I have a 1989 F-350 with an 85 carbed 460, the mechanic deleted all the fuel injection wiring and ran original relays to keep fuel pumps operational, for about a year everything has been fine. last month I had to replace the ignition box on the steering colume cause the wires melted and shorted out the alternator, replaced the ignition box and regulator on the alt, turned key and she started right up, idles good and everything, went down the road and about 4 minutes later it shuts off, turns over but won't start, looked under the hood and felt the fuel pump relays, one was hot, had a spare in the glove box and switched it out, turned key and she starts right up, go down the road again and about 4 minutes later it shuts off, switched relay again with the one I just changed and she starts up again, finally get home and she shuts off again, this time I have the hood open and the fuel gauge stills shows fuel pressure - I have a fuel regulator that limits it to 7 psi and it's still pumping. I'm at a loss.

 

Do you have a return line installed? Maybe the pump is working too hard trying to keep the 35 to 40 psi needed for the injection system. Don't know why it would work for a year and start acting up now though.

 

Thanks for your question, yes it does have a return line. The front tank never worked since the switch to carb and so I replaced the rear tank with a 40 gallon one as well as a new pump, it's all worked great until now. This thing is a tank and I really want her on the road again.

 

Since this seemed to start after the melt down on the ignition box, that is were I would concentrate, dont over think things. It ran fine for a year with the carb, and relay setup by the mechanic, so something shorted out melted your wires and damaged the ignition box, so since your getting fuel it's obvious spark that the relay is crapping out. A relay that gets to hot means there is a large load going thru it. Why? something in the coil or distributor is drawing to much juice, most of these relays can handle 40 amps max 30 amps continuous. That is alot of amps for anything, well except the starter and alternator. So you have to go back and find out what is drawing off that relay and maybe the easiest way would be to split the load and add 2 or 3 relays to dippy up the load from just the one. Use the same circuit on terminal 85 and 86 to close the relays grab 12volt power on terminal 30 and put the load on 87 for whatever it is energizing one relay for fuel pump, one for the ignition, another for the voltage regulator, I don't know what he did without looking at it, but do you get the idea? That way the relay wont over heat and shut down.

 

I forgot, if the fuel pump relay is the one, it wouldnt just stop, it would start to sputter and backfire than die. If this shuts off like a switch than it's the ignition relay, possible to energize the coil, ignition box, distributor something like that. Hope this helps!!

 

Sounds more like a bad DS Ignition module.
I am guessing it does have the DS Ignition system.

Why would he put a fuel pressure regulator on it? He should have just by-passed the HP fuel pump on the frame. Then would have been like the 85 system.

 

Let me get this straight, I disconnect the fuel pump on the frame and the fuel pump in the tank would be strong enough to push the fuel to the carb?. Put the fuel regulator on cause the edelbrock 650 would flood gas on the block. Thanks for all the info, I like the idea of increasing the relays, but the system has worked for the last year and almost 8 thousand miles. She hauls rock and split logs with an easy dumper on the back.

 

Before EFI the carb 460 only used the low pressure pumps in the tanks. When they went to fuel injection they put the HP pump on the frame and kept the LP lift pumps in the tanks that put out 7-12psi fuel pressure.
With the 460 carb set-up they also had a motorized fuel tank selector on the frame that also changed the fuel gauge from one tank to the other one.

 

Thanks again, I'm getting back under the truck and disconnect the second fuel pump, then if that doesn't change the shut downs I'll look into the ignition box.

 

Hi, Back again, I rechecked all the wires, pulled off the fuel regulator and as usual she fires right up, checked the fuel gauge at the carb and surprise it's still at the same place as it was with the regulator installed, Idled for about 5 minutes and still no problems, got into the truck and put it into reverse - fine - started out the driveway and it quits, try to start it up and it just turns over - no back fire - just turns over. Get out of the truck and put on a different relay and it starts right up. Forgot to mention when I had the 460 rebuilt I upgraded the distributor with an MSD type with a MSD 6AL multi spark box too, accidently laid my arm on it while reaching into the carb area and that thing was hot - so maybe that is my problem all along. was going to unhook the MSD 6AL and wire directly to the distributor but don't know which wire goes where and can't find my original paper work. I'm going to MSD on line and maybe they have a diagram what to do. Thanks for the info DAVID7.3, I think you were on the right track, also since I removed the fuel regulator and switched relays (before finding the box being hot) the motor did sputter a couple times and required pumping the gas to keep it going.

 

Can't just run the distributor with out an ignition box, sent an s-o-s to tech support at MSD. None of the trouble shoot info covered what I'm running into. The minute you turn that key till approximately 4 minutes that truck runs perfect!