Intermittent no start Volvo 740 sedan 1988

Pez

Hi guys,

I'm not as mechanically minded as others, but I'm trying my best to learn. I have a 740 sedan (1988) of which has an intermittent no start issue plaguing me from being able to enjoy the car.

Work done far done:

Replaced Spark Plugs

Ensure Actually getting Spark

Re-soldered Fuel Pump Relay

(note: Upon turning the key the Relay can be heard making an audible click and you can hear the fuel pump prime, although this doesn't happen when the key has been turned recently, am i correct in assuming that the fuel pump shouldn't prime every single time you turn the key quickly within short succession? I.e On for 5 seconds (pump primes) off (wait 5 seconds) On again (pump doesn't prime now)

Trouble Shooting Steps:

When the car does turn on successfully (which is a majority of the time) it can just fire up instantly and idle at just under 1k rpm.

When it struggles to start it can hear being audibly fluttering, giving it a bit of throttle will help correct this until it idles and just under 1k rpm.

The last condition is it just doesn't start at all the engine cranks and it sounds like it wants to go but never catches

On my drives the runs perfectly, doesn't cut out and will go on and on without a fault, the problem only exists in the start up process. For this reason I don't 100% suspect a poor fuel system as if that where the case i would imagine the car would cut out whilst on the road.

The previous owner had recently replaced the Crank angle sensor, without a method on how to test the sensor I'm just going off the assumption that this is okay and there isn't an issue. I've also checked the Radio Suppression radio and it appears to be making good contact and not corroded out.

Given how well it drives when it starts I'm at a bit of a loss, Any and all advice is appreciated, if anyone knows anything about the 700 series ignition module and whether this could be a culprit too I'd be interested to know!

If I've explained anything badly let me know and I'll reclarify!

Thanks

Nic

Evan11509

Hey Nic,

When the car doesn't start does it seem to be dependent on the temperature? Warm start or cold start, or doesn't matter?

As your 740 is an '88 I'm pretty sure it has an LH 2.2 fuel injection system, which would have a hall effect sensor, not a crank angle sensor. Might be worth checking the little plug on the distributor where the hall effect sensor plugs in. They do have a tendency to get brittle and break. The ignition control module could very well be an issue as well. good luck.

Pez

Evan11509
Hey Nic,
When the car doesn't start does it seem to be dependent on the temperature? Warm start or cold start, or doesn't matter?
As your 740 is an '88 I'm pretty sure it has an LH 2.2 fuel injection system, which would have a hall effect sensor, not a crank angle sensor. Might be worth checking the little plug on the distributor where the hall effect sensor plugs in. They do have a tendency to get brittle and break. The ignition control module could very well be an issue as well. good luck.

Hey @Evan11509 , Temperature doesn't seem to affect it too much, although i haven't been testing for that, Just going off my memory we've had some chilly mornings where it's fired up and also some middle of the range temp's and it's not started up. Without more of a sample size I'm unsure if i can rule out temperature at this moment though.

As for the crank angle / halleffect sensor i was under the assumption it was a crank angle sensor but i'll have to look into it.

ramrod
Please quote the VIN so we can be 100% about the model year, lots of people experience confusion about the build year vs model year

Hey @ramrod , Attached is an image of the VIN, but to save you typing it out yourself it is as follows:

YV1744886K2323330 (NOV 88)

nh2868
Hi Pez,
If it's fuel injected and the fuel pump has brushes worn out or a bad sector, it's possible that occasionally the pump won't stop spinning in a good position to restart again. However if it starts spinning the motor skips over the "bad" sector and will keep spinning. In other words, a failing fuel pump could provide the symptoms you describe. Quick and dirty check - if it doesn't start normally, give a squirt of aerostart / brake cleaner / ether into the airbox. If your problem is spark, there'll be no change. If it's fuel realated the engine will fire up for a few seconds or at least couch / splutter. (It's also possible that vibrations from the engine will then trigger the fuel pump back into life.)

