96 850T5 Hard restart after engine is hot in hot weather.

[redbeak1]

I have read the other threads and the Bosch Blue book for answers. When it's around 70+ degrees outside and the engine is hot... I stop for around 20 to 30 minutes, try to restart and it sounds like it's misfiring. I did get code P0301, P0310 a couple of times.If I wait around 5 to 10 minutes or an hour it fires up fine. When it's cold out, no problem.The engine runs great even after a hard hot restart. The problem is surely heat related and possibly from the fuel getting hot. After a couple of failed starts and stalls the engine runs great. I don't know how to repair this issue.
Here's what has been done so far:
1. All ignition components replaced including coil. Cam and Crank sensor new.
2. Fuel pressure checked. 40 psi with ignition on and engine off. Residual pressure good. Pulled vacuum off regulator(rises 10 psi), it seems like it's good.38 psi with engine running hose attached. Volvo states 43 psi. Leak test held for hours.
3. Idle air control valve tested and cleaned. Works well.
4. Vacuum hoses all replaced.
5. Compression checked on all cylinders. All checked out close to each other .
6.Fuel injection and pump relay new.
7.Mass air flow sensor clean and working well.
8. Resistance on all fuel injectors I think the # was 14.5. I do remember it was all the same. Fuel injection light tester shows all are firing.No leak around seals. Usually run Techron in gas tank.
9.Fuel filter new.
10. Coolant temp sensor was replaced along with thermostat and radiator around 5 years ago(40,000 miles).
The engine runs perfect otherwise with 147,000 well maintained miles. I used to have vapor lock in my old VW beetles.Could there be something similar going on, since this problem only shows up when it's hot? This problem has been going on for a few years here in New Jersey where luckily it doesn't stay hot for very long.

I see this is a dreaded issue with the 850's, but I haven't seen where is was resolved. Any help would be great.

[bmdubya1198]

This really sounds like an ECT sensor issue. Everything else looks good, so I don't think you're looking at anything major at least. Do you know what brand sensor was used when it was replaced?

Vapor lock is a theory that's been tossed around with 240s having a similar issue (car dies and won't start during hot weather), but I don't know that it would be an issue with the evap system on these cars.

I don't think the code is P0310, maybe P0300? No cylinder 10 on these engines .

[redbeak1]

This really sounds like an ECT sensor issue. Everything else looks good, so I don't think you're looking at anything major at least. Do you know what brand sensor was used when it was replaced?

Vapor lock is a theory that's been tossed around with 240s having a similar issue (car dies and won't start during hot weather), but I don't know that it would be an issue with the evap system on these cars.

I don't think the code is P0310, maybe P0300? No cylinder 10 on these engines .

Oh, I meant P0301(misfire on cylynder1) and P1310 ( random misfire).
I only use genuine volvo parts. I have learned my lesson about some after market stuff years ago!!!
I will double check ECT.
Is 40 psi fuel pressure in acceptable range without engine running and 38 with it running? Volvo says it should be 43, but not sure if that is with engine running?

[bmdubya1198]

Oh, I meant P0301(misfire on cylynder1) and P1310 ( random misfire).
I only use genuine volvo parts. I have learned my lesson about some after market stuff years ago!!!
I will double check ECT.
Is 40 psi fuel pressure in acceptable range without engine running and 38 with it running? Volvo says it should be 43, but not sure if that is with engine running?

Good, so it's still a possibility, but it's less likely with an OE sensor.

40 PSI with the engine off should be alright, it's a LITTLE low, but not too much. See here for more info on that: http://www.volvotips.com/index.php/850- ... ce-manual/

I don't think this is an issue.

[misha]

Fuel pressure is good since you have fpr at fuel rail.
43.5psi at 1st prime and around 35psi at idle.
Wot should again rise at 43.5 psi.

Are there any codes?
Fuel vapor lock could indeed be the issue if the valve is stuck open.
The valve is at driver's side,attached near radiator and it's vacuum line goes direct to intake manifold.It have 2pin connector.
Valve is normaly closed at rest or when disconnected and ecu turns it on when needed.
Could also be a main fuel injection relay...grey one at fan shroud...or it's connection...since you allready replaced it along with fuel pump relay.

If all above is ok...then you should perform a voltage drop test...could be that positive or negative cables are making problems...especially in hot weather.

[redbeak1]

Had misfire code only once when trying to hot start . It would rumble like it's running on less cylinders and stall. If I start again and give it gas , it would fire up better and after that runs perfect.
What is the name of the valve you are referring to? Does a 96 850 turbo have that valve? I don't recall ever seeing it. I have the ME 4.3
Thank you for all the suggestions.

[misha]

It's EVAP system purge valve.
https://www.google.com/amp/s/volvo850wa ... -tank/amp/

[bmdubya1198]

I was going to mention a possible problem with the purge valve, but typically you'll get P0445 with that. Then again, who knows with these cars. Vapor lock is certainly a possibility if it's stuck closed.

Check if it's clicking at idle, typically if you put a screwdriver/mechanic's stethoscope on it you'll hear it like a fuel injector. That's assuming the older style on your 850 is PWM like the newer valves.

[redbeak1]

I was going to mention a possible problem with the purge valve, but typically you'll get P0445 with that. Then again, who knows with these cars. Vapor lock is certainly a possibility if it's stuck closed.

Check if it's clicking at idle, typically if you put a screwdriver/mechanic's stethoscope on it you'll hear it like a fuel injector. That's assuming the older style on your 850 is PWM like the newer valves.

I see someone on Youtube who checks the 850 purge valve with a 9 volt battery to see if it clicks to open and close. I will try that and look over all the hoses. Since this is an original part, I will check this first since the ECT was changed. I wonder if heat affects the operation of the valve. I never had any purge valve codes.

I will report back any findings.

[bmdubya1198]

It's definitely a possibility, they are known to fail.