Hello Friends,

Here's a good trouble shooting problem -

A little history -

1990 740GL Wagon - Regina system - Non-turbo

Replaced In-Tank Fuel pump (only pump on Regina System) in Dec 2001 after increasing problem of stalls at stops. Ran great until now.

Same symptoms started showing up about a week ago. Computer fault codes: 321 and 122. Replaced Aux Relay but did not replace Air Sensor as dealer did not have one in stock.

Have been dealing with intermitent short in ignition and #5 fuse (dome lights, radio, etc).

Had a more experienced friend look over things and discovered several vacumn tube problems and a very dirty air intake valve (on right side of engine, under trottle body). Cleaned out the valve and corrected faulty vacumn tubes. New fuel pump seems to be functioning as we can hear it running when the ignition is on. Ran fine - no stalls - all the way home last night.

Went out thirty minutes later and starting was sluggish but managed to start. Traveled about 12 miles to a ball game and parked for about 2 hours. Noticed a little faultering at a few stops before reaching destination. After game, attempted to start - turned over a couple of times but did not start. All subsequent attempts to start were unsuccessful - in fact - there was no response what-so-ever from the engine when turning the ignition. Battery seems to be fine - lights are strong, etc. Tried to jump it - still no response from the engine.

Any ideas would be most appreciated...

Assuming that the cam is turning, you have either a fuel problem, or an ignition problem. Is the tach needle moving when you try to start the car? If it is, the ignition is probably okay. The 1990 model year has a failure record with the RPM sensor. Several brickboarders have reported trouble with the Power Stage. The Power Stage is the ignition amplifier and is mounted on the front left inside fender well. Is there fuel in the fuel rail? To find out, crack the delivery fitting open just a little right after you have tried to start the car. If fuel sprays everywhere, the fuel pump is working. there have been numerous problems with the Fuel Injection Relay and the Radio Suppression Relay on your model of car. The Fuel Injection Relay runs the fuel pump, while the Radio Suppression Relay supplies power to the injectors which are opened by grounding them at the ECU. Your model of 740 has LH 2.4 Jetronic and there is a failure history of the ECU. If the AMM is bad, the car should still start and drive, but poorly in what is known as the limp home mode.

A quick and easy test of the radio suppression relays is to swap them for each other. On your car I believe they are mounted on the passenger's side strut tower. Two relay boxes (black?) mounted side by side. Unplug them and swap them to the other's position and try starting again. If it starts you need to either replace the relays (if you have $$$ burning a hole in your pocket) or open them up and resolder them (see FAQ's for more information).

FAQ's also show fuel pump relay location. Eliminate that as a possible source of the problem by resoldering it. Can you hear the pump short cycle when you turn the key to the "on" position? If not then I would suspect this relay.

If you have problems pointing a finger at either the fuel system or the ignition then I would spray some starter fluid into the intake and see if you get a momentary running engine. I had a 90 740 with the Rex Regina and even though the pump would run and cause fuel to flow to the rail it wasn't producing enough pressure to make the system function.

Good luck.

Randy