Hi @nh2868 That's a really good idea not sure why i haven't though of that in the past i'll sort out a spare can to live in nearby the car the next time it plays up and test that out. I'm hoping it's not a fuel pump, if we where to suspect it being a bad pump which of the two is more likely the culprit, i'll need to do some individual testing of each unit once i work out how to do so to confirm this.

Thanks everyone

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ramrod

Please quote the VIN so we can be 100% about the model year, lots of people experience confusion about the build year vs model year

nh2868

Hi Pez,

If it's fuel injected and the fuel pump has brushes worn out or a bad sector, it's possible that occasionally the pump won't stop spinning in a good position to restart again. However if it starts spinning the motor skips over the "bad" sector and will keep spinning. In other words, a failing fuel pump could provide the symptoms you describe. Quick and dirty check - if it doesn't start normally, give a squirt of aerostart / brake cleaner / ether into the airbox. If your problem is spark, there'll be no change. If it's fuel realated the engine will fire up for a few seconds or at least couch / splutter. (It's also possible that vibrations from the engine will then trigger the fuel pump back into life.)

Major Ledfoot

YV1744886K2323330 (NOV 88)

That's year model 1989:

This means it's the LH 2.4 system on the engine, and diagnostics are somewhat easier.

Follow the guide at the link below to look for any codes which the engine may be throwing.

https://www.volvoclub.org.uk/faq/EngineOBDCodes.html

WRT your difficult cold-start problem - is the car parked in an area which is prone to the collection of condensation or moisture overnight?

Pez

Major Ledfoot
YV1744886K2323330 (NOV 88)
That's year model 1989:
https://cdn.ozvolvo.org/uploads/860BY65DQWCC/image.png
https://cdn.ozvolvo.org/uploads/D7Q8477CM204/image.png
This means it's the LH 2.4 system on the engine, and diagnostics are somewhat easier.
Follow the guide at the link below to look for any codes which the engine may be throwing.
https://www.volvoclub.org.uk/faq/EngineOBDCodes.html
WRT your difficult cold-start problem - is the car parked in an area which is prone to the collection of condensation or moisture overnight?

Hey @Major Ledfoot

Thanks for that, I'll have to do some diagnosis on the OBD codes in the next few days after work and post the results.

Yes the car is parked outside up in the hills here in Perth when condensation does often collect, this however was also an issue reported by the previous owner who lived in the Perth CBD (less likely to have a large build up of condensation there but not impossible) although they also had external parking for the car too.

Cheers, Nic

Major Ledfoot

^ I just wonder if condensation is forming in the dizzy cap overnight and becoming a problem with a morning cold start, which then comes good when it dries out and after a few HT zaps.

Removing the dizzy cap on a B230 head-mounted dizzy is a major PITA involving a small ratchet spanner, a set of bruised and skinned knuckles, and a good assortment of swear words. The rotor button and cap may be showing signs of old age and wear, particularly corrosion. The contacts in the cap corrode, as do the sockets where the ignition leads plug into the cap. IIRC there are three 10mm bolts which hold the dizzy cap and the dizzy cap's black cap on the dizzy, but that recollection may not be correct as the PTSD after doing this once stuck with me, so they might be 8mm heads.

The LH 2.4 distributor has no 'smarts' or anything much else in there; it's just a big rotary mechanical switch. The EZ-K does all the timing, dwell, advance, etc.

am i correct in assuming that the fuel pump shouldn't prime every single time you turn the key quickly within short succession?

Yes. The ECU 'remembers' a start attempt was made within a certain time period.

