Contour Enthusiasts Group Archives Forums General Troubleshooting Won't start, #4 fuse keeps blowing, no OBD-II

�? �? This evening, after a long evening of driving all over town, we stopped for the last time before going home at a small convenience store a few blocks from home.�?  No sign that anything was amiss up to this point.�?  I try to start the engine, and it doesn't fire.�?  It turns over just fine, but doesn't start.�?  I walked home to get my OBD-II system and a few other tools, and walked back.

�? �? The OBD-II system can't establish a connection.

�? �? When I turn the key to the ON position, I do not hear the usual fuel pump sound from the back.

�? �? On checking fuses, I find that the #4 fuse (â�?��?â�?�¢�? Daytime Running Lights (Canada)â�?�; â�?��?â�?�¢�? Ignitionâ�?�) (This is not a Canadian car, and does not have DRLs) is blown.�?  I replace it, and try again to start the motor.�?  Still no start.�?  I check, and find that the new #4 fuse has also blown.�?  I put a 30-amp fuse in (instead of the proper 20-amp) and then turn the key to ON but do not hit the starter. I immediately turn the key off again, and go out and check the fuse.�?  Sure enough, it's blown again.

�? �? So, apparently I have a short circuit somewhere in the system.�?  I don't need to try to start the engine in order to blow the relevant fuse; I just need to turn the key ON.

�? �? Any ideas where to look?

�? �? Oh, one other thing�? â�?��?��? I've noticed now that when I turn the key to ON, the CEL does not light up.�?  Shouldn't it light up whenever the key is ON and the engine not actually running?�?  Would a failure in the same circuit (Ignition?) that uses fuse #4 prevent the CEL from lighting and also prevent an OBD-II system from connecting?�?  Would this same circuit keep the fuel pump from running?

�? �? I've checked most of the other fuses in the underhood box, and found none others blown.

�? �? BTW, how do you get fuses 1, 2, and 3 out?�?  The manual says, â�?��?Have these fuses replaced by a qualified technicianâ�?�, and they appear to be locked in in some manner so that simply pulling on them won't get them out.

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Oh, one other thing ���?� I've noticed now that when I turn the key to ON, the CEL does not light up. Shouldn't it light up whenever the key is ON and the engine not actually running? Would a failure in the same circuit (Ignition?) that uses fuse #4 prevent the CEL from lighting and also prevent an OBD-II system from connecting? Would this same circuit keep the fuel pump from running?

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All of these functions require a good F4. Yes, yes, and yes.

F4 feeds the NO terminal of the PCM power relay. PCM power is required to activate the CEL light, turn on the FP, and initiate an OBD-II connection when the relay is energized by turning the ignition switch to RUN or START.

Output of the PCM power relay feeds the O2 sensor fuse (F13-15A), the coils for the AC WOT, FP, high and low speed fan relays, EVAP valve, injectors, IAC, EVR solenoid, VSS, MAF, transaxle, and the PCM.

As you can see, the list of candidate components is pretty long. Additionally, you have all those wiring runs that could have shorted to ground due to wiring insulation failure.

Personally, I'd check to see if recall 99M03 was done or is still applicable first.

Steve

Take a look under the battery compartment fuse box. There might be wiring shorted there or touching the metal. I have schematics from alldata (can post a few), or try autozone.com(possible), www.alldatadiy.com for a fee they have online manuals, buy a ford cd on ebay, check local library. This diagram may help, fuse 4 is likely the 20 amp one (of course they don't have the fuse number on the diagram!

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�? �? Well after spending all day yesterday finding nothing, I finally took it to a professional shop.�?  They got around to looking at it today, whereupon their guy quickly found a capacitor that had broken loose and melted against the EGR tube.�? �? On removing that, the problem is solved.�?  They've ordered a replacement, which I will probably pick up from them and install myself.�?  It's not a critical part; it just helps reduce interference on the radio.

Makes since, upon further review, that cap is on the F4 circuit. You're right, it's not important for engine operation.

Due the [censored] quality of the drawing in the EVTM, I actually had traced out the circuit for F9 in my earlier post. Doh!

In any event, F4 provides the power to the PCM relay coil. If this relay doesn't energize, the circuit via F9 can't get distributed.

Glad it's fixed.

Steve