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92 240 Stalling on Hot Starts

xDread92x

Member
Joined
Feb 5, 2015
Location
NC
Hey all,

I've been diagnosing a stall on hot start ups.

I spoke before about replacing the fuel pump relay, AMM, and O2 sensor. B230F and all fluid levels are good in the car.

I've noticed the issue has progressed to where I can shut the car off after driving a while and I can crank it several times and it stalls immediately each time (3 plus times). The only way I can get it going while hot is to give it gas and it takes about 15-20 sec of doing this holding the gas for the car to even out and run on its own.

If I let up on the gas at all in this process of holding it to get going the car stalls. I also smell fuel/exhaust after this process to get it going. While cold it usually starts and drives as normal. My next idea is the in tank pump.

Are the pumps/fuel system suppose to buzz every single time when put in the "on" position? I noticed the system has not been doing that lately. I will get a buzz here and there but not every time I place in the "on" position.

From research some other people have said something in the fuel system could be overheating. Its been 100'F plus here.

Thanks
 
The only way I can get it going while hot is to give it gas and it takes about 15-20 sec of doing this holding the gas for the car to even out and run on its own...also smell fuel/exhaust after this process.

So, giving it the gas means pedal to the metal, which means the throttle plate is wide open, which means intake is receiving large volumes of atmospheric air, which means when it starts that engine's pistons had too much fuel, which means, your injectors are dribbling fuel, or your CTS (coolant temp sensor) is off calibration.

>buzz every single time when put in the "on" position?

Since you claim it starts OK when cold, then this is not an issue. Best practice is to turn key to on position, wait two seconds, then engage starter.
 
My next idea is the in tank pump.

Footnote - Intake pump must be working to prevent vapor locking, which would cause vehicle to stall out while driving, or hard starting when hot. 1975 Volvos did not come with intake pump, but they had a recall that installed a new tank with an intake pump.

But, your issue tends to point to injectors or a bad CTS. Ohm spec CTS
 
How can I tell if an injector is leaking? I don’t see any leakage around each injector housing.

And could you explain the CTS and how it could be the issue? Do they just go bad?

Thanks
 
Footnote - Intake pump must be working to prevent vapor locking, which would cause vehicle to stall out while driving, or hard starting when hot. 1975 Volvos did not come with intake pump, but they had a recall that installed a new tank with an intake pump.

But, your issue tends to point to injectors or a bad CTS. Ohm spec CTS

When I had my in-tank pump fail, this is exactly what happened. City driving in hot weather, especially with less than half a tank, it would vapor lock and die while driving. Let it sit for 15 minutes, and it was good as new.

You can test both pumps independently by pulling out the fuel pump fuse and applying 12V to each side. One side is the in-tank, one is the main, though I forget which is which. You should hear something either way though.
 
I did forget to mention that this occurs no matter the tank amount. Close to E or full it stil occurs. What’s you guys thoughts on the Radio Suppression Relay? I found it in the bay and it looks super old and cruddy. From research it states you will have issues on hot starts and it controls the AMM, fuel pump relay, and injectors.

I would also like to mention that I know it states that 240s don’t have the RSR but my 240 wagon does have one on the drivers side by the power steering pump. The numbers and connector matches up perfectly with the RSR.
 
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240 doesn't have RSR. On a 740 all it does is power the injectors. Nothing to do with the MAF. Look at wiring diagrams and learn to read them.


Hot start stall could be lots of things. An electronic component could be heatsoaked and not work properly. Such as the crank sensor or powerstage.

Does it run on brake cleaner when having this problem!? Click my sig to read on starting fluid test.
 
How can I tell if an injector is leaking? ...explain the CTS

I pull the whole rack out, and energize fuel pumps via key switch to on position....Or, pull plugs, energize fuel pumps via key switch to on, and smell each cylinder.

CTS - With time, they may give a colder reading to computer, so computer increases fuel amounts. CTS can be ohm spec'ed...maybe without taking it out. There are two temp sensors, one for the computer and one for dash instrument panel.
 
II would also like to mention that I know it states that 240s don?t have the RSR but my 240 wagon does have one on the drivers side by the power steering pump. The numbers and connector matches up perfectly with the RSR.

Might be your headlight relay...dims/brights
 
I had hot start issues on my 940T.
I replaced virtually everything (CPS, CTS, power stage, IAC valve) cleaned the throttle body, adjusted the TPS, replaced intake manifold gasket and whatnot, but nothing changed.
Last weekend I changed the injectors for ones I had around from a V70, and voila, problem is now gone entirely.
Not sure what the exact problem is with the old injectors, but they are quite dirty and I assume they are leaking down after shutting off.
 
That's why is suggest disconnecting the injectors, clear flood, and try alternative fuel. Determine if it's fuel or ignition related.
 
Why would you need a second person?

I've started a couple redblocks fires doing homebrew tests. Be careful.
 
I rebult everything about 2 years ago in this wagon. Including the injectors. A good soak and new seals, caps, etc. I'm still not ruling it out for the injectors though. I will be putting in a CTS this weekend and we will see what happens. If that doesn't fix the problem then injectors will be the last and final thing I check because I have went through just about everything.

I guess injectors could still have a problem even if not showing leaks around base or outside area. It's something I will have to look into further.

If it was injectors, wouldn't it be more consistent instead of on hot start ups only?

Thanks
 
If it was injectors, wouldn't it be more consistent instead of on hot start ups only?

RE: "I also smell fuel/exhaust after this process to get it going."


Factors:

1. Temp sensor giving ECU a false (colder) reading

2. Injector(s) dribbling.

3. AMM - Informing ECU extra air is flowing, which requires more fuel. I'm not aware of any posts on this topic.

Temps sensor could have been ohm spec'ed...there are two different ones...get the right one for later year Volvos.

Myself, pulling fuel injection rack can quickly rule out dribbling injectors. On my 1993s, there are test ports to see what rail pressure is...this is where I would have started.
 
FWIW - Bad MAF Sensor? Overview, Symptoms, & Troubleshooting

"The MAF is a replacement maintenance item and I usually replace around 50,000 miles, however, cleaning can often improve sensor functionality particularly when mileage is starting to creep up, therefore I also routinely clean the MAF as part of my annual maintenance. I have heard of many different types of cleaning methods including manually cleaning with probes of some kind and use of brake fluid - even diluted acid! But care needs to be taken as the sensors are easily damaged. Personally I never physically interfere with the sensors and only use cleaners that are designed specifically for the MAF. Maintenance is easy, simply disconnect and remove the sensor and body from the car, spray the cleaning fluid as per directions. And allow at least a half hour to air dry – never use compressed air or other means to reduce drying time though."
 
FWIW installing 4 hole rebuilt/flowed injectors to my 240 made the car start with a bump of the key. it was almost startling the first time. Not that my car had an issue before(maybe a second to start) now I literally just bump the key.
 
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