Hey everyone,
This is my first Volvo. I bought it with intentions to fix it so I knew I was getting myself into a project. But I am out of ideas; maybe someone here can help.

2.9L

It has 63,000 miles on it.

I have replaced the battery and starter.

Tachometer jumps wildly when starting.

It may be turning over too slowly, but I don't know for sure.

Sometimes Backfires If I hold throttle. and try to start.

Here is a video I made of the problem.

2000 Volvo S80 Wont turn over - YouTube

 

*Update*

I have replaced the crank position sensor, and wrapped all starter power lines with aluminum foil. also checked for spark: positive. fuel injectors: positive. the computer is giving no engine/mechanical related error messages. It cranks just as fast, but only cranks for about 10 seconds or so before the battery seemingly "runs out" on a brand new battery. All visible engine grounds have been removed, cleaned, and put back on. the tach still jumps to around 1000-1300 rpm max when cranking. for the most part it stays around 300 rpm when cranking though. Ive looked around and checked that all visible connectors are connected. all fuses in the fuse boxes are good. but, it appears as if there is alot of empty space where the relays are, can anyone give a picture of the fuse box(es)? also, the engine backfires occasionally when cranking also. thanks!

I really want to get this car going and drive it! haha. but im stumped on why it won't start.

any suggestions/help would be greatly appriciated. thanks!

 

Sounds like the cam timing is off, have you checked it?

 

I have not. I dont really know how actualy. But the tach still jumps alot, up to 4000RPM sometimes when attempting to start. I tryed re routing it, but I guess I am failing? If it is jumping around, would that cause the engine not to start?

 

Also double check your fuses in the passenger compartment.

 

There are quite a few gaps where you think relays are, usually they are blank (probably because it is modular and used on other cars/models) and the car is not equipped with the related option.

 

ok so i went to check the valve timing on the camshafts. they are lined up with each other. i took off the plastic guard on the inside of the wheel well. next i removed the harmonic balancer. i am assuming that i must remove the serpentine pulley at the crank to check the timing belt pulley...? if so, do i de-tension the serpentine belt with an allen key? i could not identify which pulley was the tensioner pulley? mabey i just didnt look hard enough. but im going to make sure all three wheels are lined up.

 

You can do this while leaving the serpentine belt on,just need a 30mm socket to turn the crank, the marking on the crank is difficult to see, but its there. As far as the tach jumping, may need a ground wire from the engine to the transmission, that solved my issue.

 

there is a tsb for this concern on my 99 s80 but dosent appear to apply to your car but u might want to check it i will try to send you the info. the years are close. it is about changing the battery cable routing