New cap and rotor, plugs and wires. 740 turbo. Car ran decent before but definitely needed the tune-up.

Everything back together, car now starts but runs only for a few seconds and then dies. Firing order seems correct. L to R on distributor is 1234. So, from back to front on motor L to R order would be 1243.

I did mistakenly remove the distributor bolts before realizing they were not the bolts to the distributor cap. Could I have thrown off the timing by chance?

 

more likely, you accidentally knocked some wiring or vacuum stuff loose.

I just checked my 740T, the cylinders are numbered 1-2-3-4 from front to rear, and they are wired to the distributor port to starboard as 2-1-3-4, which is probably the same thing you're saying, just numbered differently.

below the distributor is the crank position sensor. its wiring gets pretty crusty after 20 years and if it fails, you get no spark OR gas.

 

Additional Info:

1- I have owned the car only a few weeks, drove it only once actually. On the drive to the shop for the tune-up it actually did just about stall -- this was literally right before the tune-up, so whatever is manifesting at current may just be a problem that was surfacing before and has no relation to the work I did.

2- Firing order - I'm about 100% sure it is correct. It runs great then dies suddenly. I tinkered with the order and trying other orders only made the car run like crap, so I put it back how I originally had it. 4312. Cylinders 1234 from radiator to firewall.

3- Crank Position Sensor -- This may be my issue b/c the wiring is shot. Is the CPS located under the distributor to the rear on top of the transmission? I notice a sensor here with the wiring insulation deteriorated and the white wire exposed, bare wire. Also, next to this is a cable going to the trans that has also deteriorated. I'm thinking these two may have touched?

If my CPS went bad, would my car still start and run for a few? Correct?

 

that sounds like the CPS, its picking up off the edge of the flywheel...

if the wiring is toast, it could work intermittently. the other wire back to the transmission, only thing I can think of back there is the overdrive.

 

That is probably your problem, exposed wire on the CPS is bad... The other cabel is probably the transmission downshift cable which is sheathed but is purely mechanical--no current runs through it...

 

inspect the air charge tube that goes between the mass air sensor and throttle body for splits.

 

If my CPS went bad, would my car still start and run for a few? Correct?[/quote] nope... the CPS is what toggles the spark signal for the coil. If it is totally bad.... you're walking.

 

nope... the CPS is what toggles the spark signal for the coil. If it is totally bad.... you're walking.[/QUOTE]

The spark signal to the coil comes from the ignition module not the CPS. The CPS controls timing. The engine can start with a bad CPS. It is very common for the CPS to fail after it warms up from the heat in the engine compartment.

 

the crank position sensor provides the timing signal to both the ignition and fuel injection control units. without that timing pulse, there's no fuel injection and no spark, and the car dies immediately (or doesn't start).

with bad insulation, that signal is compromised but not completely eliminated, and you'd get a range of symptoms from no-start to run sorta to run OK sometimes but not other times.

 

Any module on a GM, Ford, ......or Volvo.... is a switching device (power transistor) It requires a "high-low" signal from a switching device (usually a PM generator, but sometimes a hall-effect switch) This device is a crankshaft position sensor.... most frequently located in a fixed location such as on the rear of the engine block like the Volvo. (My Jeep 4.7L has a reluctor wheel on the crankshaft inside the crankcaes). Being that it is a fixed device, it cannot alter timing... that is done by the ECM, ECU, PCM, or whatever moniker the vehicles' computer has based on other inputs from RPM, TPS, MAF, etc.

 

As Merkur correctly stated, if you get no signal from the CPS, you are absolutely walking. There is no "fail-safe" or "limp home" with this sensor.

Check this out Engine and OBD Diagnostic Codes
and go to section 3 (Diagnostic Test Mode 2) to determine if this is your problem.