Brad

Major Ledfoot
^ I just wonder if condensation is forming in the dizzy cap overnight and becoming a problem with a morning cold start, which then comes good when it dries out and after a few HT zaps.
Removing the dizzy cap on a B230 head-mounted dizzy is a major PITA involving a small ratchet spanner, a set of bruised and skinned knuckles, and a good assortment of swear words. The rotor button and cap may be showing signs of old age and wear, particularly corrosion. The contacts in the cap corrode, as do the sockets where the ignition leads plug into the cap. IIRC there are three 10mm bolts which hold the dizzy cap and the dizzy cap's black cap on the dizzy, but that recollection may not be correct as the PTSD after doing this once stuck with me, so they might be 8mm heads.
The LH 2.4 distributor has no 'smarts' or anything much else in there; it's just a big rotary mechanical switch. The EZ-K does all the timing, dwell, advance, etc.
am i correct in assuming that the fuel pump shouldn't prime every single time you turn the key quickly within short succession?
Yes. The ECU 'remembers' a start attempt was made within a certain time period.

They are 3 8mm screws holding the cap onto the distributor. One at the top and one on each side. It's not that difficult to remove. Inconvenient yes, PITA maybe a little but not difficult.

Pez

@Major Ledfoot Ah bugger not my knuckles, they've barely recovered from the coolant hose that's above the PCV and under the intake that I had to replace! Not even sure what it's called but my friend affectionately named it the "c**t" hose. Is there any complexity with re-installing the dizzy in the correct position after removing it or is it fairly idiot proof? (Mainly referring to the position of the needle in the dizzy cap).

Cheers,

ramrod

So, if you went on a long drive for more than an hour, you're saying there is no problem but only when you turn off the engine and start it again, it runs poorly?

And, is it more an issue when the engine is cold or hot also?

Pez

Hey @ramrod I've not had an issue to date with a hot start. I haven't driven it for much more than 30 minutes at one go yet, but it seems when it's in the "mood" to start it will continue to start for the day.

The issue at the moment is only self-contained to starting up. There are 3 things that can happen when i turn the key

1) It turns on straight away and no problems (yay)

2) On occasions it idles poorly until it cuts out completely. I haven't rolled forwards or backwards at this point just waiting to see if the engine holds, sometimes this is assisted by applying some throttle to get it to maintain a proper idol of which it will hold and run properly, although sometimes this isn't enough to help and the engine will shut off.

3) The other situation is the engine just cranks and doesn't start at all.

The actual on the road driving experience is flawless and i can't fault anything. I hope that makes sense.

Cheers, Nic

Pez

Drove the Volvo to work this morning and ended up having to leave it there this afternoon and grab a lift home. No big drama, did film an example of what it sounds like when it's not starting too well. Can hear it start to catch but doesn't hold, multiple attempts to start the car was made but i also didnt want to drain the battery. I've had to attach the video as a link below.

https://vimeo.com/827559037?share=copy

ramrod

The next time it happens spray a bit of start ya bastard into the inlet

If it runs, there is a fuel delivery problem

If no change, there is a spark shortage

nh2868

From the video, it's capable of running. Sounds like a classic fuel supply issue - it's "running" on dregs of fuel vapour meaning spark is fine.

jamesinc

A multimeter is the tool you want IMO. You can check +12V at the injector plugs (rules out radio suppression relay), +12V at the coil (rules out ignition switch), you can measure DC current draw on the in-tank (< 1A) and main (~5A) pumps. For spark, you can hold the coil lead next to a grounded bolt (like the ones on top of the strut tower) and by holding the tip of the lead about 1mm off the bolt while someone cranks, you can verify spark at the coil, and you can repeat the test with a spark plug and plug lead to verify the coil is operating properly.

For fuel pump prime, I think it does prime every time you turn the key. At least in my wagon it does.

Given this is a 7/9 and you've got the head-mounted distributor up the back, it could also be a failed o-ring letting oil into the cap and fouling the contacts.

Major Ledfoot

@Brad writes:

They are 3 8mm screws holding the cap onto the distributor. One at the top and one on each side. It's not that difficult to remove. Inconvenient yes, PITA maybe a little but not difficult.

Thanks for the correction. Not difficult if you don't have Arthur Itis, you mean.?

OP, two thoughts occur: how is your in-tank pump? Can you hear it hum if you hardwire the pumps on and isolate the main pump? And - is the main pump noisy?

The other is - how's the fuel pressure regulator on the fuel rail? No signs of leaking fuel from the small vacuum line?