OK, folks, I'm getting close to that point where I call the tow truck and have them pick up the car. That's only happened one other time and the shame lasts for weeks, so help me if you can.

1989 760 turbo wagon, suddenly developed rough running, noticable power loss, and stalling at stoplights. All in the course of one 30 mile trip. Next day car wouldn't run and hasn't since. Spark has been verified by timing light on #1 cylinder giving flashes appropriate on the crank pulley during cranking. New plugs, wires, fuel pressure regulator, fuel pump relay, and fuel pump have been installed. When I replaced the fuel pump, I did not get a gusher from the inlet line to the fuel pump. It did flow, but I was expecting a gusher. I thought that might have been due to the gas cap being on and forming a hydraulic lock on the tank, nut maybe this is a sympton I'm misdiagnosing.

After cranking several times with new fuel pump, I cracked the line to the fpr and didn't get spayed. I thought this was supposed to pressurize when cranking and not bleed down right away. Is this anther clue I'm missing? I have been unable to change the fuel filter because the filter turns with my wrenches on it. I was hoping to change the fuel filter at a DIY session on Saturday, but now I may not be able to get it there.

ANY thoughts and commments would be gratefully accepted.

Thanks,

someguyfromMaryland

Here is what is going to be the whole story in about one step.I have a lot of problems with the one I bought too.Here it is your not going to get a mechanic to find these little problems.My had a heat sink that acted up [on fender],a acc vac pump bearing wore out,massive harness decay,electric fan seized,fuel pump relay broke coil wire,system relay not setting at all,windsheild rear motor goes on-off,chimes are always on,gauges worked somewhat,no spark[coil],hall sender needed work,and still cant get fuel to the injectors because of a weird problem I am trying to find.Your car may have a blocked crankcase breather doing alot of bad things to the air flow[first thing first]If it runs your in luck I spent some time on this and will get this solved soon.Usually the harness gets the whole electrical shorted before it quits.I MADE IT SHORT!

Thanks for the reply, Jon, but I think you've actually made it little too short to help! I appreciate that you're having a hard time with your car also, but if you were trying to point me in any specific direction on mine, I couldn't tell. The heat sink on the fender you mentioned, I assume, is the ignition contol module (aka power stage, I think). If you could have given me some advice on how to definitively test this for failure, I would have been ecstatic.

The rest of your description sounds like a shopping list of problems to be tackled one by one, I'm sure. My biggest problem is not having diagnostic tools capable of testing any further than I have so far. So........ the car was dragged off to the shop this afternoon. Hopefully the shop has the tools and personnel to adequately troubleshoot the car without throwing more parts at it without confirming the problem.

I'll let you know how it turns out. Good luck on yours. If there is a specific question you'd like to ask me or the rest of the list, don't hesitate.

someguyfromMaryland

been thru this before w/740 and I have to ask if when you replaced fuel pump: which one -in tank or main pump? Intank pump hose(S) could be bad,etc but it sounds like a delivery problem and you want to narrow source of problem down.It seems to point possibly to prepump feeding your new main pump? post back please,your help will come from bricksters with a lot more expertize than myself! GOOD LUCK.mark

Mark,

I changed out the main pump. The prepump is making smooth running noises I can hear from the tank fill line.

I'm wondering if there is a definitive test on a coil besides measuring resistances. I've been told you can have acceptable resistance readings and still have a coil with shorted windings that won't provide enough spark.


Still on the list to check are the Hall sensor, ECT sensor, ECU, and fuel filter. The Hall sensor is doubtful since the timing light shows a flash at the appropriate times while cranking.

Thanks for the reply.

someguy

Have you checked for proper operation of the injectors via a NOID light?? (available at most autparts stores) ... just a lightbulb that plugs into where the injector goes...

Cliff Scott
89 740 GLE 16v

Cliff,

Never heard of a Noid light, that's a new one for me. Towed the car to the shop this afternoon because I felt I had run out of diagnostics I could perform with what I have in my shop. Had I determined the injectors weren't getting a signal, I wouldn't have been able to pinpoint the failure. The ECU, ignition module, coil, etc.. can be marginal and still show signs of life to crude troubleshooting such as mine. I have a Radio Shack analog multimeter that I actually use for measuring resistance in the tenths of volts by subtracting out the known resistance of the leads and using the difference in a series loop.

Someday, I'd like to get a decent fluke autoranging VOM or an analyser, but they are hard to justify when you don't need them but once in a great while.

Thanks for the reply.

someguyfromMaryland

Certainly I am not the best at this troubleshooting thing as I have been tackling the same problem for a month now, but anyway when you crank the engine does the tach move? As for the fuel filter I am not sure what you mean when you say it turns with your wrenches on it. If your filter is the same as mine it has a large(1 1/16 maybe) nut that you hold while a 3/4 or so wrench will loosen the banjo fitting and the same with the other end. This is straight forward though so I am thinking yours is different. I too know about shame.

Tach doesn't move much at all, but the timing light fires. That's why I'm thinking the spark and timing are good. The flats on the soft Al filter casing just twist through the wrench when I try to bust the filter loose. I'm thinking if I had an impact (air or electric) the instantaneous torque would probably work to loosen the fittings. That's why I wanted to get it to the DIY session.

Thanks for the reply.

someguyfromMaryland

When my gas filter nut spun without freeing up, I had to take the whole pump / filter carrier off of the car, remove the fittings that I could off of the pump-side, put the filter in a vise, cut it open and then get a wrench (or was it vice-grips or similar) on the inside of the filter that was turning freely and that way loosened it up. Whew! what a job.

I'll be interested in the solution to your bigger problem. I'm dealing with something similar right now.

My solution to the bigger problem was to call the tow truck this afternoon. I realized I was getting into serious hours spent troubleshooting with inadequate equipment. Normally I can figure out what's wrong within an hour on a car and the rest is repair time. I've put hours into diagnosing this nostart without success and it's time to give it to someone with serious engine analyzer equipment, fuel pressure testing gear, etc.. I'm hoping a certified ASE master tech can figure the problem in an hour or two at the most.

someguy