 

I have seen the frequent mistaken notion that "timing" can be adjusted with the distributor on a car with a CKP (crankshaft position sensor) and a distributor. All one accomplishes by turning the distributor is changing KV demand between the rotor and cap terminals... thus overheating the coil and module. On a Chrysler/ Jeep, one gets a P0351 DTC from overloading the primary ignition circuit! This especially occurs on high mileage 4.0L 6-cylinder engines where the timing chain wears and stretches and causes a lack of crank/cam sensor calibration.

 

Recognizing the Crank Position Sensor controls spark as well, I am supporting the idea that my stalling problem is not the fault of the sensor. I can apply the pedal, forcing the motor to continue running with the gas being rushed in. This tells me the CPS sensor must be good providing the right spark signal to allow the car to continue running with the gas. Also, a resistance test with an OHM meter shows a reading in normal range.

Fuel filter taken off last night, examined, appeared clean, rinsed with gas, sprayed in compressed air, definitely not clogged or anything. Checked all fuses, the Lambda fuse for the fuel pump was bad, so I replaced it. Still shuts off.

So far, I have ruled out:

Fuel Filter, Crank Position Sensor, Fuses\

Problem still remains: Car starts great every time, runs good for seconds, then stalls out....

 

Make sure of basic settings...Time to break out the oscilloscope and get readings from the CKP, CMP, MAF, O2, and TPS. If you have good fuel delivery and strong spark, then you likely have a problem where the ECU is reacting to a erroneous input from a sensor. Have you tried to unplug the MAF sensor and start the car? Some vehicles will go to a default fuel table and run, albeit not great, with the MAF disconnected. This could be a valuable clue.... also, check and make sure you don't have a split in the plastic hose/tube that goes between the throttle body and MAF sensor.

 

What is an oscilloscope?

I definitely agree that this very well may be a sensor failing and causing the computer to kill the motor.

Wouldn't a OBD 1 scanner tool point me in the right direction?

Should I go through and perform resistance tests on all sensors using a ohmmeter?

 

an oscilliscope is a piece of electronics test equipment that, in real time, graphs voltage vs time. it requires some knowlege of electronics to use properly.

what OBD-1 scan tool? the OBD on a LH2.4 car is the little diagnostic block with the blinking LED thats on your left hand strut tower. each CU (igntion, fuel injection) has a different 'tap' (2 is injection, 6 is ignition), and there's 3 Diagnostic Test Modes for each of these units, read fault codes, test sensors, test actuators. see Engine and OBD Diagnostic Codes

off the top of my head, the only sensor you'd read a resistance on is the temperature sensors, these have a relationship between engine block temperature and resistance.

 

By OBD 1 scan tool I was referring to what I have heard is a scan tool that preceded the OBD II used for vehicles after 1996. I guess I assumed that since my vehicle is 1991, then my OBD II scan tool would not work for this application, and therefore I would have to get a hold of a OBD I. Apparently, this is not the case?

I am reading the Diagnostic section now, and am learning about the built-in diagnostic sub-system. Hmmm...I never knew such a system was there

 

OBD-II standardized the scan tool, on all 1996 and newer cars, but the standards only address emmissions related issues. prior to this, every car maker had their own proprietary system

the OBD-I on these LH 2.4 Volvos requires no scan tool, everything can be accessed via the blinking LED under the diagnostic block cover. Many other car makers in that era required you to have a brand specific tool.

 

Thumbs up to you Pierce for showing me the light, if you will. Very cool system these vehicles have, no scan tool necessary. And to think, yesterday I was stuck wondering what would be my next move.

Yesterday I forged on cleaning the entire throttle body, removing gunk, then double checking hoses, etc. For what it is worth, remove that possibility from the list.

I will forge on this evening and run the diagnostic system. Thumbs crossed.

 

BTW, what is the fuse titled "Heated Lambda Sensor (In tank fuel pump)?

What is this fuse for? My inquiry stems from the discovery of this fuse appearing to be failed. The "medal part" in the fuse was very odd-looking. It was badly warped, thinner and longer then a good or normal one. It was not "broken", though, so I pondered curiously whether it was still functional.

At any rate, I swapped it out for a good one. This repair had no apparent effect on the vehicle.