hey all, i’ve got a 2007 volvo s40 2.4 that someone took apart and i put back together. it fires initially but then doesn’t want to start and keeps fuel fouling the plugs. i did the timing belt and it has a fresh valve job. i put new tappets in to make sure the valve clearances were in spec and they all are. it has good fuel pressure and has spark, did a wave test on the cam sensor and it works fine, also put a new one in and still nothing. i replaced all 5 coils and plugs just to see but it didn’t do anything. ect sensor is reading accurate, and timing is still on. compression is good. any ideas? is there anything that could cause weak spark besides the coils and plugs? thanks.

 

have you checked compression?

 

yes i checked, it’s within spec.

 

Have you tried a shot of starting fluid? When I have a situation like this, I like to use it to eliminate a fuel issue (or identify a fuel issue, depending on the outcome of the test)...

And make doubly certain that the timing is correct - there's a whole lot of potential to get that wrong (never did it myownself, so I can't really add much more than that). ;-)

I'd also recommend hooking up a Volvo-specific two-way scanner (preferably a laptop running VIDA) to see if it gives you some actionable intel...

 

just tried using starting fluid with the fuel system disabled. it didn’t help much, i had to command the throttle body open to spray in there but no dice. i’ve checked timing probably 10 times and all is good. even if it was a tooth off you’d think it’d start just rough? the timing is perfect though and it still doesn’t even fire up. i’m pulling my hair out

 

Just from the symptoms (and based more on other cars I've fixed) I'd suspect the crank position sensor - those are notorious for causing all sorts of odd problems, though they do usually set a code (you DID check for codes, right?).

 

yes i checked, no codes. i can throw a new crank sensor in and see what it does and i’ll get back to you tomorrow. thanks

 

Not sure if your model has a specific relay for the injectors like the 850s do (a common failure item) so if you haven't checked to see if there's a signal at the injector connector, that may be a good think to look at.

 

i pulled out the fuel rail with the injectors and cranked it to watch them spray. they all spray like they should, not stuck open and they are evenly spraying