240 intermittent starting issues

240

My 240 has some intermittent issues when starting. It's a 1992 LH2.4 model.

Most of the time it'll start and run fine.
However there are 2 intermittent issues.

Occasionally, after starting, it runs very rough, doesn't respond properly to throttle inputs, almost seems like it's misfiring. After running for a minute, it's completely fine.
Occasionally, it'll stall immediately after starting. When I try to restart it, it'll crank for ages before actually starting. The next time I drive the car, it'll start completely fine.

There are no codes stored in the diagnostics box.

For additional context - I replaced both the ECU coolant sensor, and the crank angle sensor, probably about 30,000km ago.

Any advice would be great

John_Fraser

240

"Think" is an intermittent problem. Good time to get a compression gauge, inductive pickup timing light, and 12V test lamps (LED and incandescent). These give definite information and are as faithful as a dog. However, interpreting their results requires thinking.

Low compression in a cylinder can cause marginal ignition condition.

Check each plug lead and coil HT lead for regular pluses.

Check low side of coil for regular low voltage pulses to ground.

Instead of a new "good" FP relay remove the relay and jumper the 12V and pump socket pins. 1/4" tab crimp terminals fit the socket pins perfectly.

Since the tank pump has never been changed take advantage of the opportunity to help solve the problem. While the lid is off the tank look inside with an LED light to check for crud on the bottom. It should be shiny and clean. Don't switch anything electrical on or off near the open tank.

240

Could it be something fuel related eg failing fuel pump?

ramrod

Morning

Could be a leaking head gasket blowing out the spark at cold start.

Any loss of coolant?

240

No loss of coolant. And if it was a bad head gasket I'd expect the car to drive worse due to bad compression but it still drives really well.
Also for additional context - problem #1 usually happens when the car is cold, #2 usually happens when the car is hot.

jamesinc

Leaky injector perhaps?

240

jamesinc I replaced the injector seals (and had the injectors cleaned) maybe 4 or 5 years ago. But I guess maybe an injector has gone bad...

Ex850R

Earthing cables everywhere?

ramrod

Is there smoke out of the pipe when it runs like that?

Check spark plugs when it starts misfiring, you need to look for clues when it comes to tough to isolate intermittent problems like yours

240

@ramrod when it runs rough (problem #1) there is some black smoke out the exhaust.
I know the spark plugs were changed not too long ago. Guess I could check the condition and gap though.

ramrod

Yes

You want to check each plug individually and check to see if one or more are cleaner/wetter than the others

You have to act like sort of a detective on the crime scene with tricky problems like these

I would also carry out an injector drip test

GingerNinja

Mine started doing a similar thing when the leads to the plugs and coil got a bit old. Sometimes good connection. Sometimes no start.

ArthurH

Both issues could be caused by the ECU coolant temp sensor. They can be temperamental and cause intermittent faults, I had issues with a new Bosch sensor.

Laurie

If you have an infrared heat sensor gun check the temperature of the exhaust manifold for each cylinder after starting the engine and before runs smoothly.. Look for the coolest outlet which could indicate a wonky spark plug or lead, injector etc. This trick has saved me hours of rooting around!
Have fun,
Laurie

240

This is what all the plugs looked like. Not sure if the whiteness is a concern or the blackening around the base of the body
Image description

jamesinc

Plugs look okay to me. White is okay. Brown is the colour to worry about. Black around the base is also expected, provided it is a fine layer of carbon and not chunks of garbage.

ramrod

Does your car have a cold start injector?

Ravanelli

I would start with the fuel pump relay. Those things are always giving out. Easy to access, i always have a spare in the glovebox

jared244

Rough running after a cold start for a short period, and hard to start when hot sounds like a fuel pressure thing to me. ie not enough fuel during the enrichment period after start (can be as long as 30s in very cold conditions, less in warmer conditions). I would normally suspect a partial fail of the fuel pressure regulator, or one or both of the fuel pumps failed (or not running at all), But given it's only intermittent I'd look at the ECU and the Fuel pump relay.

As suggested above, swap out the relay with a known good one first to eliminate fuel pumps as the source of no fuel pressure. You can also tell if the relay is working by listening for the pumps priming before you turn the key to start. If you hear the pumps prime, and then subsequently have a hard start, probably not the relay.

Second, do you have a pink lable on your ecu? Given you have a 1992 car, you should have the better white lable ecu of the same number. Check it though, if its a early 1992 build you could have a pink one. They have a almost 100% fail rate eventually due to bad solder joints. The ecu drives the fuel pump relay, so could give a false indication the relay is bad, but the ecu does other things, like drive the injectors etc

As suggested above, cold start injector. 1992 lh2.4 doesn't have one, but again if you have a early 1992 you may have a pink lable ecu, and a cold start injector which is used on '89-'91 LH2.4 cars. I'd expect the car to start every time warm even if the cold start injector isn't working, so probably not this.

Last thing, if you find yourself having a hard warm start, try priming the fuel pumps twice or 3 times before starting. Tell me if that helps.

Good luck!

Anthony

A quality response Jarad, such a good forum to he on.

240

Thanks for the replies everyone, I may have narrowed it down a bit. The problem has started to become worse, the last couple of days there have been a couple of occasions the car won't start at all, from cold - will just crank until the battery starts to fade.

The fuel pump relay is a genuine Volvo one and not very old (date stamped 2019).
Also, I tested the fuel pumps by jumping between different fuses (as per instructions online) - the main pump near the LH rear wheel can be heard, so the relay definitely works.

However I was not able to get any result from the in tank pump, whether listening through the boot or through the petrol cap.

This leads me to think the in tank pump is bad. This adds up in my mind, because firstly, I could imagine how the car would be difficult to start, but OK once running, if the in tank pump is bad but the main pump is OK - i.e. the failing tank pump means the car can't get enough fuel to start, but once running, enough fuel can get to the main pump for the car to keep running...?

And secondly, the seal on the tank pump access panel has clearly never been broken and after 477,000km I'd not be surprised for the pump to fail.

For extra context - I ended up replacing the fuel pressure regulator and ECU coolant temp sensor with new parts anyway as they are easy jobs.

@jared244 to answer some of your questions - it is a white label ECU. And as mentioned above, I think the relay is fine.

Keen to hear if others agree and if so I'll buy a new in tank pump - only reason I can think of not to, is if it's typically meant to operate quietly causing it to be hard for me to hear.

Ravanelli

240 you should be able to hear the tank pump running. If not then you may have identified the culprit.