No start when at warm temperature Topic is solved

[Pavel9]

Yes, this is a mistake I made with this vehicle. In the "old days" I would go to wrecking yards*** and pull all kinds of parts as spares for Brit cars - you could get a box of parts for cheap. Then I had all kinds of substitute parts to determine what was wrong. With the Volvo, so little has gone wrong over the last 1/4 century I got out of that weekend habit. Amazon has the correct Walker MAF units for $80 Cdn - I'd better order one!
*** This was a crafty way to find out if young ladies were worth pursuing - if they slogged through the mud and held wrenches without too much complaint.........

[Pavel9]

Update... of sorts...
I don't understand why cleaning the MAF sensor caused a complete no start situation, but a few days later it started... residual cleaning fluid on sensor? Sounds unlikely. Anyhow, that problem seems to have gone away on its own!
Needed the vehicle and so chanced driving for about 40 miles non stop. At about the 35 mile mark, the engine began bucking at about 2500 rpm/moderate throttle but when I "floored it", the engine smoothed out. On the return trip 10 hours later, everything was fine.

Replaced the fuel pump relay/controller (#103) with no change. As has been reported by others, the plastic base where the #103 relay plugs in is wobbly/broken and needs strengthening.

Next step is to keep following the advice as outlined by "afranke".

[abscate]

Fuel pmp relays that fail when hot are common on these cars.

A vacuum leak or bad air hose will cause these symptoms. Pulling the MAF wire makes the engine run open loop and the impact of the air leak is reduced.

[Pavel9]

Thanks abscate, you are probably correct about the hoses...leaks.
Today, had a little time - I disconnected the battery (both terminals) pumped the brakes and waited about 10 minutes. Bang, the vehicle, warm, started up. It ran really roughly for a minute or two and then settled down. Seems this procedure gets the ECU to reset - a re-initialization?
Now the vehicle will start when warm but is still unhappy as it comes to life. Next, I'll remove as much of the intake piping as possible, the various vacuum lines and check everything for leaks properly. Then there's that "thing" under the battery that apparently can be rebuilt with junkyard VW internals.
At least this is a sort of progress?

[abscate]

The SAS pump lives under the battery and makes a jet engine sound on cold start. They fill up with water and rust out at high miles/time. You can “delete sas” with a diode , too.

[Pavel9]

Removed the big piping that allows air from the MAF collar to the throttle body - the lowest connection had partially disintegrated perhaps air was getting there? Repaired that connection carefully with inner tube wrapping and additional clamp (Replacement part from Rock Auto will be a Christmas present)... no improvement.

I guess the next (unnecessary?) part to throw at this thing is a new MAF sensor or Crank Position Sensor perhaps... I'm reluctant as why would warm starting and not warm running be off? Fortunately, have cheap alternate (electric) transportation.

[Pavel9]

Noticed something unexpected. Fuel pressure at cold startup and while running is about 40psi using a tire gauge. If the engine is shut down, within a minute or less there is almost no pressure measurable, just a quick squirt of fuel.
Surely the fuel rail should hold pressure for some time after the engine is turned off... could the pressure regulator be allowing fuel to go back to the tank rather than to the injectors when warm? A proper pressure gauge should be in our basement somewhere...

[scot850]

Yes the fuel pressure should still be at the rail for at least 20-30 minutes.

Neil

[Pavel9]

Using a tire gauge to measure fuel rail pressure may have been misleading.
Bought a cheap fuel pressure gauge kit, hooked it up (which was not straight forward since the kit didn't have the correct connection to the 850 Schrader valve) and recorded the following data points. Not what I expected!
COLD engine - starts well - 46psi at Schrader valve. Pressure maintained accurately from idle to 3000rpm.
Turned off engine before it warmed up - pressure dropped to 20psi within a 3 minutes. Turn on (no start) - pressure goes to about 40psi.
WARM engine - engine will not start - still turned ON - pressure about 40psi - turn OFF - pressure drops more slowly to 30psi in about 5 minutes.

