Car shut off while driving -99 V70 2.5T

[Eliotlm]

I would suggest if you are getting a smell of fuel you need to get under the car and follow the fuel pipes and see if you can see any signs of fuel leaking around. I'd focus on the fuel tank area. It takes a bit of work, but you may want to remove the access panel for the fuel pump behind the rear seat. You might have to remove the panel on the floor behind the rear seat to get to it. I can't recall if you have to on a FWD car. You do on an AWD. Have a good look in there and see if you can see any signs of fuel leaking around the visible part of the top of the tank. I would however, suggest the symptoms sound like it may be a failing fuel pump. As it warms up the pump starts to fail. Did the repair shop not check the fuel pressure at the fuel rail after fitting the relay? On your car it should be around 55 psi but around 50 psi is ok

Earlier cars were around 43 psi.

I'm giving both values as being a European market car, I'm not sure if a 99 is actually a 99 or like here a August 98- car is a 99. For us the fuel pressure changed in the 99 model year.

How full is your fuel tank when:

a) you get the failing pump? - If you have >1/4 tank your fuel pump should be submerged and the fuel will help cool the pump. Less than that it can expose the pump causing it to run hotter.

b) you are getting the fuel smell? If it is all the time then you have a leak somewhere. Now if that is part of this issue or a separate one we will have to find out.

One final question for now. When you fill the tank, to you just fill until the pump cuts off and stop, or do you try to add more?

The 2nd option can cause issues with the carbon filter and flood it. That can cause issues with fueling, but also fuel getting pushed out the vent on the top of the fuel pipe at the filler.

Neil.

Thank you! I will probably replace the fuel pump just to be safe as it is pretty accessible on The fwd vars. I probably have around 1/5 tank of gas. The fuel smell is only faint and sometimes but I'll check The fuel lines ones i change the pump. The fuel filter was replaced quite recently as well. I never fill tank all The way, always about 4/5 (Dont know why). Might get an EPV from The junkyard and try it out while im at it.

[Eliotlm]

This is what ChapGPT says:

Based on your description, it seems like the stalling issue could be related to the fuel delivery system or a component affecting engine management. Here are some potential areas to check, based on my experience with Volvos:

1. Fuel Pump or Fuel Pump Relay:
Symptoms: Intermittent stalling, especially when the engine has been running for a while, is often caused by a failing fuel pump or fuel pump relay. The fuel pump may not be delivering enough fuel pressure under load, even though fuel is present in the rail.
Diagnosis: The fuel pump relay can intermittently fail as it heats up, leading to the stall. A quick test is to bypass the relay (if you're comfortable) or to swap it with another known good relay from a similar circuit.
Check fuel pressure: A fuel pressure test at the rail while the engine is running can confirm whether the pump is providing consistent pressure.
2. Evaporative Emission (EVAP) System Issue:
Symptoms: Difficulty starting after refueling can often be linked to the EVAP system. A malfunction in the purge valve or other components can cause a vacuum lock or improper venting, affecting fuel flow.
Fuel smell: If there's a fuel smell after driving, it could be a sign of a fuel vapor leak, which may also be related to the EVAP system.
Check: Inspect the EVAP purge valve and hoses for blockages or leaks.
3. Mass Air Flow (MAF) Sensor:
Symptoms: If the MAF sensor is malfunctioning, it can cause erratic air-fuel mixture readings, leading to stalling and hard starting. While not always triggering an error code, an aging MAF sensor can produce intermittent issues.
Diagnosis: You can try unplugging the MAF sensor to see if the car runs better without it temporarily. If it does, the MAF may be faulty.
4. Crankshaft Position Sensor:
Symptoms: A failing crankshaft position sensor often causes stalling when the engine heats up. It can lead to intermittent issues without setting off codes, as the sensor's signal can degrade over time.
Diagnosis: If you have access to live data on your scanner, check if the RPMs drop to zero just before the stall. This could indicate a crank sensor failure.
5. Fuel Tank Venting Issue (Check Valve or Charcoal Canister):
Symptoms: Difficulty starting after refueling and occasional fuel smells may indicate a venting issue in the fuel system. If the fuel tank is not venting properly, it could cause vapor lock or pressure issues.
Diagnosis: Check the fuel tank vent and the charcoal canister for blockages.
Suggested Next Steps:
Check fuel pressure while the car is running to rule out the pump.
Inspect the EVAP system for blockages or leaks.
Test the crankshaft position sensor and MAF sensor.
Inspect fuel system components (fuel lines, charcoal canister, etc.) for leaks that could explain the fuel smell.

Thank you! Seems reasonable

[Eliotlm]

Have you checked the battery and cables. The last time I had issues like that i needed to replace the battery.

I have not but will do that!

[JimBee]

My 93 850 once died like that. There was no fault code. I replaced the fuel pump relay next day and it started right up. I drove it a short distance and it died again. Whoa. I tried a different FP relay from another 850 that I knew was good, but still no start.

This time, though, there was a code that indicated the camshaft position sensor. I replaced that with a used one I had in inventory and that solved it.

If the new fuel pump with a known to be good relay doesn't fix it, I would check the spark. If you don't have a tester that you can plug the spark plug wire into, you could pull a plug and ground the plug to the the engine while somebody cranks it from the key switch.

[Eliotlm]

My 93 850 once died like that. There was no fault code. I replaced the fuel pump relay next day and it started right up. I drove it a short distance and it died again. Whoa. I tried a different FP relay from another 850 that I knew was good, but still no start.

This time, though, there was a code that indicated the camshaft position sensor. I replaced that with a used one I had in inventory and that solved it.

If the new fuel pump with a known to be good relay doesn't fix it, I would check the spark. If you don't have a tester that you can plug the spark plug wire into, you could pull a plug and ground the plug to the the engine while somebody cranks it from the key switch.

Ive heard People mention cam shaft position sensor. I will replace pump tomorrow, and hoppfully get an evap purge valve to replace as well. If that doesnt work i will check CSP sensor

[bw711]

My 99 S70GLT shut off while driving. Turned out to be a bad voltage regulator (part of the alternator).

Have you checked voltage output of the alternator?

[scot850]

Lots of good suggestions on this. I have a question. Have yo done any work around the distributor area of the car recently? When you mention the camshaft position sensor, we had an issue many years ago with a 93 850 we had. Driving along it would randomly cut out. It would immediately restart and drive normally. Replacing the cam position sensor made no difference. The issue turned out to be a simple fix but a strange reason. When I had been working on replacing the distributor cap, I had repositioned the cam position wire too close to the distributor body. The distributor signal would overwhelm the cam position one and kill the engine. Repositioning the wire further away, the issue disappeared.

Neil.

[aahmes57]

I’ve just developed a similar issue with my 98 s70 glt. It starts right up, drives fine, the out of no where it shuts off, stalls out. It starts right back up every time but can stall at random. No idea what’s causing it.

[scot850]

Bad or worn ignition switch (electrical part), bad ground or corroded wiring to starter, battery or likes. Check the B+ cable in the kidney shaped main fuse box for discoloring of the copper B+ cable end. Disconnect it and try to carefully lift it out and see if it has melted under neath the mount which can cause shorts/fires.

Neil.

[Eliotlm]

In hopes that this thread might help someone else with a similar problem. It turned out to be the fuel pump. My suspicion is that the pump choked when getting to hot. After replacing the pump, the car ran as normal.