Gentlemen,
I have a 1996 Volvo 850 turbo 5234T engine, 73K mileage. I was driving along and noticed that my A/C started pulsing on and off. Eventually A/C quit, I drove about 10 miles and the car now died. Put it in neutral (I was going downhill) and it started again. Got to my destination and parked the vehicle. Next day, car would start, but stalled about 18 seconds later. In all cases car starts right up and dies, even if higher RPM.
For the past 2 years I would work on the vehicle on and off, but it has never continued to run longer than 25 seconds. I have read what I believe is, EVERY communication by all the Volvo forums/bays/discussions/overseas sites etc,. and still I cannot get the vehicle to continue to run. I have one distinct advantage, in that I have another (working) 1994 850 turbo 5234T that I have been swapping parts from one vehicle to another, yet the outcome has NEVER yet changed. Fixed a ton of items on the older volvo.
On the newer 1996 Volvo FUEL
New fuel pump, new fuel filter, new fuel regulator + pinched fuel regulator return hose to see if building pressure helped. Opened fuel line under vehicle passenger side with pump activated...plenty of flow. Opened fuel line at fuel rail...plenty of flow, schrader valve opened at fuel rail...plenty of flow during engine run (35-38 psi), when engine shut down (38psi). Fuel cap is tight, New Idle Control Valve + swapped with 1995 Volvo, New 103 Fuel Pump relay, plus swapped with the 1994 Volvo + jumpered out the 103 connector so the pump would continually run....no difference. New Fuel injector relay by radiator + swapped with 1994 Volvo. Removed and throughly cleaned out the throttle body including the intake pipe that usually gets clogged. Inspected each fuel injector under 15 X power loop...all injectors look fine. Cleaned injector intake ports before reinstalling injectors. When engine starts, I get a small amount of white smoke out of the exhaust pipe for a very short period of time. After engine starts, I pulled the plugs, which were very carbonized but they had a smell of fuel on them. Looking at the top of the pistons...they appear wet. With spark plugs in place, no apparent smell of fuel to the engine.
Ignition
Remember, car starts right up and dies within 20 seconds. No OBDII codes!!
Turn key in position II and all the appropriate lights come on and go out once car has started. I see the turbo gauge move, I see the RPM gauge move, I see temp gauge slightly move. RPM gauge steady at about 800 RPM. At about the 15 second mark, the car starts its stall process. If I give it throttle, it will rev for a fraction, but still dies. Battery reads 12.4 V (no Load) and when engine is running, battery reads 13.80V. Swapped battery with 1994 volvo...no difference. New Ignition module and transformer + swapped with 1994 Volvo, New Distributor cap, new rotor, new camshaft (Hall effect sensor) + swapped with 1994 Volvo.The camshaft sensor area was clean...no oil. New ignition wires + Ohm value 1.456 K Ohms - 0.702 K Ohms. Center lead reads 0.935K ohms. Put in new plugs....no difference. Swapped ECU/ECM with 1994 Volvo + seriously looked over the connector. Put in new plugs...still exactly the same.

Other
Before starting, I pulled off the MAF connector ....a little idle difference, but symptoms still exactly the same + swapped MAF with the 1994 Volvo. Pulled out the crankcase (RPM) sensor .... was clean and no metal bits present. Did not swap this part...1994 Volvo sensor a real bear to get to. But remember the engine will run every time for about 20 seconds and then dies. I have spent NUMEROUS hours examining ALL vacuum hoses including the one under the intake manifold. Found only 1 slightly hard vacuum hose, so I replaced it. I looked at ALL plastic hoses and put layers of rubber around the ones that even slightly displayed wear. I used a hand Vacuum pump to test how well the hoses would hold a vacuum. I released the serpentine belt and rotated the pwr steering, water pump and A/C compressor. I did find that the grabbing clutch plate to the A/C was fried/gone. It was difficult to turn the A/C pulley by hand.
Car turns over easily, starts easily and idles smoothly. Car will not continually run.
What did I forget to check? With everything I have done..nothing has changed.
Pat

 

WOW,

You have tried everything I can think of to diagnose. My suggestion
post this in the 850 thread and ask TECH for help.

 

Hi! Welcome to the forum.its so glad to meet you.enjoy the stay.

 

Is the wiring to the injector relay falling apart at all? I mean in the plug.
Does the tach drop off before it stalls?

 

The tach remains solid....no signs of a drop until the stall begins. No erratic movement of the tach gauge and I can hear the initial buzzing of both relays ('94 and 96)' using a stethoscope during the startup procedure. If I forgot to mention, the injector relay was swapped with the 1994 Volvo 850 turbo which works fine. My assumption is that this component is working as advertised.

 

Ok But is the terminals stable?
The rubber around the terminals crumble and fall out allowing the terminals to slide out of the plug.

 

Have you determined if this is a spark or a fuel issue. You should diagnos that first so you dont waste time on both. Easy way is with a inductive timing light and see if you losing spark or if its still firing when as it dies.

Just some thoughts as I read:
1. Cam, Timing belt, slipped a tooth or two or more.
2. Throttle position switch on the throttle body
3. Coil.

Shots in the dark though...find out if this is fuel or spark first.

 

++1 Narrow it down to fuel or spark and verify the TPS is working.

To verify, you left fuel pressure gauge attached and the fuel rail was holding 38 psi when the engine died?

If you have spark, then try monitoring the injector(s) to see if they're firing using a test light.

 

Was a solution ever found for this? I have a very similar problem with a 1995 turbo 850. Runs for 10 seconds and dies. Changed and checked all of what you listed? Please tell me you found an answer.

 

No solution has been discovered as of yet. However something new has occurred. I have not had the time to re-check the schematics. Try opening the schrader valve on the fuel pressure rail. Turn on the key, with a line connected to the rail, dump the pressurized fuel into a container.............see if your fuel pump continues to run or it runs and then stops after about 7 seconds. You will hear a click and then the fuel cuts off. Let me know your results. If you have the exact same problem I will do some research.

pgu44

 

Two things to check I can think of. One is to make sure you disconnect the connector to the AC compressor clutch. If the clutch disc looks burnt and the compressor is hard to turn the compressor has or is about to fail. It might be a delay from start up until the compressor kicks in and it kills the engine because it can't turn the compressor. It's rare, but I have seen it happen.

Second one is be ready to give it starting fluid as it starts to die. This will tell you if you've lost spark (you could also just run on four and let one arc on the valve cover to monitor it. If it runs with the starting fluid it might be a bad idle control motor letting in too much air or a pump, relay or regulator. At least you'd be getting closer.

To check the injector pulse you can also get a loan of "noid lights" from some auto parts stores. They plug into the harness in place of the injector and flash with the pulse for the injector. It's a loan, you don't have to buy them.