Hello
Still having the problem of intermitent no start with ocassional stall. Recently replaced the following: Distributor, cap, rotor, RSR, power stage (twice), plugs, wires and knock sensor. Both pumps were replaced within the last 2 years as was the fuel pump relay. Thought it was probably the relay, replaced it with old resoldered relay same problem. Re-soldered the newer of the 2 relays and still the problem remains. Car seems like it runs out of gas. Also just replaced the fuel filter. Car often restarts ok and runs good till the problem resurfaces. Checked the AMM and it appears OK. Any and all help is much appreciated. Have to get my wife's car back to being dependable or it will be my hide.
Thanks All
Brad

What shape is the battery & it's connections in? I was working on my 89 760 and had the battery out to charge it. I plopped the it back and and slipped the cables back on, but didn't snug them up really well. I thought they were on pretty well, but they would still slide around if pushed. There are 2 wires on the (+) side, and when I wiggled the smaller of the two, the car cut out, but would fire right back up. It's symptoms mimiced a lot of other well known issues (various relays, hall effect sensors, etc) . Maybe even check the other end of the wires. Clean them up really well and give them a coat of dielectric grease or something.

Thanks for the ideas. I will check those tomorrow. The battery seems fine and the connections are tight. I will clean and redo them.
Thanks Brad

Can you check your car for codes? I just resolved a hot start problem (RPM sensor) by checking the codes. I thought the FAQ said that 88-95 or so had this capability under the hood. Of course, I didn't resolve it on my own. I had help from others here.
--
John 16:33

Unfortunately my car doesn't appear to have that feature. I don't believe turbos got OBD till 1990. Would be slick if it did.
Thanks Brad

1989 wiring harnesses are fine. No insulation issues on these. What are the symptoms when the car doesn't start? You need to post more information when you make your first post requesting information. You could have multiple problems. Does the engine crank over? Does the tach needle bounce when cranking in a no start situation? Have you cracked open the supply side fuel fitting after a no start situation? The 1989 cars have a Radio Suppression Relay. Have you inspected it? I have never had trouble with one, but others including Don Foster have had Radio Suppression Relay trouble.

Add my name to the Radio Suppression Relay list. Same symptoms - intermittant no start, no spark, no tach movement, especially with damp weather. Mine was flakey fuel pump relay and the noise suppression relay, the last think I considered.

Jim Weiss
a more reliable 90 760, & 2 more

Thanks for the input. The new relays I have inspected have better solder joints, but I don't trust any Bosch realy which I haven't inspected and re-soldered as necessary. I even had one manual transmission OD relay which I could see nothing wrong with when inspected with a magnifying glass, and it worked great after being re-soldered.

Sorry, I should have provided more info. The car cranks fine. The tach needle jumps when the car is being cranked. The radio suppression relay is new. It was replaced in July. I will check if the car has fuel at the supply fitting as soon as it gets light enough to see. That is if the car won't start. The no start and stall occurs about 25% of the time. Usually the car runs fine. The problem of a stall usually happens within 50-100 ft. of a no-problem start. One thinks the car ran out of gas. Then after stalling the car usually restarts within a few trys. On a few ocassions it has taken a while longer to get it started. There are times when the car can be driven a couple of days with no problem. I am also questioning the in-tank pump. It is 2 years old. Could its failing cause these problems? Or perhaps the 2 fuel pump relaysI have tried are bad?
Thanks Brad
1989 740t

An intank pump failure will usually affect running quality when the tank is half full, or less. When the car is running, remove the gas cap and listen to the opening and you will hear the pump running. Have someone pull fuse 11 (if memory serves me right) while you listen and you will hear the pump quit.

If the tach needle continues to move (bounce) during the no run condition, the Hall effect is good.

The injectors receive power 100% of the time and are grounded by the ECU to open. Check for power at the injectors. Also check the condition of the Fuel Injector Ballast Resistor Pack (specific to turbos) which is quite near the battery, and the electrical connections to it. I have seen a questionable resistor pack that had suffered from corrosion damage from being so near the battery.

Thanks
I will check the intank pump and injectors for power tomorrow. Couldn't get the car to stall at all today.
Brad

Check the rpm sensor (LH2.4) or Hall sensor (LH 2.2): this is a frequent cause of hot restart or stalling troubles.

Hall sensor should be new, the distributor was replaced in July with a new one from FCP Groton. How often do the wiring harnesses go bad on a 89 740t? The car has 95k on it.
Thanks Brad

Your wiring harness should be fine. One question: when the car dies, does the tach needle drop immediately to zero, or does it decline with rpms? In other words, does the ignition system shut down? Or is it fuel injection-related?