I have a motorhome on a 1995 F series super duty motorhome chassis, powered by a 460 FI engine. After refusing to start, I could hear a "clicking" sound coming from what sounded like the power distribution box. After physically tapping on the cover to the power dist. box, clicking stopped, I was able to restart engine, then it stalled again with a few feet. After checking fuses, etc., I pulled the PCM relay and the clicking stops. It also should be mentioned that I was having to disconnect the neg. cable to the battery otherwise my battery would discharge down to 7.5v. overnight and I could not start the vehicle. What might be the "clicking" I heard, and by removing the relay and the clicking stopping, is it indicating a bad relay, or if by pulling that relay, does it also kill power to the fuel pump, or starter, if one of those might be the problem?

 

When a relay clicks it has low voltage on its coil.
The PCM Power relay that you pulled gives power to the fuel injectors, PCM Computer, the coil of the fuel pump relay, TPS, the transmission and a few other solenoids.

The voltage dropping over night more than likely is a bad battery. Do you not have a battery disconnect relay on the chassis side?
Does the NEG cable spark when you hook it back up every time?

By the way what is the brand name of your Motorhome?

 

Bill, thanks so much for your reply, especially for answering what exactly the PCM is responsible for. I should also have said that I had the battery load- tested and it checked fine. I started disconnecting it overnight because if I didn't, it's voltage would be so low by the morning that I couldn't get the engine to crank. (only when I gave it battery boost off the "house batteries" could I get it to crank and start). By disconnecting the neg. cable from it I would have no voltage drop. I could let it sit for a couple of weeks and it would fire right up, when I reattatched the neg. cable. But leave the batt. hooked up overnight, it wouldn't crank the next morning. I'm pretty new to motorhoming so I don't know if it has a batt. disc. relay on the chassis side, or even where to look for this. As far as the "clicking" noise from the area of the power distribution box: When it stalled the first time, I heard this click, click, click, click, click......., (in rapid and continuous sucession), so I turned the key to "off", and got out and taped on cover of it), then got back in, turned the key, heard no more clicking, so I cranked it and it fired up again, went 30', stalled again, and I went thru this 4 or more times until I finally got it parked in it's stall at the storage yard. After checking all kinds of fuses, I discovered when I pulled the PCM relay, the clicking stayed off. (but I didn't try to crank it over). I was hoping maybe it was just the relay, but thinking about the battery drain overnight, I don't have any idea of these issues are tied together, or 2 seperate issues. If that rapid clicking was actually coming from that relay, it kind of tells me that it's trying to protect something past that point. I'm just at a total loss of what to make of why this thing keeps stalling every so many feet, why I have that clicking noise that appears to be originating from the power dist. box, and when the clicking momentarily subsided those 4 or 5 times, I could get it to restart, only to have it stall again, followed by hearing that "clicking" again once the engine died. Please advise on how you might proceed. By the way, the motorhome is made by National, it's a Dolphin 533 model, registered as a 1997, but is actually on a 1995 F-Super Duty class A chassis. That's how it was manufactured. Thank you so much for your help and I'll be looking foreward to your reply. (Believe it or not, I'm a "Bill" too!)

 

By the way, when I reconnect the neg. batt. cable back up, I do not get a spark. But it sure saves the battery from depleating itself overnight when I do disc. it. And if I don't disconnect it, it's a no go on engine start. Thanks

 

Hooking the cable back up with no spark with the dead battery overnight sounds like a bad battery to me.
Or maybe the battery was discharged when you unhooked it each time.

When you hear the clicking and it stalls do you start it back up by using the button to connect the home battery to the chassis battery? If so sounds like you may have a bad alternator also or open fuse link.

Sound like the engine is stalling from low voltage.

 

Alright, thank you so much for the input. I appreciate your help.