I checked that there was no leak at new fuel filter or smell of fuel at back of the cabin (new fuel pump not leaking).
After 40-50 minutes, engine would start and run again.

So, I suspect the fuel pressure regulator is failing (crack in diaphragm that slightly seals when warm?). But fuel pump can still keep pressure up to minimum or higher.

It seems there's something else wrong.

[122sPhil]

I would start with figuring out what is missing: spark, fuel, air. Given the fact that car starts great when cold, it is highly unlikely that problem is with the air, so lets ignore it for now. Fuel-starts and run great when cold, so most likely all is good here. You should have a pressure test port at the rail, so for piece of mind, attach it there and check if the fuel pressure is at spec upon you trying to start it. Spark would be a most likely cause. I think it still should be 1 ignition coil and distributor cap with 5 wires system?(my 98v70xc was, so just by analogy i assume ). I would check for spark from the coil to the distributor. If no spark- issue is likely the coil pack which has internal short upon warming up. Yes, ecm also can act up in such fashion, but coil pack is more likely suspect. Also agree with abscate about checking resistance from temp sensor on cold and hot and compare if adequate. Good luck

- some good points made above.. !

on any older car with a coil I'd put a small bulb across the primary, during cranking it should flash indicating you have a pulse at the primary. If you start loosing that pulse, it's an ignition electronics related issue.. I find myself loosing interest in Volvo's that rely on ECU's Ive ownerd a few 240's and 740's with the B230F. the B230F was a robust engine in itself.
most of the issues I've had were cuased by faulty electronics and faults in all the unnecessary wiring , fuel pumps fuel pump relay and hoses that have come off are common causes of a crank but no start situation.
in any car theat i replace a fuel pump I wire in leads for a test lamp so I can monitor in real time , if the pump looses power. You can check fuel pressure instead. a dead prepump can cause a no start particularily if gas is empty, sometimes you can get them to start by filling up the tank. the prepump isnt; needed to run if the tank is full so adding gas can show that. so can checking the prepump by other means.
a better test it so tc connect the line from it to a gas can and watch the preump fill a gas can ,

it wil not start or fire much at all if the main pump is faulty.

if you need to change a prepump I'd first siphon the gas out. ( yes now that I suggested you fill it up, you can drain it if you need to change the prepump)

if you check the prepumo by checking for flow it proves itself. If you check the main pump by measururing flow that is good. dont start a fire!
if you check fuel pressure with a gauge it can prove it has proper pressure this checks the regulator too. if it has low fuel pressure when running wide open this can prove a clogged filter or weak pump etc.



loose hoses causing vaccum leaks can cause failure to start so I'd check any hoses relating to the crankcase ventillation and hoses that lead intot he manifold. vecuum leaks can cause problems. PCV fumes rot out rubber hoses so look around there.

Id also try this,, double up the ground from your battery to the body and or from battery to engine (temporarily)
if you loose that electrical return path, or if it becomes high resistance due to bad connections, well all your wiring needs it. and a bad ground can cause a lot of strange issues,

As a quick test, simply duplicate the ground to look for a difference, if it starts with a( black) jumper cable in place then check the ground wiring. if no difference remove it but think about cleaning up your ground cable at every connection anyway. this wont be very visible issues but are easy to rectify. dont miss your alternator grounsd ( both ends)

because the ECU is complex and relies on a lot of different sensors you can check codes and see if it gives you a direction,, there are about a thousand wiring connections that can become dirty and cause no start or other complex issues. wires that shake becime oil soaked and vibrate or exposed to engine bay temp variations are wiring degradation suspects.

old ECU's use capacitors and capacitors have a lifespan, that lifespan passed. if you are brave you can recap the ECU or if less brave but have deep pockets, you can try a replacement or reconditioned one.. but check other stuff first.

