hope that is not what you have... When was the last time the end play was checked and the tension on the Thrust bearing relieved???

 

If TBF was a culprit...youd know by how it doed.

Just died up and right now, or did it labor to its death as the tolerances decayed I would think.

Loss of fuel or spark..it'd spin a few times after losing it..TBF lockup..no after fire spin?