I have a 1991 740 n/a that just won't stay running!
The catalytic converter went out a while ago and it plugged the exhaust. I went to start it this morning and it didn't do it's usual crank twice and then fire. I cranked it 3 times, it fired up and then I put it in gear and it died again..... I pushed it back up into the driveway and pulled the muffler off and pulled a bunch of the honeycomb out of it. Then I tried to fire it up again with no muffler and it does the same fire up after cranking like 3 times then it dies. When I press down on the accelerator it sometimes will rev up and sometimes will die, but it dies after about 3 seconds anyway. I tried to fire it up with the cat removed and it still does the same and blows black smoke out of the tailpipe...
WTF is up with this thing?
I replaced the plugs, wires, cap and rotor about 6k ago. The crank position sensor wire is chewed a little, but my logic tells me that it wouldn't fire if it was bad. What's up?

 

If I unplug the tps it will start and idle for about 15 seconds and then it dies again... I just cleaned up the coil contacts too, but it didn't help.....

 

No engine or ignition codes either.....

 

Fuel pump is running and the relay is good, too.

 

No ideas?
Well, I tried taking the crank sensor out and when I was loosening the bolt the ear on the bell housing that holds it in snapped off. I JB welded it back on and it stuck.
Should I be concerned if it's not attached perfectly straight? It just counts the ticks from the tone ring on the flex plate doesn't it?
It fires up just as good (bad) as it did before I broke it.

 

I have fuel pouring out of the fuel line at the rail when I turn the key on and even more when I crank it.
I also have 11.8 volts at the coil with the key on and 10.5 while cranking.

 

Okay, I'll try my best to help since your pleas for help are going unanswered.
Pull a spark plug after cranking it, and preferably after it runs for a few seconds or so. Is it wet or dry?

 

Could you be having an ignition switch problem. If you jiggle the key after it starts will it stay running. Maybe you have a coil going bad. Are all of your instruments reading while the engine is running. If you by pass the TPS and plug off the IAC valve will it start and will it run.

 

If I bypass the tps it will run...longer, but not by much. It'll run for about 5-10 seconds instead of 1. Same goes for unplugging the iac. If I block off the iac it won't start at all. I haven't tried jigging the key a whole lot, just a slight jiggle and no improvement/worsening. Correct me if I'm wrong, but 11.8 volts rest and 10.5 while cranking with the coil removed sounds normal to me with a battery measuring 12.0 volts after cranking on it all day.

If I really ohms between the coil terminals or the terminals and the lead end what should I be getting?

Oh, and I pulled the #1 plug 3 times during the whole ordeal and it smelled gassy, but wasn't wet with fuel. All of the plugs are black from running rich, probably from the ects being mostly dead. Either way the car starts the same as it has been for a while, it just doesn't run more than 1 or 2 seconds.

Thanks for the help!

 

I'll try the combo of unplugged tps and blocked off iac too to verify. And my instruments are working, all dummy lights go on and off like normal, tach spins up (and down) fuel gauge winds up (and down)......

 

I also swapped the fan and radio suppression relays with no improvement either, although that doesn't guarantee they're working. In self test mode on the blink-box they both click.

 

I'm going to get the icm tested today. What kind of ohm readings should I be getting from the coil?

 

Agree if you unplug the TPS and block the IAC it will not start. You need to jumper out 2 of the terminals on the TPS (I need to check which 2) and then pull and block the IAC tube (don't unplug). You can turn the idle screw up a bit but it should be able to idle at 500-600rpm. Also is your O2 sensor in the system. I believe the engine runs in open loop until the water temp sensor triggers the closed loop idle. It needs info from the O2 sensor to adjust mixture. I'll take a look at some of my shop manuals.

 

You need to jumper out pos. 1 to 2 on the TPS connector. Also have you looked into the throttle body to see if it is not gunked up and clean. You may need to adjust the TB so if it's dirty it will not idle with the IAC removed. I would check this out and if dirty I would remove it and clean it then go through the resetting process for the TB and TPS. I ASSUME you have both spark and fuel pressure.

 

I have fuel pressure, although how much is unknown. The pump was replaced at the dealer about 20-30k ago. My primitive testing method was to unhook the line from the rail and put it in a jar. When I initially unhooked the line there was pressure present, and the jar filled about 1/4 cup when I turned the key to on and when I cranked 3-4 revolutions I had about a cup or more come out so pressure and volume seem good to me. Spark is trickier because even though I have an inline tester I can't see it under the hood from inside the car and it won't stay running long enough to use my inductive spark checker.

I also unhooked the return line from the fpr and the line was dry. I pressurized the line by cycling the key and even attached a hose to the outlet of the regulator and nothing came out. I then pulled vacuum on the vacuum line and still nothing came out of the regulator.
I suspect that my fuel pressure regulator is bad as well....

 

I'd first perfect that Crankshaft Position Sensor before I go on-THAT'S a biggie...

I'd take a look at the Fuel Pressure Regulator, too.

 

I figured I had it set pretty good in the bell housing. Its about 1/16th" lower on the right side than on the left. It "runs" the same as it did before so I'm pretty sure I have it in pretty close. Either way, the crank position sensor is a run or not run kind of thing and it hasn't changed the way it doesn't run.
Would a stuck regulator cause it not to run at all? I've seen cars run bad with bad regulators, but they were all leaking gas past the diaphragm. Mine isn't wet or leaking fuel, but it smells like fuel in the vacuum line.

I'm going to get my icm tested today and check the resistance in the coil, too.

 

Ok...
so I just found out another disadvantage of the bendix ignition... the free bench tests offered by parts stores doesn't include the volvo bendix ignition...
Just as I suspected, just another reason perfectly good parts get put in the trash.

I haven't found anybody online that has had even similar symptoms, or somebody who's broken down the bench testing procedure or even specs for volvo coils or icm's...

My other thought is a suspicion that fuel should've been coming out of my fpr outlet.

 

I'm a little confused on your last statement. Are you saying you get fuel out of your fuel pressure regulator? If so that should not happen and you have a bad regulator. Just to reclearify do you have fuel coming out of the FPR where the vacuum tube goes in?

 

No fuel coming out of the vacuum line, but I aso didn't have any fuel coming out of the outlet of the regulator on the return side when it's pumped up or when I'm cranking the motor, but maybe it doesn't build up enough pressure during starting/cranking to overpressurize the fuel rail and return fuel through the line.