my approach was to buy a beater , take it apart so I have spares for troubleshooting, if a parts swap does nothing i put it back as it was, then try somethign else, so as to not create duplicate issues. If you see a mechanic he will likely have a spare ECU spare ICU spare mass meter , etc.,, easy to swap. expensive to buy just for troubleshooting.

shotgunning parts is an expensive way forward. some parts like fuel pumps fuel pump relays and crankshaft sensors maybe best changed for new ..
for reasons of reliability.

check for codes determine if it has fuel pressure, determine if the injectors have a pulse. you can listen to them you can try a noid light that plugs in between the injector and it's lead.
determine if it has a spark or if the coil has a pulse when cranking, based on that I;d divide the troubleshooting into a path in order to isiolate one of those conditions.

if you spray quick start and it starts it proves you have ignition.

as you go, try to clean every ground you can find and connectors such as throttle position, air mass meter o2 sensor, clean the fuses and the fuesbox and check all the spade connectors not just the fuses.

in a 122 it had 4 fuses as time progressed things unfortunately went into a spiral of electronic dependance and overcomplexity.. when newer they were more reliable but as time progressed and as wires and connectors fail and become dirty then you can have a lot of different reasons why a car fails to start.

in my 88 740 volvo employed a "radio suppressor relay". it had notning to do with the radio and it can cause a no start situation. If you pull that relay the car will not start. I think it causes the injectors not to see any pulse. the car will still crank without it.

I do not understand why it was ever added. im not sure if the later cars had it. ( likely? )

if the car has an air bypass valve you might try to put small bulbs on it so you cna see it reacting to inpout power in real time. you may find you can check its resistance. i believe it is part of controlling the idle and works a bit like a choke except it is bypassing air into the manifild rather than choking the intake by mechanical means. Perhaps it is related. Ive seen 2 and 3 wire ones used in the 240/740 thye are a bit different from one another. I dotn think they fail often you may clean it

I cut one aparto see how it worked it was a little motor but htis motor can only make a part rotation and it opens or closes, it had no gears, its easy to bench test. Some say to keep it out of the motor itslef by keeping the motor upright , you can spray some cleaner in there .

distributor cap if it has one clean it ,look inside and check the coil and plug leads for corrosion,

I had a no start because the wire terminals on my coil got rusty, I just had to clean them it caused an intermittent no spart.

pre 88 used a hall sensor in the distributor later they used a crankshaft sensor both can cause a no start or random engine quitting. Id exampine or maybe replace the TDC sensor because of where it lives.

others here will be more helpoful with detailed electical troubleshooting .

in a 240 you can pul the fues panel out and away fromt he body in 2 minutes ot examine all the spade connectors and the fuse connections. in my 740 it requires pulling the fuse tray out which I find very awkward. It was just put in a stupid place..

I suspect later models flollowed in making these sort of connections difficult to access but of course, still possible..
fuel pump relay connections in particular, a dying ( stuck) fuel pump may have high amperage and high amps can cook the connector to the spades that the relay seats into.

if spade connectors and fuse connectors get hot they can lose spring tension because the heat anneals the spring bronze stuff. as you check try wiggling and look for connectors that are not holding ( gripping) the spades tightly.

watch for green , green is a sure sign of copper and brass parts corroding. If you see green wire or green connectors anywhere look very closely. intermittents can easily hide themselves in such places.

many of the internittent troublesone restart issues are caused by an undetected bad connection somewhere and not by some pricey part that failed. do yourself a favor and spend time cleaning connectioins, it will never reveal itself if you fix a conection BEFORE it causes such an issue , If you do not tend to them then you can trpubleshoot each one by failure and subsequent electrical diagnostics, the first option is the easiest so it is not a wast e of tine to just spend a day cleaning connections.
the contacts in the fuel pump relay are a very common cause. commonly intermittent.






I keep in my car a fuel pump relay , it gutted and jumped as "always on " mand I add a fuse ti it
, I just use it for troubleshooting, if installed, it will run both pumps for testing purposes.