Fuse keeps blown thus car cannot start

volvo
engines
s40

#1

2001 volvo s40.



In July 2010, car suddenly did not start. I towed to Pepboys. They told me that one of fuse, 20 amp, labeled “ECM for immobilizer, engine relays” was blown. They replaced it and but could not figured out why. If it kept shorting, starter needs to be replaced - they said.



Everthing went well. but a month later in late august, my wife reported the car wont start. it happened in day time. after work, i changed the fuse and it worked like a charm.



Today, about a month later, i drove the beach (4 hours) then make 3-4 short stops. no problems in starting. then, suddenly, the fuse blown again. i immediately replaced it. but it was blown again immediately. Then, i waited 1.5 hours, then change the fuse and car worked like a charm again.



question: is pepboys correct that my starter needs replaced? i think it is either the ecm ( for immobilizer) or the engine relays needs replaced because this fuse is 20 amps and starter fuse is 40 amps. ( by logic that it cannot be the fuse)



what do you think?


#2

Pep Boys is not necessarily correct. There are obviously several circuits protected by that fuse. Each one needs to be evaluated to determine the fault. A wiring diagram is essential for this. The fact that the problem is intermittent means that the fault will definitely be very difficult to find. It is easier when the fault is actually blowing fuses, but once that episode ends, everything could be testing normal until the next episode.


#3

F11 feeds F17(fuel pump) & F18(AC).


#4

Whoa! Fuse 11 is only supposed to be 10 AMPs?!?!?! RED FLAG!!!

If the fuse that is in the OP’s car is 20 AMPs, you have a SERIOUS problem. This is a dangerous situation, because the circuits are designed to handle 10 AMPs max, hence the 10 AMP fuse. Putting in a bigger fuse let’s the circuits pull more AMPs than they were designed to, and can cause an electrical fire!!! For your sake, and those that travel with you, get this to a Volvo mechanic ASAP!!

This fuse runs the ECM (Engine Control Module), TCM (Traction Control Module), SRS (air bag module), anti-spin (like the anti-lock brake module?), electronic immobilizer (attached to the security system), AND instrument panel. That’s a lot of expensive modules to check, but one or more of them is NOT working within specs if a 20 amp fuse is required.


#5

Sorry. the whole picture did not copy. Here is the correct file showing F11.


#6

There is a relay which could also be a problem. More than likely it is the fuel pump or a/c clutch.


#7

Thank you: knfenimore for the diagram and bustedknuckles for the safety warning.

In my book, it is labeled “ECM for immobilizer, engine relay”. as i read more this morning, i also noticed that the starter fuse which is 40 amps feeds to several other fuses. Not sure what it means.

if it is going to be very difficult to find the culprit, is there several electrical components that is in the proximity of this area that i can just replaced ? after all it is a 9-year old car and sooner or later, some if not all components will need to be replaced. ( i do not plan to junk and will use it as project car as it gets older and older.)

again, thanks much for the reply.