91 740 turbo......123K.....some times to car refuses to turn over, and i never know when this will happen its very erratic. The car usualy makes a hissing noise right before start up normaly, but when it dosent turn over it does not make that noise. Im thinking fuel filter. What do you think?

 

If the engine isn't turning over sounds like a starter.

 

Ahh, but that hissing noise....


Might be the fuel pump(s) or the relay. No hiss = no fuel = no start.

Go here FI diagnostics and see if it helps.

A dirty fuel filter would cause problems at higher revs, when fuel demand is greater.

 

Ahhhh i see.....where would i find the relay and fuel pump?

 

Follow the FI Diagnostics link in my previous post... depending on your FI system and year, the components are in different places.

Example, some systems have two pumps (one in the gas tank). The fuel pump relays can be in the engine compartment, either side..or near the center console. It's all completely explained.

Good Luck

 

If it were the fuel pump relays, would it start at all? Just a thought. Here's my take.
1- Whenever it doesn't start, do you smell fuel at the tailpipe?
If you do, then fuel isn't your problem, at least most of the time.
2- Hissing sound could be anything related to fuel or vacuum. PCV or EGR systems could cause these symptoms, couldn't they?
You're probably right, but I wanted to offer some things I've run into before. Usually if a car doesn't start in my shop, it's the ignition module or starter solenoid.

 

Fuel pump relay bad can cause the car to quit running when it gets hot.

The hissing may be the starter.

But I haven't gotten a clear answer on if the car cranks and doesn't start or the engine doesn't crank at all.

 

Sounds like he/she was saying that it either cranks with a hiss, or doesn't turn over at all. That could be either starter, solenoid, or ignition module (if volvo's of that year have that part). I've got to claim ignorance to some things, but I'll help if I have an idea. Hopefully, ideas don't kill. LOL.

 

To help out and be more clear.....when i dont hear the hissing the car trys to turn over but cant...when the hissing is there the car turns over.